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#1 =FB=VikS

=FB=VikS
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Posted 18 June 2010 - 18:16

TOPIC IS HEAVILY MODERATED! READ HERE FIRST!

Here is the list of airplanes performance information needed:

Sopwith Pup

Sopwith Triplane

Handley Page 0/400

Gotha G.V
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#2 MiG-77

MiG-77
  • Posts: 2651

Posted 19 June 2010 - 10:42

Profile publications perfomance figures:

Sopwith Pup:
Attached File  Sopwith_Pup.jpg   106.58KB   5220 downloads


Sopwith Triplane:
Attached File  Sopwith_triplane.jpg   202.71KB   5203 downloads


Gotha
Attached File  Gotha.jpg   182.38KB   5201 downloads


German Aircraft of the First World War:

Gotha
Attached File  Gotha2.jpg   82.02KB   5123 downloads
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#3 MiG-77

MiG-77
  • Posts: 2651

Posted 19 June 2010 - 12:00

Power curves for 260hp Mercedes D.IVa (gothas engine)

Attached File  DIVa.jpg   143.71KB   5185 downloads
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#4 JG1_Butzzell

JG1_Butzzell
  • Posts: 1363

Posted 21 June 2010 - 23:09

From Squadron/Signal publication # 173 "German Bombers of WWI in Action". No direct bibliography or referance for where they obtained the data.

Attached Files


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#5 piecost

piecost
  • Posts: 1318

Posted 28 June 2010 - 23:43

Guys,

I love this sim and look forward to more Sopwith aeroplanes.

I have found some performance data from: British Aeroplanes 1914-18, J.M. Bruce

Sopwith Pup

engine____________________________________Le_Rhone_____________Monosoupape
No._of_trial_report__________________________M.31_________________M.95A_
date_of_trial_report_________________________October_21,_1916_____May_1917
Propeller__________________________________L.P.1020_____________Vickers_57
weight_empty______________________________787__________________80
Military_load_______________________________80___________________80
pilot______________________________________180__________________180
fuel_&_oil_________________________________178__________________181
weight_loaded_____________________________1,225________________1,297

Maximum_Speed_(mph)at_ground_level________111.5________________110
______________________5,000_ft____________105__________________—
______________________6,500_ft____________—__________________107
______________________7,000_ft____________103__________________—
______________________9,000_ft____________103__________________—
_____________________10,000_ft____________—__________________104
_____________________11,000_ft____________101__________________—
_____________________13,000_ft____________98___________________—
_____________________15,000_ft____________85___________________100

________________________________________m__s_______________m__s
Climb_to______________1,000_ft____________0__55_______________–_–
______________________2,000_ft___________2__00_______________–_–
______________________3,000_ft___________3__05_______________–_–
______________________4,000_ft___________4__15_______________–_–
______________________5,000_ft___________5__20_______________5_40
______________________6,000_ft___________6__45_______________–_–
______________________6,500_ft__________–__–________________7_05
______________________7,000_ft___________8__20_______________–_–
______________________8,000_ft__________10__15_______________–_–
______________________9,000_ft__________12__00_______________–_–
_____________________10,000_ft__________14__00_______________12_25
_____________________11,000_ft__________16__30_______________–_–
_____________________12,000_ft__________19__20_______________–_–
_____________________13,000_ft__________22__05_______________–_–
_____________________14,000_ft__________25__30_______________–_–
_____________________15,000_ft__________29__10_______________23_25
_____________________16,100_ft__________35__00_______________–_–

Service_ceiling_(feet)_____________________17,500______________18,500
Endurance_______(hours)_________________3___________________1_3/4

The article quotes the engine options as: 80hp Le Rhone, 80hp Gnome and 100hp Gnome Monosoupape.

Judging by the similarity of the performance data I think that the 80hp Mono was used in the test

Sopwith Triplane

Trials conducted at Central Flying School; Speed trial on 9 December 1916, climbing trial on 7 December 1916.

weights_(with_130_hp_engine):__empty:_________1,101_lb
_______________________________military_load_____80_lb
_______________________________pilot____________180_lb
_______________________________fuel_&_oil_______180_lb
_______________________________loaded_________1,541_lb

performance with 130hp engine

maximum_speed_(mph)_at_5,000_ft________________117
_______________________7,000_ft________________112
_______________________9,000_ft________________109
______________________11,000_ft________________107
______________________13,000_ft________________104
______________________15,000_ft_________________98

_________________________________________m__s
Climb_to______________1,000_ft______________50
______________________2,000_ft___________1__45
______________________3,000_ft___________2__30
______________________4,000_ft___________3__25
______________________5,000_ft___________4__35
______________________6,000_ft___________5__50
______________________7,000_ft___________7__15_
______________________8,000_ft___________8__40
______________________9,000_ft___________10_15
_____________________10,000_ft___________11_50
_____________________11,000_ft___________13_35
_____________________12,000_ft___________15_20
_____________________13,000_ft___________17_30
_____________________14,000_ft___________19_50
_____________________15,000_ft___________22_20
_____________________16,000_ft___________25_00
_____________________16,400_ft___________26_30

Service_Ceiling______20,500_gt

endurance____________2_3/4_hours

Some further performance data from: Sopwith-The Man and his Aircraft, Bruce Robertson, ISBN 0 900 435 15 1

The data has a few typing mistakes; missing "0"s on some of the quoted heights

Sopwith Pup

____________________Test 21 Oct 16___Official figures
___________________________________released to French
Engine______________Le_Rhone_80hp__Le_Rhone_80hp__Le_Rhone_80hp__Gnome_Mono_100_hp___Clerget_80hp
__________________________________________________________________or_110hp_with
__________________________________________________________________LP710C_prop
Propeller___________LP1020__________2600D,_2200P___LP1020_________P3012/Vickers_57_______P43
Weight_empty________787____________787____________780____________856_________________850
Weight_Loaded_______1225___________1225___________1234___________1297________________1290
Endurance___________3______________3______________2_1/2__________1_3/4_______________2_1/2
Speed(mph,_ft)_____103_at_7000_____104.5_at_10000___—____________104_at_10000________—
__________________101_at_1100_____94_at_15000_____—_____________100_at_15000________—
time_to_Height______6_1/3_to_6000___14.5_to_1000_____—____________12.5_to_10000_______—
___________________14_to_10000____30.1_to_15000____—____________23_1/2_to_15000_____—
Ceiling_____________17500__________20000____________—___________21000_______________—

Sopwith Triplane

Note, being tested for/by the RNAS; speeds are in knots

Engine______________Clerget_9Z_____Clerget_9B
Propeller___________2740D,_2480P___LP2100,_AD553
Weight Empty________993____________1103
Weight Loads________1103___________1543
Endurance___________2_1/2__________2_1/2
Speed (kts,_ft)_______112.5_at_6500__116_at_6000
____________________95_at_1500_____114_at_10000
Time to Height________6.5_to_6500____6.5_to_6500
____________________105_to_15000___12_to_10000_
Ceiling_______________20500__________2200

I hope that this helps
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#6 Chill31

Chill31
  • Posts: 1891

Posted 28 June 2010 - 23:57

Frank Tallman "Flying the Old Planes"

He describes his flight in an 80hp Le Rhone powered Fokker EIII


"The tail was up almost instantly, and we lifted in 290 feet"

"Climb is at the rate of about 600 feet per minute"

"The warp is extremely stiff on the wings, but slight pressure and almost no apparent movement of the stick is enough to drop a wing in normal turn."

"The tendecny, as you level out, is to want to get both hands on the stick, for, as you pick up speed, it gets very sensitive fore and aft, and you have some difficulty not poroising"

"I settled down at 1000 feet indicating 75mph, and had completely run away from my Stinson L I camera plane."

"Unlike my experience with the SE5, there is no desire on my part to even attempt aerobatics with the Eindecker. I can't forget its well-deserved reputation for structural failures when it first appeared at the front in 1915."

"It stalls rather gently at 43 mph, and as the right wing drops, I make no attempt to pick it up."

"I have more than enough rudder to taxi back to our display area." (it is tailskid equiped)
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#7 Chill31

Chill31
  • Posts: 1891

Posted 29 June 2010 - 00:58

Frank Tallman "Flying the Old Planes"

He describes his flight in a 165Hp Warner Radial powered Sopwith Triplane
with a tailwheel. The Triplane was 300 lbs heavier than the original. Performance from a rotary would be better than stated in his book.


"I was airborn with no wind in about 480 feet." (100 degrees F, and 780 feet MSL)

"Rate of climb, even in the heat, was approximately 1000 feet per minute at 58 mph indicated."

"The three ailerons on each wing were pure delight and gave this flying club sandwich a crisp response equal to that of a Stearman or Tiger Moth."

"I climbed to the acrobatic area in slow circles, feeling out the rudder and elevators, which gave somewhat less positiveness than the ailerons."

"Stalling speed occurred at 44mph, and the plane broke gently straight ahead."

"Wide open throttle gave me an indicated airspeed at 3000 feet of 92 mph"

"I dropped the nose for a loop. With 115 mph indicated, I pulled back gently and added full power over the top, where I had 30 mph. The Tripe followed through nicely, but with a loop considerably larger in diameter than the DRI. All the way through, the wires sang like a demented peanut vendor and must have been easily heard on the ground."

"Reflecting on the differences between the two planes [Sopwith Tripe and DRI], I feel that the Sopwith Triplane is infinitely superior. It is more controllable, lovlier on the ailerons, climbs faster, and the rollout on landing is easier" (I would note that the high tailwheel on his Tripe is probably the reason it is easier to handle on the ground due to better visibility and more vertical tail exposure to prop blast.)
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#8 Vati

Vati
  • Posts: 820

Posted 29 June 2010 - 04:50

^^ Replica aircraft with completely different engine and construction should not be used as reference.
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#9 piecost

piecost
  • Posts: 1318

Posted 07 July 2010 - 19:08

From Bleriot to Spitfire
Flying the Historic Aeroplanes of the Shuttleworth collection
David Ogilvy
ISBN 1 85310 231 8

The Sopwith Pup, John Lewis

The Sopwith Pup was a fighter aircraft of the First World War, at a time when such aircraft were known as scouts. It was developed from the Sopwith 11/2 Strutter, and was ordered for the RNAS in 1916. Later, it was also supplied to the RFC, with which it became standard equipment and earned the reputation of being a first class flying machine. With the RNAS it played a major role in the development of carrier ship-borne aircraft operation. Although its official name was the Sopwith Scout, Pup is the name by which it was always known, and by which it became famous.

The Collection Pup, N5180, was the property of a private owner near Bedford until it was acquired by Richard Shuttleworth in 1936. It was, in fact, then a Dove, a two-seat variant of the Pup, and had to be re-converted back to its original form by the Collection. Since then it has appeared regularly in displays throughout the country in the form it is seen today. The motor is an 80 hp Le Rhone nine-cylinder rotary, in which the crankshaft is fixed to the aircraft, and the cylinders rotate, together with the propeller, which is fixed to the crankcase. Since most of the problems, and hence the interest, of aircraft fitted with rotary motors arises from the unique operation of such powerplants, considerable time will be spent in this article in exploring the topic, as well as looking at the aeroplane itself.

The aircraft is a wholly conventional wire and strut braced biplane, typical of its era. It is fabric covered throughout, and has the normal modern control set-up of ailerons, elevators and rUdder. In order to improve the available rate of roll, an important consideration in fighter aircraft, the ailerons are doubled, a set being fitted to both upper and lower mainplanes. The undercarriage has bungee sprung wire mainwheels set close together, and has no damping; and a swivelling tail-skid of a rather unyielding nature. Bamboo hoops are mounted beneath the wingtips of the lower mainplanes to protect them in the event of roll angle developing on the ground. A single Vickers machine gun is fitted between the centre section struts, with a heavy glass windshield mounted on the butt end near to the pilot. A synchronising gear enabled this gun to fire safely through the propeller.

The cockpit is extremely roomy, but the fixed basket seat is rather hard and uncomfortable, and the tall pilot projects a long way out into the airflow. The rudder pedals, too, are a rather long way from the seat, and the pilot is restrained by a very uncomfortable and inefficient set of straps. The field of view is good, except where obscured by the upper wing, but the suspicion dawns that the windshield is not going to be a lot of use. There is a gap between it and the fuselage upper decking, and it is extremely small. On the right is a hand pump for raising pressure in the fuselage tank, and near it a valve to adjust the blow-off pressure of the safety valve. The instruments are few, consisting of an ASI, altimeter, slip bubble, RPM indicator, oil flow glass, compass and pressure gauge for the tank. On the left hand wall are the most important controls in a rotary powered aircraft, the air and fuel levers and magneto switch. A further ignition cut-out button is fitted on to the top of the conventional spade grip control column, to enable power reductions to be made by 'blipping' the ignition circuit.

The motor is unusual in that it has only one push rod per barrel, and this operates both inlet and exhaust valves, pushing for one and pulling for the other. This was done in the interests of lightness and low centrifugal loading. Ignition is by single magneto, and the oil system is, of course, total loss. The big end system is extremely unusual in that there is no master rod as in most other radial and rotary powerplants, but the different length rods are equipped with a most ingenious system of shoes which fit into matched grooves at the big end, and which provide rotation without interference. Displacement, at nearly eleven litres, is large, but the fuel consumption is modest, and the motor extremely smooth when running.

More than one pilot, returning stunned from his first flight in a rotary powered aircraft, when asked what he thought of the aircraft, has said, 'How would I know? -I spent all my time worrying about the motor. I didn't even notice the aircraft.' I have to admit that I myself had just the same reaction, and since subsequent flights showed .that the aircraft was indeed quite normal and unexceptionable, the major content of this article is going to have to be rotary handling, with a little about the aircraft
thrown in, rather than the more normal reverse. Indeed, in view of the general awkwardness and unhandy behaviour of the rotary, it is a wonder that anyone learned to fly at all in even relative safety in the days when they were the rule. The reader might like to dwell on this as he reads on and the description develops, and contrast it with what he knows of the simplicity of modern powerplant
handling.

The pre-flight walk-round inspection is normal and is confined to the normal aspects of airframe condition, rigging tension, security of panels, tyre pressure and so on. A single footstep cut into the fuselage near the trailing edge of the lower wing enables a rather undignified scramble into the cockpit to be made. Having sat down it is normal to find that either the cushion is the wrong thickness, or that one is sitting on the straps, and so one usually stands right up again. Once these matters are sorted out, however, strapping in is rapidly completed, the controls checked for freedom and correct sense, and the magneto, fuel and air all confirmed off. Pressure is then pumped up in the tank, and the pressure blow-off checked at 2lf2 psi and adjusted if necessary. The big rotary is now liberally primed into each cylinder with a syringe and pulled over a couple of times, to suck in the mixture. This priming stage is very important, and is one of the secrets of a good start on this type of motor. The skill of the engineer in knowing just how much to give is everything. The air and fuel levers are marked withnumbered calibrations for reference, and have a friction device for locking them into the selected position. The air lever is first set open by the amount thought appropriate for the day, say half-way for a cold, dense day, rather less for a hot one, and the fuel re-checked off. This last is vital -too much fuel during a start guarantees failure. Then, with the magneto switched on, the engineer swings the propeller smartly over a couple of compressions. If the prime was right, and the motor cold -they are very awkward when half hot -it will fire at once, and with a cloud of smoke and a blast of air from the propeller, burst up to its maximum of about 1,150 rpm, rocking the aircraft wildly on its narrow undercarriage as the torque reaction sets in. It is now extremely important to have patience; a rotary can very easily be made too rich, and if this occurs it will stop, and have to be blown out before it can once again be started. The pilot waits, therefore, until the prime is almost exhausted, and the motor cuts and starts to run down. As it does this he applies fuel, using the lever on the left, while at the same time ensuring that he does not alter the air setting, to a point at which experience or a briefing tells him the motor will run. Ifhe has got it right, after a couple of seconds delay, normal for the rotary as the mixture finds its way through to the cylinders, the motor will pick up again and all is well. It is then a matter of experiment to alter the settings of air and fuel levers in sequence repeatedly until the motor runs smoothly at the maximum obtainable rpm. This will vary from day to day, but in any case should be better than 1,100. The settings of air and fuel are then noted and committed to memory for the subsequent flight.

Reducing power on a rotary can only be done to a limited extent using fuel, usually down to about 750 rpm. At this setting power is excessive still for taxying, so further reduction must be done by cutting the ignition. This is possible using the magneto switch, but it is far more convenient to do it by depressing the button on the stick with your right thumb. There is a knack to doing this, rather akin to patting your head and rubbing your tummy at the same time. Try that, then try to hold a conversation with someone at the same time, but don't break the sequence. Not easy, is it? In fact, like everything, it comes with practice, but in the early stages it is awfully easy to get confused. At 750 rpm the motor runs rather erratically, and sounds rather like a many-cylindered two stroke, but each time the cut-out is released and it picks up, it fires steadily for a few moments, and the aircraft rocks gently on its gear. Despite the apparent approach of disaster each time the motor is allowed to run down, this condition is entirely reliable; and, possibly because the motor is running lean, plug oiling is not usually a problem.

It is at this stage that the chocks can safely be waved away, and with a handler on each wing the aircraft is taxied away towards take-off. During the tllxi the handlers work hard to keep the aircraft going towards the marshalling point, and especially so if there is any wind, as the aircraft has a will of its own on gradients and in side winds. Should the motor misbehave at this stage, the handlers will also have to hold it back whilst the pilot opens up a little, clears the plugs and resets the mixture to a more reliable level. Handlers on a rotary work hard and almost need a sixth sense to help them to know what is going on. A thoughtless pilot can cause them considerable anguish, and 'have a thought for the wing men' is part of every new pilot's briefing on a rotary.

Lined up for take-off, exactly into the wind as crosswind handling is very poor, the only check really necessary is that the fuel pressure is correct. If not, it is pumped up again to the required pressure with the hand pump. Usually, the propeller wash will have helped the little windmill pump on the port centre section strut to maintain it, and not much pumping will be necessary. An assessment of oiling will have been possible before now due to the smell and blue smoke, but the glass is rechecked just in case, the handlers signalled clear and the fuel lever set in the full power position. The aircraft rocks again, swings a little, and gathers away extremely quickly as the power comes in. Now is the time to check rpm, and very slightly to reduce fuel setting as it comes up to the static value. This is extremely important as the rotary feeds mixture by centrifugal force and the increased rpm resulting from forward speed will lead to over-richness if this is not done. Slight over-richness will give a marked loss of power; more than slight and the motor will stop. A rotary that has had a rich cut cannot be started in the air again, except during a long descent. In fact, the ear turns out to be, as it so often is, a reliable guide to the state of the motor. The beginnings of the over-rich condition are evident in a slightly heavy, flat exhaust note, and action can be taken on this as well as by watching for rpm reductions.

In any event, the aircraft accelerates so quickly that the ground break arrives before the pilot is really ready for it, and although it is normal to lift the tail first this really makes very little difference to the take-off performance. The rate and angle of climb are exceedingly brisk, and the motor smooth and crisp sounding. The blast of air past the pilot is incredible, however, and it has just enough upward component to take the breath away, and unless they are fastened like a tourniquet, the pilot's goggles, too. Everyone who meets this tries the obvious dodge of ducking down into the cockpit for relief, but it is no use, the icy blast is in there too. Nothing else for it but to put up with it and to make a note to tighten the goggles for the next sortie. Those of you who have seen the Pup at displays with the pilot's hand to his head may have wondered why. Now you know -he is neither puzzled nor waving at the spectators -he is trying hard to hold his goggles onto his face so that he may contrive to see, and so to have some influence on the remainder of the flight.
In the climb, the strong helical airflow from the big efficient propeller is evident from the marked rudder deflection needed, and the gyroscopic effect of the motor is powerfully evident if turns are made. Go one way and the nose drops, the other and it rises. The higher the turn rate used, the worse this becomes. It must have been the very devil of a nuisance in a fight. The ailerons and elevators are powerful and precise, however, and all the controls are very pleasantly light. No wonder the machine had such a fine reputation. For some reason, possibly connected with its re-conversion, our Pup is rather tail heavy, and needs a constant push force on the control column to hold it in any flight condition. This naturally worsens as speed rises, and spoils what would otherwise be a very nice handling aeroplane.

At speed, adverse yaw from large aileron inputs is modest, and the usual trick of leading slightly with rudder controls it easily. Damping is good, and manoeuvrability superb. The point to watch in this regime is again the motor, because as speed rises so does rpm, and this rapidly approaches the limit. Exceeding this could easily lead to structural damage, so rpm must be controlled by reducing fuel or by cutting the ignition. Speed sufficient for a loop, the only aerobatic manoeuvre we permit ourselves, is obtained just about at the limit, however, both of rpm and the pilot's ability to retain his goggles, so we can usually get by without this expedient at a display, except for effects during low flypasts. It is in the low-speed regimes such as the top of the loop that the full measure of the gyro reaction is felt, and it takes real skill to do one exactly straight. At the other extreme, it is easy to perform a perfect clover leaf in the Pup just by doing four loops in a row and by taking no opposing action at the top. It is quite uncanny to watch the aeroplane turn sedately through 90 degrees to its
original heading without any action by the pilot.

Possibly the most awkward part of the flight in the Pup is the approach and landing. This is not, again, the fault of the aircraft, but of the complication of rotary handling. The aeroplane is a very good glider, and reducing power to the 750 rpm tickover will only result in a modest descent rate, insufficient for this purpose. Resort to 'blipping' is therefore made as well, and control of glideslope is thereafter fairly easy, the increased rate of descent being, literally, switched on and off as required. The disturbances to directional and lateral trim caused by this are unsettling, however, and the workload required to keep the approach tidy is considerable. The landing itself is not difficult, but to do it properly and to control the motor is.

The aircraft is easy to flare, being well damped even at low speed, but once in ground effect it is necessary to kill the motor completely using the button on the stick, o! the Pup will go on flying for ever, one foot off the ground. The problem lies in doing the killing for long enough to get onto the ground, without doing it for so long that the motor stops, and at the same time fly into a three-point stalled landing on an aircraft with a crisply sprung and rather unforgiving undercarriage. It is not difficult to do either, but both at once is something else again. With no brakes, a narrow track and a fair tendency to roll with sideslip, the aircraft is also always landed exactly with wind, but gusts occur and sometimes directional control becomes very bad. At such a time a burst of power is needed, because once the tail is down the fin and rudder are blanked, and although effective are very weak. Fortunately, tail skid drag helps, especially if the stick is held hard back: and the landing rollout, provided too much power is not used, is usually quite short. Hopefully, the motor is still running, and careful adjustment of it at its lowest setting can now be made as the handlers approach. Since it is now very hot, greater care than before is necessary to keep from losing it as the aircraft taxies in, and it may well prove necessary to stop and reset on the way back. I hope you have enjoyed this brief description of the problems of operating the Sopwith Pup. It is a fascinating aeroplane, all the more so for being a representative of one of the most successful aeroplanes of its age. Perhaps, too, you can now see why so few modern pilots notice anything about the aeroplane on their first acquaintance with it, and you can wonder, with me, how anyone ever succeeded in teaching himself to fly successfully in an aeroplane powered by such a motor.
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#10 piecost

piecost
  • Posts: 1318

Posted 07 July 2010 - 19:15

Evan Hadingham
The Fighting Triplanes
Hamish Hamilton

Extracts from this book concerning the Sopwith Triplane

The triplane was instantly successful. At that time no aircraft could match its superb rate of climb, and no fighter aircraft could regularly patrol at the heights it frequented. Any aircraft of the period could be out-manceuvred, by the simple expediency of a climbing turn. The compact elegance of the triplane on the ground was transformed to deadly use in the air. But above all it was almost the perfect flying machine. Light and responsive to the controls, its docility and manceuvrability quickly enamoured it to the biplane pilot. 'It would be difficult to analyse the feature in this machine that made it so attractive to fly,' wrote Major Oliver Stewart. 'It seemed light and elegant and yet wiry…. The triplane spun rather slowly, and its flick roll was also rather slow compared with other machines of the time; but what it lacked in quickness it made up in the smoothness and grace of its movements. A triplane looping looked like no other machine and gave the loops an individual quality. Irreverent pilots said it looked, when doing aerobatics, like an intoxicated flight of stairs.

'I liked the Pup better than the triplane because it felt firmer. But it was a beautiful flying machine' Sir Herbert Thompson recalls his war service in No 8 Sqdn RNAS. 'I first flew a triplane on 24 May 1917,' he writes, 'and recorded in my log book: "The best machine I've ever flown. Thoroughly in love with it." After fifty years I still am. Only now, I call her "she" not "it". 'The first time I ever saw a triplane-at Cranwell in 1916-1 remembered the organ-like hum caused by the rotary engine within that particular cowling. After flying Baby Nieuports with No II Sqdn RNAS

it was a joy to soar-and a triplane did soar. Without war load she was capable of climbing 10,000 feet in 8i minutes-terrific for those days. And with war load I took mine up to 21,000 feet, and we often used to patrol as high as 19,000 feet; for then we had the drop on any German.' Of the same squadron, Captain R. R. Soar wrote: 'In action as a fighter I can assert that she was without equal in respect of visibility: you had a grand view all round and the risk of being surprised by hostile aITcraft was less than other machines. You could spin it fast or slowly: slowly, you could pull it out by joystick control-fast, of course, you had to centralise controls. We often used to spin it down to afew feet of the hangar top. 'I can confirm all Sir Herbert says on the triplane. I don't believe it was weak in construction-I fought for over five months in a "tripe" and gave it the stick.' Indeed the triplane's unusual appearance on the ground and its unorthodox construction had given rise to widespread rumours of its weakness in a power dive. One pilot even wrote that they 'used to fold up ifyou came out of a cloud in too steep a nose dive'. On the other hand there were no recorded failures from this cause, and there is rather more evidence to suggest that in all normal manceuvres the triplane's strength was quite adequate. Flight Commander G. G. Simpson (No 8 Squadron RNAS) explains: 'There was one case of a pilot-Flight Sub-Lieutenant E. D. Crundall (now Wing Commander)-who left my Flight against my instructions and attacked a decoy two-seater Aviatik. He followed this machine down in a dive from 15-16,000 feet; when he reached about 5,000 feet he decided to pull out. He told me that when he came to opening the throttle of his engine he found it was wide open. He had taken his triplane absolutely to the limit in a dive, and the result was that the bracing wires were stretched so much one could literally tie knots in them. There was also a case of another pilot, Gerard, who received a direct hit by an anti-aircraft shell. It took all the fabric off his top plane, but he still succeeded in landing safely.'

'It was all nonsense about a supposed weakness in the Sopwith triplane,' states Air Vice-Marshal Raymond Collishaw. 'There were, unhappily, three different models of the Sopwith triplane made by Sopwith and two sub-contractors. For some extraordinary reason, the sub-contractors substantially reduced the sizes of the flying wires and the landing wires compared with the Sopwith Company triplane. The reduced sizes of the wires naturally weakened the structure when diving under full power; but history shows that there were indeed few failures from this apparent weakness. Incidentally, there were also three types of Clerget engines in use in the triplane-the French model and two English copies-the French-made model was far superior. Thus, if a new pilot found himself with a triplane with relatively weak bracing plus an English engine, he was definitely out of luck. Experienced pilots always saw to it that they possessed only Sopwith-built airframes and French engines.

'The two disadvantages of the Sopwith triplane were that it was underpowered and under-gunned. Tommy Sopwith told me that he had intended to fit the Bentley rotary in the triplane, but its availability was delayed and as he was pressed by the Admiralty to produce the triplane, he had to forgo the Bentley and fit the Clerget engines. Sopwith also considered fitting two guns on the triplane, but altered his mind when he knew only the lower-powered Clergets could be used. Had the Sopwith appeared with both the Bentley engine and two guns, the whole story of the life of the triplane might have been quite different. As things were, both the Sopwith triplane and later the Fokker triplane were the most manceuvrable aircraft to appear on the Western Front in the 1914-18 War.'

Another triplane which was employed outside the Western Front was N 5430. Constructed by the Sopwith Company, it was transferred to the RFC and arrived at Orfordness Aircraft Armament and Gunnery Experimental Establishment in late 1916 or early 1917. There Captain (now Sir) Vernon Brown took an immediate liking to the triplane: 'It was a very simple aeroplane to fly,' he explains, 'and I spent more hours on it at Orfordness than on any other. It was one of the loveliest aeroplanes I ever flew-it was so easy, it was so fault-free and non-vicious. It wasn't as fast as the SE5A or the SPAD; it wasn't such a good fighter chiefly for that reason I think-it hadn't got the performance. But for pleasant flying, I can say quite clearly that my recollection of the Sopwith triplane is the very happiest of all the aircraft I flew.' Oliver Stewart wrote that, 'Sir Vernon Brown was one of the greatest triplane pilots I remember … he successfully demonstrated that the aeroplane was capable of the whole gamut of aerobatics, and that although it did not appear to do the manceuvres with the suddenness of the biplanes, it did them with infinite grace.'

The most remarkable of all the tests carried out at Orfordness is described by Sir Vernon Brown: 'One of the things we did not understand was that as the aircraft got faster and faster, so we experienced some rather extraordinary effects. Ifwe flew fast and then did a tight turn, or, for instance, dived an aircraft and then pulled it over in too tight a loop, a sort of haziness crept up over one's eyes, rather like a mist; and there were occasions if you held the tight turn for too long where you almost passed out altogether. In order to find out what was happening Lt Jones asked me to fly at as high a speed as possible over a hut in which was a camera obscura, projecting an image on to a table. As the aeroplane, Sopwith N 5430, flew over the top its image was shown through the lens on to the paper, and, by means of a metronome, he was able to point it every second as I made circles. Mterwards it was a simple calculation to find out what "g" had been applied. The triplane was one of the best of all aircraft to do it in, because if you did black-out and lose control, it always recovered itself automatically. It was really very safe indeed.

'On one occasion the aeroplane went into the most peculiar manceuvre at one thousand feet, and it was because I had passed out altogether that I came to at only two or three hundred feet in a shallow dive. I was very lucky it hadn't dropped into a spin. During these experiments once, I heard an awful bang; I didn't know what it was, and I came down very gently. When I landed the whole centre-section was found to have been wobbling about, as one of the strainers on the centre-section bracing wires had broken. But otherwise the triplane was fortunately rather free from these vices. 'Lt Jones found by repeated experiment that I could hold 4'5 g for 10 seconds, and that I could hold 6 g for 4-5 seconds. The results of these experiments were sent up to the War Office.'
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#11 Chill31

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Posted 16 August 2010 - 02:05

The Fighting Triplanes
Evan Hadingham


Dive Performance
Flt Sub-Lt J.H. Thompson: " As I eased her back, the airspeed indicator was registering 80 knots on the second time round, but the wings had stayed on…"

"He followed this machine down in a dive from 15-16,000 feet; when he reached about 5,000 feet he decided to pull out. He told me that when he came to opening the throttle of his engine he found it was wide open. He had taken his triplane absolutely to the limit in a dive, and the result was that the bracing wires were stretched so much one could literally tie knots in them."

Level Flight Speed
"Sqdn Cdr H. Busteed recorded a maximum speed of 116 mph at ground level"

Spin Qualities
"The triplane spun rather slowly, and its flick roll was also rather slow compared with other machines of the time…"

"You could spin it fast or slowly: slowly, you could pull it out by joystick control-fast, of course, you had to centralise the controls. We often used to spin it down to a few feet of the hangar top."
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#12 Chill31

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Posted 16 August 2010 - 19:33

The Max Speeds listed in previous posts for the Sopwith Triplane are true air speeds (corrected for temperature and pressure).
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#13 Chill31

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  • Posts: 1891

Posted 16 August 2010 - 20:58

The Sopwith Pup
J.M. Bruce


Arthur Gould Lee (Pup Pilot and Air Vice-Marshall) "What saved us from being being shot down in droves like B.E.s and R.E.s and F.E.8s and D.H.2s and Sopwith and Nieuport two-seaters was the Pup's agility at all heights, which made us a difficult target in a dogfight…ut once engaged in a fight, we couldn't withdraw, for the Pup was slower than every other German fighter."

Arthur Lee "At 8,000[ft] the Pup is completely outclassed by the Albatros. You can't get away, you've got to fight it out with one gun against two."

Arthur Lee "I admit, I prefer to meet Huns at 17,000 ft upwards, for then we no longer fight at a disadvantage"

Also, note the Pup has a steerable tail skid.

Some performance figures

Speed (for 80hp Le Rhone/80 Hp Clerget)
Ground Level: 108 mph
6500 ft: 110mph true airspeed
10,000: 106 mph true airspeed

*Additional Speeds from speed trial 21 October 1916 (these are TAS)
5000 ft: 105 mph
7000 ft: 103 mph
9000 ft: 103 mph
11000 ft: 101 mph
13000 ft: 98 mph
15000 ft: 85 mph


Climb
1,000 ft: 0+53
4,000 ft: 4+00
5,000 ft: 5+05
6,000 ft: 6+30 (6+05 for 80 Clerget)
10,000 ft: 12+45
15,000 ft: 25+00

*additional climb times from 21 October 1916 test
1,000 ft: 1+05
2,000 ft: 2+10
3,000 ft: 3+30
4,000 ft: 5+00
5,000 ft: 6+25
6,000 ft: 8+15
7,000 ft: 9+55
8,000 ft: 12+00
9,000 ft: 14+05
10,000 ft: 16+25
11,000 ft: 19+20
15,000 ft: 32+40
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#14 gavagai

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Posted 16 August 2010 - 21:03

Arthur Lee "At 8,000[ft] the Pup is completely outclassed by the Albatros. You can't get away, you've got to fight it out with one gun against two."


Speed (for 80hp Le Rhone/80 Hp Clerget)
Ground Level: 108 mph
6500 ft: 110mph true airspeed
10,000: 106 mph true airspeed

Judging by the airspeeds of the Albatros fighters in RoF, one of the above sections is false. Or maybe we ought not to judge by that.
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#15 Chill31

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Posted 16 August 2010 - 21:53

Gavagi, what do you mean?
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#16 WWBrian

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Posted 16 August 2010 - 22:06

Arthur Lee "At 8,000[ft] the Pup is completely outclassed by the Albatros. You can't get away, you've got to fight it out with one gun against two."


Speed (for 80hp Le Rhone/80 Hp Clerget)
Ground Level: 108 mph
6500 ft: 110mph true airspeed
10,000: 106 mph true airspeed

Judging by the airspeeds of the Albatros fighters in RoF, one of the above sections is false. Or maybe we ought not to judge by that.


gavagai - think of two cars drag racing a 1/4 mile racetrack.

CAR A - crosses finish line at 4 seconds @ 200mph
CAR B - crosses finish line at 5 seconds @ 210mph

…which car is "slower"?

You can have a faster top speed - but take longer getting there. I suspect that is the Pup

(using arbitrary numbers in above example)
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#17 gavagai

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Posted 16 August 2010 - 22:59

Gavagi, what do you mean?

If the Pup is as fast as the stats you cite, then it will easil run down the D.II, and be about as fast as the OAW D.III. That is clearly at odds with your cited anecdote. But, again, the source of the contradiction is probably not from your post.
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#18 WWBrian

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Posted 16 August 2010 - 23:55

*( Chill31's post removed apparently)*

98 at 6500?


:?


How about 106mph at 6500 as here –

An actual flying original
( screen cap of pdf file - sorry for poor quality )

Attached Files


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#19 Chill31

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  • Posts: 1891

Posted 17 August 2010 - 00:01

The Sopwith Pup
J.M. Bruce

RNAS report 29 November 1916
"Under the present conditions, the machine is considered second to none as a fighting machine. At 16,000ft she ahs the speed and climb of every HA [Hostile Aircraft] encountered up to date and, although the Nieuport 110hp Le Rhone, for instance, manoevers much quicker, the height lost in doing so is very noticeable."

"It has been noticed in fast dives, the machine surges up and down considerably, making it very difficult to keep sights on target. Otherwise she dives splendidly at well over 138 mph with no apparent harm to the machine."
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#20 Chill31

Chill31
  • Posts: 1891

Posted 17 August 2010 - 00:06

WWBrian,

The 106 mph that you reference is TAS not indicated. In TAS 106mph is ~94mph.

I deleted that post because I felt like I was putting my opinion instead of data
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#21 Chill31

Chill31
  • Posts: 1891

Posted 17 August 2010 - 00:21

Another telling quote on dive performance:

"15. It is recommend that the calculations of this machine be gone into at once and that it be sand tested. It is doubtful whether it is sufficiently strong to stand up to a dive and sharp flatten out. The ability to do so is necessary in this type of machine."
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#22 SYN_Vander

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Posted 09 September 2010 - 11:29

I'm not sure if this is the right place to post, but: I remembered I used software developed by MIT to calculate performance of an airfoil I had to design for an unmanned aircraft once (in university). I noticed this software is now (a couple of years actually) freely downloadable here:

http://web.mit.edu/d...blic/web/xfoil/" onclick="window.open(this.href);return false;">http://web.mit.edu/d...blic/web/xfoil/

I remember it was pretty good at calculating pressure distributions for low Reynolds numbers (the visous effects would be quite noticable for my aircraft). Have you already used software like this to calculate Cl, Cd etc for the airfoils? Or are the Reynolds numbers already too high to consider this?

EDIT: and MSES where you can model multiple elements. would be great for predicting pitching moments when using ailerons -> Hint: Fokker DVII :)
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#23 piecost

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  • Posts: 1318

Posted 11 October 2010 - 18:25

SE5a trim Curves with variable incidence tailplane

This plot was taken from the following paper:

The Spinning of Aeroplanes by L.W. Bryant & S. B. Gates.
Proceeding of the Royal Aeronautical Society, Fifth Meeting, Second Half, 62nd Session (3 March 1927).

It contains plots of pitching moment coefficient “m_alpha” versus incidence. Note that data is given for very high angles of attack since the topic was spinning.

The contemporary British definition of pitching moment coefficient was:

m_alpha = Pitching Moment / ( Density x Velocity^2 x Reference Length x Wing Area)

The reference length is not defined; it is likely to be either the wing chord or the distance from the wing to the tailplane (measure from their respective leading edges ?).

The Pitching Moment is taken about the Center of Gravity position for various values of h, where h is distance aft of the wing leading edge (of the upper or lower wing?), expressed as a fraction of the wing chord.

The diagram gives tailplane setting angles ranging from –6.5º to 5.5º, the total range of tail settings is likely to be greater.

The text which accompanied the graphs is as follows:

"Curves illustrating this point and referring to an SE5 complete model with alpha_T = -1.5 [tailplane setting angle] and eta=0 [elevator angle] are shown in the upper diagram of FIG 20. The change in m_alpha at a given alpha above stalling when h is increased by 0.1 is of the order of 0.025. It must be noted, however, that a change in C.G is usually accompanied in practice by a compensating change in tail setting which will keep the aeroplane trimmed at a constant incidence. The effect of this practical limitation is illustrated in the lower diagram of FIG 20 where the tail setting has been adjusted for trim at alpha=10º."

Attached Files


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#24 piecost

piecost
  • Posts: 1318

Posted 11 October 2010 - 19:07

The Spinning of Aeroplanes

With regard to the modeling of spinning flight of WW1 aeroplanes I have found some useful information in the following paper:

The Spinning of Aeroplanes by L.W. Bryant & S. B. Gates.
Proceeding of the Royal Aeronautical Society, Fifth Meeting, Second Half, 62nd Session (3 March 1927).

This is a large paper and I will extract parts which I consider relevant. I plan to make several posts. My comments appear in [ ]

[Note that contemporary British notation for non-dimensional aerodynamic coefficients differ from modern practice. For example:

KL = Lift / Density x Velocity^2 x Reference Area
KD = Drag / Density x Velocity^2 x Reference Area
m_alpha = pitching moment / Reference Length x Density x Velocity^2 x Reference Area]

The Pitching Couple in Straight Flight Above Stalling Incidence

The breakdown of the suction on the fore part of the upper surface of an aerofoil which is characteristic of stalling incidence introduces as significant a change in the pitching moment as in the rolling moment due to rolling.

Above stalling, the most notable aerodynamic characteristics of aerofoils, and of biplanes of conventional section and arrangement, are as follows:-

1) the centre of pressure recedes quickly at first and then more slowly from its most forward position at or near stalling to the mid-point of the chord in the neighborhood of alpha=90º. Broadly speaking its rate of movement decreases with increase of incidence.
2) The resultant force is approximately perpendicular to the chord from alpha=20º to alpha=90º
3) The resultant force increases slowly with incidence, the variation being usually not more than 15 % between alpha=30º and alpha=70º.

Thus in general, the wings provide above stalling incidence a pitching moment which is stable for any position of the center of gravity. The slope of the curve of pitching moment against incidence is at given incidence roughly independent of the C.G., and, subject to limitations in detail, the stable slope gets less steep as the incidence increases. This is in striking contrast to the behavior of the aerofoil below stalling where it is statically stable only for forward positions of the C.G. It also explains why a large incidence above stalling cannot be maintained in straight flight with elevators of normal size

[FIG 18 Note: h = 0.35 means that the moment reference point (Center of Gravity) is 35% of wing chord aft of the wing leading edge. It does not define how it is measured on a staggered biplane; whether from upper or lower wing.

The upper graph gives pitching moment coefficient versus incidence

The lower graph shows the centre of pressure coefficient, which represents the position on the chord at which if the resultant force is taken to act there will be zero pitching moment. ]

The curves for monoplanes and biplane wings in Fig 18 show that a definite distinction must be drawn between the properties of monoplanes and biplanes. In a monoplane the normal force continues to increase slowly right up to 90º, but in a biplane the blanking of the upper aerofoil at large angles causes a sharp drop in normal force above a certain incidence. This critical incidence will obviously be a function of stagger. The center of pressure of a monoplane (see lower diagram FIG 18) recedes at a roughly constant rate up to 90º; and that of a biplane with forward stagger after alpha=30º. Shows no striking difference in movement beyond alpha=80º. The critical incidence at which normal force begins to fall is for 30º stagger in the neighbourhood of 70º, and until this incidence is reached the slope of the ma curves for the monoplane and for the biplane with large stagger is not markedly different (see upper diagram FIG 18).

When, however, we turn to the biplane of no stagger, not only do we find the normal force commencing to fall off at as low an angle as 50º, but also the C.P. remains practically stationary between 30º and 60º (see FIG 18 again). There is therefore a region of neutral stability or slight instability indicated by the ma curves for the zero stagger biplanes; and further ma for the wings is much smaller when stagger disappears, if the C.G. is unchanged. It appears that between alpha=30º and alpha=60º the effect on pitching moment of a decrease in positive stagger is in such a direction as to facilitate the attainment of high angles of incidence.

When the biplane has more common stagger of the order of 15º or 20º there is usually a marked decrease in the stable slope of the pitching moment curve between alpha=30º and alpha=60º; this is perhaps of special significance when an explanation is sought of the noticeable change of spinning conditions produced by factors which are the cause of relatively small differences in pitching moment balance (e.g. the rotation in the rotation of the airscrew).

The only published experimental evidence on the contribution of the tail unit to pitching moment up to alpha=90º is from the SE5 model, and it is remarkable in showing that the stable moment actually increases up to alpha=90º. (A curve of Km due to the tail is is shown in FIG 19). Thus the conception that a surface at the end of the fuselage stalls shortly after the main planes, with a consequent decrease of stabilizing moment, is quite inapplicable. We must infer that the normal force coefficient of the tail continues to increase up to 90 6 at a greater rate than the wings. This must be de at least in part to the gradual disappearance of wash from the wings.

[ FIG 19 note that Km = pitching moment / density x velocity^2 x reference Area
No horizontal scale for incidence is given, since the text refers to data at alpha=90º; I assume that the scale goes from 0º to 100º in 20º steps. This gives zero pitching moment at approximately alpha=8º. ]

We have finally to consider the effect on m_alpha of a change in the longitudinal C.G. coefficient h. Since the force normal to the chord is roughly constant between alpha = 20º and alpha= 60º the curves of m_alpha against alpha will be roughly parallel for different values of h within this range. Curves illustrating this point and referring to an SE5 complete model with alpha_T = -1.5 [tailplane setting angle] and eta=0 [elevator angle] are shown in the upper diagram of FIG 20. The change in m_alpha at a given alpha above stalling when h is increased by 0.1 is of the order of 0.025. It must be noted, however, that a change in C.G is usually accompanied in practice by a compensating change in tail setting which will keep the aeroplane trimmed at a constant incidence. The effect of this practical limitation is illustrated in the lower diagram of FIG 20 where the tail setting has been adjusted for trim at alpha=10º. This shows clearly that under the practical limitation of fixed trimming speed in normal flight, the variation of m_alpha with h at a given spinning incidence is less than half the above mentioned variation. In practice therefore, a movement of the C.G. will have only a comparatively small effect on the biplane of pitching couples in the steady spin, except possibly in the case of biplanes of small stagger and poor elevator control where a forward movement of the C.G. may be sufficient to reduce considerably the risk of failure to recover from fast spins at large incidence. It is chiefly important in determining the character of the static longitudinal stability at stalling incidence. Thus in the illustrating figures, the aeroplane is statically unstable at alpha=10º if the C.G is further back than 0.3. n such a condition there will be a tendancy to stall and the danger of the incipient spin is increased.

The Pitching moment Due to Rate of Pitch

m_q, the pitching couple due to the rate of pitch, is of some importance in the balance of pitching couples in a spin since, as we have seen, q, besides being appreciable in a typical spin, may have either sign.

FIG 21 [J – assume is propeller advance ratio]

We are dependent for the estimation of this quantity on tunnel measurement of the rotary derivative Mq, by the oscillation method. This applies in strictness only to small values of q, but as the rate of pitching in a fast spin is never great, the application to spins may be a fair approximation,. Mq has been determined for incidences up to 35º on a 1/5 scale model of the Bristol Fighter. In applying these results we must assume that mq is proportional, at a given alpha, to qs/V. according to the formula

(V/qs) (mq) = (1/Ss^2 rho ) (Mq/V)

FIG 21 shows values of (V/qs) (mq) for the model with the airscrew removed and also with the airscrew running in the high speed condition. It was observed in the course of the experiment that the decrease in (V/qs) (mq) at stalling is largely an effect of the wings, the moment from which is actually positive at stalling. The tail provides a moment which is roughly constant at all incidences.

The increase in (V/qs) (mq) when the airscrew is running is an effect of the increased velocity over the tail.

Attached Files


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#25 piecost

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  • Posts: 1318

Posted 12 October 2010 - 19:04

Nieuport 17/23 Replica

Taken from P1lot July 1999 (published in the UK)

Dimensions:
Length 18 ft 10 in
Height 7 ft 10 in
Wing span 26 ft 11 in
Wing Area 159 sq ft

Weights & loadings
Equipped empty 1,0851b
Max take-off weight 1,3801b
Useful load 295lb
Usable fuel 24 imp gal
Max wing loading 8.7 lb/sq ft
Power loading 111blhp

Performance
Max speed 96 kt
Cruise speed 80 kt
Stall 45 kt
Range 150 nm
SL climb rate 800 fpm
Service ceiling 18,000 ft
Take-off distance 350 ft
Landing distance 250 ft

Engine: Warner Super Scarab seven-cylinder air-colled radal, producing 165 hp at 2,250 rpm. Propeller: two-bladed laminated wood 90 x 63 in

Be careful, early aeroplanes don’t handle at all like modem ones warned James Gilbert, editor of Pilot when I told him I was to fly a replica 1917 fighter. James should know because he flew WWl replicas in films In the sixties and seventies. "Their structures are more flexible, power is often limited, and the controls can be unresponsive. Take care.

I already knew of some of this, but a quick revision of books by Janes. by Neil Williams, Frank Tallman and Darrol Stinton provided further food for thought. None had flown a Nieuport 17, but all agreed that most pre-1920s designs had serious limitations as practical flying machines. There was one consolation: this example had a radial engine rather than a cantankerous eighty-year-old rotary.

At first glance. folk may think this com­pact aeroplane is a scaled-down replica, but no. It is full-size. Builders John Day and Bob Gauld-Galllers deliberately chose to repro­duce a small type, to fit into their restricted workspace. They used Wait Redfem's plans; he had previously drawn plans for a Fokker Dr.I replica, and later did the same for the D.H.2.

His information came from the con­temporary Gennan Rozendaal drawings taken from a captured French example, this being the only surviving documentary evidence of Nieuport construction.

Redfern made a few basic changes, including replacing the wire-braced wooden fuselage with a stronger, stiffer steel­tube structure, but the components' external shapes and dimensions were retained, with square-section longerons and round verticals. The type had a history of losing its lower-wing in flight, so he beefed up the root fittings and improved torsional bracing. He also hid differential drum brakes in the hubs, because without them the fixed tail-skid would make ground manoeuvring virtually impossible, and Bob and John wanted to be able to get around the country for air displays. Despite these practical modifications, wherever possible within their limited resources they tried to make their replica Nieuport just like those embattled over the French trenches.

Early in the project they spent a whole day in the Brussels Army museum measuring and photographing the only surviving genuine Nieuport 17. That, like their replica, was actually a Nieuport 23, a later sub­type which differed from the better known Nie.17 only in the position of its Vickers gun on the upper fuselage. The RFC removed the Vickers completely in favour of an over-wing Lewis on a Foster mount, so the model difference was irrelevant.

Construction took the dedicated duo 5,000 man hours and more than five years.

The radial engine was not easy to find. After several years of searching they finally located a dismantled 165hp Warner Super Scarab in Virginia. Rebuilding and overhauling this brought more challenges, but provided them with a reliable powerplant. The Scarab normally develops 165 hp at 2,2250 rpm, but using the big mahogany propeller limits its rpm to 1,800. So on take-off it only produces about 120 hp, similar to the proper Le Rhone or Clerget rotaries.

There are few flight instruments. The genuine non-sensitive altimeter is just below the coaming on the left and reads from zero to 20,000 feet in just one sweep of its hand. The ASI is similarly placed, on the right, and its face is a work of art. Taken from a Tiger Moth, it was overhauled and recalibrated, then Bob changed its needle's shape and position to mimic a Nieuport's and made a new face calibrated in knots and dated '1918' to suit. The tachometer is below it and to the right; the compass is out in the airflow, tucked beneath the upper wing ahead of the struts; and a slip indicator is screwed onto the vestigial windscreen's wooden frame. The oil pressure gauge is where the oil pulsator went; there are a couple of less important engine dials tucked out of the way, and that's it!

The aeroplane has a starter to make it independent at air displays, but to reduce weight this is usually operated using external power instead of a battery. Today a battery was installed and the weight minimised by loading just ten gallons of avgas (enough for an hour and a quarter). So I selected the fuel and master switch On, retarded the manual ignition just a whisker, cracked open the unusual elongated throttle lever, groped for and found the brass magneto switches up in front of the cross-member ahead of me and pressed the starter button. That great big wooden propeller turned a few degrees but then stopped against the hot engine's compression. Releasing the button, I pressed it a few more times in quick succession to 'bump' the prop around, and was eventually rewarded as it turned with gently increasing speed until I realised it was running quietly under its own steam. Having been warned that the brakes would not hold against high power, I carried out the engine run and pre-flight checks on the chocks.

Taxying was the next challenge. John and Bob had made it clear that, contrary to normal practice, the stick should be held fully forward to reduce the strain on the flexible aft fuselage. They also advised that, when turning, the only way to over­power the fixed tail-skid was to apply full rudder and brake in the required direction and blast the tail around with a burst of power against the depressed elevator. "Don't worry, that tail is so heavy and the brakes are so gentle you will never stand it on its nose."

As with all early aeroplanes, assistance is vital in anything of a breeze; we had fifteen knot gusts at thirty degrees to the runway, so, with John holding one wingtip and Bob on the other, I waved away the chocks and gently opened the throttle. Then I looked ahead. Ah! All I could see were a big, round, red-striped cowling, a myriad struts and wires, a tiny triangular Windscreen, the compass, and yes, way out in the background on either side between the wings, the distant turf of the taxiway. With luck Bob or John would warn me if I was about to taxi into a 747.

Despite its differential brakes, the Nieuport's turning circle was worse than a supertanker's, but luckily we were close to the threshold. Manoeuvrability was so poor, and my vision so restricted by the wings, that I had to rely on the wing-walkers' eyes to check the sky above and behind and the runway ahead. Once we were aligned and my assistants had retired to a safe distance, I had no option but to light the blue touch-paper. Applying a generous dollop of left aileron to stop the wings lifting, I cautiously opened the throttle, working hard to stay straight with coarse prods of rudder. Remembering John's advice, I held the stick neutral fore­and-aft, waiting a while to lift the tail to be
sure I had enough slipstream for full con­trol. I probably raised it a little too soon, for I got a brief glimpse of the clubhouse between the cabane struts before I kicked this wayward filly back into line.

Moments later we were airborne and climbing strongly when I realised I had not even fully opened the throttle. Pushing the lever to the stop gave an instant improvement in climb with a slight nose-up pitch and a further leftward yaw, easily corrected with a dab of what was quickly becoming apparent as a very light and powerful rudder. It was perhaps a shame not to hear a rotary's continuous muted fizzzz, but the Scarab's steady, sturdy throb was wonder­fully reassuring and truly brought the little aeroplane to life. With a climb like this, no wonder it was an effective interceptor.

As we soared up into the circuit at sixty knots, kiting into the strong and increasing headwind, I was careful not to make any sudden or coarse control movements until I had the measure of the machine. Then I experimented gently, finding that the ailerons were indeed heavy and the elevator less so, while the rudder was particularly light. I left further experimentation to a sensible altitude.
Something I soon noticed was the difficulty of reading the ASI, down in the cockpit on my right, while wearing goggles. And yet those goggles were vital, because my head was buffeted any time I moved it away from directly behind the tiny wind­screen, or allowed the nose to wander. I soon realised the Nieuport is as happy flying sideways as straight ahead, and shows absolutely no tendency to straighten up or roll wings-level by itself-we would now say it lacked lateral or directional stabili­ty-but of course this was desirable in what was really a flying gun. The Lewis could easily and quickly be pointed any­where, and it would stay pointing that way long enough to finish the job.

Investigating the handling further, I found the rudder was much the lightest and most effective control. The ailerons were less impressive, and pretty heavy, but still more effective than those in many a modern American light-plane. Not having any differential gearing, they caused quite a lot of adverse yaw, but no more than an Auster or Tiger Moth. Co-ordinating with the correct squeeze of rudder gave a reasonable roll rate provided I used enough muscle; it took less than three seconds to roll from 45 degrees of bank one way to the other, and once in a turn the aero plane went around on rails.

To my relief the Nieuport was longitudinally stable even with full power (which may account for Fullard's criticism that it was 'unwieldy'). Nevertheless, this little aeroplane was more manoeuvrable than I had expected, although it felt bigger than it really was. It reminded me of a Stearman.

Visibility was restricted in unusual areas. Sideways, upwards and to the rear it was excellent, and thanks to that small lower wing it was not too bad looking down, but the forward view was disappointing. My eyes were just below the upper wing, so there was a narrow band between it and the horizon in which only the struts and wires caused some obstructions, but any­where below the horizon was either completely obscured by that fat cowling or restricted by the cabane struts and wood­framed windscreen. Following a curving, diving attack the Nieuport pilot would have needed to bob his head up and down and from side to side to keep his quarry in view, unless it was absolutely fixed in his sights.

The climb performance was remarkably good; we reached 3,000 feet in a mere 3 1/2 minutes, so I was soon able to investigate the lower end of the speed range. The stall came at just 39 knots with the top of the cowling only just on the horizon. A slight but sharp right wing-drop at the break was instantly arrested with prod of rudder, but the response was quite lively, and I suspected that it might not be hard to overdo this and provoke a prompt a flick.

I was not too concerned should the machine enter a full-blown spin, recalling the advice of that expert in the handling of vintage replicas, Darrol Stinton: 'Look for low aspect ratio fins and rudders, with plenty of plenty of rudder beneath the tailplane and elevator… long tail arms and deep rear fuselages with sharpish corners..’ Nieuport's body may not be over-long, but it has all the other attributes, plus a heavy fuselage with light wings, so its effective rudder should be able to force it out of any but the flattest of spins.

My formal handling investigation over, with a was now able to relax and enjoy this delightful little machine. It cruises at 77 knots with 1,600 rpm at about half throttle. The plans quote a 'maximum speed' of 96 knots and B3459 achieves exactly this at full throttle. Unfortunately the PFA authorities have taken this figure as of Vne, so one must be careful not to let the nose drop. Nevertheless I could make plenty of tight turns and turn reversals, and was soon flying a series of exuberant and enjoyable wingovers.

As the verdant Hampshire fields rose and fell between the wings I soon found myself looking for targets, and promptly spied a commuter train wending its way across the countryside. Ground attack! Another carefully executed, throttled-back, wing-over quickly centred it in my sights and it was dispatched in seconds.

I reduced power to get the feel of the controls at low-speed and without the benefit of propwash. RFC pilots always approached in a glide without the engine, because one could never be sure a rotary would pick up again when needed. Using a trickle of power was very reprehensible, and referred to derisively as Иrumbling in’. They would have silenced their rotaries with the ignition cutout button on top of the stick; I simply had to close the throttle.

There is no trimmer, so the nose has to be held up to maintain a 65-knot approach speed. The already steep glide can be made truly precipitous with a Sideslip if needed. In case I botched the landing I made a couple of practice go­arounds too. The engine picked up immediately, the aeroplane came back into trim and the leftward swing was easily controlled. So, apart from the difficulty of see­ing directly ahead, the approach should not be too difficult. It was the touchdown and subsequent events I was uneasy about.

Foremost in my mind were John's stories of their early ground loops, and the certain knowledge that those diminutive tail surfaces were completely blanked by the turbulent wake from four generous fully-stalled wings. John warned me to be ready on the brakes, both to control a swing and to get it stopped as soon as possible. "Have your fingers on the mag switches too, we like that prop." He also echoed my unspoken misgivings when he suggested I land on Runway 03 rather than 08, with the twelve-knot wind coming from the Northeast.

I too favoured this direction because, with the wind on right, I could squint over the left side of the cockpit, which I prefer, and because, with plenty of open ground upwind, the breeze was likely to be stronger and steadier, with fewer gusts. I intended gliding steeply (as recommended) and landing a little deep, to avoid the bumps over the road before the threshold.


His final comment? "On 03 there is plenty of space for you' to lose control without hitting anything too solid. Thanks, John! At least I had the benefit of a ten-knot headwind component; even if was thirty degrees off the runway heading.

The ASI was too far down to my right, and too close to my eyes for me to glance in at it and refocus more than occasionally, so I concentrated on keeping the attitude and you'll need to have the stick fully back steady with the upper wing's leading-edge covering the hazy horizon as I swung onto a gently curving approach.

Holding the stick back with a constant force was not easy, but far from impossible; every time I did check the ASI it read exactly 65 knots, so I was reassured. The ailerons lightened up nicely at this speed and were still surprisingly effective.

With the engine now just burbling quietly at my feet, I could see the individual prop blades idling across my view ahead, and I realised I could hear the slipstream's music gently soughing contentedly in those braided wires. My nose caught occasional tendrils of tangy exhaust where a real. Nieuport pilot would have breathed the piquant aroma of half-burnt' castor oil.

More of John's words came back to me: "Let the speed bleed back to sixty over the fence, hold it off just above the ground, and you’ll need to have the stick fully back to land. It's the most 'three-pointy' aeroplane I know."

The Nieuport has small wings, significant drag and comparatively small mass, so I feared I would have to get the flare exactly right, with the aeroplane virtually stopping in mid-air as I raised the nose. I also remembered Bob had warned was not much 'give' in either the main leg bungees or the tail skid.

I decided to forget mag switches for the moment, instead tensing my left arm for a prompt but careful application of power to make a late go-around if things got out of hand. I could try groping for the mags afterwards, when I was safely on the ground. Lifting my heels from the floor I poised my toes over the brake pedals. This delightful little aeroplane was not going to get away from me!

It all turned out to be much easier than I had anticipated. I held a gentle side-slip be fifty feet, straightened, eased the stick rearwards, corrected the gusts with aileron, and scale kept her six inches off the ground as she slowed quite quickly, and pushed her straight as the stick hit the aft stop. That big, round view-obscuring cowling seemed much higher than it had in the stall, but she settled sweetly on to the turf on both main wheels, the tail skid touching just a moment later.

There was just the tiniest tendency to feint to the left, which I promptly stamped on with a jab of rudder; then, under the influence of that dragging tail-skid shoe, we promptly rolled to an uneventful halt. I taxied carefully back to their hangar, discovering in the process that, at full lock it was difficult to avoid kicking the bulk­ head with the brake pedals which did not help the ample turning circle.

As I gently shut down the engine I became aware of a dull ache in my right arm, but my feeling was of triumph and exhilaration; that sensation only slightly dampened by clouting my head severely on the Lewis gun as I but sprang in elation from the cockpit.

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#26 piecost

piecost
  • Posts: 1318

Posted 13 October 2010 - 17:18

The Spinning of Aeroplanes

Another extract from the following paper:

The Spinning of Aeroplanes by L.W. Bryant & S. B. Gates.
Proceeding of the Royal Aeronautical Society, Fifth Meeting, Second Half, 62nd Session (3 March 1927).


The Couple due to Rolling - Autorotation

It is well known that the behavior of an aerofoil mounted symmetrically in the wind tunnel so that it can turn about an axis along the wind and through its centre changes sharply as the angle of incidence is increased through the stalling angle. Below stalling, the aerofoil is extremely stable in roll, any impressed rolling motion being quickly damped out by the air reactions.

Very soon after the stalling angle is passed, instability in roll is apparent; the aerofoil begins to rotate as soon as the wind is turned on, and the rate of roll increases to a steady and stable value, which is called the autorotation speed and corresponds of course to zero rolling moment. This behavior is characteristic of an incidence range of some 10º above stalling, but in the region of alpha=30° a second change is observed. The aerofoil is now again stable in roll for small displacements, but if it is given a sufficient angular velocity it will rotate faster until it once more reaches a steady and stable state of rotation. These characteristics persist for another short range of incidence, usually between 30° and 40°, after which the aerofoil returns, to its below-stalling behavior and continues so until the incidence reaches the neighborhood of 90º.

We may distinguish, the two types of instability by saying that in the first region the aerofoil exhibits spontaneous autorotation and that in the second it exhibits latent autorotation. It is found that a biplane' mounted on an axis between its planes exhibits two similar ranges of incidence in which it can be made to rotate steadily, but its behavior after about alpha=40° is markedly dependent on the arrangement of its planes. If its stagger is positive its subsequent behavior is similar to that of the monoplane; if its stagger is zero or negative the range of latent autorotation passes into a second, region of spontaneous autorotation which in extreme cases has been observed to continue up to very large angles of incidence.

An explanation in outline of these phenomena can be obtained by simple consideration: of typical lift and drag curves of aerofoils and aerofoil arrangements. Consider for instance the monoplane lift and drag curves shown in Fig 11. The lift curve rises sharply to a maximum at stalling incidence and proceeds to descend gradually to zero at alpha=90º. The downward slope is constant in type and about a quarter of the upward slope, but there is almost invariably a characteristic wave between alpha=20º and 40º. The drag coefficient constantly increases to a maximum at about alpha=90º but there is a marked increase in slope above stalling. Now suppose an aerofoil to be moving in a straight line horizontally. If the left hand side (looked, at in the direction of motion) be suddenly given a rising motion, the incidence of that wing will be decreased (see Fig. 10). The lift and drag vectors are thus rotated backwards and the vertical force on the wing will be the net effect of the altered amount of lift and the vertically downward component of the drag. If the initial incidence is below the stall the lift will be decreased owing to the smaller incidence while the drag component also produces a decrease in the resultant vertical force on the left hand side. Thus there arises a powerful couple tending to stop the rotation and the aerofoil is very stable in roll in normal flight.

If, however, the initial incidence is above the stall, the decreased incidence on the left hand side produces a greater lift and smaller drag, and the increased incidence on the right hand side a smaller lift and a greater drag. The lift and drag effects are now opposed, and there will' be an increase of vertical force on the left hand side and a decrease of vertical force on 'the right hand side unless the drag component is greater than the altered lift. Thus a couple may be Set up tending to increase the rotation and the aerofoil if left to itself will autorotate.

It follows from this line of argument that an aerofoil is ,stable or unstable for small displacements in roll according as d_kL /d_alpha, + k_D is positive or negative. Now the condition for spontaneous autorotation is instability when the aerofoil is started rotating from the rest, and so the spontaneous autorotation ranges can be studied in an elementary manner by the simple method of marking the incidences at which the slope of the lift coefficient curve is equal and opposite to the value of the drag coefficient. Returning now to the, monoplane lift rand drag curve (Fig 11), the negative lift slope is first equal to the drag at some such point, as A, just above stalling. The next point of equality is at B and AB is the spontaneous autorotation range. In the case of the monoplane it usually happens that the recovery of the average negative lift slope after B is too slow to keep pace with the increase of drag, and so there is no more spontaneous autorotation until possivbly in the neighborhood of 90º, where the negative lift slope may increase. The range of latent autorotation is not revealed by this method, since it is a phenomenon of finite range of rotation. It is essentially aconsequnece of the wave in the lift curve between 25º and 40º, and occues typically between B and

We are now in a position to understand something of the difference in autorotation properties as between monoplanes and biplanes of various arrangements, A biplane will always give a smller drag coeffienct at large incidences than a monoplane of the same aspect ratio because of the blanking of the upper plane by the lower, and for the same reason a biplane of zero or negative stagger and small gap/chord will have a smaller drag coefficient than one with positive stagger and large gap/chord. The three types of drag curves; (1), (2), (3) coalescing below alpha=40º, are indicated diagrammatically in FIG 11. (3) represents an extreme type in which K_D is, on a very rough average, constant after about 40º, while (2) is typical of a conventional biplane. There is a smaller lift effect of the same kind, but as the slope of the lift curve is not markedly altered; the total effect may in a first survey be attributed entirely to drag differences. For the typical biplane (2) the negative lift slope overtakes the drag coefficient again at some point as C, and remains greater than it until D, after which the drag predominates. The latent autorotation BC therefore passes into the second spontaniou autorotation range CD. The main effect of the flat drag curve (3) is to remove D to very high incidences and prolong the second spontaneous autorotation range.

We may now study in more detail the autorotation and rolling couple characteristics of monoplanes and biplanes. The rolling couple coefficient l_p = L V^2 / S s rho is a function of alpha and lambda = p s / V, and the autorotation rates are those values of lambda for which l_p=0.

[where: L is the rolling moment
V is the airspeed feet/second
S is Wing area (feet^2)
s is span/2 (feet)
rho is air density (slug/ft^3]
p is roll rate (radians/second) ]

FIG 12

A diagrammatic analysis in rough outline of sets of curves of l_p against lambda as they define the three typical regions of autorotation is attempted in FIG 12. The region (a) of spontaneous autorotation is typified by a maximum above the axis, the region (b) of latent autorotation by a minimum above the axis, and the second region © of spontaneous autorotation by a maximum above the axis and a wave in the low incidence cures which persists after the region (b) is passed.

A striking example of the more familiar autorotation diagram, in which lambda is plotted against alpha under the condition l_p=0 is shown in FIG 13. This diagram referes to RAF 15 monoplane, and to the Bristol Fighter, Springbok and B.A.T Bantam biplanes, for which the staggers and gap/chord ratios are:

Biplane Stagger Gap/chord ratio
Bristol Fighter 18º 1.0
Springbok 4º 0.85
B.A.T. Bantam 0º 0.81

The Springbok and Bantam results lack the unstable values of lambda in the latent autorotation region (between alpha=30º and alpha=50º); but in the Bristol Fighter experiments l_p was measured, and these values show that the wings have a small region of autorotation (from alpha=27º to alpha=32º) and no second region of spontaneous autorotation , at any rate, below 40º. FIG 13 shows the fundamental difference in autorotative properties between a biplane of stagger of the order 20º and a gap/chord of the order 1.0, and a biplane of stagger approximately zero and gap/chord about 0.8. The influence of the tail unit, although considerable, does not obscure the essential character of the divergence. The curve for RAF 15 is typical of monoplanes.

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#27 piecost

piecost
  • Posts: 1318

Posted 15 October 2010 - 12:30

The Spinning of Aeroplanes

Yet another extract from the following paper:

The Spinning of Aeroplanes by L.W. Bryant & S. B. Gates.
Proceeding of the Royal Aeronautical Society, Fifth Meeting, Second Half, 62nd Session (3 March 1927).

Balance of Couples in the Spin

In a study of the balance of couples in the spin it is more convenient to consider rolling and yawing moments referred to body or chord axes, since the rolling moments can then be considered to be independent of the tail unit to a first approximation. We therefore complete the discussion of the asymmetric couple due to rolling by reference to its components l_p and n_p

[l_p is rolling moment due to roll rate, n_p is yawing moment due to roll rate]

Vector diagrams for the four biplanes of different staggers and gaps are drawn in FIG 14, the extremities of the vectors being joined at constant values of lambda (0.3, 0.5, 0.8), and values of alpha being marked on the curves. The most notable features of this diagram are:

(a) Change of stagger from 30º to 0º causes a very pronounced positive increase in l_p at most values of alpha and lambda. For 30° stagger l_p is negative except for alpha>50º; for zero stagger it is usually positive for alpha>30º. Each curve of lambda constant being displaced to the right.

(b) n_p is usually positive, it is less than 0.01, and its variation with alpha and lambda is very much smaller than that of l_p. This is plainly a consequence of the fact that the force parallel to the chord is comparatively small at all angles incidence.

© The effect of a change in gap is unimportant compared with that of a change in stagger.

In the foregoing no account has been taken of the contribution of fuselage and tail to the couple due to rolling. This contribution is mainly a couple about the normal axis at right angles to the chord, i.e., it is an addition to the couple n_p arising from the rotation of the wings. There is little doubt that in a fist spin at large incidence the body and tail must be providing a yawing couple opposite in sign to that due to the wings, and therefore in general in a Sense to reduce the rate of spin. Further, since the tail unit when rotating about an axis inclined to the wing chord at an angle alpha is subject to an effective sideslip equal to (ps/V) (l/s) sin(alpha) which increases with incidence and rate of roll, we might predict a rapid increase in side force on the tail as incidence and rate of spin increase. But the tail moves in the shadow of rapidly rotating wings, and the presence of a general sideslip of the machine as a whole adds asymmetric couple to the complexity of the aerodynamic conditions, so that the simple argument from effective sideslip may have to be considerably modified before it can be applied to an actual spin. Some recent work on the Bantam model has established the fact that n_p due to the model without wings is always in a direction to retard the rotation. The contribution of the fin and rudder of the Bantam to n_p at large incidences has, however, been shown to be very small indeed, and this has been proved to be on account of shielding by the tailplane and elevators. The relative wind impinges upon the latter at a large incidence and from beneath so that the fin and rudder located above are very effectively shielded; indeed; in the neighbourhood of 60° incidence, n_p due to fin and rudder on the Bantam actually becomes positive for a positive value of p.

No doubt the above conclusions are applicable in some degree to all conventional aeroplanes when spinning at high incidence, although information so far is not forthcoming on any other model than the Bantam.

The relation between the autorotation of an aerofoil and the spin of an aeroplane has often been expressed by saying that without the autorotative property spinning would be impossible. . This is a good summary if too much is not read into it. The discussion has shown that there are certain ranges of values of alpha and lambda for which Lp and L’p are in such a sense as to increase the angular velocity p [roll rate, radians per second]. It appeals to be almost certain that the autorotative property is the crucial preliminary to spinning; it provides the mechanism by which a large angular velocity can be built up in the entrant motion. On the other hand, it must not be inferred that spinning must occur at or near an autorotative speed of the wings, even though we, have seen that in a typical spin the aeroplane is turning about an axis nearly coincident with the wind axis, and that the inertia couple about the wing axis is small. The fact is that there is another component of the motion besides p namely, sideslip-which makes a large contribution to the asymmetric couple. There is a strong probability that even a moderate amount of sideslip will at certain incidences produce rolling moments of such magnitude as to remove the rate of roll in the spin far from the autorotative rate if the sideslip moment is to be balanced.

We have seen that a decrease of stagger increases both the range and magnitude of the autorotative couple, and so makes it extremely probable that biplanes with small or negative stagger will reach faster spins than those with considerable positive stagger. There is much full-scale evidence in support of this. The Springbok and the B.A.T. Bantam, biplanes with stagger almost zero, have both developed very dangerously high rates of spin. Full-stale spinning experiments which were carried out some time ago on the BE2c with three values of stagger, also confirm this result (FIG. 15). The curves for zero and negative stagger acre not so well defined, as that for positive stagger, but the evidence, certainly established the result that the positive stagger arrangement led to a smaller rate of spin at a given incidence than the other two arrangements. It should be remarked, however, that the effect of zero stagger on the balance of pitching couples is also in the direction to facilitate the growth of ultra-rapid spins at large incidence, and it is not at present clear how far the faster spins accompanying the absence of stagger are due to the rolling moment phenomena and how far to the pitching moment.

The Asymmetric Couple Due to Sideslip

The question of sideslip occupies a position of central importance in the later theory of the spin chiefly on account of the magnitude of the asymmetric couple which tunnel tests have shown that it produces at incidences above stalling.

According to strip theory calculations of l_v [rolling moment due to sideslip velocity] due to wings, it should be proportional at small values of beta [sideslip angle], to beta, d K_L / d_alpha and the dihedral angle r, and should therefore change sign at stalling. This theory gives a rough approximation to the facts below stalling, except that there is an appreciable rolling, couple to be much less with zero dihedral which is not provided for in the formula. At or above stalling, however, the formula ceases altogether to apply both for monoplanes an biplanes. Wind tunnel tests on several complete models have shown that at a given beta and r [dihedral] l_v continues to increase at least up to an incidence of 30º, and although no systematic tests have been made of biplanes alone, it is almost very much less certain that this must be primarily a wing effect. In the case of a biplane at large incidences the explanation may be that the blanking of the upper plane in symmetrical flight above stalling would, when there is sideslip, be decreased at wing tip towards which the sideslip occurs and increased at the other wing tip. This effect, which would also be accentuated by the blocking action of the front part of the body, would tend to set up a rolling couple of opposite sign to 20 that indicated above stalling by the strip theory.

Typical values of l_v, n_v [yawing moment due to sideslip velocity] obtained on a complete model are shown in FIG 16, which refers to the Bristol Fighter. It will be noticed that n_v also increases rapidly in an incidence range which extends far above stalling. There is some evidence that in the normal flight range the contribution of the wings to n_v is small; at any rate it is easy to control the amount of weathercock stability by varying the fin and rudder area. The large increase in n_v up to alpha= 35º is difficult to reconcile with the assumption that the wing contribution continues above the stall, to be small compared with that of the tail unit. There is no material for the further analysis of this couple, but it is highly probable that the wings provide above stalling an increasing stable yawing couple (wind axes) which completely swamps the probable decrease in the contribution from the tail unit.

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#28 piecost

piecost
  • Posts: 1318

Posted 26 October 2010 - 16:57

Replica Fokker EIII

Extract from:

Flying the Old Planes
By Frank Tallman
Doubleday & Company, New York
1973

Engine Le-Rhone 80 hp

The cockpit is in the centre of a rather wide-chorded wing and is comfortable with a protective windshield. The flight instruments include tach­ometer, air speed, oil pulsator, and altimeter. In addition to the mixture and throttle controls there is the characteristic German control stick with its dual handles, which is certainly most necessary in this aircraft.

Starting the Le Rhone engine is much the same as with other rotaries, except that the 8O-hp Le Rhone is an easy-starting, delightfully smooth­running engine.

… My two favorite types of rotary engines are the 160-hp Gnome and the BO-hp Le Rhone, and this particular 80 Le Rhone runs like a lovely watch…

You prime each cylinder with gas from a squirt can after bleeding the oil pump (by removing the cap), then turn the gas valve on, and push both throttle and mixture controls on full until the fuel runs out the overflow. This fulfils the pre­starting check. Usually one pull will start the engine. With both air-mix­ture and throttle back, the engine idles smoothly and you feel a great deal of thrust from its high-pitch wood propeller. Checking the coupe (cut-out) button on the stick and hav­ing the mechanic check that the engine is oiling properly (in other words, throwing the castor oil all over the place) is all that remains to check before takeoff.

The temperature was sixty-five de­grees and the wind steady at twelve knots at Orange County Airport on the day I took my first flight in the Eindecker. With throttle and air-mixture controls pushed forward, the Le Rhone revved up and the Eindecker began to roll. The tail was up almost instantly, and we lifted in 290 feet. The immediate reaction when air­borne is, "How in Hades did an inexperienced pilot ever fly this bucking broncho?" Climb is at the rate of about 600 feet a minute.

The warp is extremely stiff on the wings, but slight pressure and almost no apparent movement of the stick is enough to drop a wing in normal turn. Because I over-control on the rudder, I lock my heels on the shock cord for the landing gear, which is directly under the rudder bar. The tendency, as you level out, is to want to get both hands on the stick, for, as you pick up speed, it gets very sensitive fore and aft, and you have some difficulty not porpoising.

I settled down at 1000 feet, indi­cating 75 mph, and had completely run away from my Stinson L I camera plane. With the engine idled back and with a 360-degree turn, I come up on the camera plane and slide into position on his wing with slight rudder. For the picture session I am in period costume. Strangely, the downwash from the slots, or ailerons on the Stinson, seems to adversely affect the Eindecker and draw it in toward the other plane like a magnet. Only by dropping sharply away from the camera plane can I solve this problem, but at the same time it rather obviously dis­gusts the photographer, who was all set to shoot.

Later, when the photographing is finished, the Eindecker gets its chance to really prove itself as an aircraft.

Unlike my experience with the 5E5, there is no desire on my part to even attempt aerobatics with the Eindecker. I can't forget its well-deserved reputation for structural failures when it first appeared at the front in 1915.

The pearl of information that I have saved until now is that the Eindecker series, like our modern jets, had full flying elevator and full flying rudder-in short, no fixed surfaces. Perhaps because of lack of aerodynamic knowledge in the early days, the elevator and rudder are perpet­ually hunting and feeding the attendant change back through the control system to the pilot. I found this same feedback in the early Bleriot but it was nothing like the constant heavy pressure present in the EIII.

…The full flying rudder and elevator nibbles endlessly at one's hands and feet in flight…

Perhaps the major flight characteristic ever present is the feeling that if you took your hands off the stick or your feet off the rudders, the Eindecker would turn itself inside out or literally swap ends. It stalls rather gently at 43 mph, and as the right wing drops, I make no attempt to pick it up. I just turn into the down­wing. Steep turns at altitude, climbs, glides, shallow dives, chandelles, and lazy 8's, all of which it does nicely except for the uncomfortable control feedback, complete our flight check.

Coming in to land on our busy air­port has its problems. Aircraft are parked on the edge of our grass strip, which is about 100 feet wide and 800 feet long. As I turn into final at 300 feet, the Le Rhone is barely ticking over and holding about 50 airspeed. The E III settles nicely. I have good visibility, and it pays off cleanly, but with ade­quate time to touch in a three-point attitude at about 38 to 40 mph. Alternating my finger on and off the coupe button, I have more than enough rudder control to taxi back to our display area.

As I climb to the ground, still dressed in an original German World War I pilot's uniform, I have a sud­den urge to click my heels and stiffly salute, not the Fokker Eindecker, but the men who had to fly it in combat.
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#29 piecost

piecost
  • Posts: 1318

Posted 26 October 2010 - 16:59

Replica Fokker Dr1

Extract from:

Flying the Old Planes
By Frank Tallman
Doubleday & Company, New York
1973

Engine: 165-hp Warner

I have seen a number of the DRI copies, but so far have flown only ours. Reports vary considerably on their characteristics, and at least one owner admitted to me that he enjoyed flying it about as much as if he had climbed into a hive of bees in a bathing suit.

In the case of our DRI, the re­builders early in the game decided that the squirrelly flight characteris­tics of the triplane and my tales of horror of riding behind a 110-hp Le Rhone in another antique airplane suggested a modern power plant. The only American engine that has rotary facial area and sufficient horsepower was the 165-hp Warner engine, and these are now getting exceedingly scarce; but they located one.

Basic construction of our DRI with the Warner engine closely paralleled the original.

…they found that in a three­point attitude, taxiing it about was a good deal like trying to engineer a hundred-car freight train from the caboose. It's blind! Also, on taxi tests the skids were put on the wingtips for use and in expectation of ground loops.

Swinging into the cockpit past the cut out in the middle plane, one won­ders what happened to the world ahead, for you can only see to the sides and rear. Controls are straightforward. The stick lacks the strange top section that looked like the rear side of a toaster and includes a throttle and gun trips that must have seriously restricted control in combat.

The Warner is a lovely engine, and it started on the first pull, but taxiing was a chore and good for one stiff neck for each thousand feet of taxi­way. Checking controls for freedom of movement and checking mags, I turned onto the runway. My rudder became effective in about fifty feet of takeoff roll and the elevators brought the nose onto the horizon, so that I could actually see ahead for a change. The triplane was airborne in about three hundred feet, with a eight-knot wind directly on the nose. The climb­out was at about 55 mph, and as I begin a climbing turn I felt ailerons as stiff as a boiled shirt; it felt like our old Navy Hup helicopters when we turned the hydraulic boost off. You very nearly need both hands for the ailerons.

Climbing up to altitude and settling down for an hour cross-country, I was struck again by the in-flight ap­pearance of the upper wing so far above and so lightly hung on. It looked like the designer's after­thought. I was cruising at a pleasant 95 mph, but in looking back at my tail surfaces, I noticed a considerable flutter, at which point my eyes dropped to my chute harness to see that everything was buckled and to hope that less than forty days had elapsed since the chute's last inspection. Since the fixed-elevator surface apparently did not want to part company with the aircraft, I relaxed a bit and then remembered that the stan­dard Dr1 had a camber top and bottom and was not built as this one had been, with a flat surface.

Getting used to everything except the Mack truck-like ailerons, I stalled the plane, and it fell through at about 50 mph, usually dropping the right wing. Recovery was easy and loss of altitude slight. Putting the red bird in a Lufberry circle, I could see how you could cut the circle small enough to nearly chew off your own tail. In a climbing vertical reverse, the three­wing concept worked well.

In a fit of daring equal to grabbing a live leopard by the tait I decided to try a loop. Picking up to 120 mph, I pulled up, but because of the place­ment of the wings it was hard to orient with the horizon. It was a most uncomfortable feeling. Unfortunately I was a little slow and did not pull tight enough at the top, and barely got over. As the triplane fell through, I wondered whether the whole stack of wings might not collapse like a club sandwich being sat on by a fat lady. My nerves took longer than the DRI to recover from the loop, and I vowed that the air show combat act would have to be restricted to tail­chasing. With aircraft scattering like a scarecrow in their midst, I entered traffic and had no trouble in staying with the slowest student. Choosing to land on a dirt strip (fortunately equipped with a wind sock I glided in, and nose down had good enough visibility so that I didn't feel I was conning a nuclear sub.

Flaring out, the DrI loses speed fast, levelling down at about 45 mph with a rather wobbly feet and blanking out almost completely of the tail surfaces, so much so that as you are rolling along you might as well have a broomstick for company in the cockpit.

After a number of additional flights in the triplane, several years went by before I climbed into its cockpit again. But the day I did, it was with complete freedom from worry and question. But I was shortly to have the same awakening that an ice-cold shower brings in the morning. It was a rather routine flight, but what a hair-raising climax!

Coming around for my first landing, I misjudged and touched down three-point, with one wing low. There was a sharp, stiff bounce, like a mule kick. I poured throttle but had no control with the rudder and elevators stalled out due to lower wing burble. I left the runway ninety degrees off heading, thanks to torque, and cut cross-country like Patton's tank brigade. It took nearly two hundred feet, with a total lack of control before the tail flew enough for me to get back in the air.
From now on, like a C-47 troop car­rier driver, I make all triplane landings wheels first, dropping the tail only late in the landing run, with a prayer each time to Icarus or other flying gods to keep me straight.

This triplane of ours has gone through a painstaking development process equal to the Saturn rocket, and now really looks like Richtofen's airplane, with his colours and mark­ings. It has infinitely better aileron control than it had originally, due to control cable relocation and alteration of aileron hinges. It's now fun to fly.
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#30 piecost

piecost
  • Posts: 1318

Posted 26 October 2010 - 17:00

Original Fokker DVII

Extract from:

Flying the Old Planes
By Frank Tallman
Doubleday & Company, New York
1973

Engine: Wright Hispano Suiza 150 hp

“What a sweetheart": This is my No. 1 thought as the candy-striped German Fokker DVII breaks ground. By any pilot's standards it is a delightful, exciting airplane.

Unfortunately, in our DVII we had an Hispano Suiza for power instead of the regulation Mercedes. The change goes back many years to Men with Wings, a picture Paul Mantz did using the DVII. By that year (1937) the World War I Mercedes was beginning to show definite signs of age, and because Hissos were available, one was used with no basic structural changes in the aircraft.

Once settled in the DVII with a couple of Spandaus six inches away from your mustache, you realize this is a warplane, and in case of accident and no shoulder straps, you might very easily permanently shift that Kaiser Wilhelm appearance. Were this the original DVII, we would need two mechanics to start the Mercedes, one to twist the prop, the other to lock in the compression release when the engine fires. Looking for engine instrument indications in an original Fokker DVII is blindman's buft for like all German World War 1 airplanes poor instrument location, with every unlikely spot being used, except the underside of the pilot's seat.

In taking off, the tail comes up immediately, with complete rudder control. The temperature is 68 degrees, ground elevation is 52 feet, and we are airborne in 383 feet in a 9-knot wind. What a completely responsive airplane! The ailerons are sheer de­light, and the climb out is a revelation after flying other Allied and German aircraft of World War I. Levelling out at 3000 feet, the DVII indicates 110 mph, and trues out at 118 mph. There is no windshield, and you tend to lose your goggles if you look anywhere except straight ahead.

Stalls are straight forward and hang on until 49 mph on the clock and then fall straight ahead. Loops cover about 800 feet of sky, and when started at 120 mph carry through beautifully, with no tendency to fall out at the top.

Strangely, to the vertical point, the ailerons of the DVII are all anyone could wish. Following through the inverted phase, the roll slows down. As with the P-12, the full slow roll is on the order of nine seconds.

Spins of one turn in either direction are smooth and precise in either direction. No snap rolls were attempted, unfortunately, because of time limitations.

Landings with the DVII, as with many other aircraft of that period, are much different than with their World War II counterparts. As you come in on your grass or dirt surface (it had better be one or the other, because of the tail skid), you'll find the DVII moving quite a bit faster than you anticipated and touching three points hot and skittish at about 55 mph. The only directional control is throttle, and a real blast over the rudder is necessary to stop any turning on landing. In case anyone thinks the World War I aircraft are an easy job to fly, I have watched an experienced, many-houred Stearman crop-duster pilot land the DVII and go from wing­tip to wingtip, missing a ground loop by the proverbial gnat's eyelash, be­fore grinding to a nerve-shattering halt.

As you taxi in with the DVII, you can only compare its inborn strength, reliability of power plant, and smooth, easy inflight control to its Allied World War I counterparts and realize that the Germans were as far ahead with this airplane in World War I as they were in World War II with their operational jet aircraft and V-2 rockets.
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#31 piecost

piecost
  • Posts: 1318

Posted 26 October 2010 - 17:06

Original Pflalz DXII

Extract from:

Flying the Old Planes
By Frank Tallman
Doubleday & Company, New York
1973

Engine original Mercedes

Once in the nice battleship­gray cockpit, your nose is assailed by the strong fuel smell until you find that the tank is in the floor directly under you. With incendiary ammuni­tion aboard, what a lovely location for a sausage roast!

The Pfalz does not suffer from an oversupply of instru­ments, and there is no panel as we know them today. Instruments are stuck around as haphazardly as a modern artist's paint strokes.

Along with the inverted ram's horn on the stick, there is a radiator control shutter, a mag switch, and a fuel valve. There was no firewall in these airplanes, and it was a distinctly unpleasant feeling to see the rear of the Mercedes engine block. With six cylinders, each with the bore of a butter plate, a compression release is provided. The cockpit is not deep, and seated on my ever-present parachute, I felt like a penthouse dweller.

With my feet in the stirrup­equipped control bar, gas on, radiator shutters closed, motorcycle throttle on stick cracked, and an athlete standing on the wheel with his hand on the compression release, the Mercedes fired on the first pull and ran un­evenly until the compression release was locked. The Mercedes idled slowly and a bit unevenly, with the valve springs rattling like castanets.
Taxiing to the takeoff point with runners on the wingtips, I got no real rudder response. I checked to clear myself and was on my way, with the intention of getting the feel of the aircraft on a straight high-speed taxi run.

While the acceleration of the Mercedes seemed slow, the tail was up in fifty feet, and rudder response was good. The only problem was a wide-open throttle, which I couldn't close. In the space of telling I was flying. General balance and feel seemed good, so I climbed out around the field with the stuck throttle. This basic trouble was to plague me through my entire flying with the aircraft and, while in time I got rid of the motor­cycle twist grip throttle, which was on one of the ram's horns, still the stand-by throttle on the left wall of the aircraft was inadequate and was made for the hand of a Tom Thumb.

The flight was fast, and I ran away from a PT-19 as if it were moored. Wind blast was severe, for the only protection was the German tachometer mounted between the two Spandaus. Without an airspeed indicator my speed was arrived at by pacing other aircraft. Control response in the air was precise, and fast on elevators and rudders, but as in some of the spade-grip British aircraft, the aileron movement was restricted, and the inverted ram's horn kept hitting my thigh.

Visibility was excellent, and wide­open airspeed appeared to be better than 120 mph. The climb, as with many World War I planes, appeared flat, but actually was better than a thousand feet a minute, and I easily climbed away from most of the civilian aircraft. The approach was flat and fast, about 65 mph, and I moved with the alacrity of a mongoose to get the tail down as it settled. Fortunately, the first landing was in a good headwind and mild, for the tail skid bit before I realized how little control the Pfalz has because of the blanking out of tail surfaces by the lower wing.

Not all flights with the Pfalz were to be even half as easy as this first one. The flight went fairly well but was punctuated by the once again locking of the inadequate motorcycle throttle, and when I fell back to the standby throttle, it broke off. I flew fifteen minutes holding the rod of the throttle pushed forward. With this handicap the second landing had enough hair on it to satisfy an orangutan. Among the many aircraft I have been lucky enough to fly, this DXII has no peer in pure cussedness, and each landing presents enough emergencies and handling problems to make an instant trip to the local pub not only desirable but an absolute necessity.

Some years ago, the fine Air Force Museum at Wright-Patterson Air Force Base had a World War I aviation get-together, and many period aircraft were transported in for the celebration. Like many lessons learned the hard way, after assembly I did not flush and refill my fuel tanks. In a cross downwind at five hundred feet, the Mercedes decided that it didn't like its old fuel and quit. Because of the ram's horn stick and lack of ailerons, I could not make a steep enough turn to get into the area I was shooting for; consequently I wound up on an active runway at Wright Field in a ground loop that made the whip at the local amusement park look like a ride in a wheelchair.

[search youtube for "1962 WWI PILOTS CONVENE"]

The Pfalz stood on its nose in the centre of the runway, and I tied up the runway until enough bodies came out to get the ship back on an even keel. Sizable damage had been done, largely to my pride, but a stick change was made instantly; now the ram's horn is only in for show, with a straight stick used for flying.

Coming, as it did, late in the war, the pfalz stacks up pretty well when measured against other types I have flown. Its speed above 120 mph will run away from the Spad, Fokker DVII, or SEs. Aerobatically it is clumsier and larger than any of these airplanes and with a slow roll rate, only loops seem pleasant. Diving speed must also have been great enough to run away from nearly everything.

Landing a Pfalz is harder than in any other World War I job except a DRI. In play dogfighting with our other World War I aircraft, the speed of the Pfalz seemed to be its one redeeming grace.
One mechanic propping the engine, while the second mechanic on the wheel holds the compression release on the rear case of the Mercedes.
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#32 piecost

piecost
  • Posts: 1318

Posted 26 October 2010 - 17:07

Replica Sopwith Triplane

Extract from:

Flying the Old Planes
By Frank Tallman
Doubleday & Company, New York
1973

Engine Warner 165-hp radial,

Consequently, certain modernization changes were made that did not spoil the appearance. For power, instead of the cranky and unpredictable rotaries, a Warner 165-hp radial, fortunately with almost identically the same frontal area and appearance, was substituted. A battery, starter, and generator were included to make the old bugaboo of the Armstrong starter unnecessary. Wire wheels of the proper size were designed and beautifully built, with a brake inside the hub and completely unseen.

The basic fuselage was constructed out of square steel tubing of the same dimension and greater strength than the original wire-braced wood longeron. The cockpit layout was made identical to the original, including the handsome brass plates bearing the name of the manufacturer, Sopwith Kingston on the Thames, and one stating that the Vickers gun had a Scarff-patented interrupter gear. Instrumentation was modern but necessary due to the different engine.

It was a brutally hot September day, with ground temperature over 100 degrees.

Lack of the traditional Spade grip, while not liked by the purists, still gives infinitely more throw to the controls. The standard rudder bar gave me trouble only because of a brake pedal, which had a nasty way of hooking the sole of the shoe on my bum leg, always at the wrong time.

The Warner started easily, and vis­ability while taxiing out was pure pleasure after the truly blind DRI. The midwing on the Sopwith butts against the fuselage and allows for­ward visibility, though narrow in scope.

I taxied out to the end of the run­way, and after running up the Warner 165, turned into the wind. Runway altitude was 780 feet, and temperature was an even 100 degrees. Pouring on the coal, I left the tail on the ground for about 100 feet, then raised it instantly. I got an unexpected torque swing to the left and went off the narrow runway, clipping the growth like a McCormick reaper. Full oppo­site rudder and aileron brought me slowly back along with a sudden wet­ness in my palms, and I was airborne with no wind in about 480 feet. Obviously the triplane was heavier than the original (by more than 300 pounds), and without the slow, big, propped rotary, the performance suffers.

Climbing out, I was struck by the typical rotary torque feel that had occurred on takeoff. Rate of climb, even in the heat, was approximately 1000 feet a minute at an indicated 58 mph.

The three ailerons on each wing were pure delight and gave this flying club sandwich a crisp response equal to that of a Stearman or Tiger Moth.

I climbed to the acrobatic area in slow circles, feeling out the rudder and elevators, which have somewhat less possessiveness than the ailerons. Stalling speed occurred at 44 mph, and the plane broke gently straight ahead.

Wide-open throttle gave me an indicated airspeed at 3000 feet of 92 mph, and, edging the throttle back, I dropped the nose gently for a loop. With 115 mph indi­cated, I pulled back gently and added full power over the top, where I had 30 mph. The Tripe followed through nicely, but with a loop considerably larger in diameter than the Dr1. All the way through, the wires sang like a demented peanut vendor and must have been easily heard on the ground, more than a half mile down.
The Tripe's structure in aerobatics felt solid and secure. Part of this no doubt was mental and engendered by the physical size of the plank struts.

In slow rolls without an inverted system, the Warner cut out at the inverted position, and it was necessary to finish dead stick.. Somehow, like most old beat-up aviators, you pick something for a horizon line, but in a roll with the Triplane, you have a feeling of three artificial horizon bars, and you are not sure which to pick. In a Cuban 8, you have to select a reference point well below the horizon, but by that time you have picked up speed, and the feeling on rollout is akin to a pilot with acute arthritis trying to manoeuvre a flying venetian blind.

In mock combat with an extremely fine pilot, ex-Maj. James Appleby, flying the Fokker Dr1, I would have had an edge flying the Sopwith Triplane because of the stiff and slow ailerons on the Dr1, but both aircraft have their limitations; the skill and experience of the pilots are more important than the actual physical differences between the two planes.

Throughout this most exciting test I was plagued by a steel, fiber glass, and wooden leg, which slipped off the rudder bar (because of a lack of rub­ber sole on my bad shoe).

Coming in to land, I sensibly chose the grass area and not the narrow­surfaced runway. I touched down rather faster and sooner than antici­pated at about 52 mph, at which point my bad shoe sole hooked behind the brake pedal; by vigorous jabs of both legs sufficient to move the Taj Mahal, I rolled to a stop straight ahead, wiped nineteen gallons of salty water off my forehead, and taxied back.

Reflecting on the differences between the two planes, I feel that the Sopwith Triplane is infinitely superior. It is more controllable, lovelier on the ailerons, climbs faster, and the rollout on landing is easier.

Taxiing back with the Sopwith Triplane and physically being able to see ahead and reflecting on the lovely ailerons and flight characteristics, I couldn't help wondering whether Rheinhold Platz, when he developed the German Fokker DRI almost a year later, had for some reason totally ignored the lessons that any pilot could learn simply by sitting in and later flying Mr Sopwith's most desirable club sandwich.
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#33 piecost

piecost
  • Posts: 1318

Posted 26 October 2010 - 17:09

Original SE5E (SE5a)

Extract from:

Flying the Old Planes
By Frank Tallman
Doubleday & Company, New York
1973

Engine: Hispano-Suiza 180 hp

Somewhat more than five thousand were constructed before the end of hostilities, and Bishop and McCudden and other Allied aces owe many of their victories to the strength and lovely handling qualities of the SEs.

Your hand comes easily to the British circular spade stick. The rudder bar is set off the floor and has a top for your foot so that it cannot slip off when the plane is inverted. Throttle and mixture are on the right on a little shelf, and the mixture con­trol when full open is to the rear when your throttle at the same time goes forward! Instruments are airspeed, compass, oil pressure, water tempera­ture, altimeter, switch and booster mag and gas shutoff.

All Hisso engines have to be loaded up with throttle back and switch off and the propeller moved back and forth until you get some fuel over­flow. Check carefully to see that your gas valve is on. When "contact" is called and the prop is swung "clear/' rotate the booster mag handle, and the engine will catch and start easily with a gentle rumble. It idles nicely below 500 rpm, which unfortunately is the last stop on our tachometer. After allowing the water temperature to rise and checking oil pressure mags, you are clear.

The day of this flight there was a wind of 10 to 15 knots directly on the nose. The temperature was 75 degrees, the ground elevation, 87 feet.

The heart-lifting thrill of shoving the throttle forward is never lost, at least to me, and it was there as I pushed forward the control of the SE5. The tail levelled almost instantly. Because the propeller is slow-turning (about 1500 rpm on takeoff), you have no appreciable torque and very low noise level. The SE5 was airborne in 246 feet, and could have gotten off somewhat sooner. You have nice positive feet and you are climbing out at about 75 to 80 mph with a rate of climb approaching 900 feet a minute.

My experience in the SE5 is limited, and just flying in it is a considerable thrill, I suppose a la Battle Aces or War Birds. I would be chasing the Ercoupes and Cubs out of the traffic pattern if I had the Lewis and Vickers machine guns mounted.

Straight and level at 3000 feet, I noticed slight tail heaviness, even with the trim tab wheel forward. The cockpit was comfortable, with fine visibility and very little windflow. Wide open I was indicating 127 mph and 1650 rpm at 3000 feet. Settling back to cruise, I locked my belt and brought the stick back for a stall. It pays off gently, but with a sharp right-wing drop at an indicated 52 mph. Invariably, in a stall the right wing dropped. I tried a spin-one turn nicely, cleanly to the right; un­fortunately, it would only spiral to the left and, I believe sensibly, I did not try to force it in. With any air­plane over fifty years old I eat a little raw heart with aerobatics, for no matter how carefully you check it, anything can fatigue in this length of time.

Not using a G meter, I was careful to keep heavy stick pressures out of my work with the SE5. Checking my area, I pulled up into vertical reverses in both directions, and it held on nicely and reversed well with rudder. Looping at 135 mph went well but got slightly soft at the top, where I was indicating about 60 mph, but it came through without my hanging on the belt and apparently looked good from the ground. Cuban 8's went well but the engine spewed fuel out on my descending half roll and cut out for a period of four seconds. It slow rolls to the left nicely, with about eight seconds to complete, but you need 115 mph entry speed to carry you through for the time the engine is out. Unfortunately, in rolling to the right it resists strongly, and you get a roll that is impossible to do smoothly and that takes much time. Flick rolls or snap rolls were nice to the right at 85 mph but completely impossible to the left, for it stalls straight forward and will not snap with any combination of movements. I heaved a sigh of relief that our temperatures and pressures were ok on the Hisso} and headed for home. In checking the water temperature I unconsciously checked the radiator shutter lever.

The traffic pattern speeds work out nicely with todays light planes and as I circled for a green light and got it, I started a gentle turn into my grass area, holding about 75 to 80 mph indicated. By now the strangeness of flying with my left hand and using the throttle with my right was gone. Like all early aircraft and most biplanes, they payoff rather fast, and in attempting to check my touchdown speed on the airspeed indicator I bounced but caught it with stick and a little rudder. It indicated about 53 or 54 mph. The rudder was quite positive, and the steerable tailskid was extremely helpful. Because of the steerable tailskid this airplane is one of the few World War I planes that can be landed on a concrete runway, but again only with great caution, much room, and lots of cold sweat until you finally stop moving.

Pouring on the throttle, I went around the field again, more to prove that I could make a better landing than for any other reason. It was air­borne in about fifty feet; I climbed out nicely, and on my second ap­proach I carried a little power, flared it out, and set down like a hen on a basket of eggs. As I taxied up to the parking area I let the engine idle, then shut it off with the mixture control and switch.

The SE5 that I flew is an original British SE5, manufactured in England. After the war Eberhardt Steel Company in the United States was com­missioned to rebuild the SE5’s to be used as a U. S. Air Service fighter trainer, and this airplane was one of that batch. As nearly as I can determine, the major change made by the rebuilders was the plywood covering on the flat areas of the fuselage, which added to the strength.

The Wright and Hispano Suiza engine which puts out an honest 180 hp, must be the third or fourth engine in this plane. There are no log books but I estimate the aircraft to have had over a thousand hours and it has been rebuilt several times.
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#34 Cptn_Goodvibes

Cptn_Goodvibes
  • Posts: 255

Posted 29 October 2010 - 01:29

G'day,

Am sure aircraft performance has been thoroughly debated on the forum. I'd just like to add some information from the Appendix of a publication, "Manfred von Richthofen. The man and the aircraft he flew". Author. David Barker. Apart from this, can only add that there doesn't appear to be seperate perfomance data for the Albatros DV and DVa. I personally think the quoted speed of 107mph is about 10mph too low, but will leave that to the experts. Unfortunately, it does'nt say at what altitudes. On this, I can only offer that although rotary engines have excelent power to weight ratios, they're performances do fall away at higher altitudes in the thinner air. Again, am sure the experts of ROF have got this covered. My appologies if the attachments are out of order. Your dealing with a computer luddite here. Enjoy.

Attached Files


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#35 hq_Reflected

hq_Reflected
  • Posts: 4711

Posted 29 October 2010 - 06:11

Engine: Hispano-Suiza 180 hp

The in game SE uses a 200 HP Viper engine so it's a bit different. Thanks for posting anyway, interesting read!
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#36 piecost

piecost
  • Posts: 1318

Posted 29 October 2010 - 14:18

Yes, I was sure to be clear about the engine type, the Frank Tallmans Fokker DVII even used a Hisso !

If I get around to it I will post all the Specifications from the books. I believe that these were a mixture of figures tested from the actual aeroplanes and those from other sources (I doubt that he tested the service ceiling!)

SE5E/SE5a

Engine:__________180-hp Hispano-Suiza
Empty Weight____1400 lbs
Useful Load______550 lbs
Gross Weight_____1950 lbs

Maximum Speed__127mph (indicated at 3000ft)
Rate of Climb_____870 fpm
Stall Speed______52 mph (indicated)
Endurance______2.5 hours approx
Service Ceiling___19,000ft
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#37 gavagai

gavagai
  • Posts: 15541

Posted 29 October 2010 - 14:37

Apart from this, can only add that there doesn't appear to be seperate perfomance data for the Albatros DV and DVa. I personally think the quoted speed of 107mph is about 10mph too low…

Notice that it lists the D.II as being faster with its weaker 160hp engine than the D.III and D.Va.

But did that stop them from publishing it? ;)
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#38 Cptn_Goodvibes

Cptn_Goodvibes
  • Posts: 255

Posted 29 October 2010 - 20:41

G'day gavagai,

Yes I quite agree. However, I wouldn't be too critical of the Author. Am happy that he provided the information in the first place. As you may have noted, rightly or wrongly I took the liberty of briefly including my own personal thoughts and observations. Especially in regard to the D.V's and quoted speeds where the height is not mentioned. It is a problematic issue and I'm glad that I don't have to make the call on it. I can only conclude that the D.III and D.V's had to be better in some way to the D.II to warrant further production. That said, I've never flown a real Albatros and whilst I'm a "fat, balding, old fart", I'm definitely too young to be WW1 flyer or someone that had this knowledge. I think there's a captured D.Va at the Australian War Memorial in Canberra, but I can't see them letting me take if for a spin anytime soon. Also, being a "full switch simmer" from day one, I'm patently ignorant of exactly what speed the Albatroses are flying in ROF. While I have some knowledge in these areas, can heartly agree that my opinions can be challenged or ignored and should always be questioned, like all history should.

The ROF developers have an unenviable task in providing the best, most realistic product possible using the limited resources at their disposal. I may not agree with them on some things, but they're the ones with a business to run and there is no intention of criticisim from my quarter. Indeed, we are fortunate that the 777 team seem to be listening and providing constant feedback. Am sure that they are taking constructive comment onboard. The author is in the same position as the rest of us who post about aircraft. My intention in the post was only to provide information that may be helpful to the developer and their clients. And yes, I do favour the Alby series and am always happy to see favourabe comment on it. I particularly like the D.III and will hopefully see you online some day in the skies above the trenches.

Regards,
Vibes
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#39 piecost

piecost
  • Posts: 1318

Posted 03 November 2010 - 19:03

Sopwith Camel replica

extract from P1lot magazine November 1981

Engine: Warner Super Scarab

Right from the beginning my relationship with the Sopwith Camel was one of love, fright and freezing. I loved her because she was utterly unique, and a part of our heri­tage. She frightened me by what might be euphemistically termed her 'handling qualities', and also by her engine's depressing propensity for going to sleep on the job. And she froze me nigh to insensibility on all but the balmiest of summer days; no other aero­plane I have ever flown exposes its proprietor to the gale of its pas­sage in quite the same way.

I first made acquaintance with her because a friend's friend was looking for pilots for the Leisure Sport Warbirds display team of World War I aircraft. She was a replica, of course - but what a replica! This was no scaled-down mewling puppy of an aeroplane; this was the works, full-sized and seemingly of monstrous propor­tions, dwarfing a Tiger Moth and making a Pitts look like a control­-line model. She was, moreover, built (by that great character Viv Bellamy) almost entirely to the original plans, the only real departure from 1916 being the use of a Warner Super Scarab radial engine in place of the original Clerget or le Rhone rotary.

Sitting in her with the engine running for the first time, my elation became tinged with certain thoughtfulness. I had never flown behind a Scarab before, and this one sounded like several advanced TB cases staging a coughing contest (Which I later found is the way all Scarabs sound). Furthermore, the whole aircraft was shaking in sympathy - not with the eager vibration of most biplanes before they take to the air, but a sort of dispirited shivering as if a collection of geriatric spare parts were all trembling with their own individual agues. The long flying wires twanged like loose harp­ strings, and the bottom wings exhibited a peculiar rippling shudder as they drifted in and out of some harmonic of their own. ~ And on top of all this there was the Rotherham pump twiddling away none too far from my starboard ear. This device is a wind­driven airpump with a twelve-inch propeller. It works rather like a model aeroplane engine in reverse, and its function is to pressurise the Camel's fuel tank in order to perpetuate the flow of fuel to the engine. In the First War the Rotherham pump was mounted in various places on the aircraft, apparently according to the constructor's whim of the moment. Some Camels had them on a forward centre section strut; some had them on a rear; and still others had them mounted down below on an undercarriage leg. This one, for some undisclosed reason, had the infernal thing on the starboard rear centre section strut, just where the driver in a moment of inattention could stick his mush into the propeller arc. There was certain inevitability about this, and the only surprise was that when it eventually happened it was someone else who got a quick-release ear.

Taxying a Sopwith Camel, I next found, is a matter which demands considerable attention. Rudder response at taxying speed is nil to zero unless you indulge in great blasts of power to blow the tail round. But if you do this you also make the aeroplane go faster -and this is not desirable because the Camel has very low wing­loading coupled with marked dihedral on the bottom Wings, so that if she is pressed to proceed cross-wind at more than a sedate waddle she exhibits a most alarming tendency to roll over on her back.

In contrast, the take-off is no problem at all -or at least, once again, it is no problem provided you are pointing exactly into wind: if you are not, there is a most interesting few seconds while the into-wind wing tries to climb up over your head. Normally you just open up, pick the tail up, and the Camel grinds placidly into the air a few seconds later, after an incredibly short ground roll.

Then on the first flight, your flying lesson begins. Sitting amid the noise and wind, staring at the world between the barrels of the twin Vickers guns, the realisation rapidly comes upon you that the controls of this flying machine feel most peculiar. The rudder and elevator are very light and sensitive while the ailerons are astonishingly heavy, and appear to have practically no effect on anything at all. Heaving the stick from side to side produces a sort of drunken wallowing, like a politician trying to duck out of a commitment. A suspicious glance at the vibrating wings reveals that the ailerons are in fact still connected up -and the sight of them moving sluggishly in the airflow suggests the answer to the conundrum: the Camel has four enormous ailerons, and they are quite simply far too big. Furthermore, they have all the design subtlety of a quartet of barn doors. Frise effect, slotting, balancing, differential -these weren't even words in the aviation dictionary in 1916 when this lady was conceived, if you wanted your aeroplane to roll faster you just made the ailerons bigger. (And then, presumably, wondered why it didn't roll faster … ) Those huge control surfaces so degrade the airflow over the wings that not only is their primary effect vastly blunted, but at the same time the drag thus engendered is awe-inspiring. Adverse yaw completely overcomes the normal secondary effect of roll, so that if you are so misguided as to take your feet off the Camel's rudder and then bank (say) to the left, the stubby round nose will instantly zap off to the right and keep going. Coupled with basic yaw instability, this characteristic is so pronounced that the aeroplane's 'natural' flight regime is in fact the side-slip: if you let go of everything she will immediately rack herself into the steepest slip­ping turn she can manage. All this combines to create a weird feeling of flying on a knife-edge when you first clatter into the air. It takes several minutes before the realisation trickles through that this loutish yawl-roll combination is not so much actively dangerous as merely different: this is flying a la 1916, and the cosseting comforts of inherent directional stability and effective aileron technology are many years in the future. One is just left reflecting that if the Camel was one of the best of the World War I flying machines, Gawd only knows what the worst were like …

These first few minutes aloft are interesting for other reasons, as well. On my first flight, for example, so overcome was I with the awesome control disharmony that I did for some minutes forget to check the fuel pressure gauge. When I finally ducked down to peer at it on the shivering and rudimentary instrument panel the needle was sitting on four or five psi, way over the 2 1/2 psi red-line. The transition from ground-running to flight had caused the Rotherham pump to speed up and vastly over-pressurise the fuel tank, an event which I had been sternly warned was Not A Good Thing. With visions of the tank going off like a bomb six inches behind my seat, I grabbed for the manual pressure relief valve in the cockpit and opened it fully. A jet of Vaporising fuel shot across my knees from the nozzle, and the pressure needle promptly sank to zero. I shut off the valve, gave the hand wobble-pump a few strokes to stoke things up a bit and the bloody fuel pressure immediately went off the clock again. Becoming aware (quite correctly) that this was my initiation into what was obviously going to be an ongoing problem in Camel driving, I then strove vainly to find a position for the highly sensitive relief valve lever which would maintain something like the correct pressure.

I was thus engaged when my eye was arrested by the oil pressure needle, which was sinking slowly in the west.. The time had come, it rather seemed, to place the aeroplane back on the ground.
In the event this proved easier than I had expected, the only mildly exciting moment being when I initiated the final side-slip. Conventional slip entry - with bottom stick and top rudder - is a marked overkill in the Camel, since slipping 'is what it naturally wants to do anyway. My first attempt produced a lurch like a double­decker bus falling over, immediately followed by the discovery that slipping this particular bird requires bottom stick and bottom rudder pressure, to prevent the manoeuvre tightening up on itself.

After that the actual landing was an anti-climax. The Camel sits down slowly and gracefully in any attitude between wheeler and three-pointer, and the big bungee undercarriage gives a nice soft ride rather like a Tiger Moth. The only critical thing is that once again you must be exactly into wind, and you must also be ready with the beetle-crushers to keep it straight. Swaying around on top of those tall wheels the Camel always feels as if she's about to ground-loop, but never actually does. (Well … not very often, anyway).

So ended my first Camel flight, after six minutes in the air. When everything came to a stop it was suddenly quiet enough to hear myself think: and I remember hearing myself thinking that any prolonged association with this flying machine was likely to prove an interesting and educational experience, to say the least. I was right: My next flight, which was supposedly a cross­country, ended after twelve minutes when an oil pipe broke and lubricated my plates-of-meat instead of the engine. I placed the aeroplane on the ground at -of all places -a Royal Naval helicopter station, gliding dead-stick past the tower towards a patch of grass while some genius on the balcony flashed a frantic red light at me. The next flight lasted five minutes before the oil pressure packed up again. So did the next flight. And on the flight after that, due entirely to my own pig-headedness I did contrive to become lost in a snowstorm, which is a most unfunny proceeding in a Sopwith Camel. The only saving grace was that the Scarab at last relented and condescended to keep running. I emerged from the experience, very much shaken, to make my first unforced Camel landing. The relationship was taking shape.

The next round of the battle was aerobatics. All that time Leisure Sport had the Camel and their Fokker Triplane, along with a trio of Tiger Moths and various other items of machinery. To their ever­lasting credit they did not limit the old warbirds to normal flight, but actually encouraged us to perform mild aerobatics for our display routines. Thus I found that the Camel performed tight little loops, well-behaved spins, good stall-turns, and somewhat ponderous barrel rolls. Slow rolls, however, were something else again. She would just about do it if you insisted, but you had to start at nigh on Vne , use both hands to crank on full aileron -and then wait. And wait. And wait. She took 23 seconds to go round (compared to about six seconds in, say, a Chipmunk), and that 23 seconds felt like a fortnight. After the first 100 degrees or so the engine would pack up and you were left rolling in hideous slow motion with only the howl of the wind in the wires for company. Treading the rudder very gently -for only a touch too much out-roll rudder would be enough to overcome the ailerons and stop the roll altogether, leaving you stuck on your back like some helpless airborne turtle -you finally regained erect flight with perhaps 80 mph left ,whereupon you had to wait several more seconds before the Scarab would cough and splutter and belch and finally struggle back to its normal asthmatic blattering. (In the end I did slow rolls at three or four shows before sanity prevailed and I dropped the exercise as being too hard on both the airframe and the nervous system).
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#40 piecost

piecost
  • Posts: 1318

Posted 15 November 2010 - 17:22

Rudder Effectiveness at High Incidence
Data on SE5a, Bristol Fighter & BAT Bantam

Extract from: Royal Aeronautical Society, Proceedings of the Eight Meeting, First Half 61st Session

THE CONTROL OF STALLED AEROPLANES by Professor B Mervill Jones.

“Conventional ailerons on a stalled wing exert their moment about an axis inclined upwards and forwards through angles between 15° and 30° from the: wing chord, the maximum moment which they can exert being represented by a coefficient of about 20

This coefficient may be looked upon as a number defining the relative moment exerted by different controls, after allowance has been made for variations in air density, size and velocity of the aircraft. Its precise definition is:

1,000 x Moment / p x V^2 x S x s, where
p is the air density,
V the velocity of the aeroplane,
S the area of the wings, .
s the semi-span of the wings.

The same coefficient will be used later to express rudder power.

To interpret the meaning of "sufficient rudder power" we must look a little, more closely into the reason why a powerful rudder is required in the stalled state. The first point to notice is that it is not required so much to cause the aeroplane to yaw, as to prevent it from yawing in an undesirable direction. An essential feature of the incipient spin is that it consists of a combined roll and yaw, in the sense that the falling wing tip is retarded; if this yawing motion can be checked, or reversed, by the use of the rudder, the incipient spin can be stopped.

Now, when the ailerons are not used, the yawing moment which the rudder has to counteract arises mainly from the fact that the wings are rolling, and it is easy to see how this yawing moment is generated and that it will be definitely limited in magnitude. When a stalled wing is rapidly rolled the rising tip meets the air at a smaller incidence and becomes unstalled, whilst the falling tip meets the air at a greater incidence and remains stalled. Now the air reaction on an unstalled wing acts forward of the perpendicular to the chord" whilst that on a stalled wing acts almost perpendicularly to the chord. Hence the rising wing is forced forward more than the falling wing and a yawing moment is called into play. But there is a very definite limit to the amount by which the reaction upon it wing can be inclined forward of the perpendicular to the chord, so that there must be a corresponding definite limit to the yawing, moment generated by a rate of roll, no matter how fast the rate of roll may be.

Wind tunnel experiments upon the effect of rolling show this to be so, and no wing yet tested has shown a coefficient of yawing moment much greater than 10, whilst for normal thin wings the maximum coefficient is of the order of 8 or 9. It does not require a very rapid rate of roll to generate a yawing moment of this magnitude, but no further increase in the rate of roll generates a yawing moment greater than this.

It follows that rudders which will produce, on stalled aeroplanes of the types tested, a yawing moment of coefficient greater than 10, will be able to deal with the moments generated by the wings. When they can do this, theory and experiment agree in confirming that they can always be used to restore the aeroplane to an even keel, by forcing forward the falling wing and so generating a rolling, moment in the sense to lift it again. Fig; 1 gives some idea of the powers of the rudders of various aeroplanes.

FIG 1.

In this figure abscissae are the incidences of the main wings and ordinates the coefficients of the yawing moments given by the rudders moved through 20° from their neutral position. Several of these rudders could be moved further than this, with a consequent increase in moment, but 20° has been chosen for comparative purposes, because experimental wind tunnel data existed for models of all these aeroplanes with this rudder setting.

The universal falling off in rudder power on stalling should be noticed; this is due to the rudder becoming shielded from the relative wind by the body and elevators. It will be noticed that this reduction of power, considered as a

proportion of the power in normal flight, is, as might be expected, much greater for small weak rudders than for large powerful ones. The interesting region from the point of view of the present discussion is that between 20º and 30º incidence of the main wings , and here trhe effective rudder power of most of the aeroplanes tested is much less than the coefficient of 10which is considered the minimum desirable a few moments ago. The only standard aeroplanewhich approaches those requirements is the SE5. here the rudder could be moved through over 30º, and the maximum moment developed had a coefficient greater than 10. unfortunately I have not been able to obtain reliable statistics as to the number of accidents which have occurred tto this aeroplane throught the incipient spin*; but in my experience I know of none..

*Accidents due to a long continued spin have n bearing on the present discussion, the processes involved in checking an established spin being different from those for checking an incipient spin.

The large ruddered Avro is purely an experimental aeroplane with a fantastically large rudder, which has in fact been found to be large than is required to check spin inn any stage of development

Turning to the other end of the scale we see, in model A, an example of rudder shielding, so great at very high incidences, as to rendr the rudder practically useless. This model was used in an interesting research upon the shielding of rudders, an FIG 2, taken from R.M. 965, shows some results of this research, which will help me to describe the features in design which lead to defective rudder power in stalled flight.

A is an elevation of the tail of the model in its original form. Here the fin and rudder are low and do not project beyond the body, which was oval section. This arrangement gave the defective moment curve A which we have already considered and which is shown above.

B shows the rudder and fin greatly increased in area and moved backwardsso that the rudder projects behind the body and works in a Vee-slot in the elevators. The rear part of the body is also altered so as to end in a vertical knife edge, and is raised so as to make the top line of the body horizontal in flying position. This arrangement gave the greatly improved moment curve shown, above.

C and D are alternative arrangements, giving nearly as good results as B but with less fin and rudder area. In C the effect is obtained by raising the rudder, and in D by moving it backwards and causing it to project well beneath the body.

In general it may be said that a low fin and rudder, which does not project behind the body, or is directly over a continuous elevator, will be defective when the aeroplane is stalled, and that the defect will be accentuated if the body is short and thick, broad in plan near the tail, and has its upper line much curved downward. It is not always practicable for the designer to have the rudder power of his aeroplane tested out on a model in a wind tunnel, and he will therefore want to know how large to make his rudder in order to give the required power. No exact figure can of course be given, because exact figures depend, as we have seen, upon details of design. When the rudder is small and badly placed in relation to the body, its power may be very dependent upon these details of design, but if it is on the large side by comparison with present practice and attention is given to the points mentioned, its power is not so sensitive to details of design and can be roughly estimated from its size and position.

The power of the rudder depends upon its own area and that of the fin in front of it, and upon the distance of those areas behind the, centre of gravity of the aeroplane. A convenient way of comparing these quantities in different aeroplanes is to multiply the combined area of fin and rudder by the distance of their centre of area behind the centre of gravity of the aeroplane, and to divide this product by the area of the main wings and their semi-span. The resulting ratio may be written S"l" /Ss and ,is often called the " rudder volume," because the dimensions of each half, of the ratio are those ,of volume. In the majority of aeroplanes of the present day l" is not far different from s, so that the" rudder volume" is approximately the ratio of rudder and fin area towing area. This rudder volume cannot be a complete criterion of the action of the rudder, because it does not take account of the proportion of area of rudder and fin, but if the rudder is not appreciably less than half the total, it is probably the best simple criterion available.

Fig. 3 shows the coefficients of the moments obtained from the rudders of a variety of aeroplanes plotted against "rudder volume." The figure relates to 25° incidence of the main planes and a 20° rotation of the rudder from the neutral position. It is, at once apparent that, with the exception of the Bristol Fighter and model A, points relating to the remaining models fall roughly into a band which is sufficiently narrow to suggest that if attention is paid to, the features of design just enumerated, an approximate guess as to rudder power can be made from a knowledge of rudder volume. I have drawn my own idea of a good mean line through these points and it suggests that, with good design, a moment of coefficient at least 7 should be attainable from a rudder having a volume of 0.05 when it is moved through 20° from the neutral position.

Wind tunnel tests show that the moment given by a rudder is nearly proportional to the angle through which it is moved, up to at least 30° from the neutral position; hence it would appear practicable to lay down the rough generalisation that a well designed and placed fin and rudder, capable of being' moved through 30° from the neutral position, and having a "volume" not less than 0.05, should give a moment of coefficient 10. If the distance of the fin and rudder behind the centre of gravity is approximately equal to the semi-span of the wings, this reduces to the very simple rule:
Fin+Rudder area 5 percent of the area of the wings.

It is again necessary to emphasise the point that the requirement of a moment coefficient 10, which can be met by a good fin and rudder of volume 0.05, applies to the conventional British biplane of thin wing section only. Other wing combinations may call for different rudder powers. There is reason to suppose, for instance, that wings which are tapered in chord and camber may call for smaller rudders, whilst wings having a large camber near the tip may require larger rudders.
I have said that given a rudder of sufficient power a reasonably alert pilot should be able to check the incipient spin in any stage of its development and restore his aeroplane to an even keel without using the ailerons.

In general, it may be said that if an accidental or intentional stall during the approach to a landing ground is contemplated as a possibility, then it is important to provide the best possible control at that instant; if the movements required for that control can be made similar to those required in normal flight, so much the better. When a pilot stalls a conventional aeroplane with weak rudder, he feels as though he has lost both his ailerons and his rudder. Restore to him either of these organs, by providing either a special aileron or a powerful rudder, and he will be able to prevent the spin from occurring, but will feel as though he has lost the other organ. Restore to him both these organs and he will find that his control in stalled flight is not greatly different from that to which he is accustomed in normal flight. Finally it is worth noting that with the possibility of such a deadly occurrence as the incipient spin always present, there is much to be said for providing two entirely independent means whereby it can be prevented.

We have discussed the results which ·can be achieved by the use of a powerful rudder and special ailerons. Let us very briefly consider the question of cost in weight and performance. Taking the rudder first; if a rudder such as that used experimentally in the Avro with a volume 0.096 were required, the cost would be very serious, but fortunately, a much smaller rudder than this is sufficient; a volume of 0.05 being indicated, both by theory and practice. A rudder of approximately the latter strength was used on the standard SE5, and is used at present on one of the most successful fighting aeroplanes. A crucial test of the matter was that of redesigning the rudder of the Bristol Fighter in accordance with these ideas.

The new rudder illustrated in Fig. 4 with the old rudder shown dotted for comparison has a volume of about 0.046 and has been universally reported, by all pilots of experience who have tried it, to effect a great improve­ment in the flying qualities of the aeroplane.

The lecturer asked for any information as to crashes on :the SE5 as a result of an incipient spin. I have always understood that McCudden was killed in this way. I believe he spun from about 200 feet into the ground.

Major C. K. Cochran-Patrick said: …

I think I can answer to some extent one of the questions he asked. With regard to S.E.5's, I remember, during the war, once in 1917 on an aerodrome in France collecting in the space of a fortnight no less than three SE5's that had spun into the ground from a low height. They had been piloted by new pilots just out from England, and it is quite possible that the accidents happened owing to the fact that the pilots were inexperienced. Major McCudden flew into a tree; he did not spin into the ground. This point leads us on a little further. The lecturer mentions at the beginning of the lecture the danger of the incipient spin catching the pilot off his guard, and I have been trying to recall cases of a pilot spinning into the ground. As far as I can remember myself, no experienced pilot has spun into the ground and killed himself on a machine: which did not flick into a spin.

Machines can get into a spin in very different ways. De Havillands and Avros and big machines get into a spin fairly slowly, and you have time to realise the danger and stop it, though you cannot stop it without losing height and diving. Others definitely flick into a spin. The Sopwith Camel and Spad go into a spin so quickly on occasions that even an experienced pilot does not realise it until he has done half a turn. The moment you realise a 'machine is in a spin you can stop spinning in half a turn.

Curiously enough, machines which flick into a spin stop easily. Having stopped a machine spinning, you then have to bring it out of the dive which follows and in that process you usually hit the ground. I suggest that the lecturer should concentrate on elevator control in a stall. I do not know anything about the aerodynamical problems concerned, but it seems to me that the reason why you cannot bring a machine quickly out of the dive which follows a spin is that the machine is not going fast enough to give the elevator sufficient control. If you could make your elevator sufficiently powerful to at least alter the angle of the machine, you would hit the ground with your undercarriage instead of end on.

Probably what is necessary is something which will definitely tell the pilot that the machine is about to stall, and then give him control when it is stalled. The combination of the two would, I believe, eliminate fatal accidents. “

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