Jump to content


Photo
- - - - -

Current ROF Airplanes Flight Model Data Topic.


  • Please log in to reply
127 replies to this topic

#41 =FB=VikS

=FB=VikS
  • Developer
  • Posts: 1246

Posted 09 July 2011 - 13:16

The Maximum Angular Velocity of Aeroplanes

Reports & Memoranda No. 670 March 1920

[turn time for: Camel, DH4m FB27 & HP 0/400, Loop time for: Pup]

Experiments on the Rotation in the Slipstream of a Tractor Aeroplane

Reports & Memoranda No. 643 August 1919

[Sopwith Dolphin]

Thanks!!!
  • 0

#42 piecost

piecost
  • Posts: 1318

Posted 09 July 2011 - 20:16

VikS,

I'm glad that it is interesting. I can obtain copies of the R&M reports given here:

http://naca.central....reports/arc/ar/" onclick="window.open(this.href);return false;">http://naca.central....reports/arc/ar/

If you have any requests…

If not, I will continue posting reports which I think could help. I will post more reports about downwash soon.
  • 0

#43 =FB=VikS

=FB=VikS
  • Developer
  • Posts: 1246

Posted 10 July 2011 - 00:08

VikS,

I'm glad that it is interesting. I can obtain copies of the R&M reports given here:

http://naca.central....reports/arc/ar/" onclick="window.open(this.href);return false;">http://naca.central....reports/arc/ar/

If you have any requests…

If not, I will continue posting reports which I think could help. I will post more reports about downwash soon.

Anything interesting on SPAD VII except the infos from Windsock/Profile/Aircam ?
  • 0

#44 piecost

piecost
  • Posts: 1318

Posted 10 July 2011 - 17:49

SPAD VII

Extract from:

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

Attached Files


  • 0

#45 Kwiatek

Kwiatek
  • Posts: 680

Posted 10 July 2011 - 18:58

Nice reading Piecost :S!:

Have you maby similar data for performance in flight about other planes expecially Albatros, Pfalz, DR1, DVII or Nieups etc?

( i mean not Windsock/Profile)
  • 0

#46 piecost

piecost
  • Posts: 1318

Posted 10 July 2011 - 19:31

Kwiatek,

Find below links to posts for the aircraft you requested. The only report I have regarding the Albatros series is the DVa replica residing in the Fleet Air Arm museaum in Yeovilton, UK. The only thing I found about it was that with the more modern Ranger engine installed it required 81kg of lead ballast in the nose! (Ref: Flying Qualities & Flight Testing of the Aeroplane, Darrol Stinton).


Nieuport 17/23 Replica: post#25 Data Topic for Airplanes Performance.

Nieuport 28 (clipped wing?) Data Topic for Airplanes Performance.

Pfalz DXII: post 31 Data Topic for Airplanes Performance.

Replica Fokker Dr1: post#83 Data Topic for Airplanes Performance.

Fokker DVII: post#30 Data Topic for Airplanes Performance.
  • 0

#47 piecost

piecost
  • Posts: 1318

Posted 11 July 2011 - 21:15

Exploration of the Airspped in the Airscrew Slipstream of a Tractor Machine

Reports & Memoranda No. 438

Attached Files


  • 0

#48 piecost

piecost
  • Posts: 1318

Posted 11 July 2011 - 21:15

Exploration of the Airspped in the Airscrew Slipstream of a Tractor Machine

Reports & Memoranda No. 438

…continued

Attached Files


  • 0

#49 piecost

piecost
  • Posts: 1318

Posted 11 July 2011 - 21:21

investigation of the Downwash Behind a Biplane

Reports & Memoranda No. 426

Attached Files


  • 0

#50 piecost

piecost
  • Posts: 1318

Posted 11 July 2011 - 21:28

The Comparison of the Manoeuvrability of Aeroplanes by the Use of a Cinematograph Camera

Reports & Memoranda No. 851

[pitch, roll & yaw rate of an SE5a]

Attached Files


  • 0

#51 piecost

piecost
  • Posts: 1318

Posted 12 July 2011 - 20:51

COMPARISON OF THE FLYING QUALITIES OF SINGLE AND TWIN ENGINED AEROPLANES.

(ROYAL AIR­CRAFT ESTABLISHMENT REPORT No. K.1514.)
By Squadron Leader R. M. HILL, M.O. A.F.C.
Communicated by the DIRECTOR OF RESEARCH,
AIR MINISTRY.

Reports and Memoranda, No. 747. April, 1920.

1. Summary.The report, while making reference to the flying of multi-engined aeroplanes, deals primarily with the handling of aeroplanes with two engines, as distinct from the single-engined type. The essential differences from the pilot's point,of view between the single anld multi-engined types are ,outlined, and the subject is approached purely as the pilot would approach it; that is, as one who accepts the type as he finds it, and must use it intelligently, appreciating its faults and its excellencies, so that he may be cautious of the one and sensitive to the other. The report is not intended as a criticism of any particular type, and assumes that the various types have their own peculiar justification.

2. Introduction.- I feel that the following notes might prove of. some use, in view of the fact that considerable experience with multi-engined aeroplanes has been allowed to accumulate without its being definitely written down. Broadly speaking, all moderrn aeroplanes are similar to fly, but different types of aeroplane do need different handling; and if there are two categories under which aeroplanes might be classed, and which require a differentiation from the flying point of view than any others, they include respectively aeroplanes which have more than one engine and which have not.

In this report a single-engined aeroplane is taken as one which has one propeller, that is, one thrust axis: and a twin­engined aeroplane as one that has two thrust axes, parallel to the fuselage and approximately on the same level. The modern four-engined aeroplane as a rule has also two thrust axes, disposed similarly to the twin.

Considering that the great bulk of aeroplanes in service has been of the single-engined type, and that the twin or multi-­engined type is a comparatively new departure, the amount of special experience of the latter is small compared to that of the former.

A pilot trained on the single-engined type might well be excused for thinking that his experience would be fully adequate to meet any contingency that might arise on the twin-engined type. But unless he uses this experience with care, and selects that only which is essentially applicable to say a twin-engined aeroplane, there are certain errors into which he may easily fall. It should therefore be worth while to try and make an analysis, to note where such a pilot's experience will be useful to him, and, more important, where it may lead him astray, unless he ,brings an open mind to bear on the problem.

In general the analysis will be confined to the difference between single and twin-engined aeroplanes, as being more straightforward and more directly useful at the present time. An appeal is simply made to first principles, to which a pilot who flies with his head will instinctively revert in case of difficulty or bewilderment.

When all is going well in flight, or apparently going well, which may be a very different matter, an insensitive pilot will often fail to appreciate unnecessary risks that he may be incurring. If, while incurring such a risk, something unforeseen happens, he is unable to meet the danger coolly and intelligently; for unless he has, going back to first principles, anticipated, these risks in a level-headed way, he cannot with reasoned confidence make a rapid decision and carry it through.
There is no doubt that the twin-engined type involves greater concentration in flying, simply because the pilot has more to look after; he has to cope with the difficulties met with every day in the single-engined type; but, in addition, he may meet with certain extra ones involved in the twin, the cumulative effect of which has undoubtedly led in some cases to crashes which might have been avoided had these difficulties been justly appreciated. These crashes on twin-engined aeroplanes gave rise to an exaggerated idea of their abnormal or dangerous behaviour under certain conditions, the reason for which was but dimly realised and highly coloured by quite unjustified feelings. If a calm appeal to reason had been made, these difficulties would have been seen to be perfectly normal, and only to be expected as inherent in the design.

Let us consider what factors in the design are the most vital to the pilot, and then how they influence his handling of the aeroplane.

3. Control and Design. - Undoubtedly, for pure flying, that is the pilot's part in the maintenance of an aeroplane in flight, control will be uppermost in the pilot's mind, and as such claim nearly all his attention in flight. Control may be roughly divided in two; control of the aeroplane and control of the engine or engines.

I think that the key to the problem may be said to be the correct appreciation of how the two parts of the control react on each other. A failure to appreciate this, an attempt to treat subconsciously the two parts as separate, involves grave confusion. It may be argued that a modern aeroplane is perfectly controllable without engine or engines; and that to make things simpler, the aeroplane control may be thought of and analysed alone. This statement is very misleading because it is so near the truth. Just where it falls short of the truth, the difficulties commence, and in two main directions.

Firstly, when the power is completely shut off, the two elements of aeroplane and engine control are most nearly separate in the pilot's mind. Theoretically, with an aeroplane control complete in itself, a pilot might carry out any manoeuvre what­soever, using gravity as a motor. Even if the aeroplane control were complete in itself, it could not be made complete enough to meet effectively the control requirements of the aeroplane between all engines on and no engine on. It is obvious that in some aeroplanes these requirements are far more comprehensively met than in others, which means that the pilot can only regard this as a genuine difficulty which so far applied design has failed to overcome completely.

Secondly, in practice, especially with twin-engined aeroplanes, the aeroplane control is not complete in itself. Although recourse to it alone is necessitated in a forced landing with no engine or engines, in which case the best possible use has to be made of it, in actual fact most modern aeroplanes pass the accepted standard of controllability when their control at low speeds is bolstered up by the use of engine to assist the rudder, for instance. If the same standard were demanded without any engine many aeroplanes would fail to come up to it. I know cases where Handley Page, Vickers Vimy, and even Bristol Fighter aeroplanes, have been extremely difficult to manage when approaching an aerodrome in rough weather without engines or even with engines­throttled right down. The engines had to be applied solely to render the control effective. This is taken for granted by pilots and scarcely thought about.

4. Effect of Engine on control.- Even the most modern aeroplane engine may be controlled in two ways, firstly by the pilot, and secondly by mechanical faults, including faults in the, petrol system. The effect will be foreseen in the first case, may be violent and unforeseen in the second, and in general, influences: the aeroplane in four ways :­

(a) The presence or absence of slipstream will, by affecting the tail, influence the longitudinal and lateral trim of the aeroplane.

(b) Simultaneously the position of the thrust axis or axes relative to the centre of gravity will do the same when the thrust is varied.

© The engine torque varies with the horse-power developed, and naturally affects small single-engined aeroplanes to a much greater extent than large aeroplanes.

(d) The gyroscopic effect of a rotary engine may influence aeroplane when it is manoeuvred.

It will seen from the above that reactions of a complex nature may be taking place, with all of which the pilot must deal.

The pilot may be carrying out a manoeuvre approaching the limit of his aeroplane control, when engine failure will suddenly introduce a completely new set of conditions involving possibly a total loss of control.

5. Effect on Single-engined aeroplanes.- Before considering in detail the effect of engine on the control of multi-engines, it will be well to examine shortly that of single-engined aeroplanes. This must be done just so far as it affects the pilot and his power' of control over his aeroplane. There will be two main considerations; the effect of the engine on the aeroplane and the consequent movements of the controls as the pilot varies the power at will or for some particular purpose, and secondly the effect of sudden engine failure. If the pilot varies the power at will, he knows what he intends to do, and therefore has a general idea of the effect on the aeroplane. The most important, of course, is that of the slipstream on the tail. Assuming that the tail portion consists of a fin and rudder, tail plane and elevators, and that these are partly in the slipstream, various and sometimes unsymmetrical loads will be applied as the power' varies.

(a) The air of the slipstream is washed downwards. It is, also given a rotary motion by the propeller. If it were possible to design the fin symmetrically in the slipstream, there would be no force on it. However, in practice, this is very difficult to achieve, owing to the angle of incidence of the wings when landing and other considerations. Therefore in nearly all modern aeroplanes there is a tendency to turn one way with engine on r in some aeroplanes violently, in others less violently. Some of the former were provided with a shock absorber on the rudder bar to relieve the pilot's feet of strain. It was found possible to neutralise some of this turning tendency by balancing the upper portion of the rudder on the R.E.9 aeroplane. It was thought that as the upper part of the rudder was clear of the slipstream, the balanced portion had a neutralising effect owing to its angle when the slipstream was acting on the fin and the rest of the rudder.

It may be noted in passing that it has been observed that the smaller the diameter of the propeller the more violent is the action of the slipstream on the fin. A Lion D.H.9A was turned out with a propeller of a certain diameter, and exhibited a violent turning tendency. By increasing the diameter of the propeller the turning tendency was reduced to reasonable proportions.

Again, the slipstream acts on the tail plane. Most modern aeroplanes are provided with a movable tail, which is specially necessary on aeroplanes with high powered engines, for the purpose of rendering the pilot's aeroplane control adequate to meet the control requirements from engine full on to engine off. It should be noted here that the tail cannot be operated very quickly, especially in the case of a wheel control. That is why, if possible, a lever should be provided, apart from its other advantage of registering the position of the tail plane to the pilot.

Slipstream acting on a tail at a negative angle will render the aeroplane more tail heavy engine on than engine off. According to the design of the aeroplane this feature is in evidence to a greater or less degree. Pilots naturally like an aeroplane which has a small difference of trim engine on and off. In some aeroplanes the range of movement of the tail plane is not sufficient to provide adequately for this difference of trim, and elevator control, which should be available for emergencies, has to be used up in trimming the aeroplane in what ought to be its normal range of flying speeds. The greatest fault of the modern aeroplane is its inadequacy of control at low speeds, and if it is out of trim as well the fault is accentuated.

With stable aeroplanes it is possible to ascertain immediately whether the tail plane has sufficient range for flying requirements, as the aeroplane with elevators free will take up definite stable trimming speeds if they exist; with unstable aeroplanes, or aeroplanes only stable at low speeds, the problem is more complicated, and it is necessary to measure the forces on the control stick. For instance, if a pilot flies an aeroplane without any knowledge of its stability, he may find that it is nose heavy with full engine at 80 m.p.h. If it were a stable aeroplane it would be certainly as nose heavy, if not more so, at 50 m.p.h; however, if unstable, it might quite well have a neutral trimming speed at 60 m.p.h. (no force on the control stick) and be actually tail heavy at 50 m.p.h.

(b) In most single-engined aeroplanes the position of the axis of thrust, unless the aeroplane be designed for some special purpose, does not affect the pilot nearly so seriously as the effect of the slipstream. Its actual effect cannot be dissociated from that of the slipstream as it occurs simultaneously, but the axis of thrust is not usually at a great distance from the centre of gravity of the aeroplane. It should be noted that its effect may add to or subtract from that of the slipstream. Although not strictly relevant to engine control, the effect of the opening or closing of radiator shutters, especially with underslung radiators, has a marked influence on the longitudinal trim.

© The engine torque is in generated a small effect. It was noticeable on the D.H.2 when the engine was switched on and off, and on other small span aeroplanes. If the engine is operated gradually the torque is difficult to detect, but with an engine like a Monosoupape Gnome, which is switched off and on Without throttling, the effect on a small span aeroplane is at once apparent.

(d) As far as I know the gyroscopic effect of a large rotary . engine, with one or two exceptions, only arises nowadays with single-engined aeroplanes, and so consideration of it hardly assists a comparison with multi-engined aeroplanes. However, on a single-engined aeroplane this effect is felt in almost every natural manoeuvre that a pilot can carry out.

As the engine power is varied, its relations to the aeroplane control, as in (a), (b), © and (d), have been discussed as separate factors in a complex effect, such as the slipstream on the fin; or the position of the axis of thrust in its relation to the longitudinal control. But these in flight are so closely interrelated, at least to the feel of the pilot, that it may be well to consider the whole in relation to practical flying.

It might first be mentioned that the pilot may be flying along steadily and using his controls to overcome unsymmetrical forces due to, say, slipstream. The slipstream may disappear due to engine failure, and cause the unsymmetrical forces to disappear also. Because for the moment the pilot has become accustomed to them the effect is just as upsetting as if the aeroplane were subject to symmetrical forces, and unsymmetrical ones were suddenly introduced. Any sudden change of trim may necessitate the use of the aeroplane controls to maintain rectilinear flight, and the ease of doing this depends on whether the pilot is near to the margin of his control or not.

If the pilot is running up his engine on the ground, and proposes to do so without the tail being held down, he naturally opens the throttle gradually and pulls up his elevators to their maximum. The propeller, due to the position of Its thrust axis, is trying to pull him on to his nose, and he has to rely on the slipstream to make his elevators effective. It may be that his wheels are far back in relation to the centre of gravity and his elevators will not hold down the tail. If he opens the engine suddenly he will certainly tip on to his nose.

Similarly in getting off, the engine power is being increased, and the pilot is adjusting his elevators as the aeroplane gathers speed and the slipstream varies over his tail. As he gets off he will probably have to counteract the turning tendency with his rudder, or he will swing badly. He may have a slightly overbalanced rudder, in which case, at a very low speed, the rudder, when acted upon by the slipstream, may behave in a curious way, and cause him to swing from side to side.

Suppose when the aeroplane has arisen to about fifty feet the engine fails; the absence of slipstream may accentuate any possible tail-heaviness, and if the pilot is not quick with his elevators the aeroplane will automatically stall itself. Added to this, the pilot has been overcoming the turning tendency, owing to the slipstream on the fin, with his rudder, and may not appreciate immediately that the turning tendency has vanished. Thus he will tend to swing in the reverse direction, the force now being applied by him. His attitude in flight will then be highly dangerous.

If an inexperienced pilot flies an aeroplane with a strong turning tendency and a large alteration in longitudinal trim engine on and off, he may do something like this: he takes off with the tail wheel adjusted for climbing. He flies round, and before gliding in to land he winds the wheel full back. He throttles right down, glides in, and finds that he is going to overshoot badly. He decides to open the throttle and go round again for another attempt. He forgets, or has not time to wind the tail wheel forward. He finds that the nose goes up very easily, in fact too easily, the airspeed drops and a violent turning tendency develops. Before long he invites complete loss of control.

6. Effect on Multi-engined Aeroplanes.-As was mentioned before, the following remarks will be mainly confined to aeroplanes with two axes of thrust parallel to the fuselage and approximately
on the same level. Aeroplanes with three and four axes of thrust are just touched on.

The principles underlying the effects (a) and (b) mentioned in paragraphs 4 and 5 are the same for all aeroplanes. The engine torque © does not have much effect, while the gyroscopic effect (d) is not relevant nowadays to multi-engined aeroplanes. Therefore only (a) and (b) will be elaborated. The effect of the engines in large aeroplanes is considerably more important, as at present there is no device in common use to assist the pilot -in overcoming the large forces which may arise.

(a) A modern twin-engined aeroplane may have a monoplane or a biplane tail, and from one to four rudders. These may be entirely out of, or parts of them may be in either slip-Stream. On most modern aeroplanes the propellers revolve the same way, and so both slipstreams have the same sense of rotation. 'These apply unsymmetrical forces to the tail, which could be neutralised if the propellers revolved opposite ways. This was, I believe, done in the case of some early examples of the Handley Page 0/400. For economy the engines are now both made of the same hand. The effect of slipstream is similar to that on a single-engined aeroplane, only rather more complicated, and of course larger forces relative to the pilot's strength are introduced.

Suppose that a twin-engined aeroplane has two fins and rudders and that each fin and rudder is to some extent affected by the slipstream of each engine respectively. If one engine fails and its slipstream disappears, one rudder and fin is at once reduced in effectiveness. Since the rudders are interconnected the whole rudder control is reduced just when it is most wanted.

An experiment has been proposed in which the fins should be offset in such a way that, if one engine fails, the slipstream of the other, acting on the offset fin, should to some extent neutralise the turning tendency set up.

It is quite obvious that the turning tendency is most violent at low speeds, for example, when the aeroplane is climbing or taking off the ground; and on most twin-engined aeroplanes it is not possible to fly straight on one engine until a certain airspeed has been attained. This air-speed is usually considerably above the normal climbing speed.

(b) In a multi-engined aeroplane, the effect of the slipstream is important enough, but what is more important still to the pilot is the position of the axes of thrust. If there are two, they must at least be just over a propeller's diameter apart, and probably more if they are to be kept fairly low and the fuselage has to come between. It must be remembered that the aeroplane has to be controlled getting off the ground; and the lower the axes of thrust, the less liable is the aeroplane to tip on its nose before it has gathered sufficient speed for the elevators to be effective.

Apart from this, the fact of having these two axes of thrust disposed as they are introduces unsymmetrical forces of the most violent description if one engine fails. The violence in
various aeroplanes varies, due to engine power relative to size of the aeroplane, distance of engines apart, and the characteristics of' the tail. In any case, momentarily it is a troublesome thing thing for the pilot to have one engine fail when near the ground.

Naturally in any good design it is essential to keep the axes of thrust as close as possible to reduce the pilot's difficulty.

It will be on the rudders that the pilot will rely to help him if one engine fails. If added to this he has one or two more axes, of thrust disposed above the others, fresh complications arise, and render the problem of control still more complex. His elevators will now be involved, and besides the presence or absence of slipstream on the tail, the position of the top axes lnay introduce large forces. I do not think that, unless a really reliable power plant can be designed, it is fair to ask a pilot to cope with such a complexity of control, especially as It occurs on aeroplanes the size of which bring him towards the margin of his controlling powers by reason of his lack of strength. In a large aeroplane, control surfaces, though efficient, if too large for the pilot to operate successfully, are bad enough; control surfaces, small enough for the pilot to use, but too small for the control requirements of the aeroplane, are useless.

Three thrust axes parallel and in a horizontal have been used with greater success, as the pilot should mot find it so hard, owing to the increased size of the aeroplane In proportion to the power of each engine, to use his and centre power unit, or his port and centre or both outsede thus always being able to fly Without one unit.

Thrust axes disposed in a vertical plane are not only difficult in the air, but much more so on the ground, where the pilot has to manage a structure which must run along the ground on its wheels to gather speed and has to use his power to gain speed while his controls are ineffective owing the lack of it.

In getting to know an aeroplane with variously disposed thrust axes, the pilot should thoroughly familiarise himself with the various effects of the engines on the aeroplane and his power of controlling it under all circumstances - not wait for an engine to fail suddenly when he may be near to the margin of his control. Thus, when near the ground, he will see to it that he keeps as well as he can within the margin of control which happens to be small in any direction, to allow the maximum to meet an emergency. On the other hand, he will probably find that a judicious use of the engines may be made to assist his control, as in removing drift when landing and in other ways.

The design of most flying boats requires that the thrust axis or axes be comparatively high up, and I believe that considerable difficulty in flying arises out of this. In large flying boats it is, of course, possible to trim the boat by moving the crew about, but even this cannot be done with great rapidity. A high centre of thrust will mean that the boat will be much more nose heavy engines on than engines off. Probably this can be to some extent neutralised by taking advantage of the effect of the slipstream over the tail. Even then, if the engines refused to run properly when gliding down near the water, it might be quite possible for the boat to lose airspeed and approach stalling point, and for the elevator control to be insufficient to put the nose down.

As has been emphasised before, an awkward position on a very large machine is far worse for the pilot than on a small and easily controllable one.

7. Details of Engine controls on Multi-engined Aeroplanes - A consideration of the effect of the engines on the aeroplane naturally leads up to a discussion of how the pilot controls the engines, and what means he has of knowing how his engines are behaving apart from the feel of the aeroplane and the sound of the engines. What he is immediately concerned with are his throttles, the control of his petrol system, and his revolution indicators.

In a twin-engined aeroplane the pilot has much to occupy his attention. One of his hands is occupied with the wheel or control stick, in conjunction with his feet on the rudder bar. He must use his throttles at a moment's notice, so that they must be very accessible and easy to operate. There are two kinds in common use, one consisting of two simple levers side by side, the other of one lever which opens both engines at once, or can be rotated to open one and close the other. There is a difference of opinion among pilots as to which of these is preferable. The first kind has the advantage of showing approximately how much open is each throttle, the second of allowing the engines to be varied with greater ease. However, in the latter case the pilot cannot tell with great precision what is happening to either engine except by the feel of the aeroplane or by looking at his revolution indicators. To those who have not flown an aeroplane with two engines running at once it perhaps may not be immediately apparent that the pilot has lost his chief means of detecting quickly any ill behaviour of an engine. In flying a single-engined aeroplane he constantly listens to the engine, which should afford him at least some warning if it is going to fail. When both engines are running at once it is quite difficult to tell if one engine is not running as it should do, and the pilot is compelled to look at the revolution indicator or judge if the engine is missing slightly by smoke from the exhaust.

It is surprising how well a pilot can learn to manage the twin lever type of throttle, if the levers are the right distance apart, neither too close nor too far, but just so that he can with a rotary movement of the palm of his hand push one lever back and the other forward. Even on German aeroplanes, where the throttles were provided with ratchets, this was to some extent possible.

Where there are four engines to look after, the differential type of throttle lever is almost imperative, and the engines have to be run in pairs, as on the Handley Page V /1500. The essential thing to guard against is too much rotation of the lever to open one engine and close the other completely. This should in no case exceed 90°. If it actually exceeds 180°, as was the case on an early Vimy, the pilot may have one engine full open and the other closed, and actually try to turn the lever the wrong way to equalise the engines, and simply jam the throttle. If this occurs when he must act quickly, he is in a difficult position.

The system of wires and rods and the brackets which support them should be designed with the minimum of whip, so that the pilot knows exactly what he is doing when he moves the throttle lever. In complicated systems such as are bound to arise on twin-engined aeroplanes, whip is liable to occur unless the system is well designed and fitted. If the pilot has throttled down and is landing and the airspeed is very low, one engine opening slightly on its own owing to whip in the throttle control will cause him to swing violently.

Two experiments are to be carried out on a D.H.l0, one in which a synchronising gear is to be fitted to the throttle levers, the gear to be driven off each engine by means of flexible drives. The effect of this should be, in case one engine drops revolutions, automatically to throttle the other to the same revolutions. It should be possible to throw the whole gear out of action by means of releases on the throttle levers. The other experiment is to take advantage of the fact that in case of the failure of one engine, the pilot would naturally push very hard on the rudder bar to keep the aeroplane straight. In doing so he would throw into action a gear fitted to the rudder bar to throttle down the engine which was still running.

Hitherto the revolution indicators, owing presumably to the unreliability of long flexible drives, have been in nearly all eases fitted on to the side of the engine unit. The pilot cannot see them both at the same time, and has to look round first to one side and then to the other in order to do so. When taking off this is extremely awkward, and until a satisfactory transmission is obtained by which they can easily be fitted on to the dashboard, this serious difficulty will remain. For the pilot's convenience, two dials side by side would be the neatest arrangement. He would be able to synchronise his engines with great precision and ease. In a four engined aeroplane two dials with two superposed needles each could be employed.

When flying a multi-engined aeroplane, probably the ideal way would be to open all engines out slowly and together. In practice, say with even four engines, pilots cannot do this, but always prefer to open ~one pair first, and then the other pair.

This works quite well if none of the thrust axes are high off the ground; if they are, the awkwardness of opening the engines with low thrust axes and those with high thrust axes simultaneously will add to the natural difficulty of axes in such positions.

A frequent cause of engine failure on multi-engined aeroplanes has been a failure of the petrol system. If the petrol system is complicated, as is often the case, no pilot should take the aeroplane into the air without spending sufficient time on the ground to familiarise himself with its operation in every detail. In some cases the petrol system has failed owing to a mechanical defect, in other and probably more frequent cases, it has failed owing to incorrect handling by the pilot. Even if the pilot has spent some time in studying it, there may be extenuating circumstances attending a failure to handle it correctly in the air, owing to the pilot's mind being so occupied.

In very large aeroplanes the petrol system is usually handled by a mechanic, who is supposed to anticipate the pilot's requirements, so that whatever the pilot chooses to do with the engines, he may have an adequate supply of petrol. In this case the pio9t is left considerably freer to look after the aeroplane, but owing to the increased size and number of engines, he has still a great deal to do, excluding the drain on his physical energy, owing to the weight on the controls.

It was largely owing to war requirements, that is of rendering the petrol system still workable when parts of it might be out of action due to gunfire, that petrol systems became complicated. Peace requirements demand a return to the simplest kind of system, and one that imposes the least possible strain on the pilot. Unfortunately the most likely time for the petrol system to give trouble on an untested aeroplane was when it was taking off the ground at a low air-speed, as the trouble which could not be detected or located when running up on the ground, arose as soon as the aeroplane commenced to fly.

The above remarks simply emphasise the necessity for making the p~lot as comfortable as possible, for giving him a simple, accessible and easily understood mechanism for controlling the engines and petrol system, so that he may have attention left for appreciating correctly the effect of the engines on the aeroplane and using his aeroplane controls in the best way.

8. Practical Flying Notes on Twin-engined Aeroplanes.-These notes are based on flying experience with the Handley Page 0/400 fitted with twin Rolls Eagle VIII engines; an experimental one fitted with four 200 h.p. Hispano engines, mounted in tandem pairs; the Vickers Vimy with Twin Fiat and Twin Rolls engines; the German A.E.G. Bomber, and the D.H.I0 with Twin Liberty engines.

The Handley Page 0/400 was introduced and flown for a considerable time on service, without any serious troubles being reported, due to turning tendency caused by engine failure on twins. This was mainly due to the fact that relative to the power of its engines, the aeroplane was of large dimensions. If one engine dropped revolutions the turning tendency was not violent, the whole aeroplane being comparatively sluggish, due to its large moment of inertia. Curiously enough the fact that it had overbalanced rudders, though sometimes commented on, was not seriously complained of. These rudders undoubtedly did cause the aeroplane to swing from side to side when taking off the ground, and if they were abandoned in the air they immediately took charge and set up a violent swing. There was, however, little force required to prevent them doing this.

Nowadays Handley Page aeroplanes have the propellers both of the same hand; some earlier examples had propellers of opposite hand, and the difference between the two arrangements was felt by pilots. There is a turning tendency due to slip­stream, which, though not very marked, can be detected when both propellers revolve the same way. Where the propellers revolved opposite ways the turning tendency entirely disappeared.

It was when aeroplanes of smaller dimensions for the same power were flown that the first serious trouble arose due to the failure of one engine. The Vickers Vimy and the D.H.l0 both swung violently round if one engine failed, the latter more quickly than the former, owing to its small size. If the pilot is taking off the ground and has not had time to gain sufficient airspeed to fly straight on one engine, the obvious thing to do if one engine fails is to throttle the other right down, and if he cannot, by putting the nose down, attain this speed before being compelled to land, he must land wherever he is. There is no other alternative. Not only is this the case, but he must be very alert in throttling down the engine that is still running, or otherwise he will find that the aeroplane is swinging round flat, and thus his longitudinal control has lost much of its power; in fact on an aeroplane like a D.H.I0 the safest thing is undoubtedly to switch the engine off. This course immediately deprives the pilot of the assistance of any engine power, and if he can afford to control the aeroplane with the engine throttled down and not switched off, his glide is flattened and he has more chance of landing on a good piece of ground.

If there is any whip in the throttle control, the pilot will find it difficult to open the engines out evenly, either with the twin-lever type or the differential type of throttle. Whip in the throttle control of a single-engined aeroplane is annoying, but not a serious difficulty to the pilot as in a twin.
Before attempting to taxi out on a twin that has not been tested, the pilot should take all preparatory measures that are possible on the ground to ensure that his petrol system will be

satisfactory in the air. If the petrol is pumped up to a gravity tank, which feeds the engines, he should make sure that the delivery from the gravity tank is considerably in excess of the amount required by both engines, by taking the petrol flow at both carburettors simultaneously, both with the tail-skid on the ground and the aeroplane in flying position. If he is sure of an adequate flow from his gravity tank, then he is sure of enough petrol to tide him over the first few hundred feet of his climb, which is the difficult period from the aeroplane point of view. He should run up each engine separately so that he may listen to it without being confused by the noise of both running at once. He should make sure that his throttles work easily, and do not slip backwards or forwards when the hand is removed from them.

It is always wise to taxi for a certain distance before taking off (even though it is possible to take off from the position of running up), so as to give the petrol pumps (if the petrol system includes them) a chance to work a little. It is then possible while taxiing to give one or two bursts with each engine to see how it opens out, allowing the aeroplane to swing round either way.

Unless the pilot is not only accustomed to the type, but is also familiar with the particular aeroplane, it is unwise to attempt a fancy take off, such as across wind with one wing down, or by opening the throttles violently and pulling the aeroplane off the ground at a low air-speed. This may be done on a single­engined aeroplane without involving much risk if the engine fails. The pilot should open the throttles gently and take a good run over the ground if it is smooth enough to permit of this, and even when he has left the ground he should hold the nose down near the ground until he has attained an air-speed of 60 m.p.h. If one engine fails and he is 15 feet off the ground doing 45 to 50 m.p.h.., he has no chance whatsoever of controlling the swing of the aeroplane. He has only to try this at a safe height by switching off one engine at various air-speeds from 50 m.p.h. upwards and he will soon find out his power of controlling a swing. A DH.10 will swing through 90° in about 3 seconds if one engine is switched off at 50 m.p.h. The safest way to take off is with one hand on the throttles so that if one engine fails the throttles may both be pulled back. If the pilot puts the nose of the aeroplane down it will then commence to glide, and if he has sufficient height to attain the air-speed at which he can fly reasonably straight on one engine, assisted by a judicious use of bank, he can then again open out his sound engine, and use it to carry him on and effect a landing on good ground. If he is very near the ground and an engine fails, even before he can throttle down the other engine, the aeroplane will have swung through a certain angle, and thereby considerable drift will have been set up which, if there be no room to sideslip,

it will be impossible to eliminate before touching the ground. Thus he is almost certain to damage his undercarriage, though probably nothing of a more serious nature will occur.

When taking off in bumpy weather the aeroplane is slewed about in the bumps, and the sound of the engines is always less regular than in calm weather. It adds to the pilot's difficulties in detecting a faulty engine, as he can only tell this by the feel of the aeroplane, the sound of the engines, or by the revolution indicators. His first method of knowing is impaired by the bumps, as a bad bump sometimes feels similar to a swing under the influence of engine; his second method by the fact that both engines are running together and the sound of the good one obscures the sound of the bad one; his third method by the fact that it is very awkward to look round at the revolution indicators, especially when he cannot tell by other means which is the defective engine. As laid out in detail, these difficulties appear of the gravest nature. In practice an intelligent pilot has always his flying instinct to help him, which is a very difficult thing to define; but it is clear that the greatest caution should be exercised, due to the special characteristics of this type of aeroplane.

Once the pilot is clear of the ground, he may then relax his concentration, as any temporary difficulties of aeroplane control due to the effect of the engines can be dealt with in a more leisurely manner.

9. Conclusion. - Every good pilot, when he really gets to know an aeroplane, whatever its possible defects or complexities of control, evolves his own methods of ensuring safety during phases of flight which demand cautious handling; not only does he do this, but with surprising flexibility he accustoms himself to the peculiarities of engine and aeroplane control and develops an extraordinary skill in dealing with them so that he can render the aeroplane as docile to his wishes as one which involves comparatively simple problems of control.
But the pilot is undoubtedly in a much safer position if he has approached the problem using his reason to its fullest extent, rather than by trusting his instinct for everything; and he will always have new types, with peculiarities of their own, which need careful study. What is encouraging for the pilot is the fact that as time goes on applied design will step by step overcome the difficulties which were at one time thought to be insurmountable except by human flying skill.

The report has discussed the effect of the engines on the aeroplane; how this influences the pilot in controlling the aeroplane; how the pilot controls the engines; and finally the application of the whole to the flying of a twin-engined aeroplane.
  • 0

#52 piecost

piecost
  • Posts: 1318

Posted 12 July 2011 - 20:54

A Comparison of Heat Dissipation of an underslung & nose Radiator on SE5 (SE5a & SE5b)

Reports & Memoranda No. 738

Attached Files


  • 0

#53 piecost

piecost
  • Posts: 1318

Posted 12 July 2011 - 21:02

THE INFLUENCE OF MILITARY AND CIVIL REQUIREMENTS ON THE FLYING QUALITIES OF AEROPLANES

By SQUADRON LEADER R. M. HILL, M.C., A.F.C.,
OF THE EXPERIMENTAL SECTION, R.A.E.

Presented by THE DIRECTOR OF RESEARCH.
Reports and Memoranda, No. 678. June 1920.

(1) SUMMARY.-In §§ (2) and (3) is discussed the relation of the pilot's senses to the behaviour of an aeroplane in flight. The reason for this discussion is that the consciousness of the flying qualities had to be developed and their nature realised before a coherent idea could be formed of them.

§§ (3) and (4) deal with these qualities as a definite set of ideas, and the influence of military and civil flying requirements on them is discussed. § (3) is based on past experience. § (4) is an application of this experience to problems of the present and future. Finally, suggestions are made giving the writer's view of the most important directions in which experiments should be carried on.

(2) The Nature of the Flying Qualities of an Aeroplane.-It is difficult as yet to express "manoeuvrability" and "stability" quantitatively, or to define the inter-reaction of the personal factor with control. Of what certain aeroplanes feel like there is a prevailing conception that is used as a criterion by which definitions of these elusive properties are made. It is a conception moulded from a blend of qualities, various in kind and in degree, the result of the designer's attempt to give the pilot the most liberal scope for handling the aeroplane by means of his senses of sight and touch under all conditions. When the qualities which underlie the conception come to be analysed a multitude of obscurities is found; the attempt to investigate, define and classify them is involving years of research.

For a long time it was left to the pilot to translate his con­ception of the feel of an aeroplane into terms generally intelligible; ­ his description was coloured by his own predilections and as such was inimical to scientific handling. More recently, however, attempts have been made by means of recording instruments, or, failing these, accurate scientific observations, to apply a quantitative analysis in the light of which the conception can be exam­ined. It is hoped that obscure differences of opinion among pilots may be made intelligible, and a large mass of evidence accumulated which should relate more closely the practice of flying as an art to the theory of aerodynamics.

By a process of evolution this point of view has developed Itself. In the early days of ~flying there must have come a growing consciousness of specific flying qualities; once they were appreciated, came the desirable to improve those which furthered practical objects. In. short, flying, once a practical proposition, was shaped bytwo main considerations, military and civil.

(3) The Realisation of the Flying Qualities. - During the Infancy of mechanical flight the sheer hazard of remaining aloft must have to obsessed the pilot that he had little opportunity for speculation about the flying qualities of his aeroplane, much less about what was desirable and its attainment. So long as he was on an even keel and in no imminent danger of losing control he was satisfied. Mechanical flight was in itself the end. Not until it was applied to some purpose beyond the mere demonstration of its existence were qualities sought particularly favourable to any purpose.

The demand that aeroplanes should fulfil certain conditions started to breed particular flying qualitiesl but to bear any meaning, or for their need to be brought home to him, these flying qualities had actually first to be experienced by the pilot - as It were by chance. He had to do a vertical bank before he knew what he desired of a rudder. His senses were the only medium for the expression of the qualities; their attainment was neither possible to any extent by scientific prediction, nor by accumulated experience, since there was none. Although the pilot must have realised vaguely that certain qualities were desirable they were as yet outside the range of his experience.

Early aeroplanes, such as the Wright biplane, must have required an equilibrist of the first order to fly them. Their qualities as flying machines must have taxed human skill to the uttermost in satisfying the elementary requirements of flight; in other words, while Just rendering the maintenance of equilibrium possible, they were bad.

At the outbreak of war aeroplanes were beginning to be used for commercial purposes, and a small amount of military development was in progress. A Cody biplane was not more favourable to military requirements than a Grahame White. The influence of practical requirements on their flying qualities had not as yet been very marked.

(4) The Influence of Military Requirements on Flying Qualities. - As soon as the pilot found himself on service the consideration, of taking off, maintaining equilibrium, manoeuvring and landing, that very consideration which had so sharply focussed his attention vanished from his mind. He had a machine which would take him into the air and give him a striking position or a view of enemy country, and the realisation of battle was far more impressive' than that of the flying risk. That the disappearance of preoccupation with the flying risk should make room for a truer appreciation of flying qualities seems strange, yet for the first time the pilot could review the qualities of his aeroplane in a detached mood, for his attitude was completely altered.

Military requirements changed so rapidly that those who flew found it difficult to express coherent requests for improvement, but small improvements yielded apparently disproportionate results, due to the operation of the human element. Although the limitation of the normal human senses is a fixed coefficient, the increasing efficiency of the mechanical contrivances gave the pilot behind the machine increased confidence; not in direct proportion to their increase in mechanical efficiency, but in proportion to that increase multiplied by the confidence it bred. A trimming tail­plane may make all the difference in the world. Fresh departures in design introduced new tactics, and in those tactics was born the stimulus to new design.

Improvement would have been still more rapid had not a steady flow of production to be maintained, a break in which would have meant disaster at the front. If the requirements were diverse and subject to rapid change, at least some of the broad issues were clear.

Performance.- High performance compensates for many deficiencies in other respects and ranks first of the qualities in the confidence it gives. Many fighting aeroplanes, after being flown on service for some time with certain engines, were fitted with more powerful ones. In most cases the increase of power made them pleasanter to fly, and added a feeling of security in the air. Up to a point the controls were rendered more effective without an excessive increase in weight, but beyond this point the increased power simply made the controls heavier and the added weight discounted the value to the pilot of their enhanced effectiveness. The 110 h.p. Morane monoplane, the 90h.p. DH.6 and the 150 h.p. B.R.l Camel were generally considered an improvement over the same aeroplanes fitted with 80 h.p., 70 h.p., and 110 h.p. engines respectively; but when the 200 h.p. Arab Bristol Scout F (which serves as an example though it never saw service) was fitted with a 300 h.p. Cosmos Mercury, the weight on the controls was increased out of all proportion.

On service, performance is the prime means of attaining the effective striking position; it is the life of the fighting aeroplane, the capacity to manoeuvre, the power to out­distance an opponent, the extra two or three miles an hour which is everything to those who have experienced it. It gives height quickly and the possibility of very high speed in bursts that aerial combat requires. It should always be borne in mind how much lower is the ceiling of an average formation of aeroplanes than that of a single unit.

View -Its psychological effect on the pilot makes this quality most important for military purposes. In an aeroplane designed for every requirement of war if such a one can be imagined, the pilot wants the maximum view generally; because it inspires confidence, and particularly because It enables him to keep his opponent in sight. If the pilot feels boxed in with a sense of lurking danger his effective handling of the aeroplane is destroyed. The Fokker monoplane pilots, because they could only see below them in diving position made a practice of diving once only, and If the opponent was missed went right down out of range. Fine manoeuvrability is useless if unrelated to an opponent which the pilot can see.

View is attained by the position of the pilot in the fuselage relative to the wings and tail, by the absence of unnecessary obstruction caused by the fairing necessary to protect him and reduce resistance, and enhanced by manoeuvrability whereby he can quickly and adjust his arcs of vision. Manoeuvrability and view are thus closely interdependent; one is used by the pilot for the consecutive elimination of his blind arcs, the other to manoeuvre to good effect based on his increased arcs of vision. On an aeroplane with bad ,view, owing to his acute sense of ignorance of his opponent’s position, the pilot cannot manoeuvre effectively either to see better or to fight more vigorously. If he can see well initially he can use his manoeuvrability to advantage in both these ways.

© Manoeuvrability.-An aeroplane may be utterly dependent on the pilot for its control, such as the Spad and Sopwith Camel; or if trimmed correctly it may maintain a normal attitude of flight with the pilot's hands off the controls and possibly his feet, such as the S.E.5A. This, for which in practice the pilot has usually had to pay by a certain loss of manoeuvrability, should in the ideal aeroplane involve no such penalty. The Martynside F.4 is a big advance in the right direction.

Assuming his opponent to be flying an aeroplane of equal performance, the pilot can gain a favourable striking position only by out-manoeuvring him. The real fighting pilot manoeuvring for position is not often showy, but every turn is the result of exquisite judgment and foresight. To shoot effectlvely he must have a responsive but steady gun platform. Finally, If hi engine is crippled he must have manoeuvrability to make himself a difficult target.

Stability. - Suppose, even in a single seater scout the pilot wants to rectify a gun stoppage or look at maps, he will find his task an extremely difficult one if the moment he releases the longitudinal and lateral control the aeroplane nose dives or stalls. The ideal aeroplane which is to carry out the whole range of military duties should undoubtedly be stable. In such an aeroplane the pilot may require to examine detailed maps and compare them with the ground, adjust bombsights, care for his guns, work a wireless key, apart from concentration of the aeroplane instruments. If the pilot loses touch with the horizon by moving his head about, looking at objects inside the aeroplane or on the ground, or at aeroplanes above, and his aeroplane is unstable, it immediately runs away with him.

The late Captain Ball used to take advantage of this in breaking up hostile formations. Each pilot in the formation would be keeping station with his eyes fixed on the leader, using at the same time his sense of the horizon. Captain Ball found that by creeping above the formation un­observed and firing a few shots he could make the pilots look up instinctively, lose concentration of control and open out. These Albatross and Halberstadt Scouts were almost certainly unstable.

Loading. - This undoubtedly influences the control of an aeroplane. In general, a heavily loaded aeroplane is seldom "flicky" on the controls, if balanced elevators with no tailplanes are excluded. Heavy loading always makes landing more precarious, but within limits this is not serious in an aeroplane for war purposes. It appears to contribute in some measure towards a steady gun platform, in the Spad and Nieuport Scout, for example.
Steadiness.- There is a certain quality which is differentiated in the pilot's mind from stability, and which for lack of a better word may be called" steadiness." It is usually the result of large dimensions, and where the aeroplane is small is influenced by loading.

Comfort.- The comfort. of the pilot influences his whole appreciation of the flying qualities of the aeroplane. During the war the pilot's comfort often had to give place to considerations such as the complete accessibility of the guns and the convenience and position of the ammunition drums.

The qualities of a fighting aeroplane most obvious to the pilot have now been stated, but only incidental mention has been made of their interdependence. In actual fact they are very closely associated, and if a quality is taken, as it were, out of its context, it is frequently misappreciated. Some instances of this inter­dependence may now be mentioned.

Manoeuvrability, the kinds of responsiveness concurrent with light and heavy loading, stability and steadiness are flying qualities; view and comfort influence the pilot's appreciation of' them.

Provided that the aeroplane is suitable to the engine, the pilot of' a high performance aeroplane is the gainer in everything. Compare, for instance, the 110 h.p. Nieuport Scout with the 80 h.p. Morane Scout, the S.E.5A. with the Sopwith Camel. The small dimensions of the Spad assisted its view and manoeuvrability, but for military purposes, such as bombing, a certain steadiness as apart from stability is required. This steadiness usually involves large dimensions. It can be present without, though it is often assisted by, stability. The load and fuel for bombing and long distance reconnaissance again involve large dimensions. For single seater and small two seater fighting aeroplanes manoeuvrability is essential. Small dimensions run parallel to manoeuvrability, and of the possible results good view is a great asset, while heavy loading usually improves the gun platform. The popularity of positive stability has been in the inverse ratio of its adverse effect on manoeuvrability.

The attempt to solve the problem of these requirements naturally resulted in many different types of aeroplane. Although difficult to embody flying qualities universally favourable in one type, it was found that where one quality was sacrificed a compensation of a different kind was gained. For instance, where manoeuvrability was lost owing to large dimensions, more guns could be carried for the same reason. Thus, in some cases, a fairly effective compromise was made; in others, however, certain qualities were definitely sacrificed.

The above remarks may be better illustrated if they are applied to a definite military type - for instance, the single seater fighting scout. A scout pilot requires the following :-a steady and responsive gun platform, and a highly manoeuvrable aeroplane, which will allow him to leave the controls to look after his guns without running away with him.

Assuming the striking position to have been gained by performance, the requirements of the platform and the flying qualities which make or mar as manoeuvrability, loading and stability, may now be examined.

The ideal aerial gun for a single seater scout should be susceptible to sensitive intentional movements, without appreciable time-lag. If rigid it is easy to keep the sight on the target, but not to bring there. It must, however, respond evenly to the pilot's hand, not so as to disturb his aim. In short, the pilot wants to nose of the aeroplane with one of his limbs, instead of to regard it as a separate agent, to be forced, coaxed, or juggled into the correct position.

Take the essence of manoeuvrability. The aeroplane must respond easily to rapid course movements, while resisting sufficiently for the pilot to feel it; it must be readily swung through 360º in almost any plane, and yet be delicate enough for the sight of the fixed guns to be registered. If "flickiness" which gives the impression of extreme manoeuvrability, is present in a high degree, then, especially at high speeds, the aeroplane will not be a steady gun platform. If its converse "stiffness" which gives the impression of extreme steadiness, is present, then at similar speed the aeroplane will not be a responsive gun platform. The gun platform must be responsive without being "flicky" and steady without being "stiff." It should not be necessary either to sacrifice the best qualities of manoeuvrability, if this "flickiness" or "superliveliness" in favour with so many pilots, can be dispensed with, or to impair them by "stiffness" in the guise of steadiness.

The steady gun platform should rather be enhanced than adversely affected by a kind of manoeuvrability which is at once an asset to the man in his ro1e of gunner and pilot.

It seems that "flickiness" is to some extent a function of loading, and "stiffness" of stability; that responsiveness is independent of loading, but obviously affected by "stiffness." Take the Sopwith Pup, which is about neutral with elevators fixed, and the Spad, which is just unstable with elevators fixed; the former lightly loaded, the latter heavily. The Spad goes into the dive at a touch, yet settles quickly at any desired speed and is a steady gun platform, whereas the Pup is inclined to be "flicky" and to hunt. Both are beautifully responsive.

In my experience heavily loaded scouts are rarely" flicky" and often very responsive. It may be for this reason. A lightly loaded aeroplane flies at a smaller angle of incidence (and consequently nearer the angle of no lift) than a heavily loaded one, and a small intentional change of incidence on the former may have a much greater effect on the actual loading of the wings in flight than an identical change on the latter, which at the same speed flies at a greater angle of incidence. Thus the lightly loaded aeroplane feels less steady than the heavily loaded one. Again, an aeroplane behaves so differently at its various speeds and angles of incidence, and may make a good gun platform at some and a bad one at others. The times when steady shooting is most vital are during a dive and a zoom. Heavy loading is advantageous in every way except a zoom, where light loading gives a lower stalling speed. When considering the relative weight on the controls in diving and zooming, the increase of weight due to high air-speed must always be allowed for.

Over the effect of stability on manoeuvrability a controversy raged fiercely and passed through various phases. The early scouts were eminently unstable; those with fixed tailplanes, longitudinally unstable elevators free; those with no tailplanes and balanced elevators, violently unstable elevators free, and some stable with them fixed (Halberstadt), some unstable (Morane).

There was a reaction against the first unstable types, and a highly stable type was produced. Immediately a school arose which preached against a high degree of stability and maintained that really good manoeuvrability was spoilt by it. Yet if an aeroplane is to look after itself at all it must possess a certain amount of longitudinal and lateral stability, the latter involving all the questions of the rudder and fin. The fighting pilot, just as physical comfort in an aeroplane gives him a feeling of security and enhances his powers of endurance, needs assistance from the aeroplane rather than interference in his many duties, more especially If his physical reserve power is diminished owing to altitude. He wants assistance both when his hands are on the controls and when they are removed.

It is quite clear that extremes of stability should be avoided. The highly unstable aeroplane makes a big call on the pilot's energy the whole time, runs away with him if he leaves the controls, and renders him liable in the course of violent manoeuvring to get into extremely awkward positions in which he is very vulnerable.

The highly stable aeroplane, on the other hand, while it will fly itself at most speeds with a trimming tail, is usually less manoeuvrable, stiff and unresponsive in a dive, and generally more unwieldy.

Take the Sopwith Camel and the S.E.5A., two conceptions diametrically opposed. The S.E.5A is stable with.elevators free, the Camel unstable with them fixed. The Camel is more lightly loaded than the S.E.5A., and has, with the exception of the rudder, more powerful controls. In a dive the Camel is"flicky". probably due to its lighter loading and excessive longitudinal instability; the S.E.5A.is very steady, but dull to small intentional movements. In a zoom the Camel improves greatly owing to its lighter loading and instability; the S.E.5A. is inclined to become languid, and its stability near stalling speed draws down the nose, so that a large backward movement of the stick has to be made.

In flying a Camel, the pilot has always to be making small movements of the controls in the endeavour to pick up a steady speed, which it is difficult to maintain. Going into a dive, compared with the S.E.5A., the elevators of the Camel work the reverse way. The control stick, though initially pushed forward, has to be pulled right in again, while the S.E.5A. If the stick is pushed forward, will drop its nose, creep up to its trimming speed and stay there. The S.E.5A. is impossible to fly inverted; the Camel may remain so unintentionally.

The above remarks show up some great advantages of positive stability. At the same time there is no doubt that the conception of the Camel as a fighting aeroplane made an irresistible appeal to a certain class of pilot. The effectiveness of a fighting aeroplane must be taken as the product of its flying qualities and the confidence they inspire in the pilot. Considering its instability with all the attendant disadvantages, the Camel was a surprisingly good war aeroplane; but it never could be comparable with the S.E.5A. because, even assuming that it possessed certain qualities that were equal or even superior, the difference in performance ­ from 7 to 10 m.p.h. at 15,000 feet - and in view, gave the S.E.5A. a Superiority that only flghting pilots really appreciated.

(5) The Influence of civil requirements on Flying qualities. ­ The order in which the flying qualities of military aeroplanes were taken was intended as far as possible to bear reference to their importance to the pilot. They were so closely interdependent that in a given aeroplane the lack of a flying quality, insignificant in itself, might seriously detract from the value of a vital one. If; then, allowance is made for this, the qualities of civil aeroplanes will be treated in a similar way. In the following section the flying qualities discussed will be those for commercial aeroplanes, as that is assumed to be by far their most important civil use. The small single seater sporting type will be ignored.

If commercial aeroplanes are to compete successfully with other forms of transport, they must compete on grounds of speed, economy and reliability, but such an achievement will not be of the slightest value until a standard of safety nearer to that reached by the railway and steamship is attained. There is still a tendency to set up a false standard of safety; a cross-country flight is safe If thought of in terms of flying, but is it yet so compared with the present means of transport ? The commercial aeroplane must transport its freight of passengers, mails or cargo in a shorter time, including the time of collection from and distribution to business centres, than could be done in any other way; the service must pay and must attract and retain the confidence of the commercial and travelling world. Safety in war was almost synonymous with striking power; safety in peace is absolute. Every quality, every line of research, every effort at improvement should lead in this one direction. Just as the pilot's attitude changed when he went on service, now it must again revert, this time with a great fund of experience behind it.

The most pressing difficulties of the moment seem to be those of flying to a place and landing when there is mist down to the ground, of the comparative unreliability of the light aero engine, of the space which any aeroplane requires to land in, and of the Imperfect control of small aeroplanes at low speeds and large ones at any speed.

Safety.-Any quality that is observed after the engine or engines have been once started will be regarded as a flying quality. A ship, even before it gets under way, is already supported in its element; an aeroplane is not, so there are qualities desirable other than these confined essentially to the air. It is necessary to consider the aeroplane under two general sets of conditions; firstly, in flight, and secondly, leaving the ground, landing, and the subsequent run. The importance of the second set is frequently under-estimated, although from it probably come the greatest losses from a commercial point of view.

Even if the aeroplane's power plant were made as reliable as that of any other form of transport, the aeroplane would be incomparably worse off. The engines of a ship stop and there is a considerable period before any danger need usually be anticipated; the stoppage of an aeroplane's engines implies great danger from the absolute safety point of view. So to compete on a similar basis, the motive power of the aeroplane should theoretically be made more reliable than any others. The maintenance of an all-weather service increases the probability of crashes due to forced landings. It is not sufficient not to risk a crash oftener than every six months; humanly speaking, crashes must be avoided.

This report is not concerned with the development of the power plant itself, but it should be noted that the measure of its reliability is the equivalent to the pilot of mental freedom; and while he has anything to do with the control of it in flight the mechanism must be simple and easily understood. It seems that for some time the pilot will at least control the throttles of his engines; the time is not yet near when he can do so by telegraph. It has been suggested that his case is parallel to that of the submarine commander who has to make rapid use of his engines in shallow water; but no machinery-short of his own hand gives the pilot confidence when he himself is "in shallow water." The effect of his engines is so bound up with the effect of his aeroplane controls that any lag in response, even if small, would utterly upset his mental concentration.
But he could, with advantage, be relieved of many controls connected with the engines and fuel supply which are now a source rather of embarrassment than assistance to him. Even in fairly large aeroplanes an engineer is not usually considered worth his weight, although on a modern twin engined aeroplane the pilot has really too much to look after as well as fly.

The pilot may be almost up to the limit of his achievement in simultaneous concentration on the various elements of his control mechanism, and in exertion of physical energy in flying. Little more should be expected of him than he now gives in controlling a large aeroplane; indeed, every effort should be made, as the aeroplane grows larger and more complicated, to leave him freer both mentally and physically. That is what can be done for the pilot in the direction of safety.

For commercial use, the single-engined type of aeroplane similar to the D.H.9A in type may well persist, owing to its general handiness and straightforward control in the air.

It is probable/that there will be a more definite adherence to the multi-engined aeroplane of the Handley Page 0/400 and V /1500 types, which will bring them into common use. It is certain that larger aeroplanes still will be tried, bringing with them acute problems of control. There is something attractive from the commercial point of view in the giant type, and in order to make it a really safe proposition a long process of experiment will be necessary. Pilots have coped with most of the difficulties of control on the smaller aeroplanes because the control forces involved have been comparatively small. Similar difficulties in larger aeroplanes are liable to be under-estimated, because the effect on the pilot of the greatly increased forces is not fully enough appreciated. On a small aeroplane the pilot thinks nothing of suddenly opening the throttle with the tail adjusted for gliding; on a larger aeroplane variation of engine power without appropriate tail adjustment may introduce extremely large forces on the pilot's hand.

Apart from fire in the air, the risk of which is steadily diminishing, the phases of flying which embrace most of the sources of danger are those of leaving, flying near and approaching the ground; in the first and last cases the speed is frequently near to stalling speed, and in all three there is little time to rectify an error in control. Given enough height a pilot should be able to overcome almost any difficulty of control. At a safe altitude the sense of having plenty of time to overcome difficulties assists him to act calmly, which is nine-tenths of the battle. A pilot is exceptional if he has the coolness to hold the control stick forward steadily while attempting to recover from a spin very near the ground, although he knows that it is the only means of saving himself. The instinct to forget that he is stalled, to use his elevators as if this were not so, overcomes his reason, and precipitates many crashes that might possibly have been avoided at the last moment. -When just about to hit the ground in a spin there is sometimes a strange unaccountable sense of the controls being jammed, of which I have heard from others and had personal experience. This all goes to show that the pilot cannot be treated in any sense as a machine and that the instinct to use the controls in a direct way, when the situation demands the use of an indirect one, is powerful under the influence of emotional stress.

If the pilot of a large aeroplane, with a complicated control due to the effect of variously disposed thrust axes, were asked to control it without being given the feel of the controls, his success would depend rather on a display of his own skill than on the amenities of such control. It is not the feel that leads him to make mistakes with the controls, but a false instinct near the ground which operates against his better judgment; to the pilot the feel is one of his most valuable means of maintaining equilibrium. It is essential for some considerable time to come that he should be allowed his sense of touch as well as of sight to control the aeroplane. But feel is not enough; the pilot must have his sense of horizon or certain instruments to make three­dimensional control possible.

It has now been proved that aeroplanes can be flown perfectly in continuous cloud or mist by the use of the turn-indicator, bubble, airspeed and compass, so long as the speed is kept, say, ten to fifteen miles an hour above stalling speed; but the decrease in power of the control, with the correspondingly rapid onset of large disturbing forces at speeds approaching stalling, at once make the aeroplane feel capricious. The use of instruments becomes increasingly difficult, and it is at these speeds that an aeroplane leaves or approaches the ground. Supposing that a device that would automatically land the aeroplane on reasonably smooth ground had been perfected, and that by some n1eans provision had been made, such as a system of captive balloons, to convey to a pilot approaching the position of the aerodrome that there were no obstructions within a reasonable distance, the control at low speeds would have to be greatly improved before he could, with confidence, manoeuvre the aeroplane to land it.

It is assumed that all commercial aircraft will fly above cloud and mist up to heights at least of 10,000 ft. There are, however, very few days on which the clouds are not in layers, so that it should be possible to observe the balloons at a reasonably low altitude. In short, it does not seem impossible that a pilot could be brought by means of wireless to the approximate position of approach to the landing ground obscured by mist or very low cloud, that the balloons could be arranged so as to give him its exact location, that he could set the aeroplane to a steady glide at a certain distance from the balloons according to their height, and that a device fixed to the aeroplane could flatten it out on to the ground in safety. It is even conceivable that in time this sequence of operations might be brought to a reasonable pitch of safety, though it is beyond doubt that the first experiments aiming at the solution of this difficult problem would not be free from danger.

Stability.-Commercial aircraft will have to be stable. It is practically impossible, without a great expenditure of the pilot's energy, to fly an unstable aeroplane through continuous cloud. The larger the aeroplane the worse it is for the pilot. The great achievements of the Vickers Vimy seem to detract from the positive value of stability. When trimmed to fly reasonably, it is only just stable at low speeds, and unstable throughout .the rest of the normal flying range. It can only be said that its achievements have been in spite of this handicap.

In dealing with military aircraft emphasis was laid on the "stiffness" arising from extreme positive stability, which was directly opposed to responsiveness for the gun platform. If the degree of stability required for commercial aircraft results in a loss of responsiveness, the loss should not be so important, firstly, because a lower degree of responsiveness will serve for navigation, and, secondly, the larger aeroplane is naturally more sluggish, so that the effect of stability on responsiveness is less marked. Extremes of stability in large aeroplanes result not so much in lack of responsiveness as in the appearance of large forces on the control stick; in the case of positive stability in the direction of a return of the trimming speed, in the case of negative stability of a divergence. The Handley Page 0/400 would only feel nose heavy in a dive if it were badly out of trim; a Vickers Vimy feels so because it is trying to diverge from its unstable trimming speed. At 120 m.p.h. this force is so considerable as to cause the pilot great exertion in pulling the nose of the aeroplane up.

All commercial aeroplanes should be at least as stable laterally as the S.E.5A. With engine full on and rudder held to fly straight, the aeroplane describes a lateral oscillation which appears to continue indefinitely without increasing or decreasing. With propeller stopped and rudder free, a similar oscillation occurs, seemingly in tune with the logitudinal period. This amount of stability in a larger and steadier aeroplane would give the pilot a, very fair basis for navigation, but if it were increased to any extent it would probably render the aeroplane too stiff for sensitive control. The instability in this respect of the Rolls Bristol Fighter makes it extremely difficult to keep an accurate compass course even when not in cloud. Some examples of the Puma Bristol are really bad, and the nose will swing to either side if continual checking movements of the rudder are not made.

With a form of tail adjustment which can be used quickly an aeroplane which possesses a considerable amount or longitudinal stability should be responsive enough for commercial flying requirements. The various factors which affect longitudinal stability, such as the C.G. position and the relative size of the tail, have long been the subject of close mathematical investigation, but judging by present practice insufficient application of this work has been made In the analysis of certain characteristics in which the pilot is vitally interested. Some aeroplanes are extremely sensitive to changes in the position of the load, others can be loaded up in the most extraordinary way and yet can be quite comfortable to fly. The Avro training biplane and the Handley Page 0/400 are examples of the latter; the R.E.8 and Vickers Vimy of the former.

Highly unstable aeroplanes like the early D.H.6 and the Sopwith Camel were usually trimmed to have an unstable trimming speed (no force on the stick) somewhere near their comfortable cruising speed, engine at half throttle. - With engine full on the unstable trimming speed was increased and they felt tail heavy throughout the greater part of their normal speed range; with engine off the unstable trimming speed was lowered and they felt nose heavy throughout the greater part of their range. At the same time in a general way instability decreased towards stalling and increased at high speeds. If they were not trimmed so as to feel tail heavy engine full on over the lower part of their range, there was a large force to hold them up in a dive. The Sopwith Dolphin and the Sopwith Dragon normally trimmed, seem to have an unstable trimming speed with full engine at about 90 m.p.h. If the factors affecting stability are changed to make an aeroplane less unstable one of two things seems to happen; either it becomes in trim at nearly all of its speeds - a characteristic much appreciated by the pilot - or it becomes stable at low speeds and actually shows a stable trimming speed, while retaining the characteristics of great instability at high speeds, showing at some point an unstable trimming speed. The flying feel at speeds between the stable and unstable trimming speeds is of extreme interest, for the aeroplane hesitates as if it could not make up its mind what speed in this range it should settle at. This is a characteristic of the Vickers Vimy. If an aeroplane is made more stable still, it wants to return violently to its trimming speed, and considerable force comes on to the control stick. By the position in the speed range of its trimming speed a pilot says it is nose or tail heavy. The operation of this force is intelligible to him, but where two trimming speeds of an opposite character occur in the normal range, his justification can well be understood. He cannot then express nose or tail heaviness in simple terms.

Between the stable and unstable aeroplane at and near the stalling speed there is a great difference in behaviour which affects ease of landing. The stable aeroplane tries to put its nose down violently, and necessitates a vigorous upward movenent of the elevators at stalling. Unless the upward movement is correct in time and amount, the tailplane bumps badly on the ground. The unstable
aeroplane only needs a smaller and more deliberate upward movement. The amount of longitudinal stability should not be so great as to make landing really difficult.

There seem to be certain harmonious combinations of the factors mentioned above which should produce a pleasant amount of longitudinal stability without much force on the control stick at any speed, which should eliminate undue sensitiveness to small changes of C.G., and allow fully enough responsiveness for commercial flying.

Manoeuvrability. - In commercial flying, beyond a relatively low degree of responsiveness for other purposes, manoeuvrability is scarcely wanted by the pilot except to ensure safety. Although it obviously takes more time to carry out a given manoeuvre on a large aeroplane than on a small one, what must be ensured is a normal response to the controls. Time taken by the aeroplane to assume a desired bank is very different to time lag between the pilot's intention to bank, i.e., his initial movement of the controls, and the actual commencement of the banking. Whatever the size of the aeroplane, the pilot must be confident that it will 'answer at once, although it may take a considerable time to complete the manoeuvre. For instance, a severe drift to starboard near the ground may be neutralised by a sideslip to port. If the aeroplane is sluggish in answering to the controls put over to sideslip, the drift may have assumed such proportions as to make it impossible to side­slip the other way. If, on the other hand, it answers immediately, the drift can be kept under control.

The average single-engined aeroplane is fairly satisfactory on the controls except at low speeds, and the control forces are not usually such as to embarrass the pilot. The present twin and four-engined aeroplanes are less satisfactory, mainly because the control forces are relatively larger, and also because of the introduction of more than one thrust axis. It would be a large step beyond this to ensure that the resultant thrust from more than one propeller passed always through one point, and thus simplified the aeroplane control. Therefore, apart from the necessity of improving the control of any aeroplane near stalling, it will be vital to investigate every means of keeping the control forces on the pilot's hand as small as possible consistent with adequate control surfaces.

One method, that of sub-dividing control surfaces, such as a rudder, into several rudders of smaller chord, has met with considerable success; for, although balanced control surfaces may be fairly safe on smaller aeroplanes if the proportion of balance is reasonable, they are not so on large ones. Though normally they feel light and easy, near stalling they may feel very heavy. Multiple unbalanced surfaces on a large aeroplane do not normally feel so light as an equivalent single balanced one, but they do feel normal at all speeds.

Another method is to employ some form of relay control to reduce the control forces while retaining the feel. A large aeroplane can never feel exactly like a small one because it is bound to move more slowly, but could the pilot be left with a certain proportion of the force on the controls he would be given some indication of what was happening: In the relay controls tested on the ailerons of a Handley Page 0/400 at the R.A.E. a step has been made towards the controlling of big aeroplanes, and at speeds considerably above stalling these controls might be employed with safety. But, although they greatly reduce the forces, the relation of their feel to that of the ordinary control is not close enough for a pilot to use them with confidence in taking off or landing. They are in the stage where they could well be used when at a height to reduce the fatigue of controlling an aeroplane that could be safely taken off and landed Without them, but not on an aeroplane which, in being taken off, might require more force than the pilot could safely be asked to exert. They do not introduce the violent caprice of a highly balanced control surface, but where they are to be relied on utterly any abnormality on their part is unsafe. When the Handley Page 0/400 was put on a bank with the relay control in gear, and the control stick put back to normal, there was a tendency to continue to bank even with the best type of relay control. That is, there was a tendency to overshoot in each case the normal movement of the controls, for which the pilot had to make an allowance. It will be seen that combined with the behaviour of the longitudinal control of a. stable aeroplane when getting off or landing, the effect of relay controls in their present state would be too much for the pilot, even though the forces were not large. The difficulties experienced with these relay controls should not be insurmountable if they are experimented with sufficiently, and in my opinion a limit to the size of the aeroplane has been reached even judged by, the present standard of safety in control, if relay controls are not developed.

Especially in considering the control of large aeroplanes, the set of conditions obtaining when the aeroplane is running over the ground at less than stalling speed and is only partially airborne is most important. An aeroplane may be made to balance and to be controlled safely in the air but may have an abnormally high C.G. with regard to the wheels. Such a structure is top-heavy on the ground and will occasion the pilot difficulty in getting it off. To ensure safety under these conditions the C.G. and thrust axes should be kept as low as possible consistent with air requirements. On a twin-engined aeroplane like the D.H.IO a considerable tipping tendency is felt when the engines are first opened out and before the tail plane and elevators become effective. Even if the engines are opened out with reasonable deliberation, this is a sudden effect, and the pilot has to pull up the elevators to their full extent to counteract it; it is one which might assume very large proportions in getting off a large aeroplane with C.G. and thrust axes high relative to the ground. The position and design of the undercarriage is also an important factor in taking off the ground. The present types of undercarriage, mostly the product of military requirements, should be capable of extensive improvement. If a pair of wheels, strong enough to take the whole weight of the aeroplane, could be arranged well forward, the tipping tendency when getting off and possibly landing, could be prevented from becoming serious. Undercarriages like this would involve more weight, but it might be weight well expended.

Large aeroplanes will never be so difficult to land as small ones because, irrespective of loading, they are bound to be more sluggish and give the pilot more time to think. However, a device which, hanging below the undercarriage, would flatten out the aeroplane from a steady glide by operating the elevators as it came in contact with the ground, would be a great asset if it could be perfected. The chief obstacle at present seems to be the uneven behaviour of the aeroplane just above stalling speed. As the incidence approaches stalling the speed drops so quickly that a slightly incorrect use of the elevators utterly spoils a good landing. To reproduce by an automatic device the use of the elevators while landing will necessitate the device being far from a simple one.

(d) Performance.- High performance ranks by no means first of the requirements of a commercial aeroplane. Its value is relatively low in the sense that other considerations may be allowed in some degree to interfere with it without sensibly impairing the value of the aeroplane. It is unnecessary here to emphasise what has been said about performance in war; perhaps pilots have come to look on an aeroplane with a performance less than that of the latest military ones with a certain contempt, but on a service it may be considerably more economical to use aeroplanes whose performance has not been pushed to a high figure. Provided that they can compete favourably with other means of transport, little more, for the moment, is required.
A comparatively low cruising speed would be adequate if it were not that the effect of an adverse wind may halve the ground speed. In order that a considerable reserve of speed may be in hand the figure of this cruising speed must still be kept high. Climb should not be so important as speed, its main value being to enable the aeroplane to rise from the ground more rapidly and hence with greater safety. Present-day aeroplanes of the twin-engined type take a considerable time to get off when fully loaded, and are compelled to climb at a low altitude over any obstacles in their line of flight. If the aeroplane feels definitely under­powered, the pilot suffers from lack of confidence, and getting off near the ground may have to manoeuvre at a low speed. Provided, then, that it has enough power to feel a safe flying machine when fully loaded, its actual speed and climb will almost certainly be settled by commercial requirements.

(e) Loading.-It is probable that commercial aeroplanes will be fairly heavily loaded. Up to a certain point a heavily loaded aeroplane feels steadier to fly than a lightly loaded one, and when it has to land after a journey it should have used up the greater part of its fuel so that its stalling speed will be lower than at the start. Excluding developments in wing design, on twin-engined aeroplanes it would be unsafe to exceed the present-day figures for loading. If they are to be exceeded, the first step is to see if the present fixed form of wing could be improved on, and by means of full-scale experiments to investigate the practical value, if any, of wing surfaces variable in form, without more regard to mechanical neatness and simplicity than is demanded by accurate working conditions. The ultimate value of such 'wing surfaces will always be relative to the extra weight they involve, so that a further step would be to see if they could be made light enough, consistent with the requisite strength, to be practicable.

(f) Steadiness.- Commercial aeroplanes flying for long distances will have to be navigated; in the case of large ones by a regular navigator. It has been advanced that for navigation a comparatively low degree of responsiveness is required, but the aeroplane must be steady and capable of being flown at a steady airspeed if reliable observations are to be taken. In large aeroplanes, which will probably be stable, this steadiness will come partly from size, partly from stability; but in the smaller types everything should be done to render the conditions favourable to the maintenance of a good compass course. The D.H.9A is good in this respect; the Rolls-Royce Bristol Fighter unsatisfactory.

(g) View. - For commercial flying the pilot wants a good view downwards and generally of the horizon to assist steady flying. His view upwards is not so important. I have not flown an aeroplane in which the pilot is completely enclosed, but should imagine that this would have an adverse effect on the handling of the aeroplane. The average pilot likes to be well screened, but at the same time dislikes a cramped, shut-in sensation when flying owing mainly to military considerations, where the best view was essential; it has been customary on multi-engined aeroplanes to place the pilot right in the nose of the aeroplane, in which position he undoubtedly has the best view. But if the aeroplane turns on to its nose, not necessarily involving a very serious crash, he is likely to sustain considerable injury. It might be worth while to see if the pilot could be placed just behind the wings in a large multi-engined aeroplane, without losing the essential arcs of vision that he requires. As far as the feel of the aeroplane is concerned he would be better off, for, provided that he is not unreasonably far behind the wings, the fact that he has them subconsciously in view assists his sense of balance. If, however, the pilot is too far behind the C.G. or too far in front, the aeroplane does not feel so responsive, owing to the reactions that the pilot experiences on his own body. If it is not essential for view that he should be seated in the nose, it would certainly be much safer to place him where he is less liable to risk of injury from a minor crash. This applies most forcibly in an experimental type of large aeroplane.

(h) Comfort.- There are no considerations which should prevent the pilot's being made as comfortable as possible. The fairing should be so arranged that it screens him perfectly, allows him a. perfect view of his instruments, and the best possible view outside. It should be brought up close to his head and slope away in an uninterrupted line from his eyes as far as possible in all directions. Some cockpit fairings are too low round the pilot, while their contours actually prevent him either seeing his instruments well or having a good view downwards without craning his head outside, so that it has actually been necessary for the pilot to duck his head to see the top instruments on the dashboard, while gaining nothing by the shape of the fairing. Its design should receive the closest attention.

It is perhaps unnecessary to emphasise the importance of arranging the control stick, rudder bar and throttle levers, so that the pilot may operate them without unnecessary effort. Although this point has often been brought forward there are aeroplanes still being built in which the pilot's comfort has not been sufficiently studied.

In the above paragraphs an attempt to analyse the flying qualities desirable in civil aircraft has been made, in which what seem to be the most fruitful lines of experiment have been suggested. I recognise that in nearly all these directions some experimental work has been carried out, and I do not claim that the suggestions are necessarily new. I simply wish to emphasise those which seem most important to me as a pilot. They may be summarised as follows :­

(a) That new developments in large multi-engined aero­planes should be rigidly examined in the light of the pilot's capacity to deal with them as a human being. That he should not be required to do too much.

(b) That the effort that is now being made to relate the pilot's flying requirements to the phenomena of stability should not be relaxed; that closer investigation of the undue sensitiveness of some aeroplanes to small move­ments of C.G. should be made, and that it should be a definite aim to produce a degree of positive stability which pilots have every reason to appreciate and none to criticise.

© That on large aeroplanes the gain to the pilot due to the sub-division of large controlling surfaces and the effect on his control should be further investigated.'

(d) That the question of relay controls should be followed up, and the maximum flying experience gained with them as soon as possible.

(e) That the control at low speeds of all aeroplanes should be investigated with a view to improvement, and that every means should be tried to improve the control of aeroplanes where they tend to turn or pitch due to variation of thrust.

(j) That further experiments should be carried out to solve the problem of an automatic landing device, attempts at which have been made at the R.A.E.

(g) That definite full-scale experiments should be proceeded with to ascertain the practical value of wing surfaces variable in form.

(h) That the question of seating the pilot behind the planes in a large multi-engined aeroplane should receive consideration.

(k) That small details which may increase the pilot's comfort should not be ignored.
  • 0

#54 piecost

piecost
  • Posts: 1318

Posted 19 July 2011 - 23:31

SPAD VII

Note post#53 has some information about SPAD stability - it doesn't say which one

Attached Files


  • 0

#55 piecost

piecost
  • Posts: 1318

Posted 27 July 2011 - 00:04

An Analysis of the Component Weights of Aeroplanes

Reports & Memoranda No. 676

[Camel, SE5, Pup, Dolphin, Snipe, RE8, Bristol Fighter, DH11, DH10, FE4, Vimy, HP 0/400 HP 0/1500]

Attached Files


  • 0

#56 piecost

piecost
  • Posts: 1318

Posted 27 July 2011 - 00:06

An Analysis of the Component Weights of Aeroplanes

Reports & Memoranda No. 676

[Camel, SE5, Pup, Dolphin, Snipe, RE8, Bristol Fighter, DH11, DH10, FE4, Vimy, HP 0/400 HP 0/1500]

…continued

Attached Files


  • 0

#57 piecost

piecost
  • Posts: 1318

Posted 01 August 2011 - 03:14

extracts relivent to the SE5a

THE MANOEUVRES OF INVERTED FLIGHT
THE JOURNAL OF THE ROYAL AERONAUTICAL SOCIETY

PROCEEDINGS
SECOND MEETING, 59TH SESSION

From the autumn of 1920 onwards Bulman and Flying Officer Scholefield, D.C.M., commenced to fly inverted on the S.E.5A, an aeroplane that possesses a marked degree of longitudinal stability; and, although it had not up to that time been considered possible, they were able to maintain steady inverted night on this type.

PART II.-INVERTED FLIGHT

General Remarks

The more stable an aeroplane is in normal flight, the more difficult is the pilot's task of maintaining the inverted position, and vice versa. It is therefore relatively easier to fly unstable aeroplanes like the Sopwith "Camel" and "Snipe" inverted than stable aeroplanes like the S.E.5A. The "Bat Bantam," which is about neutral in stability at normal flying speeds, falls between the two extremes.

Before the behaviour of individual aeroplanes is dealt with, a note on the management of the engine is necessary. The petrol systems of aeroplanes do not make special provision for petrol supply to the engine when inverted. It is only by chance that in one or two aeroplanes petrol continues to be supplied to the engine; and independently of the petrol system a stationary engine with a float carburettor will cease firing almost immediately on inversion. Although the method of attaining the inverted position by means of a half loop is suited to stationary-engined aeroplanes on account of the absence of gyroscopic effect, the wisdom of turning the aeroplane upside down with the stationary engine running and allowing it to cut out, is questionable. A certain amount of petrol is bound to be spilt out, the presence of which is undesirable inside the cowling. Unfortunately an aeroplane cannot be half looped on to its back without the engine running, and Bulman, has frequently done this on the "Bat Bantam" and the S.E.5A for experimental purposes, If petrol can be supplied to it, a rotary engine with a block tube carburettor will continue to fire.

3 The Effect of the Controls in Inverted Flight

(b) Application to Particular Aeroplanes

S.E.5A.-For inverted flight on the S.E.5A, which is longitudinally stable in normal flight, the best position for the tail adjustment is two-thirds forward. Fully forward it would obviously do the maximum to assist inverted flight, but the excessive nose-heaviness that it causes in normal flight introduces an awkward condition at the commencement of inversion and during the final stages of recovery.

Before inverting himself by the half looping method Bulman tried a series of normal loops, watching the airspeed indicator all the way round. Whether the loop was commenced at 100 m.p.h. or 120 m.p.h. the speed at the top did not exceed So m.p.h. He finally commenced his half loops for inversion at 115 m.p.h., waited. till the aeroplane was just over the top of the loop, pushed the control stick right forward and throttled his engine down. The engine appeared to fire for 10 to 15 secs. after inversion; but if the inverted glide was prolonged the propeller stopped, even though the airspeed indicator showed 80 m.p.h. In any case the aeroplane stalled immediately on inversion, and the stick had to be held firmly forward while the nose dropped and the aeroplane gained speed. The greater the speed at the top of the loop, the less was the stalled drop; under average conditions the nose only fell 15° to 20° from the horizontal.

Bulman and Scholefield both performed the slow and quick half roll for inversion. They commenced the slow half roll at 75 to 85 m.p.h. at about half throttle but throttled right down on inversion; for if the throttle was left open tbe engine restarted with a violent jerk during the recovery. Bulman gave rudder and aileron in the desired sense of rotation, and after the wings had passed the vertical pushed the control stick fully forward. As he approached the inverted position he took off aileron and rudder. Schofield differed by pulling up the nose slightly at the commencement of the manoeuvre; and instead of continuously applying rudder until nearly inverted, gave rudder during the initial stages, centralised it as the wings passed through the vertical, and then gave it again in
the same sense. He also found that he could apply it in the opposite sense after the wings had passed the vertical, which corresponds to Gerrard's experience on the "Snipe." The aeroplane did not approach stalling at any time, and Bulman, though he experienced a small amount of sideslip, found remarkably little tendency to yaw off his course. Scholefield however found that if he did not allow some yaw he experienced considerable sideslip. All the control movements in this manoeuvre, allowing for the firmness required with the S.E.5A, were comparatively slow and gentle (see Fig. IV.).

Bulman commenced the quick half roll in a similar way to the ordinary roll, by giving aileron and rudder in the desired sense of rotation and pulling the control stick back, With the exception that he made these control movements rather more gently. When nearing the inverted position he pushed forward the control stick, took off aileron and centralised the rudder. At the commencement of inverted flight he found that the aeroplane was as much stalled as when looping into the inverted position. This could be mitigated to some extent if the half roll could be commenced with no more backward movement of the control stick than was just necessary to induce the rolling motion. In manoeuvres such as the quick roll, which seem to involve auto-rotation, the elevator, in controlling the angle of incidence, is the Important factor in governing the motion.

3 The Effect of the Controls in Inverted Flight
(b) Application to Particular Aeroplanes

S.E.5A.- Contrary to expectation the S.E.5A provd relativly amenable to the controls in inverted flight; its main difference from the unstable types lay in the posiion (about three-quarters way forward) in which the control stick had to be held to counteract its powerful self-righting properties. Scholefield found no difficulty m aileron technique to counteract a dropped wing, but was considerably puzzled by the use of aileron to carry out banked turns. As was explained previously, the bank-necessary to produce an inverted turn is the reverse of that for a normal turn. Apart from this the controls had to be used as a whole more coarsely and vigorously on the S.E.5A, a feature that to some extent applies to its behaviour in normal flight. Although it was possible not only to fly the S.E.5A inverted, but even to stall it inverted, Its self-righting properties were such that, as far as investigation was able to show, no mishandling of the controls would result in the development of an inverted spin. If it be granted that the "Bat Bantam," with its extraordinary controllability, is an exception, the suppression of the risk of an involuntary inverted spin has generally to be paid for by a certain loss of ease in inverted manoeuvres and by the extra force which is necessary to keep the nose of the aeroplane from falling.

Bulman found that, with tail adjustment two-thirds forward, he could stall the S.E.5A inverted at 70 m.p.h. Just prior to the stall it wobbled laterally, and frequently dropped the right wing. Though my experience relates to a different example of this type, I found that it was more often the left wing that dropped. In both cases the aeroplanes were, as far as the pilot could tell, in correct lateral trim. With the tail adjustment in the above position the aeroplane felt nose heavy both in normal and inverted flight; and although in the inverted stall the characteristics of instability were searched for, they could not be detected, being masked perhaps by the lack of elevator control. It is interesting here to note the difference between the S.E.5A and the modified "Camel," both of them longitudinally stable aeroplanes with powerful self-righting properties in inverted flight. The relatively long fuselage and effective elevator control of the S.E.5Aenabled it to be stalled inverted in a similar way, apart from the greater control force necessary, to the unstable aeroplanes.

4 Resuming Normal Flight
(b) Application to Particular Aeroplanes

S.E.5A. During the half looping recovery the S.E.5A, in common with the "Bat Bantam," tends, if the pilot is not careful, to lose a considerable amount of height in the inverted dive. On the S.E.5A the pilot has the control stick further forward to maintain inverted flight than on an unstable or neutral aeroplane. The necessary backward movement of the control stick is therefore considerably greater, for in all the types investigated, the final position of the control stick for swinging the aeroplane round is fully back.

Although the slow roll for recovery, if skilfully performed, need only involve a comparatively small loss of height; the nose of the S.E.5A tends to drop so much that the pilot may lose as much as 700ft. in his initial efforts. When he is flying at low speeds inverted the control stick is nearly full forward. To commence the roll he pushes it along the dashboard to give aileron in the desired sense, and gives rudder in the usual way. As the wings pass the vertical the aeroplane will sideslip downwards, against its rudder. At this point the control stick must be pulled back along the side of the cockpit and, together with the rudder, finally centralised when the aeroplane has come round to normal flight. In unstable aeroplanes the corresponding control movement amounted to a circular sweep on one side of the cockpit; in the S.E.5A this sweep is elliptical, with its major axis fore and aft of the aeroplane. The difference in movement arises from the necessity of using the elevator more coarsely. After the wings have passed the vertical the aeroplane, in addition to sides-slipping. wants to yaw against the rudder. In the case of a right-hand half roll from the pilot's point of view it yaws to the left, and vice versa. The tendency of the S.E.5A to yaw in the slow half roll for recovery seems more marked than in that for the attainment of the inverted position. Bulman suggests that when rolling into the inverted position, the pilot has the advantage of the engine with its consequent slipstream effect on the rudder until the last moment, whereas during recovery the slipstream effect is absent. If, by allowing the nose to drop, the pilot gains sufficient speed to compensate for this, the symmetry of the manoeuvre is lost (see Fig. VI.).

PART III -SPECIAL INVERTED MANEOUVRES

The Inverted Spin

Finally I tried an inverted spin on the S.E.5A. I set the adjustable tail at its maximum incidence, thus producing considerable nose heaviness in normal flight: I made the usual control movements and the aeroplane entered an inverted spin in much the same way as the modified "Camel." The rate of spin was less smooth, with a noticeable kick. The S.E.5A showed no tendency to fall into the inverted Spin; in fact the pilot had to be determined with the controls to produce it at all. Once produced it was, in spite of the "kicking," perfectly definite and consistent. The recovery was more direct than on any other of the aeroplanes examined.

3 Conclusions

Though if anything more longitudinally stable than the modified “Camel," the S.E.5A was the more controllable aeroplane in inverted flight because of its effective tail.

When the S.E.5 was right way up it was stable and would stall suddenly, but when upside-down it was unstable and stalled gradually
  • 0

#58 piecost

piecost
  • Posts: 1318

Posted 04 August 2011 - 22:35

Notable Performances of British Aeroplanes Seaplanes & Airhips

ACA 1918-19 Vol 1

Attached Files


  • 0

#59 Tom-Cundall

Tom-Cundall
  • Posts: 5549

Posted 05 August 2011 - 07:43

Not sure if this is the right place. This is from this quarters WWI aero Magazine:

In the S.E.5a and other similar aeroplanes, the landing pattern is entered at approximately 70 mph and approximately 800 feet above the ground, unless local rules provide otherwise. On the downwind leg, flying opposite to the direction of landing around a quarter mile laterally from the runway, the power is cut back to cause a gentle decent when parallel to the approach end of the runway. At reduced power, airspeed is maintained by lowering the nose. As long as the pitch of the wind in the wires is constant, the pilot knows that the airspeed also remains the same.

A lightly loaded S.E.5a stalls at no more than 35-40 mph, just like a Piper Cub, an Aeronca Champ or any similar types of light aircraft. However, unlike more modern aeroplanes, the S.E.5a does not handle as well when approaching the stall. The stall itself is very mild and is easily recoverable with no tendency to spin, but control when approaching the stall is marginal.

The controls of the S.E.5a get very spongy and loose when below 50 mph; so, when approaching to land, a pilot must keep the airspeed up until very near touchdown. As with all aeroplanes of this era, wind variations and the high drag of the machine at low airspeeds mean it is necessary to maintain a good margin of safety with regard to airspeed in the pattern and approach.

Vinnie [Vinnie Nasta] would hold around 70 mph, descending right through the base leg and onto final, not reducing airspeed any further until very close in. Because of all of its drag, the S.E.5a slows down very quickly when the power is reduced and/or the nose is raised. On short final, the power is brought back to just above idle and the aeroplane is slowed to around 50 mph, indicated by a slight lowering of the pitch of the wind, and the aforementioned softening of the feel of the controls. Vinnie said that he always knew when the airspeed was below 70 mph because the ailerons, in particular, but also the rudder and elevator became more and more unresponsive as airspeed decreased, and much more control input became necessary to make any changes in the attitude of the aeroplane.

The round-out for landing is delayed and performed as close to the ground as possible. Wheel rather than three- point landings are virtually always done in most of the WWI era aeroplanes for three reasons: 1. visibility remains fairly good as long as the nose is level or low. Once the tail comes down, forward vision is highly impaired. 2. As mentioned, these aeroplanes are, with few exceptions (i.e., the Fokker D.VII) highly unstable near the stall as is the situation when performing a three- point landing. 3. The S.E.5a’s rudder becomes blanked- out by the fuselage and is virtually useless when the aeroplane is in a three-point position.
In the S.E.5a, to bring the nose up to level off at around five feet above the ground requires almost full back stick. Once the nose is level, the stick is returned to neutral, power is brought back to idle, and the machine is positively flown onto the ground at approximately 45 mph. Very soon after touchdown the aeroplane decelerates rather quickly, and the tail comes down fast.

As with all WWI era aeroplanes, it is crucial that the aeroplane is landed absolutely straight with no crabbing or side slipping when touching the ground. Any side movement at all upon landing almost always causes a groundloop which is mostly uncontrollable.

After touchdown, once the tailskid is on the ground, there is no longer much, if any, directional control. Of course, the S.E.5a, like most aeroplanes of this era, has no brakes or steerable tailskid or tailwheel. Runners meet the aeroplane at mid-field and hold onto the wingtips to keep the aeroplane from groundlooping. This method is presently in use at the Old Rhinebeck Aerodrome and echoes a similar method used during the early years of aviation.

In the S.E.5a, all movement on the ground is very difficult - requiring the said runners to steer the aeroplane at all times while it is moving. Vinnie said that the controllable throttle certainly made applying the required power a bit easier, though.

  • 0

#60 piecost

piecost
  • Posts: 1318

Posted 06 August 2011 - 12:48

Mutual Interferences of 2 Model Airscrews and Sopwith Dolphin

Reports & Memoranda No. 572

Attached Files


  • 0

#61 piecost

piecost
  • Posts: 1318

Posted 06 August 2011 - 12:48

Mutual Interferences of 2 Model Airscrews and Sopwith Dolphin

Reports & Memoranda No. 572

…continued

Attached Files


  • 0

#62 PikAs53

PikAs53
  • Posts: 169

Posted 15 August 2011 - 14:43

After reading all the books from Windsock, Signal and Osprey I must say that all the data which comes up doesn't impress me anymore. The more books you take the different data you get. Especially in for the Albatros, Camel and Dr.1.
The problem is, nothing in these figures is tested or evaluated with the same standard, so figures concerning speed differing widly, for the Dr.1 in the extreme.
On the other hand, reports of the pilots who actually fly these crates are constantly being ignored. But these are for me the most reliable sources concerning the performance of an airplane.
Again the Dr.1 as an example. The speed given in most books for this plane is equal to or higher than that of the Albatros (any model), only exception is Ospreys Duel series Nr.7, Sopwith Camel vs. Dr.1, where it is stated that ID Flieg made tests where the speed reached was about 20km/h slower than that what was posted by the Fokker factory.
On the other hand, almost all descriptions of the pilots state that this plane was extremly maneuverable but way to slower to initiate a dogfight or to run from it. Also in Duel Nr.7 page28 is a statement of Richthofen where he claims that JG1 could have shot down six times as many planes if it wouldn't have for the inabillity of the Dr.1 to keep up with them. There are hundreds of statements of pilots, german and allied that say the same. Than how can it come that despite these declarations the Dr.1 is one of the fastest planes in the game.
The same is also true for the Camel and the Pup. There is no doubt about the maneuverability of these planes. But pilots very often stated that they couldn't run from the "Huns", but had to stay and fight.
Here in the game the german Albatros and Pfalz DIII are completly obsolete again either of the two. They are slower and less maneuverable. And taking in consideration to reduce the maneuverabillity of the Pfalz DIII is an absolute overkill leaving an unrealistic allied planeset with too fast planes against a set of german planes which underperform in any aspect. And this despite all the statement of the real pilots of the "Great War".
So my request: please also take the pilot statements into consideration, cause this is what was actually really happening then. Not the doubtful figures we find in the various books with unreliable tests.
  • 0

#63 piecost

piecost
  • Posts: 1318

Posted 18 August 2011 - 18:52

Full Scale Stability Experiments with RAF14 Wing Section
Reports & Memoranda No. 505

[FE2c & BE2e downwash]

Planes we'd like to fly: FE2
post #8

"Conlusions - It appears from the series of experiments described in this report and in R. and M. 326 that the tail efficiency of a pusher aeroplane is of the order of 80 per cent. and that the tail efficiency of a tractor 60 per cent., due to interference effects. The rate of change of downwash due to the wings is in both cases approximatly 0.5, but this must be increased in full scale work by 15 per cent. to 20 per cent. to allow for the aircsrew."
  • 0

#64 Carrick58

Carrick58
  • Posts: 13

Posted 05 September 2011 - 17:55

Just a suggestion. Why not use the Replica s in New Zealand as Flight models for the D V and Dr 1 or as many as possible. They already have done the home work on these and other models plus they fly the finish product so they could explain the whys and where fores . I am sure that Peter Jackson and his team invested a lot of time and effort.
  • 0

#65 piecost

piecost
  • Posts: 1318

Posted 09 September 2011 - 19:18

Pilots' Notes for the Handling of World War 1 Warplanes and their Rotary Engines

[Avro 504 100HP Gnome Monsoupape, Sopwith 1 1/2 Strutter 130 HP Clerget, Sopwith Pup 80HP Le Rhone]

Attached Files


  • 0

#66 mozza

mozza
  • Posts: 137

Posted 13 September 2011 - 07:55

RAE Farnborough - Orginal Handwritten testing notes from the Public record Office KEW, London
SE5a French built HS engines. AVIA6/29250

Attached File  P1040239.JPG   2.96MB   880 downloads

Best regards,

Mozza
  • 0

#67 J30_von_Hammer

J30_von_Hammer
  • Posts: 35
  • LocationTexas

Posted 18 December 2011 - 01:15

Stick with me, I'll get to my Pfalz comment-
First, my background. I'm a private pilot, A&P mechanic, R/C flyer of WWI types for a long time, Red Baron 3D player since Red Baron 1 and 2, and was also the developer of the 'after market' fm's that were used in the Great War wargame series put on by my squad JG2. I come from the old school background when we started coding computers with 1's and 0's, then punch cards, then Fortran and Basic, then Pascal, and after that I got behind. But, I feel I have a very good understanding of logic and how things work.

I wish I could just have the RoF fm portion of software available with an editor similar to RB3D (but with ALL the parameters) to also create fm's for this game and simply make them, and submit them for review, rather than go around and around with talk. There is too much in variables with each player, joystick, settting and how they fly, and everybody wants their plane to be a winner.

So, here are my basic concepts of the WWI planes. In the end, it is mainly all about power and weight, and a little about drag. A great book to read which finally gave me hope in the history world is "Three Wings for the Red Baron". This is the first non-typical historian (most of whom only know color schemes and pilot names, not techical aeroplane info) who wrote a book I really enjoyed reading for a technical background, which is what I always like to study, of these planes and the fight to win the techno war- the real aero war of WWI.

IF I were running this show, the first thing I would do is develop engines, just like a real plane is develoepd, they start with the engine. All this stuff about that plane is too fast, and that plane is too slow, will get cut in half just by developing engines and sticking to them, and never any reason to change them.

A Le Rhone 110 will always be what it is, unless you add wear and tear to the program. A Mercedes 120, 160, 180 180a, 180au, etc are what they are. I helped to overhaul a 180au out of a real D7 myself. The horsepower can be determined and set down as a solid data point.

Next, I would develop a propeller series. If you notice in photos, you will see different props on the same plane types. They also experimented with diameter and pitch, but you don't see historians talking about that either 'cause they ain't technical enough to, and nobody seems to do any research on diameter and pitch of the old props. For this game, you can select a basic set of diameters and pitch, and, of course, let the players select them too if you want. They will change the top end speed, or acceleration speed possible. Ever think that is why some pilot reported different flight characteristics? hmmm… But, for the sake of simplicity, you can keep it to one prop for each engine, and just stick to it on all planes using that engine.

Now, in all the reading of all the accounts and talking to real pilots flying rotary engine and inline engine aircraft, one thing sticks out- the engine and prop combo pretty much sets the primary top end speed of the plane in level flight. (hang on to that airframe for a moment). So, a 110 LeRhone will pull a N11 (turned N16 with the 110) about as fast as it will a Pup, or in a Dr1, it will also go about the same speed as well. A 160 Mercedes will pull a Pfalz about the same as an Alb. The amount of thrust is the same. Get the engines figured out, and you save yourself a lot of software work because you don't need to create an engine performance set for every plane anymore. You just 'install' the engine to the airframe and get what you get- like real planes.

Next, create the airframes. This is where the differences will show (now we bring that in). More wires equals more drag, but more importantly, more weight equals lessor performance.

The Alb D1 and D2 had the 160 engine, but the D2 was tiny bit faster, when they go rid of the Windhoff radiator 'ears'. (I Wish they would add the Alb D1, just a wrieframe change and they ahve a new plane to sell, and it's cool looking, but has more of a blind spot with that top wing).

The Alb D3 was the copy-Nieuport attempt to gain maneuverability with wing style. All they really needed was to lighten up and clean up more, like a Pfalz D3. The Alb D3 also had an improved engine, the 160 IIIa It was a higher compression engine. Better at higher alts, but only added less than 15hp, (and hp in a long stoke, big a** piston, low rpm, hight torque engine is not the same as a modern engine- so 15hp does mean something).

The Alb D5 had the same engine, but lo and behold, a lighter and more cleaned up design, but again note that the improved airframe did not do a whole lot to improve performance of the Alb- same basic engine as the D3, with a good idea of aileron cables running through the top wing- nice when the bottom wing leaves, and 4 less wires in the breeze). Again, note, not much improvement- troops complaining it sucks, not an improvement as promised. Alb D3 goes longer in production than the D5!

Enter the D5a. Now they really muck it up and try to improve the airframe, which makes it heavier. More work on the IIIa engine and it's now referred to as the 180 IIIa and the performance is for sure better, and less loss of power at alt. But all the added weight of engine and airframe, with no change in wing area, results in a faster speed level, but less performance than desired for climb and turn.

And then enters the Pfalz D3 ( I wish they had a D3 as well as the D3a, just another cool plane that only needs a wireframe). This is more or less what Albatross should have done. IF the Pfalz D3 would have come out at the same time as the Alb D1/2/3, it probably would have been the mainstay fighter. Streamlined, so even with just the 160 it is a bit faster than the Alb D3, but slower than the D5a- (hey, there's that engine difference again). A Pfalz D3 with the 180 probably would have been considered better, but I'd have to run the numbers on it. Poor Pfalz, not in the political circle enough.

So, I don't agree the Pfalz D3 is too maneuverable. I agree it's a bit slow, but I'm ok with that, as it only had the 160 engine with a fairly clean airframe of lessor weight. It should fit right in between the Alb D3 and D5a somewhere.

I like flying the Pfalz because it feels better as a plane, but I would say it's not maneuverable enough in roll. In fact, you can't hardly roll it at all. Try it. Try to do a nice victory roll with the Pfalz. Now, go watch the Blue Max movie (when men were men and planes were planes, and no computer flying photography). The Pfalz they built for the movie was considered the best flying plane of the whole bunch. When they let George Peppard fly one of the planes for fun, they made him fly the Pfalz. When I contacted the group selling the planes, they said the Pfalz was the best flyer. Nimble, light on the controls, no flutters, good smooth flying plane. AND, to top that off, it only had a 1930's vintage Gypsy engine (120 I think it was) in it, which was actually underpowered and heavier in weight compared to the original Mercedes, and if you notice the prop, that is much smaller due to the higher rpm engine type.

These WWI planes were designed for the powerplant at hand, low rpm, high torque, big props (we're talking 8 foot or better diameter). Watch after Stachel shoots down his 'Se5' and does the victory roll. That is the closest you'll ever see a real Pfalz flying. But, you can't even do that with this fm. That means to me the Pfalz is not maneuverable enough.

Why does everybody in fm developmetn for WWI think these planes need to fly badly? The last guys doing fm's for RB3d made planes that flew really bad. IF they did that type of design for real, more guys would have died. The RLM would not have accepted them either. The British planes will roll faster than the French or German since they use ailerons on all wings- sure, that is aerodynamics. Look at a Gypsy Moth vs a Stomp- same basic plane, same basic engine, but 2 vs 4 ailerons. IF you've been to Rhinebeck you can actually see the difference, and it is actually pointed out to you by the announcer and demonstrated by the pilots in the air!

Most planes will have a close result of elevator throw, however, the heavier plane, especially using more throttle, will tend to create a bigger circle. The lighter plane a smaller circle, that is just physics. I can see that in my model planes even. Ever notice some old board games gave a turn speed? Ever play the old Janes WWII fighters? In real planes, when you start doing the really tight turns, you actually throttle down. To get real tight, you want to throttle down as low as you can to the stall point, without stalling, and using maximum elevator, produce the tightest turn you can, and turn around a point, using the wign tip as a pointer at a ground object for reference.

In this game, if you try to slow down to tighten up your turn, it usually stalls out quick or gets you killed. In RB3d, I had some of those planes, especially the Alb D5, working better turns with lessor throttle. The Allies never figured that one for the most part I think, but that was confidential info from our side.

So, I say develop the engines first, if you do that, then there is really no arguements that the public can make against you. It's a fixed design. They can only argue about what planes had what engines. THEN make an airframe and every bit of frontal area, non-aerodynamic obtrusion, and draggy wire adds whatever resistance per square inch, or wire diameter, and then develop a weight of aircraft (hey, more items the public can't complain too much about), and even with giving all controls on all planes the same amount of throw, you will start to see the differences naturally come out.

The "Three Wings…" author is right on with his reasoning as to why the triplanes came into existence at all, when they are actually not all that good. The Sopwith did well by some lucky combats seen by prominant people, and gee, all they did was take a Pup, put three wings on it basically- oh, and went from an 80b LeRhone to a 110hp Clerget! What if they just took a Pup and put a 110 on it? They would have had something there. The Dr1, still a 110 rotary, but hey, no flying wires, extremely light compared to most biplanes, power to weight very good. Still about the same speed as a LeRhone 110 can pull, but the rotary did well because it was the lightest power to weight engine of the day.

Fun fact, the inlines were around 4 to 5 lbs of weight per hp. The rotaries were around 2 lb per hp. Today's piston engine is around a half a pound per hp.

So no, I don't agree the Pfalz D3 is too maneuverable. It's one of the few planes that is starting to feel like it's sorta on the path to correct for me. The DFW actually is one of the best flying planes for quality of flight and how a plane should feel. That is even closer to the right path.

Follow a process on this plane design stuff, and it will work 80% or more of the hair pulling out of the design process I'm sure. I'd love to be a beta testor and help, but I have to work too much these days. But, I wouldn't mind being given a test flight here and there for an opinion.

Thing is, when the real dudes designed their aircraft, they were honestly trying to make them fly as best they could. I get the sense from game design, that they are trying their best to run down a design into something inferior to simulate some other goal. Build them like real planes, in logic, and they will fly nice, and if done properly, the differences should come out very similar to the real thing, and unfortunatley, since we all get to 'live another day', the facts as to what plane is truely better than another will come true, and stay true, and there will be nothing you can do to make it better at that point.

This type of game is most fun and best when it's all novice players. After too many go pro, the next level becomes who can be the best team players, and use a wingman. That is what tips the scales. That is how it went in real flying. By the end of the war, when pros met pros, a lot more came from flying in numbers and luck than the individual flyer. Gen Trenchart didn't care about the Red Baron's success, he knew that if he put enough bullets in the air, one day one would find him, and it did. That is how it goes.

IF this game doesn't work on the ability to run war games, like we did with RB3d, then it will lose it's glimmer after awhile. Doing missions in a war game becomes the next major step for this game. The Great War would probably still be running as a yearly event if it weren't for the hackers who ruined the game. People loved that event.

ok, there are my 2 cents. Maybe in the wrong spot, but I'm here at the moment.
  • 0

#68 piecost

piecost
  • Posts: 1318

Posted 11 January 2012 - 01:44

Flying Qualities & the Flight Testing of the Aeroplane

Dyrrol Stinton

[Sopwith Camel, Rotary Engine, Clerget, Bentley BR1]

Attached Files


  • 0

#69 Waxworks

Waxworks
  • Posts: 630

Posted 24 January 2012 - 17:38

This is from a book by Kurt Jentsch quoted in 'Jasta Boelcke' by Norman Franks. Jentsch was given the opportunity to fly the Jasta's captured SPAD on a visit in August 1918, before applying for a transfer from Jasta 61.

'The Spad sat in the air wonderfully and responded to the slightest touch of the controls. In addition, the engine ran without knocking because of its fine 'V' form. This is why these craft sit quietly in the air, there is not any swinging back and forth as with our aircraft, which is caused by the type of construction of the stationary German motors.'

'In wing performance, the Spad towers over our aircraft. The loops and banks flown by me confirmed my assumptions in the end.'
  • 0

#70 NewGuy_

NewGuy_
  • Posts: 4114

Posted 24 January 2012 - 18:47

TOPIC IS HEAVILY MODERATED! READ HERE FIRST!

Here is the main subjects, which are discussed on the forums, is you have current data - post it here.

1) Sopwith Dolphin horizontal speed

2) Albatros D.Va horizontal speed

3) Pfalz D.IIIa - maneuvers too good, horizontal speed too low

4) Nieuport 28 maneuvreability

5) Nieuport 11 maneuvreability

6) Nieuport 17 maneuvreability and speed

7) Se5a engine overrev (already taken as confirmed, will be fixed)

8) Fokker D.VII roll speed.

Out of this list, the bottom four machines have been addressed. So, I would imagine that the N28, Alby DVa, Sopwith Dolphin and Pfalz DIII are up next for review, unless there has been a change in the order of priorities. When the next machine will be reviewed is unknown to me, though. I haven't heard anything directly from the team about changing the Camel and the DR1, though, admittedly, there was no suggestion of affirmative action to change the FM of three of the four changed by the team. Only the SE5a, item number seven, informs the reader that something was confirmed as an issue, warranting official redress. :S!: MJ
  • 0

Something something SPAD. Something something then dive away. 


#71 piecost

piecost
  • Posts: 1318

Posted 24 January 2012 - 19:02

All my Dolphin information

Dolphin Speed and Specification
post#139
  • 0

#72 piecost

piecost
  • Posts: 1318

Posted 17 February 2012 - 14:59

Wind Tunnel Tests of Fokker EIII & DVII


I managed to find the university wind tunnel test of radio control models of the Fokker EIII and DVII. The report hints at future work, unfortunately, I cannot find any.

The paper was written by Scott Eberhart, who wrote the earlier performance and tactics paper. I consider this to be a better piece of work and definitive for determining the aerodynamic coefficients of these aeroplanes.

The test approach seems reasonable and most of the potential sources of error were identified. They state that no wind tunnel corrections were made.

It is mentioned that the tests were performed with the tailplane/elevator fitted and absent. The moment curves suggest that the tail was fitted – no setting angles were given.It is assumed that the lift and drag data are for the same configuration. It is usual to test lift curves without the tailplane fitted since the tail complicates the result. It is assume that no attempt was made to trim and so the drag polars should be modified to account for this.

The tests were performed in a rush; which prevented a more in-depth investigation. The biggest disappointment to us may be that CLmax was not measured for the DVII . I assume that this was prevented due to incidence limits on the model mounting or concerns with model loads. The EIII exhibited a gentle stall indicative of high Reynold’s number trailing edge separation, rather than a nasty laminar bubble induced / leading edge stall. Unfortunately the stall was not achieved at the higher Reynolds’ number.

An interesting comparison is that of the DVII results to the R&M 817 tests 1921 which I posted elsewhere on this forum.

How to do the Albatros series justice
post#123

This gave a CD0 of 0.030 while the recent test gave 0.071. However, it is not a fair comparison since the 1921 test lacked fuselage, undercarrage or tail! R&M 603 for the SE5 suggests that the drag coefficient (CD) of the non-wing components amounts to about 0.048. Crudely adding this to the 1921 data wing brings the drag up to the recent value!

The DVII demonstrated a relative insensitivity to scale effect, unlike the EIII. I was surprised at this since I imagined that the thin wood and fabric leading edge on the EIII might fix a forward transition and remove the Reynold’s dependence.

It would have been useful to investigate the use transition fixing on the wings. This could be used to simulate a higher Reynold’s number than achievable in the tunnel and could give a useful indication of full scale maximum lift and minimum drag.

A major source of error may occur due to the geometry. Flying models are contrained by practicalities, which are not applicable for bespoke wind tunnel models. This was briefly discussed in the paper. The models were taken from Protor radio controlled model kits. Even if the kit was the most scrupulous in its faith to the full sized plane, certain details may be compromised to achieve a buildable, practical flying model. Geometry may be difficult to reproduce at the model scale. For example; can the leading edge ply bend around a tight enough radius?

It would have been useful to accurately measure a section on each wing to compare to full-scale and to indicate build quality issues (surface steps and waveness). Leading edge radius and trailing edge thickness are likely to be over-scale, struts over-thickness and of incorrect section. Control surface hinge gaps are likely to be over-scale and may cause an unrepresentative high drag. It is best to cover them with tape. The control horns and the holes in the covering for the push-rods would be over-scale and another source of drag.

Seemingly insignificant details such as the edges of the covering material may cause steps on the lower leading and trailing edges with significant effect on the aerodynamics. The covering material will be relatively much thicker than that on the aeroplane and will sag and billow differently in the airflow. Less important on the DVII with its ply leading edge.

Items such as wires, struts (and wheels?) would have been sub-critical Reynold’s number and generate too much drag. A boundary layer trip strip of tape or surface roughness might be applied. Alternatively, those components could be removed (where possible) i.e. DVII wing struts and their theoretical full scale drag added to the data.

The bracing wires on the EIII were required structurally and for warp control. As identified in the report, the non-scale end fittings were a source of erroneous drag, but an estimate of the erroneous of the wire drag could have been made.

It was a shame that no pilot was carried in either model, to the detriment of the drag. Just as important was the representation of the internal cavity of the cockpit. Fuselage bulkheads/screens bounding the front and rear of the space should have been represented. The complex flow past the pilot, into and out of the cockpit, would be more representative.

Care may have been needed to ensure that no non-scale leakages into/out of the hollow structure were caused. In this test it was not clear whether the air could enter the model DVII fuselage through the radiator grill and exit via the cockpit/tailskid aperture!

In contemporary wind tunnel testing of British aeroplanes care was made in the choice of mesh to represent the pressure loss through the radiator and the proper path of the cooling air.

The EIII model had a blanking plate in place of a scale engine, this was likely to have cause a higher drag than is representative and might cause a flow separation with impact on the pitching moment curves (I can’t see evidence of this in the data). The engine “firewall” on the real plane was not solid outside of the width of the box fuselage, the sidecheeks were open at the bottom to allow cooling air to escape.

Items on the cockpit decking such as exhaust pipes, guns and windscreen might be important. Frank Tallman wrote in Flying the Old planes that he thought the windscreen on the Sopwith Camel may have caused a burble over the tail.

Attached Files


  • 0

#73 piecost

piecost
  • Posts: 1318

Posted 28 February 2012 - 22:59

Comparison of Quest for Performance Drag Polars for Fokker EIII & DVII with recent wind tunnel test

wind tunnel test details in post#72

Attached Files


  • 0

#74 piecost

piecost
  • Posts: 1318

Posted 28 February 2012 - 23:06

Quest for Performance Drag Polars Compared to those from Reports & Memoranda of the Aeronautical Research Committee

The first plot compares aircraft for which both sets of data are available. Significant differences are seen.

The second plots all the aeroplanes found from both sources. Both sets of data cover similar ranges at low lift but the polar approximation of drag at high lift under predicts the drag as the stall is approached.

The R&M data is based on glide tests so includes the drag of stationary propellers (worth approximately 0.01 KD. THe Quest for Performance data is thought to not include this.

Attached Files


  • 0

#75 Gunsmith86

Gunsmith86
  • Posts: 842

Posted 24 July 2012 - 21:13

German planes speed:
surce:
http://www.flightglobal.com/pdfarchive/view/1918/1918%20-%200824.html

Pfalz D.IIIa

captured german plane;
a speed of 102,5 m.p.h. at 10000 ft
10000ft = 3048m
102,5 m.p.h. = 164.95 KM/h

ROF store data for 3000m
3000 m — 144 KM/h

164.95 KM/h - 144 KM/h = 20.95 KM/h slower at 3000m than a used captured D.IIIa in real live.


Next one is not on the list but it has the same problem:
Halberstadt CL.II
surce:
http://www.flightglobal.com/pdfarchive/view/1918/1918%20-%201132.html
This machine had a 180hp Mercedes DIIIa engine and was test flown by allied pilots 1918.
They reported a Speed of 97 m.p.h. at 10,000 ft., 1,385 r.p.m.


10000 ft =3048m
97m.p.h = 156.1 KM/h

ROF store data for 3000m with D.IIIa engine
3000m - 135 KM/h

156.1 KM/h - 135 KM/h =21.1 KM/h slower than a used real plane.


Edit: have made a mistake the difference are because ROF store data are in IAS and data in the links have to be TAS which is about 2% per 1000ft higher than IAS. In this case ROF store data are just 2-3 KM/h different from real plane which is very good i would say.
  • 0

#76 gavagai

gavagai
  • Posts: 15541

Posted 24 July 2012 - 22:12

gunsmith, RoF store data is IAS. What is highly suspicious about the RoF Pfalz D.IIIa is that it has the same TAS on the deck and at 3-4km.
  • 0

#77 2Lt_Joch

2Lt_Joch
  • Posts: 184
  • Locationcanada

Posted 05 November 2012 - 13:48

Albatros D.Va speed

Max speed of production aircraft in recorded WW1 tests is most likely in the 165-175 kmh range.

The 186 kmh speed @ 1 km (116 mph @ 3280 feet) appears to be either a mistake or from a D.IIIau/BMW engined prototype.

I have been looking into the existing flight tests of Mercedes D.III engined planes and had produced an excel spread sheet for my personal use.

The data shows 14 tests.

Image

The speed figures in bold are from tests of captured aircraft.


Planes with D.III engines had a max. speed range of 165-175 kmh, although the 175 kmh achieved by a Alb. D.II with a D.III engine looks like a bit of an outlier.

Planes with a D.IIIa engine had a max. speed range of 168-172 kmh.

Planes with a D.IIIau engine had a max. speed range of 178-189 kmh

Test #3 shows the official top speed of the Alb D.V as stated by the Albatros factory: 165 kmh.

Test #9 is the most reliable since we have an english translation of the original German report, which states the type, weight, altitude and RPM of the engine. The test was also measured with the German theodolite method which was accurate within 3%.

The only result which looks really out of place is #12 which is the figure often quoted as the top speed of the Alb D.Va: 186 kmh @ 1 km (116 mph @ 3280 feet). It is very high for a D.IIIa engine and even high for a D.IIIau engine.

I tried to track down the source of this test, but that appears to be lost or non-existent.

The aircraft profile series which came out in the 1960s and which was fairly complete at the time never mentions that figure, in either no. 43 dealing with the Alb.D.I-III or no. 9 dealing with the Alb. D.V. Aircraft profile no.9 only shows the 165 kmh official speed figure. It does however explain that Albatros had entered two special Alb. D.Va prototypes in the 1918 1st fighter competition, one with a D.IIIau engine and one with a BMW engine. The plane with the BMW engine set a climb and altitude record for the type.

The first mention of the 186 kmh speed appears to be in the late 1960s in Purnell’s history of the First World War. Purnell’s was a magazine series which published a history of the Second World War which was very successful. This was followed up by a companion series on WW1. The magazine was aimed at the general public. The series was also reprinted in book form. I own the one on WW1 aerial warfare which came out in 1973 and which lists that speed (116 mph at 3280 feet) without mentioning any source. However, the same book lists the Sopwith Camel as having a top speed of 122 mph.

Some have pointed to the book: "Die deutschen Militärflugzeuge 1914-1918" by H.Stützer and G.Kroschel as a source. That book is out of print, but it was first published in 1977 and looks like a general overview of WW1 German aircraft. It may just be copying the figure from Purnell’s history of WW1.


However, If the 186 kmh speed was recorded by a D.IIIa engined production Alb. D.Va, then it would raise other questions, such as:

1. Why were German pilots disappointed with the performance of the Alb. D.V over the Alb. D.III and only rated it a marginal improvement? a 10-20 kmh speed increase from the Alb. D.III (165-175 kmh) to the Alb. D.V (186 kmh) would have been a substantial improvement.

2. Why was the Alb D.Va scrapped in favour of the Fokker D.VII? If a D.IIIa equipped Alb D.Va had a top speed of 186 kmh, then a D.IIIau engined Alb D.Va would have a theoretical top speed of 196-201 kmh which would be 5-10 kmh faster than the top speed of a Fokker DVII with the D.IIIau engine. Why would the German Air service abandon a proven fighter type (Alb D.V) in favour of a brand new and slower type?

I suspect the 186 kmh figure is either an error in Purnell’s or may perhaps reflect the max speed of the D.IIIau or BMW engined prototype at the first fighter competition. Since there appears to be no source for the figure, it is hard to tell.
  • 0

#78 gavagai

gavagai
  • Posts: 15541

Posted 05 November 2012 - 15:56

You still haven't accomadated the skeptical points we have raised in the past:

1. Captured aircraft data is not a unreliable source
2. The Germans did not measure TAS with the same methods as the British and French.

You would like to a have a straight-forward comparison of the available performance data, but it is just not possible, Joch. The apples-to-apples data we need does not exist.

1. Why were German pilots disappointed with the performance of the Alb. D.V over the Alb. D.III and only rated it a marginal improvement? a 10-20 kmh speed increase from the Alb. D.III (165-175 kmh) to the Alb. D.V (186 kmh) would have been a substantial improvement.
Because the Albatros D.III was faster than the figures you give here. Threads at the aerodrome say 175kmh @1km, and estimated 180kmh @sealevel.

2. Why was the Alb D.Va scrapped in favour of the Fokker D.VII? If a D.IIIa equipped Alb D.Va had a top speed of 186 kmh, then a D.IIIau engined Alb D.Va would have a theoretical top speed of 196-201 kmh which would be 5-10 kmh faster than the top speed of a Fokker DVII with the D.IIIau engine. Why would the German Air service abandon a proven fighter type (Alb D.V) in favour of a brand new and slower type?
The D.VII had superbly balanced controls, was easy to fly, and more structurally sound. It also had a better rate of climb with Mercedes engines than the Albatros.

I suspect the 186 kmh figure is either an error in Purnell’s or may perhaps reflect the max speed of the D.IIIau or BMW engined prototype at the first fighter competition. Since there appears to be no source for the figure, it is hard to tell.
We will never know.

P.S. your 122mph Camel figure is for a BR1 or LeRhone engine. The only account we have of a Camel being faster than an Albatros is from Paul Strahle of Jasta 18, who fought two Camels near ground level (and survived!). TC reported to us that the Camels he fought were from a squadron that had Le Rhone engines. That gives good indication that the maximum airspeed of the Albatros D.V(a) near sea level was somewhere between a Clerget and Le Rhone Camel, i.e. circa 112-122mph.
  • 0

#79 Markow

Markow
  • Posts: 201

Posted 05 November 2012 - 16:31

hmmm
  • 0

campribV.png


#80 gavagai

gavagai
  • Posts: 15541

Posted 05 November 2012 - 16:49

Also, I forgot to mention that Albatros D.III data is usually in reference to the early version with a 160ps Mercedes D.III engine, not the 170ps Mercedes D.IIIa engine that was installed in the later OAW Albatros D.III.

Lastly, Joch, your estimate of how much the D.IIIau engine would improve airspeed at sea level is overestimated. The D.IIIau mainly improved performance at altitude; the throttle was not to be opened up completely at sea level.
  • 0


0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users