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Data Topic for Airplanes Performance.


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#81 JG14_Josf

JG14_Josf
  • Posts: 7

Posted 28 June 2011 - 19:05

piecost,

Take the aircraft g tolerance limit chart and then look at the EM Chart by John Boyd next to it, and note that G load is also on the John Boyd EM chart, a curve in the upper middle and right.

That EM chart isn't WWI planes specific, but it is the only EM chart I could find where some of the information referring to the chart claims that the EM chart was plotted based upon actual flight test data, and that EM chart is claimed to be derived from flight tests done by Chuck Yeager and (perhaps) John Boyd, with a captured Mig 15, and their own F-86. Note how the Mig 15 has a higher measure for pilot G tolerance. I make those claims based upon the biography of John Boyd, and the Web page the chart is found.

Plane ———- G tolerance
F-86 —————- 7.0
Mig 15 —————7.5

Note the data in the WWI quote in this thread:

Plane ———- G tolerance
F-86 —————-7.0
Mig 15 ————–7.5
WWI ——- ———6.0 (for 4 to 5 minutes)

In order to find that plot on that diagram Chuck Yeager and/or John Boyd flew specific tests that can be done in the game, and those specific tests can be simulated, and the results can be plotted, and you can plot any of the WWI planes in the game on that same EM chart.

Look at the two lines on the left going up from the lower left to the high peak where corner velocity is reached and note the shape of those lines.

The higher climb rate plane, the Mig 15, with the lighter wing loading, and the lighter power loading, has a line that is offset to the right and a line that arcs more severely as it progresses to higher speed and higher g. The Mig has the less performing accelerated stall line, but the Mig has the better performing "sustained" turn line (level flight). It can be said that the Mig is single superior and the F-86 is single superior, and that neither plane is double superior, and neither plane is double inferior, based upon that EM chart.

Once you study that accelerated stall line you can then find out what John Boyd set out to figure out, which is the same thing the WWI pilots tried to figure out, and the same thing that the WWII pilots tried to figure out, and that was why some planes on paper were not as good in reality.

John Boyd, and most of the best fighter pilots, were not satisfied with ambiguity, then had to know, call it a gift, or a burden, but they had to know, and they found out.

This:

I am not sure that we shall ever be able to put down everything about this very debated question in black and White -personal preferences will always have a good ideal of weight. But we shall gradually clear up a number of uncertainties which now trouble us, and the time will come when we shall be able to say to a man, “that machine will do what you want, and it is better for that purpose than any other machine," and if he says he cannot make it do what he wants, we shall be able to say that the fault is his and not the machine's. At present we are inclined to hang our heads and go away and try to satisfy what are in many cases purely personal prejudices."

That accelerated stall line curve or arc on the EM chart is the accelerated stall line, and it is not the “sustained” stall line, and that line, the accelerated stall line, on paper, will be the same stall line for each plane if the calculation in the program assumes that the production of lift by each wing, from the measured level flight stall speed, will be a function of how drag increases square with velocity, which, as far as I know, is a common assumption, on paper, and I don’t have that formula at hand, it is on an old hard drive, or I may be able to re-find it on the Web – later. Find the 1 g stall line, use the formula, and estimate the accelerated stall line, and each wing will have the same curve, but each wing may start from a different starting point, at the 1 g stall line.

Who chooses the method by which the 1 g stall line is determined?

The “on paper” assumption can be such that the accelerated stall line shape is the same for each plane but moved to the right or left as each plane starts from a different starting point, and therefore the assumption “on paper” is such that the plane with the lower stall speed will always turn better, at any speed, along that accelerated stall line, because it will always be to the left of the plane with the higher level flight stall speed, and that makes sense, on paper.

Which test is chosen to find that accelerated stall line, or is that accelerates stall line based only on calculation?

When actual accelerated stall tests are done, the actual flight test data may plot out differently than the assumptions on paper, as that EM chart illustrates. An accelerated stall test is a specific, and more complicated, flight test, whereby the plane is loaded down through a level flight turn from highest possible g down to the stall, and the measure of that INCREASING radius turn from high g to stall is plotted on the graph.

I almost wrote the word “decreasing” radius turn, which is a very good illustration of why a person (me) will assume the wrong thing, if the actual data is not shown conclusively, and objectively, to the person doing the assuming. A loaded deceleration flight test, to plot out the accelerated stall line, is an INCREASING radius turn, and the turn rate decreases, as the g load decreases, even though the speed decreases; because energy is dumped rapidly.

Note the vertical scale on the left; it is turn rate. The higher up the scale the faster the turn rate, and note the lines fanning out from low left to high right, those are turn radius lines, and the higher up and left the smaller the turn radius. Note how the F-86 decelerates in that level flight turn on almost the same turn radius, while g and speed decrease, the turn rate decreases. See it? Note how the Mig-15 is outside the F-86 turn.

It is true that a maximum performance turn is the highest g possible at the slowest speed possible, and that can lead a person to think that a maximum performance turn is performed at the slowest speed possible – assuming that g force is somehow going along with that assumption, which it is not going to do without the energy required to do it.

The energy used to make a maximum performance turn is not the engine thrust; the energy used to make a maximum performance turn is excess speed and or excess altitude, and to plot an EM diagram, to find the true curve of that accelerated stall line, the plane has to start out at a very high speed and then turn into that maximum performance turn, and then the engine can’t keep up, the speed is used up in the production of lift, which produces massive amounts of acceleration, and that energy is drained out during the loaded deceleration test turn in level flight, only velocity is used as the available energy to perform that turn, the engine adds some, but on WWI, or WWII, or Korean war planes, the engine power wasn’t even enough to go straight up, which is 1 g, not 2, not 3, certainly not 7.5.

A flight simmer, or gamer, will assume that the Mig-15, on paper, will out turn the F-86.

What do you see on that chart?

What did history record?

Who picks the information used to simulate history?

What can the program do? Does the program assume that each plane will have the same exact accelerated stall line arc, because someone picked a simplified calculation, which is good enough, to simulate air combat?

Note how the EM chart plots a useable corner velocity, based upon test results done by combat test pilots, Chuck Yeager is a famous WWII fighter pilot turned test pilot, and John Boyd, although not as famous for combat flying, was very famous among fighter pilots for beating, in mock combat, all but one opponent, and doing so in less than 40 seconds, and John Boyd went on to invent and produce Energy Maneuverability, or re-invent it, since many of the best fighter pilots knew it intuitively (it seems to me at least) if not on paper.

You wrote:

1. Pilot g limits are modeled, I don't know how it is done.

That is the useable corner velocity variable unless the aircraft limit is lower, and then the aircraft limit is the useable corner velocity variable. I think that the Korean war EM chart is a predetermined g limit that the pilots chose and then flew based upon a combination of variables that included a need to stay well below aircraft tolerance limits. As to why the Mig 15 is a higher g limit, I don’t know. It doesn't help the Mig 15, because the accelerated stall line is inferior, even though maximum g limit for the Mig is higher.

If the program code models each shape of that accelerated stall line the same for each plane, as a function of that square with velocity factor, then pilot g limit becomes a very sensitive variable in the simulation, perhaps much more so than it should.

If the program code does not model a different pilot g limit for each plane; whereby each plane is modeled with the same pilot g limit, or to put that in other words: each user of the game will grey out or black out at the same g limit, in the same time span, no matter which plane is producing the g force, and if the curves for accelerated stall are all the same shape for each plane, but each same shape curve for each accelerated stall line is moved right or left on that horizontal velocity line, where a plane with a slower level flight stall speed is more to the left, with the same shape accelerated stall curve, and a plane with a higher stall speed is more to the right, then that pilot g limit, combined with that same accelerated stall arc shape, means that any plane with a slower stall speed will out turn any plane with a higher stall speed at any speed when both planes are at the same speed.

That is clearly not the case in the EM chart, since both planes plot out with nearly the same minimum g minimum speed accelerated stall plot, and the F-86 has a corner speed higher up and further to the left of the corner speed for the Mig 15. Certainly the Mig 15 has a much better "Sustained" turn performance curve.

Inside (to the right) of the accelerated stall line arcs, for both planes in the EM chart, are “sustained” stall lines, where the Mig 15 obviously dominates the F-86.

Specific flight tests determine the accelerated stall line plot, and different tests determine the “sustained” stall line plots.

An accelerated stall line test includes a loaded acceleration test, where the plane is flying very fast in level flight and then turned to maximum performance, holding maximum g, holding the plane at CLmax, or best L/D, until just before the plane runs out of energy in level flight, and that is one of the ways that the accelerated stall line is plotted.

The “sustained” turn test is done the typical way, a pilot starts turning in level flight and turns and turns until the smallest “sustained” turn is repeated, around, and around, while altitude is kept constant, and while airspeed is kept constant, and theoretically the wing angle of attack will be at best L/D, or CLmax, which, if I am not mistaken, is the same angle of attack. The engine power powers the turn as the wings are loaded up to use that engine power most efficiency.

Which stall line is the stall line used more in air combat?

The “sustained” turn is only used when both planes in combat are flying level at stall trying to turn inside each other.

The accelerated stall line is everywhere else where the pilot is either fighting black out or fighting a plane that is pitched back beyond CLmax, and pitched back much farther than CLmax, well past the best climb angle, or best sink rate angle of attack, well past CLmax and well into the buffet, and well into the stall angle of attack, or past it.

If the simulator code does not program different, or true, accelerated stall lines, if it “fudges” that calculation, by some arbitrary assumption, of low fidelity, then that is what it does, and from that point I can describe the consequences of that low fidelity “fudging” by referring to much of the writing done by Robert Shaw in his book Fighter Combat, which has become known as The Bible to some fighter pilots.

I can elaborate on that subject; involving single superior, double superior, and double inferior aircraft match-ups, with energy versus angles tactics, and why they work, and why one plane is a better energy fighter, like the F-86, and another plane is a better angles fighter – like the Mig 15 – generally speaking – and which tactics work and which tactics don’t, such as nose to nose turns or nose to tail turns, and barrel roll attacks, and something that is very interesting, in Fighter Combat, called the sustained turn technique, which isn’t about a “sustained” level flight turn at slow speed – it involves geometry and baiting a better angles fighter into burning more energy, followed by a pitch up, zoom climb, and pitch back.

Those types of single superior engagements (not double superior or double inferior) would (probably) not be possible if the fidelity of the general flight model was such that each plane has the same exact shape on its accelerated stall line – as far as my experience goes so far. A low fidelity flight model where the accelerated stall line was the same shape for each plane would be one where the slower 1 g stall speed planes would always be the better angles fighter and the better energy fighter, or double superior, even if the slower 1 g stall plane has a lower top speed, rendering the higher 1 g stall plane a hit and run, or team tactics fighter plane, at best.

I rambled on and into that subject anyway, there is much more to it.

As for the users being inspired to help improve the fidelity of the combat flight sim market, as a whole, I think that there is much to be overcome in the department of assumptions being published as facts.

Games have been around long enough to cause users to assume much too much for that measure of subjectivity being couched as objectivity to expect it to vanish overnight.

Back to your chart: it can be used to overlap a similar chart for each plane where each pilot g load, for each plane, is superimposed, so as to get a better idea as to where the useable corner speed is relative to each other plane's corner speed, and that is the speed at which, and the g load at which, one plane will turn inside another plane, for however long that advantage lasts in the actual simulator.

Knowing these things makes it very difficult to explain why one plane, in the game, will turn inside another plane while the user flying the targeted plane is blacking out, and the attacking plane is going faster, not blacking out, turning inside, and pulling lead sufficient to hit the target. If one plane is flying slower, at black out, and therefore the turn rate is maximized, at the pilot g limit, and the other plane is closing the gap, thereby going faster, and the other plane pulls from lag pursuit, to pure pursuit, to lead pursuit, going faster, then the attacking pilot must be able to tolerate more g force, there is no other explanation, especially if it is on both track files, from each plane.

One plane going faster pulling more g, pulling inside the slower plane's turn, while the slower plane is going slower and blacking out the pilot, means, one thing.

If the idea is to flight test only corner velocity, at a specific altitude, then the pilot can begin a maximum performance diving spiral turn through that specific altitude, and the usefulness of this test is not just for plotting a dot on a graph, actually piloting the test can help the user understand the forces involved.

Such a test will be the highest g possible, at the slowest possible speed, which will then be the highest turn rate possible, and it will also be the tightest turn radius possible, and it will be a much smaller turn rate, and a much smaller turn radius than a “sustained” level turn; because of the fact that altitude is being spent in the work of accelerating the mass of the plane on the lift vector.

During such a test a speed will be found, more or less, as the pilot fights the controls to maximize the performance, and that will be corner speed at the altitudes that the plane dives down through, and that speed can then be compared to the level flight acceleration test speed where maximum acceleration was measured, somewhere in the middle of the level flight speed range.

A. Maximum rate of acceleration in level flight is at X velocity.

B. Corner speed is found at Y velocity during a diving spiral, and noted at the same altitude as the level flight acceleration speed test.

That corner speed, in that diving test, will also measure energy retention as a function of how fast the plane loses altitude, and this isn’t to difficult to understand, since a modern plane isn’t too far away from being able to climb at corner speed, and it may take some thinking to get that straight in your head, or in my own thinking if I miss the mark.

Just do the test, before claiming to know better, and you may find valuable information that cannot be conveyed well with words, or formulas.

Get to maximum altitude. Start a right turn (or left, or both, one way one test, and another way during another test) and fly the plane so as to balance just above stall, just before the feed back information (visual if no force feedback is on your system or in the program) indicating stall occurs, and find either the structural limit of the plane or the pilot g limit on the way down in a diving spiral.

What should happen as dive angle increases, or as the pilot lowers the nose pointing below the horizon looking forward during the diving turn, speed will increase with increases in dive angle, the pilot will have to endure more g load (or the plane will break up) as speed increase above stall, the pilot pulls back on the stick to arrest the speed increases, but not too much or the plane will stall, or the pilot raises the nose, or decreases the dive angle, so as to slow the plane down, so as to keep from blacking out, but not too much or the plane speed will drop below stall. Meanwhile the plane orbits down a tube.

After a few tries the pilot will get a feel for it and the track file will be like an empty paper towel roll stood on end as the plane flies down the middle with each 360 turn losing nearly the same altitude. The same plane will not be able to fly inside that radius in a “sustained” level flight turn at minimum level flight sustained turn speed, such as a turn fight with an enemy while both planes are on the deck chasing each other’s tail, with no room to dive away, which isn’t any good if the diving plane has a much lower rate of acceleration, trying to get away from another plane that can catch up easily.

Which is the essence of the double superior or single superior concept; as the tighter turning plane that cannot accelerate, in a dive, as fast as the wider "sustained" turning plane can, one is superior at angles tactics, and the other is superior at energy tactics, assuming that the program is of high enough fidelity to know the difference.

Better energy fighting planes can't just keep turning and turning and expect to win a fight against better angles fighters, as explained by Robert Shaw in Fighter Combat.

If the program doesn't know the difference then that amounts to each plane being either or double inferior or double superior, and that has nothing to do with top speed, and that has everything to do with acceleration, or Energy Maneuverability, which can be illustrated by that EM diagram accelerated stall line, compared to the "sustained" stall line, or the difference can be explained with flight tests, such as level flight acceleration tests, or loaded deceleration tests, or that spiral dive corner speed test, compared to that "sustained" level turn at constant slow speed test.

That is a giant wall of test, and not something the casual user has an interest in, which isn’t an attempt to disparage any other interests, just a note in appreciation for anyone who shares such an interest. There is much to this subject, much more than a casual interest uncovers.
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#82 piecost

piecost
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Posted 28 June 2011 - 22:10

Thanks for the post, this needs some serious thought.
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#83 piecost

piecost
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Posted 06 July 2011 - 18:49

I may have found some evidence for the "corner speed" of the Camel.

see: Current ROF Airplanes Flight Model Data Topic. post# 37

The Maximum Angular Velocity of Aeroplanes
Reports & Memoranda No. 670 March 1920

"An examination of the analysis of accidents shows that at one time a number of accidents occurred due to the wings of Camels breaking during rapid turns, and the possibility of this is shown very clearly from the above Table. The calculated load factor of 5.4 was that existing on these machines at the time these accidents occurred; this value was subsequently appreciably increased"

The report calculates the limiting angular velocity (for strength) is 1.06 rad/sec, that is 60 deg/sec.
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#84 JG14_Josf

JG14_Josf
  • Posts: 7

Posted 11 July 2011 - 15:10

Navair reports

Scroll down to figure 6.15
Instantaneous Turn Performance

I re-found those documents. Note the last symbols in the URL: c6.

Change that last symbol to c5.

http://www.aviation.org.uk/docs/flighttest.navair.navy.milunrestricted-FTM108/c5.pdf

Scroll down to figure
5.6
TYPICAL SPECIFIC EXCESS POWER CHARACTERISTICS

Then scroll down to:

5.4 TEST METHODS AND TECHNIQUES
The principal test method for obtaining Ps data is the level acceleration.

All that is derived from John Boyd's work.

Ps = V[T/W - D/W]

Note how increases in thrust move Specific Excess Power up and right on the chart:
Figure 5.11
EFFECT OF INCREASED THRUST ON SPECIFIC EXCESS POWER

Note how increases in parasite drag move Specific Excess Power down and left on the chart:
Figure 5.10
EFFECT OF INCREASED DRAG ON SPECIFIC EXCESS POWER

Ps (Specific Excess Power) = V (airspeed) times [T/W Thrust divided by weight - D/W Drag divided by weight]

Note that drag is divided by weight too. Think about how that works. There are ways to illustrate how that works.

Example:

When a plane has lost thrust, or when a plane is a glider, there will be that same angle of attack where CLmax is found, and on that angle of attack the plane will travel the farthest distance for any given altitude. On that glide path any increase or decrease in angle of attack will result in less distance traveled. That is derived from L/D or Lift divided by drag.

What is the airspeed during that flight at CLmax?

D/W

Drag divided by weight determines the airspeed.

A plane with engine off, or a glider, will have a glide speed as it travels down its best glide angle, or best glide speed, and what happens when the plane looses fuel, or when the glider dumps ballast?

It slows down.

It goes the same distance if it is heavy and fast, and it goes the same distance if it is light and slow.

Drag is divided by weight, which means that the mass of the plane reduces the net force of drag, and this can be seen another way.

Two gliders are side by side at the same speed and both are going straight up in a vertical zoom climb, they are exactly the same glider except one is twice the weight of the other, which one goes to a higher altitude in the zoom climb?

The effects of weight are shown on that web page scrolled down to:
Figure 5.9
COMPARING EFFECT OF INCREASED GROSS WEIGHT WITH INCREASED
NORMAL ACCELERATION

Go back to c6
Find:
Figure 6.31
SPECIFIC EXCESS POWER VERSUS TURN RATE

Note how turn rate reaches maximum, at a loss of energy, at CLmax, and note the increase in energy loss after the pilot exceeds CLmax and the plane is pitched further back.

Find:
Figure 6.32
SPECIFIC EXCESS POWER VERSUS TURN RATE COMPARISON

Note how a plane can have a tighter turn radius at a higher rate of energy loss. That cannot exist in a game if the fidelity of the software is low, or if the simulated flight model does not calculate D/W, or drag divided by weight - which can be tested.

If two of the same planes are side by side, engine off, and both planes are gliding at best glide angle, CLmax, and one plane is full of fuel, full of ammo, as heavy internally as possible, and the other plane is as light as possible, but both are externally the same drag, then the heavy one will reach the same maximum distance faster than the lighter one, in reality.

If that doesn't happen in the simulator, then the simulator isn't simulating D/W.

Find:
6.4.1 WINDUP TURN

Then:
6.4.4 LOADED DECELERATION

Those tests are used to plot accelerated stall lines.

If the game is of low fidelity the accelerated stall lines may plot out all the same, no matter which plane is tested and plotted out on an accelerated stall line, all the curves may plot out to be the same exact shape, unlike that very different shapes shown on that one EM chart attributed to John Boyd when Chuck Yeager helped test the captured Mig-15 against the F86, in the effort to figure out why the F-86 was dominating the Mig-15 in air combat.

I can look further, later, for the simple formula used to calculate lift limit as a function of drag increasing square with velocity, based upon a level flight 1 g stall speed, but such calculations assume a universal wing efficiency factor, as far as I know.
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#85 piecost

piecost
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Posted 11 July 2011 - 21:01

Josf,

Thanks for the post and the documents, they warrant a careful read.
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#86 piecost

piecost
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Posted 17 August 2011 - 23:03

Reduction of Aeroplane Trials for the Purposes of Aerodynamic Comparison & Prediction

Reports & Memoranda No 608

[performance of SE5a, Albatros Scout 160 Hp Mercedes, Pfalz Scout 160 HP Mercedes]

[note: the type of Albatros is not given. Jane's Fighting Aircraft of World War 1 shows photos of a DI (in German markings with BU marked on the fuselage) - this could have been captured & tested? The same source gives details of Pfalz DIII 4184/17 captured by the British on 26 Feb 18

Also note: the performance figures are normalised to a standard wing loading and power loading]

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#87 piecost

piecost
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Posted 17 August 2011 - 23:04

Reduction of Aeroplane Trials for the Purposes of Aerodynamic Comparison & Prediction

Reports & Memoranda No 608

[performance of SE5a, Albatros Scout 160 Hp Mercedes, Pfalz Scout 160 HP Mercedes]

[note: the type of Albatros is not given. Jane's Fighting Aircraft of World War 1 shows photos of a DI (in German markings with BU marked on the fuselage) - this could have been captured & tested? The same source gives details of Pfalz DIII 4184/17 captured by the British on 26 Feb 18

Also note: the performance figures are normalised to a standard wing loading and power loading]

…continued

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#88 piecost

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Posted 01 September 2011 - 11:42

Reduction of Aeroplane Trials for the Purposes of Aerodynamic Comparison & Prediction

Reports & Memoranda No 608

[performance of SE5a, Albatros Scout 160 Hp Mercedes, Pfalz Scout 160 HP Mercedes]

missing page

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#89 piecost

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Posted 01 September 2011 - 11:47

Lift & Drag of SE5 Aeroplanes. Comparison of Full Scale & Model Results

Reports & Memoranda No. 739

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#90 piecost

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Posted 01 September 2011 - 11:53

Experiments on an SE5a Aeroplane with modified Control Surfaces

Reports & Memoranda No. 687

[elevator & rudder angle to trim]

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#91 piecost

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Posted 01 September 2011 - 11:56

Forces & Moments on a Model SE5a Yawed, Rolled & Pitched

Reports & Memoranda No. 546

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#92 piecost

piecost
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Posted 01 September 2011 - 17:16

SE5a CLmax

The following reference:

Flight Model ….

post#40

page 878 gives the stall speed for SE5a as 54 to 56 mph

Assuming a weight of 2050lb, sea-level ISA conditions & a wing area of 250ft^2:

SE5a CLmax = 1.16
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#93 piecost

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Posted 02 September 2011 - 06:27

Measurement of the Derivatives Mq & Nr for a Number of Aeroplane Models

Reports & Memoranda No. 580

[pitching moment due to pitch rate & Yawing Momement due to Yaw Rate for SE5, BE2C, FE2D]

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#94 piecost

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Posted 03 September 2011 - 10:44

Effect of Sideslip on a model SE5a

Reports & Memoranda No. 831

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#95 piecost

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Posted 03 September 2011 - 10:46

Effect of Sideslip on a model SE5a

Reports & Memoranda No. 831

…continued

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#96 piecost

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Posted 03 September 2011 - 10:50

The Lateral Stability of SE5a in Gliding Flight

Reports & Memoranda No. 846

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#97 piecost

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Posted 03 September 2011 - 13:40

Experimental Determination of Tailplane Characteristics

Reports & Memoranda No. 761

[SE5a, RE8]

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#98 piecost

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Posted 03 September 2011 - 13:41

Experimental Determination of Tailplane Characteristics

Reports & Memoranda No. 761

[SE5a, RE8]

…continued

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#99 piecost

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Posted 03 September 2011 - 13:48

The Determination of Rotary Derivatives

Reports & Memoranda No. 809

[SE5a]

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#100 piecost

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Posted 03 September 2011 - 13:49

The Determination of Rotary Derivatives

Reports & Memoranda No. 809

[SE5a]

…continued

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#101 piecost

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Posted 03 September 2011 - 13:55

The Best Glide angle for an Aeroplane in wind with the Engine Shut Off

Reports & Memoranda No. 544

[RE8, SE5a, Sopwith Camel, Handley Page 0-400, DH9]

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#102 piecost

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Posted 03 September 2011 - 13:57

The Best Glide angle for an Aeroplane in wind with the Engine Shut Off

Reports & Memoranda No. 544

[RE8, SE5a, Sopwith Camel, Handley Page 0-400, DH9]

…continued

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#103 piecost

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Posted 03 September 2011 - 14:03

Cushioning Effect on Aeroplanes Close to the Ground

Reports & Memoranda No. 754

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#104 piecost

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Posted 03 September 2011 - 14:09

Lateral Control at Large Incidence, Yawing & Rolling Moment due to Aileron on SE5a Model

Reports & Memoranda No. 773

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#105 piecost

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Posted 03 September 2011 - 14:11

German Ailerons with Wash-out as assessed by the Royal Aircraft Establishment

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#106 piecost

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Posted 12 October 2011 - 17:05

Effect of Stagger & Decalage on the Auto-Rotation of a RAF15 Biplane

Reports & Memoranda No. 733

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#107 hq_Jorri

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Posted 18 December 2011 - 13:25

Article from Air Enthusiast about the design faults in the lower wing of the Albatros, with calculations for critical speed and comparison with the SPAD 13.

Some conclusions:
'Given that the measured top speed (in level flight) of the Albatros D V was 103 mph (166 km/h), the predicted critical speed of 118 mpg (190 km/h) is reasonable. If the error margin is 15 per cent, the critical speed could have been as high as 135 mph (217 km/h) - a speed that was probably easily attainable in a power dive.'

'Given the SPAD's top speed of 131.5 mph (212 km/h), the analysis indicates a critical flutter speed of range centered above 300 mph (483 km/h) and thus probably well in excess of the operational speeds attained even during combat. The analysis unambiguously shows the SPAD to be immune to flutter problems, as confirmed by its operational record.'

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#108 gavagai

gavagai
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Posted 18 December 2011 - 14:05

Jorri, that is not data. It is a hypothesis, maybe an untestable one.
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#109 piecost

piecost
  • Posts: 1318

Posted 18 December 2011 - 21:16

Thanks for posting Jorri, an interesting read and well worth posting. It may not be data but is relevant.

'Given that the measured top speed (in level flight) of the Albatros D V was 103 mph (166 km/h), the predicted critical speed of 118 mpg (190 km/h) is reasonable. If the error margin is 15 per cent, the critical speed could have been as high as 135 mph (217 km/h) - a speed that was probably easily attainable in a power dive.'

If we take the margin of error (why 15%?) the other way and assume that the simulation might over-predict the flutter speed then the critical speed could be coincident with the top speed (103 mph)! I'm think that if the flutter speed were even as as low as 135mph then the aeroplane would be unusable in combat.

However,

one should not place too much emphasis on the exact numbers, however

It does lend credibility to the flutter theory and so is useful.

As far as the numbers go; I tend to be skeptical about theoretical predictions without knowing that the person has direct experience in that field (on that particular aeroplane type) or has carefully validated the methods. Can the same assumptions about structural response and stiffness be made for wire braced wooden structures as are well established on cantilever aluminum ones?

This may have been food for thought for those setting the the never exceed speed on the replica

Notes on Flying the D.Va …..
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#110 BillyKid

BillyKid
  • Posts: 77

Posted 09 January 2012 - 17:20

Wanted to contribute another set of tables. These are from the Harleyford Publication Fighter Aircraft of the 1914-1918 War

I am not looking for an arguement, these are intended as another source for the developers.

Keep in mind the key on pages 212 and 213, stats are given in mph, gallons, feet/inches, ect.

Attached Files


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#111 piecost

piecost
  • Posts: 1318

Posted 23 February 2012 - 03:29

The Controllability of Aeroplanes with Special Reference to Rapid Turning
Reports & Memoranda No 212

[BE2c, FE8, FE4, FE2b, RE7]

Attached Files


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#112 ImPeRaToR

ImPeRaToR
  • Posts: 7902

Posted 05 April 2012 - 12:41

Source: Die deutschen Luftstreitkräfte im Weltrkiege - Georg Paul Neumann
DL: http://archive.org/d...enluf00neumgoog" onclick="window.open(this.href);return false;">http://archive.org/d...enluf00neumgoog

Image

Image

175km/h for Cl.II


Image

Image

175km/h for Albatros D.II
165km/h for " D.V like we have now!
200km/h for Fokker D.VI
218km/h for Fokker D.VII w/ BMW

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#113 MiG-77

MiG-77
  • Posts: 2651

Posted 05 April 2012 - 13:07

175km/h for Cl.II

And 168km/h for Cl.IV. But look for climb rate of Cl.II…



175km/h for Albatros D.II
165km/h for " D.V like we have now!
200km/h for Fokker D.VI
218km/h for Fokker D.VII w/ BMW

200km/h for both Fokkers.
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#114 WW1EAF_Paf

WW1EAF_Paf
  • Tester
  • Posts: 1458

Posted 05 April 2012 - 13:17

Also interesting to compare DFW and Cl.II climb.
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#115 ImPeRaToR

ImPeRaToR
  • Posts: 7902

Posted 05 April 2012 - 13:28

175km/h for Cl.II

And 168km/h for Cl.IV. But look for climb rate of Cl.II…



175km/h for Albatros D.II
165km/h for " D.V like we have now!
200km/h for Fokker D.VI
218km/h for Fokker D.VII w/ BMW

200km/h for both Fokkers.

Oh I accidentally read the "Nutzlast" collumn, lol :D
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#116 gavagai

gavagai
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Posted 05 April 2012 - 17:05

Imp, that's a 1920 publication. What was his source for that performance data? It would be a mistake to presume it is independent confirmation of Entente performance data, especially when the figures you give parrot figures we've previously seen.
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#117 ImPeRaToR

ImPeRaToR
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Posted 05 April 2012 - 17:24

Well most likely they used German sources but I don't know :)
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#118 J5_Rumey

J5_Rumey
  • Posts: 1180

Posted 05 April 2012 - 18:15

According to this the DRI should do 200 Km/h :shock: ?!? And climb to 5000 meters in 14 and half min. Also the speed 165km/h is for a albatros DV not a Dva like we have in-game, actually a big difference if we talk about possible engines?
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#119 volatile_void

volatile_void
  • Posts: 55

Posted 05 April 2012 - 18:52

Well most likely they used German sources but I don't know :)

According to the Title page:

Attached File  diedeutschenluf00neumgoog_0007.png   31.57KB   514 downloads

Unter Mitwirkung von 29 Offizieren und
Beamten der Heeres- und Marine-Luftfahrt
nach amtlichen Quellen herausgegeben von
Georg Paul Neumann
Major a. D.
(im Kriege Hauptmann in der Fiegertruppe)


With the participation of 29 officers and
officials of the Army and Navy Aviation
according to official sources published by
Georg Paul Neumann
Retired Major
(in the war a captain in the Fiegertruppe)



Section A.IIIa specifically was contributed to by:

Attached File  diedeutschenluf00neumgoog_0016.png   93.1KB   514 downloads

Herrmann, Lt. d. Res., Halle a. Saale;
im Kriege Lt. d. Res., Flugzeug- u. Schlachtstaffel Führer

Neumann, Major a. D., Berlin;
im Kriege Hptm., Adjutant des Inspekteurs der Fliegertruppen, Führer u. Kdr. von Flg. Abtlgn.

Siegert, Oberstlt. a. D., Berlin;
im Kriege Oberstlt. und Inspekteur der Fliegertruppen.


Looks rather official.. :)


..but 200 km/h for the Dr.I :o :?
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#120 gavagai

gavagai
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Posted 05 April 2012 - 18:58

Yes, very trustworthy indeed. I thought we were past the belief that aircraft data from WW1 is reliable?

But, do carry on, it makes for an entertaining distraction.
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