Stability and Control characteristics of the Early Mark Spitfires

[IvanK]

And supposedly the clod spitfire doesn't in YOUR opinion meet some standards in your mind that you refer to without quantification.

All this stuff about things being measurable and to defined standards then when asked how you find them in the Sim all we get is:

"Fly the airplane in the buffet and time your turn.

Pull back on the stick, release, and note the behavior of the airplane.

Fly at Vmax, pull hard back, hold it at full deflection, and note the behavior.

Fly the airplane trimmed for slow flight, let go of the stick, fire the guns, and note the behavior.

I have played the game and note the behaviors as I play. Just because I don't spend my time making excel spreadsheets does not mean the points are invalid."

When others actually go out there test and document and show their results you jump on them questioning every detail of their efforts. ... what were the conditions etc etc.

Please give us a break and at least practice what you preach !

[DC338]

It was not until the design was evaluated under a set of measured and defined standards that the longitudinal instability was quantified and fixed in the Spitfire.

Can you explain this further. Fixed As a result of NACA? How? Surely not.

Can we have a analysis of figures 16 17 & 18 pointing to the instability in these test? It would appear tha 15 is an anomaly when compared to the later test.

[Crumpp]

Can we have a analysis of figures 16 17 & 18 pointing to the instability in these test? It would appear tha 15 is an anomaly when compared to the later test.

It is different conditions.

In Figure 15 we see the result of the pilot just pulling the stick back and entering a turn. That is the inherent stability of the aircraft without pilot input. It tells us the workload the pilot needs to exert.

In figure 16, he pushes the stick forward in the measuring equipment.

In figure 17 and 18, he demonstrates the stability thru careful flying.

Figure 15, In other words it is the measured results of what happens if you are new player and you turn the Spitfire and keep the stick pulled back like a stable aircraft to maintain the turn.

In figure 16 we see the proficient but not the expert at controlling the aircraft. He pushes forward and his ability to control the aircraft improves. He still is not getting that steady level of acceleration.

In figure 17 and 18, we see the pilot carefully matches the unstable accelerations to produce a steady level of acceleration.

Klem,

The aircraft in the game acts stable both static and dynamic. It returns to trim and dampens the oscillation. Only in a steady state climb does it begin to act neutral.

I don't know the games code, but it seems like they made it "just statically stable" in level flight without the dynamic instability. When an aircraft enters a climb, the stability margin is reduced so we see the neutral static stability.

The spin modeling is excellent for a game. It took an average of at least two turns to recover when correct input was held. I liked it.

The stall behavior when reached is good too.

The issue is the amount of control required to maintain a turn is not representative of the longitudinal instability.

The inability to exceed the airframe limits. You can pull as hard as you want on the stick without fear of breaking the airplane.

The buffet effects are under modeled. In the game, The turn rate improves IN the buffet without any advantage for correctly flying a maximum turn rate performance turn. The turn performance does not begin to taper off until just before the stall when the slope becomes rather steep. That is not correct. Turn rate should decay in the buffet as a function of the strength of the buffet.

The buffet itself is under modeled. It is like a nibble when we see from the NACA report it imparted noticeable accelerations on the aircraft. Those accelerations are quantified in figures 13 and 14 of the NACA report.

In other words, your turn rate in the game improves in the buffet until just before the stall point and the airplane does not shake as the real thing.

That is part of the stall warning. The idea is to have it so you know to back off and not stall. It is essential to the control of an longitudinally unstable aircraft to have that large and distinct stall warning as well as the ability to maintain control in it. The large accelerations warn of the impending stall and increase the power required to make the turn. This also encourages realism. He rewards the players that fly on the edge to the nibble and back off to smooth air. It has the added benefit of precisely defining that point to an experience player.

[Crumpp]

you jump on them questioning every detail of their efforts.

I am sorry if that is your perception. It is not the case or my intention.

I only post to try and help the testor's efforts.

For example, posting aircraft performance test's without the conditions for both aircraft and atmosphere does not tell one if the airplane is performing at it should under other conditions.

It should not be surprising that those questions come up when the information is not presented only the results.

[NZtyphoon]

Originally Posted by Crumpp

In England, Jeffery Quill was the Chief Test Pilot for the development of the Spitfire. If it met his standards in his opinion, without quantification, it went forth despite the some early testing investigating the longitudinal instability, his acknowledgement, and all the warnings found in the Operating Notes that are the result of longitudinal instability.

It was not until the design was evaluated under a set of measured and defined standards that the longitudinal instability was quantified and fixed in the Spitfire.

Alas Jeffrey Quill - he spent thousands of hours in flight, testing and developing real Spitfires in real conditions, and thus we find out that he had no idea of what he was doing by an American sitting in front of a computer who had "tested" the Spitfire a couple of times on a flight sim and he did find it wanting. And because of Quill Spitfires went forth unstable and drunken in their flight.

Thus it was the Yanks who came to the rescue and fixed the hitherto unstable machine by waving their magic flight reports and inertia weights and speaking in unison "Fix this Spitfire it does not meet our standards!" The British quavered and lo! they fixed the Spitfire forever. And the tale told by Quill, that the inertia weights were fitted after the discovery of badly loaded Spitfire Vs in Fighter Command service was horse pucky.

[Crumpp]

Thus it was the Yanks who came to the rescue and fixed the hitherto unstable machine by waving their magic flight reports and inertia weights

1. Did inertial weights get added to the design to fix the Longitudinal instability....YES.

2. Did this occur during the Battle of Britain.......NO, the longitudinal instability was not fixed during the Battle of Britain.

3. Should the Spitfires modeled in the game exhibit the longitudinal instability.....YES.

4. Do they now exhibit the longitudinal instability in the game....NO.


As "yanks coming to the rescue"....that is a very myopic view and far from the truth.

It was Gates and Lyon's efforts that brought a measureable standard to the UK aviation authority. Yes he based those standards on the NACA's efforts just as the NACA based part of their standards on his work.

And the tale told by Quill, that the inertia weights were fitted after the discovery of badly loaded Spitfire Vs in Fighter Command service was horse pucky.

And I suppose they added the inertial elevators to the Spitfire Mk I because nobody in the RAF could read a load plan or do a weight and balance?

I am sure there was an issue in the Mk V when it first came out with the operators incorrectly loading the aircraft. That certainly did not help the longitudinal instability of the design making a bad situation much worse, but it was not the reason for the longitudinal instability.

[Crumpp]

Can you explain this further. Fixed As a result of NACA? How? Surely not.

The inertial devices added to the elevator control is the fix for the longitudinal instability.

You add weights to the control and those weights act to artificially increase the amount of control force required.

[NZtyphoon]

Bug #415 and this thread

[Crumpp]

Bug #415 and this thread

Maybe, but it is not because the stability and control characteristics are modeled in the game or that they cannot be modeled.

More to do with community politics than aircraft behaviors.

[Crumpp]

IvanK says:
When you started this thread its purpose was to discuss this issue as it pertained to early mark spitfires IRL, not for a bug tracker entry

I thought you all wanted realism in your game. I see that is not the case.