Stability and Control characteristics of the Early Mark Spitfires

[Crumpp]

The control is satisfactory as regards "feel" and response, but would be improved if the movement of the control column for a given movement of the elevators was slightly greater

http://www.spitfireperformance.com/k5054.html

Longitudinally, the aircraft is stable with centre of gravity forward, but is unstable with centre of gravity normal and aft with engine 'OFF' and 'ON'. Longitudinal stability records are attached.

http://www.spitfireperformance.com/k9787-fuel.html

[Glider]

I hate saying this Crumpp but when are you going to read the evidence you put forward?

K5054 is the prototype and the report did say what you said it did for the movement of the elevators.

K9787 is the very first aircraft delivered for the RAF and in this report to do wth the elevators it says:-
The gearing of the elevator control and elevator trimmers which were considered too high in the prototype are satisfactory in this aeroplane.

ie Elevators fixed for production aircraft

While you are at it can I have your test pilot reports that support your statement or is this it?

[robtek]

There is also still no evidence in form of provable data that the data presented by crumpp is not correct.

[NZtyphoon]

Originally Posted by Crumpp

What is funny is the next aircraft I was going to discuss is the Hawker Hurricane. Sir Sydney Camm may not have understood swept wing theoy during the war but he was a master of stability and control design. The Hurricane was a wonderful gun platform and had near perfect longitudinal stability. His other major designs, the Typhoon and Tempest also exhibited the same characteristics.

Interesting that the Pilot's Notes for the Typhoon I note:

39. General Flying
(i) Stability. - The aircraft is stable directionally and laterally, but is slightly unstable longitudinally...

Tempest V Pilot's Notes:

44. General Flying
(i) Stability. - The aircraft is stable directionally and laterally, but is slightly unstable longitudinally.

[Al Schlageter]

Originally Posted by taildraggernut

Yes, it ran it's course a while ago....anyway looking forward to the 109 debate, is is coming soon?

There won't be one as the 109 was perfection personified as it is German.

[Crumpp]

Typhoon I

Yep and notice the Typhoon Operating Notes lack the warnings of the Early Mark Spitfire notes.

1. No bracing in turns required

2. Lack of warnings about overloading the airframe

IIRC, the Typhoon's issues did not stem from stability and control design but low velocity flutter in the tail.

It was reported in a couple of flights as longitudinal stability issues but not measured.

It turned out to be a q-limit issue. I think early Typhoon's even had a few structural failures because of it.

[NZtyphoon]

Originally Posted by Crumpp

IIRC, the Typhoon's issues did not stem from stability and control design but low velocity flutter in the tail.

Wrong, once again - the tests observe that the Typhoon had fore and aft instability (page 2 para 5), no mention of your "low velocity tail flutter" - as it was the Typhoon's operational history showed that it did make a good GA aircraft. The Tempest, which had no sign of "low velocity tail flutter" also exhibited the same characteristics, contradicting your statement:

Sir Sydney Camm may not have understood swept wing theoy during the war but he was a master of stability and control design. The Hurricane was a wonderful gun platform and had near perfect longitudinal stability. His other major designs, the Typhoon and Tempest also exhibited the same characteristics.

[Crumpp]

The "instability" was low velocity flutter and was not caught until the end of the war.

The tail problems turned out to be due to elevator flutter and were cured by modifying elevator balance, but that didn't happen until very near to the end of the war.

http://www.airvectors.net/avcfury.html

The RAE did not have a standard for stability and control.

ONCE again, there is nothing else in the Operating Notes in either the Typhoon or the Tempest that pertain to any kind of longitudinal stability issue. Had their been an issue, it would reflect in the cautions.

This is in sharp contrast to the early Mark Spitfires whose Operating Notes are filled with warnings of symptoms that are the result of longitudinal stability.

[camber]

Crumpp,

I keep hoping you will try and answer Glider's question. If the Spit had such objectional handling characteristics, why is there such a huge body of pilot's reports stating otherwise?

Your position seems to be to me that all such reports don't warrant any thought or comment as they do not represent hard data. I disagree, and don't seem to be alone on this. I don't see how you can convince many others including myself unless you try to come up with some explanation and try to address the discrepancy. Don't you have an opinion?

If you were a young pioneering stability control engineer in 1940, what would YOUR approach be? Judging from this thread, you would collect hard data with precision and evolve intuitively appropriate standards. Then you would ignore all test pilot's feedback of whether or not your proposed changes were desirable. After all, they are not control and stability engineers and cannot understand how their combat aircraft should operate. I don't think you would be playing much of a role in the future of aviation after that.

camber

[Glider]

Originally Posted by robtek

There is also still no evidence in form of provable data that the data presented by crumpp is not correct.

On one side we have the views of the German, American and British test facilities, as well as the pilots who flew them that the SPitfire is easy to fly. Nowhere in any of these does it say that is was difficult or uncomfortable to fly.

Everyone agrees that there was a slight instability but either it wasn't noticable or it was easily dealt with.

On the other side we have Crumpp's view that because there is a slight instability that it was difficult/uncomfortable to fly. He also said that he had the reports from the test establishments and test pilots to support that view.

He has been asked many times to supply these reports from the establishments/pilots which he has failed to do. When he does supply something it turns out that the first is on the prototype and the second confirms that the issue on the prototype has been solved in the first production aircraft. So far there is nothing else submitted.

Its worth remembering that no one forced him to say that he had this supporting evidence, it was Crumpps statement.

I am afraid that I am starting to believe one of three options:-

a) He never had the supporting evidence and tried to bluff his way out of a problem
b) He does have the reports and they don't say what he wants them to say, so he isn't posting them
c) He has the reports, they say what he want but for some reason he will not submit them

Of the three options C is looking more and more unlikely. I truly hope that I am wrong and that he does have support as A and B are not good options