Stability and Control characteristics of the Early Mark Spitfires

[robtek]

I'd like to repeat that being unstable or negative stability is NOT desirable for any airplane, as the pilot, or today electronics and hydraulics, have to work all the time for a controlled flight.
For commercial planes, were safety is the highest priority, positive stability is desirable.
For fighters, or aerobatic planes, neutral stability is the non plus ultra.

[Crumpp]

During WW2, however, the demands of production testing thousands of aircraft meant that each factory adopted its own techniques, designed to test aircraft to an acceptable standard, as quickly as possible, before delivery: this did not mean that there wasn't a standard set by the RAE, simply a divergence of ways in which it was done at a production level. The same thing happened in the 'States, each factory adopted a testing regime broadly following the NACA guidelines.

Once again, a standard is a standard. The Air Ministry and the RAE did not have one.

The United States had a standard during the war. That does not mean every airplane met that standard. Most aircraft were designed before the standard was adopted. It does mean, they designed to meet, tested to meet it, and implemented design corrections to meet the adopted standard. Part of that report and standard is included in the very first post in this thread.

The design firms in the United States were obligated to meet a standard. Supermarine was under NO Obligation to correct the Spitfire. It as already in production and service. It took the NACA, Gates, and mounds of evidence of the instability before a simple correction was adopted.

With the right information, figuring out how much weight to add to your elevator bellcrank is no different than a weight and balance. Once more, a designer can add springs, bungees, weights, and other devices to increase or decrease the control force as he wants.

Facts are the RAE relied upon the individual talent of the engineers and the opinion of the pilots.

Not all engineers are equal. For example, Sir Sydney Camm was very talented with stability and control design. His designs reflect that. RJ Mitchell certainly missed the mark on the Spitfire.

Is a stable aircraft more or less maneuverable than an unstable one.

It does not matter how maneuverable an aircraft is if the pilot cannot control it.


That is the Spitfire's issue. Nobody is claiming it should be less maneuverable. The longitudinal axis should be so maneuverable as to be very difficult to precisely control.

Generally speaking, all aircraft above Va can exceed their airframe limitations. You can do it more easily in the Spitfire.

It is also harder to precisely control in a turn. The strength of the buffet determines the scope of the effects of the stick shaker zone. Hitting stick shaker in a Spitfire is easier due to the longitudinal instability.

Properly modeled, the Spitfire has world beating performance. While not the most agile fighter, it is fast, climbs well, and excellent rate of steady state turn.

The majority of fighter pilots in World War II never got into a single dogfight. Most kills occurred without the "victim" even knowing the opponent was there behind them.

So all those anecdotes about "easy to fly" are worthless without the context and a comparison of pilot skill. I would love to fly a Spitfire and throw it around the sky on a sunny afternoon.

That is not the same as dog fighting. Dogfighting is what you do in this game and it has very little if anything at all to do with the actual events or history. An actual simulation of WWII would be zero fun. For the vast majority of pilots, it was lots of tedious flying to be killed without ever seeing who did it. For a few, it was a few seconds of terrified maneuvering before death and for a rare few that we still talk about today, the thrill of the hunt.

The NACA and the RAE agree that the aircraft was difficult to precisely control in a turn. It was twitchy airplane. The airplanes characteristics are measureable, definable, and everyone who was involved with the airplane agreed upon them.

The Spitfire should take time and skill to master. Once mastered, reward its aficionados with the performance they expect.


I think this thread has about run its course. Time to submitt the bugtracker.

[Crumpp]

Please start into my use of "stick shaker"....

[Crumpp]

Alex Henshaw on flying the Spitfire

How many actual dogfights did Henshaw get into in an early mark Spitfire??

None.

How many in any Spitfire??

What Mark of Spitfire is that on the magazine cover?? What Mark was the topic of this thread??

[NZtyphoon]

Originally Posted by Crumpp

How many actual dogfights did Henshaw get into in an early mark Spitfire??

None.

How many in any Spitfire??

What Mark of Spitfire is that on the magazine cover?? What Mark was the topic of this thread??

What does it matter how many dogfights Henshaw got into - how many have you got into? How many Spitfires have you flown? And since when has this thread been a discussion on dogfighting in the Spitfire anyway?

Nor does the mark of Spitfire on the cover have anything to do with the article.

[Crumpp]

Where is your evidence that Supermarine was under no obligation to correct the Spitfire?

They knew about it in 1936!! Do you really think Supermarine is that stupid it took them four years to fix it???

It cost's money to add things to an airplane. Even more money to fix an issue that is the designers fault.

[NZtyphoon]

Originally Posted by Crumpp

They knew about it in 1936!! Do you really think Supermarine is that stupid it took them four years to fix it???

It cost's money to add things to an airplane. Even more money to fix an issue that is the designers fault.

Who knew about what in 1936? and no Supermarine were not stupid. And what relevance does the last statement have to with anything?

[Crumpp]

How did NA comply with the "standard" when they fitted the P-51B/C/D with rear fuel tanks

They restricted its use when full to non-combat flying. It was prohibited to dogfight with a specified amount of fuel in the tank.

That was so the CG would be within specs......

[NZtyphoon]

Originally Posted by Crumpp

Once again, a standard is a standard. The Air Ministry and the RAE did not have one.

The United States had a standard during the war. That does not mean every airplane met that standard. Most aircraft were designed before the standard was adopted. It does mean, they designed to meet, tested to meet it, and implemented design corrections to meet the adopted standard. Part of that report and standard is included in the very first post in this thread.

The design firms in the United States were obligated to meet a standard. Supermarine was under NO Obligation to correct the Spitfire. It as already in production and service. It took the NACA, Gates, and mounds of evidence of the instability before a simple correction was adopted.

Absolute nonsense, once again Crumpp - you clearly have no clues as to how the British aviation industry operated in wartime. Where is your evidence that Supermarine was under no obligation to correct the Spitfire?

How did NA comply with the "standard" when they fitted the P-51B/C/D with rear fuel tanks, thus turning the machine into one that was highly unstable when the tank was full? Was the "standard" adopted before or after the P-51 was designed; before or after the modifications to the P-51?

How did Grumman correct the undesirable elevator characteristics of the F8F-1 to meet NACA standards? Was the "standard" adopted before or after the F8F was designed?

[Sandstone]

Originally Posted by Crumpp

:That is the Spitfire's issue. Nobody is claiming it should be less maneuverable. The longitudinal axis should be so maneuverable as to be very difficult to precisely control.

This is where you don't convince me.

The Spitfire certainly did have undesireable pitch stability, but was it enough to make it "very difficult" to control precisely? I don't think it was. I think this because pilot accounts seldom mention longitudinal stability and because low-hours pilots flew it without problem. You obviously think it was, but this interpretation doesn't seem to be backed up by much in the way of evidence and, to me at least, comes over as no more than an assertion. Certainly, nothing convincing has been presented.

You say we shouldn't consider Spitfire pilot acounts. But if we are to determine how much of a problem was actually caused to real Spitfire pilots by the stability issue then that is exactly what we have to do. I can't see any way round this.