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Thanks, winny. That is now pretty clear to me. Wouldn't have made sense to put weights to the tail in order to improve stability. It would just worsen it.

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Originally Posted by 41Sqn_Stormcrow (Post 422887)

Thanks, winny. That is now pretty clear to me. Wouldn't have made sense to put weights to the tail in order to improve stability. It would just worsen it.

Yeah, it was only a small weight, 3.5 or 6.5 lb, depending on which wing was fitted, the lighter was for browning wing heavier for cannon wing, added to the actual control cables. It was about 3 quarters of the way down the fuselage.

"The stall warning possessed by the Spitfire was especially beneficial in allowing the Pilot to reach maximum lift coefficients in accelerated maneuvers. Because of the neutral static stability of this airplane, the pilot obtained no indication of the lift coefficient from the motion of the control stick, nevertheless, he was able to pull rapidly to maximum lift coefficient in a turn without danger of inadvertent stalling...."

A nice feature in a fighter !

If the Spitfire was such a terrible a/c, at least according to Eugene, why did the USAAF accept them for service?

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You might find the following RAE comments of the NACA test to be of interest, in case you havn't already seen them.

You might find the following information useful....

Gilruth's developed the concept of stick force per G, control movement measurement, and pretty much wrote the standards of measurement for stability and control as used by the NACA.

Only two nations in the world had stability and control standards during World War II, the United States and Germany.

The NACA's measurement and classification system developed by Gilruth was not published until 1941 and was classified. It was not released to Allied Nations until 1943.

Even Gates, a very prominent RAE researcher who pioneered stability and control standards for the RAE was not privy to them during his 1942 "dash around America" tour of the United States research facilities. Gates was the one who defined Aerodynamic Center, stability margin, and maneuver points during his lifetime. He had a passion for stability and control and published some 130 papers before his death. Before him, the neutral point was termed the metacentric ratio.

Unfortunately, nobody at the RAE paid much attention to Gates and it was not until post war that the United Kingdom adopted any defined standards of what is acceptable and what is not in terms of stability and control. When they did, it was a mirror of Gilruths work at the NACA.

So, by what standard is the RAE refuting the NACA? The answer is really none. The RAE had no defined standards of stability and control except subjective opinion.

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Originally Posted by Crumpp (Post 422960)

Still doesn't prove the Spitfire was a dangerous aircraft to fly; apart from that I'd like to see Crumpp provide some documentary evidence that Spitfires regularly broke up in flight during spin recovery.

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Originally Posted by JtD (Post 422055)

Stick fixed is just one version of static stability, you're keeping the elevator angle constant over a speed range and check how the aircraft responds. In case of the Spitfire, no trim change occurred, so the plane would keep the same AoA over the entire speed range at the same elevator deflection. That's neutral stability.

First of all, stick fixed is not a version of static stability. Stick fixed is a control term and just means you are using the maneuver point that the pilot, controls, and the mechanical linkage has friction and mass. Static stability is the aircrafts initial reaction to displacement.

It has absolutely nothing to do with keeping the elevator constant. It is about the oscillations.

The other version NACA was looking at is stick force stability, if you want to call it that, where you are keeping the stick force constant through the speed range and check how the aircraft responds. In case of the Spitfire, stick force increased with the speed, which in turn leads to smaller elevator deflections which means some sort of positive stability.

They are looking for a stable gradiant. They are not keeping the force constant, they are looking for a slope as it moves away from trim speed. They are looking for a smooth increase in stick forces. The stick forces will change as they are based on velocity.

The Spitfire was dynamically stable.

The longitudinal dynamic stability (Long Period Oscillations) was neutral or negative as recorded by the NACA.
All for longitudinal stability.

;)

I didn't say any of the parts in bold, which you claim to be quoting from me.

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I'd like to see Crumpp provide some documentary evidence that Spitfires regularly broke up in flight during spin recovery

First of all, let's get what I said correct. Feel free to point out where I make any reference to "regularly". That is your own pointy tin foil hat theory.

I said it could happen to the Spitfire. The Operating Notes clearly warn the pilot of the hazardous longitudinal stability characteristics.

http://img546.imageshack.us/img546/8...ramedamage.jpg

http://img209.imageshack.us/img209/9...amedamage2.jpg

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I didn't say any of the parts in bold, which you claim to be quoting from me.

Right, I did the bold.