A newbies impression of the 109 and spit

[Crumpp]

Yep, this is why i hate the war stories as technical or performance "evidence". Interesting stories, but nothing more Best example is the maneuverability. Both sides said they're all turned better than the other side. Ok, but what were the circumstances of the situation? That is very little read, and one of the most important thing in the pre-battle situation.

Exactly. Conditions mean everything and without them, it is useless to draw general conclusions.

I think the point is, that in a spit, during a stall-recovery, it is extraordinarily easy to exceed the stick movement necessary to overload the airframe.

Much more easy as in the comparable planes, which needed more stick-travel and force.

Right, the majority of the warnings in the Spitfire Operating Notes are in relation to the unacceptable longitudinal dynamic stability.

How would this effect your game?

It compresses the turn performance differences especially for large angle of bank turns. The Spitfire is harder to control precisely in that condition and the stall is extremely rough and will result in a spin.

It is like that punk skateboarder kid. He can do some really cool tricks but when he makes a mistake, it is a whooper.

The Bf-109 on the otherhand has those LE slats on a flat top polar. It is like a a racing bicycle with training wheels.

Read the stall behaviors:

http://kurfurst.org/Tactical_trials/...ls/Morgan.html

It has yaw-wise stability issues but stall behavior is typical for an aircraft equipped with LE slats. It simply stops flying and begins to descend. No violent behaviors and no tendency to spin at all. LE slats are a typical anti-spin device if you want to spin-proof an airplane. They really are like training wheels.

Both airplanes have excellent stall warning with adequet control and can be flown in a partially stalled condition. The Bf-109's stall is a non-event and the Spitfires is a the begining of wild ride.

It is no wonder you read anecdotes of Bf-109 pilots who swore the airplane would outturn the Spitfire.

[JtD]

In case some folks can't be bothered to read the NACA tests, I'll post a part to put the "unacceptable longitudinal dynamic stability" into proper perspective.

STALLING CHARACTERISTICS IN MANOEUVRES

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....
With gun ports closed, the pilot was able to pull the stick far back without losing control or interrupting the turn. The airplane tended to pitch down when stalled and to recover by itself if the stick were not pulled back. It would be possible for a pilot pursuing an enemy in a turn to bring his sights on him momentarily by pitching beyond the stall without fear of rolling instability.
With gun ports open, a right roll occurred if more than about 10° up elevator were applied. This reaction caused the airplane to roll out of a left run and into a right turn. ... In spite of the lateral instability that occurred in turns with gun ports open, the pilot was able to approach maximum lift coefficient closely because of the desirable stall warning. The maximum lift coefficient reached in turns from level flight with flaps up was 1.22. The airplane could be flown beyond the stall at even lower lift coefficients.

CONCLUSIONS

The Supermarine Spitfire airplane possessed stalling chareteristics essentially in compliance with the requirements for satisfactory stalling characteristics given in reference 1. These characteristics may be summarised as follows:
1. Warning of the comlete stall was provided by the occurrence of buffeting that set in at speeds several miles per hour above the minimum speed and by the rearward movement that could be made with the stick after the start of the stall flow breakdown without causing violent motions of the airplane.
2. Stall recovery could be made by application of down elevator, although the recovery from a roll was somewhat slower than has been measured on some previously tested airplanes.
3. The airplane exhibited no dangerous ground-looping tendencies in landing. Tail-first landings could be readily made without the occurrence of either lateral or directional instability due to stalling.
The airplane possessed some unusual characteristics in stalls that are not required in reference 1. The motion beyond the stall was not violent and an unusual amount of lateral control was available in many flight conditions, even when full up elevator was applied. The good stalling characteristics allowed the airplane to be pulled rapidly to maximum lift coefficient in accelerated maneuvers in spite of its neutral static longitudinal
stability.

Eventually, the longitudinal stability was not unacceptable. The Spitfire was accepted into service with about 20+ military air forces, was built in 20000 examples, and is still being flown today. Unacceptable longitudinal stability would mean acceptance into 0 air forces, and a production of a handful of examples, and none would be cleared for flying today.
However, it is true that the Spitfire did not meet all the requirements set by NACA in "Requirements for Satisfactory Flying Qualities of Airplanes". Other planes that failed to meet all the requirements were for instance the P-39 or the XP-51.

[fruitbat]

Interesting stuff JtD.

you sure thats the same NACA report, lol.

[VO101_Tom]

Originally Posted by JtD

Eventually, the longitudinal stability was not unacceptable. The Spitfire was accepted into service with about 20+ military air forces, was built in 20000 examples, and is still being flown today. Unacceptable longitudinal stability would mean acceptance into 0 air forces, and a production of a handful of examples, and none would be cleared for flying today...

This instability was fixed in the Spit V.
Several Spit pilots complained that the Spit V felt sluggish. Of course the flight characteristics was not worse, just more stick movement and force was needed. iirc Crumpp showed a couple of documents about this.

[lane]

Originally Posted by JtD

In case some folks can't be bothered to read the NACA tests, I'll post a part to put the "unacceptable longitudinal dynamic stability" into proper perspective.

Eventually, the longitudinal stability was not unacceptable. The Spitfire was accepted into service with about 20+ military air forces, was built in 20000 examples, and is still being flown today. Unacceptable longitudinal stability would mean acceptance into 0 air forces, and a production of a handful of examples, and none would be cleared for flying today.
However, it is true that the Spitfire did not meet all the requirements set by NACA in "Requirements for Satisfactory Flying Qualities of Airplanes". Other planes that failed to meet all the requirements were for instance the P-39 or the XP-51.

Hi JtD,

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

[NZtyphoon]

Originally Posted by bongodriver

recovery....reshmovery and where the hell did that quote come from anyway, Spitfires did not break up in spin recovery but some did break up recovering from dives because granted the Spit was built a little delicately for it's sensitivity in pitch.

According to Alex Henshaw about 25 Spitfires were known to have broken up in flight; the majority of those were Spitfire Vs which had been badly loaded at a squadron level pushing their cg too far back, and breaking up during dive recovery. As Jeffrey Quill explained, this helped lead to the addition of bob weights in the tail, then the larger mass balances on the elevators. Some of these are documented in Morgan and Shacklady.

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


OT slightly; NACA's report on the P-47D which had some problems of its own; one of the few fighters to meet NACA standards was the P-51H.

Putting weights to the tail for what purpose?

[NZtyphoon]

Originally Posted by 41Sqn_Stormcrow

Putting weights to the tail for what purpose?

Better to say inertia weights (or bob weights) were added to the control circuits of the elevators - I'm not sure if later Spitfires with the bigger elevator mass balances continued to use them.

[NZtyphoon]

Originally Posted by Crumpp

The Bf-109's stall is a non-event and the Spitfires is a the begining of wild ride.

That's not what the NACA report says:

"The motion beyond the stall was not violent and an unusual amount of lateral control was available in many flight conditions, even when full up elevator was applied. "

[winny]

Originally Posted by 41Sqn_Stormcrow

Putting weights to the tail for what purpose?

The weight was built into the elevator circuit, in simple terms it was used to counteract the effect of light elevators and high g forces. The weight was effected by the g forces so if there was a high load the elevators needed more force to move them.

It was fitted to spitfires to solve the problem of spitfires breaking up when pulling out of a high speed dive, which was a known, and big problem at the time.

Because the elevators were so light pilots were pulling out of the dives and over stressing the airframe. There were loads of examples of this happening.

So basically the more g that was pulled the harder the elevators became to move. As far as I know it had nothing to do with any instability.