A newbies impression of the 109 and spit

[Crumpp]

No...it seems to just show some FAR's for certification in the US, much like American light aircraft certificates show UK/European requirements

It is a fact all convention signers follow the same rules, principles, and procedure for aircraft airworthiness.

That is why we all use the same regulations and quote them.

Here is a quick highlight of the worlds aviation conventions. The only thing state and military aircraft are exempt from is the navigation rules.

They still must abide by the convention airworthiness standards.

October 1919 , Paris : Convention Relating to the regulation of Air navigation

Sovereignity over Airspace.

Standard for airworthiness

Certificates of competency for crews

Definition of aircraft

http://www.fabioaddeo.com/2011/02/26...nd-agreements/

[Crumpp]

A load factor of 2.5 G's......wow massive, the Spit airframe could stand 10 G's

10G's asymmetrically? You think?

[bongodriver]

Originally Posted by Crumpp

10G's asymmetrically? You think?

Yup

[bongodriver]

I can't be bothered to wait for you to browse wiki or scour the internet for other obscure stuff....

You don't really seem to even know what asymetrical g load is, remember that thread about roll rate at high speed? well......diving a spit to 400 mph and applying max stick roll force.....thats aymetrical loading my friend.....I don't seem to recall wings peeling off in those tests, if it could take those asymetrical loads then there is no way in hell it will break up in spin recovery no matter how sensitve the elevator is or how staticaly neutral it is.

[robtek]

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.

[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.

[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. "

[Crumpp]

Yup

Well you are dead wrong bongodriver.

First of all the 10G's is to the failure point. It is 10G's on a single axis and assumes a perfect airframe. That 10 G's represents a 100% chance the airframe will be permanently deformed and we run a good chance of having the airplane turn to confetti. This is why the POH warns the airframe will certainly fail if this limit is much exceeded.

Our we run the risk of damage threshold is lower than that at 6G's.

That too, is 6G's on one axis with a perfect airframe.

Just like your car suspension wears, so does an airframe. It is not the spars or major structures that fail first, it is the ribs, skin, and supporting structures. An airframe flexes in flight, even at 1G. Gusting, accelerations, and turbulence all add wear to the airframe and lower those limits. It is just like your cars suspension wears from driving all the bumps it has to absorb.

Asymmetrical loading significantly reduces the airframe limitations. The average is about 20%. So our 6G damage limit is now 4G's with an asymmetrical loading.

Our normal spin recovery AVERAGES about 2.5G's so on AVERAGE we could spin a Spitfire safely as long as the pilot correctly and precisely applied the control inputs.

But wait, he has a very hard time being precise with control inputs especially when he is subjected to the same accelerations. Oh yeah, when he steps on the rudder, it also produces even more acceleration on the longitudinal axis adding to his difficulty.

He has 1.5G's to play with before he can damage the airframe. The airframe is now weaker and will fail at a lower point.

Now let's add in the vertical load from gusting...Oh crap we are at the threshold in light turbulence!! The POH also warns of this! Coincidence?

You botch the recovery, damage the airframe, and it re-enters the spin, as the POH once again warns the pilot about. Why can you re-enter a spin so quickly and must build up your speed? In any airplane if you don't have enough speed you can re-enter the spin. In the Spitfire is especially important. The pilot needs that speed to have better precision on the controls. He only has 3/4 of an inch of stick travel to use up all of this angle of attack at 5lbs per G. The heavier he can make that stick, the more precise he can be in controlling the acelerations. If he re-enters the spin with a damaged airframe his chances are even less of coming home.

Now do you see why spins are prohibited in the Spitfire? The average time you spin the airplane, it will come out "just fine". The margins between "just fine" and disaster are tighter than you think.

If the pilot could precisely control the accelerations and did not have the yaw-wise pitch up, it would be a much safer aircraft to spin.

[Crumpp]

diving a spit to 400 mph and applying max stick roll force

What is a max stick force roll at that speed? Don't confuse stick forces and control surface deflection.

You realize that 400 mph is well over Va so full control deflection will exceed the airframe limits on just one axis......

Think about what you are saying in this claim.