Stability and Control characteristics of the Early Mark Spitfires

[Crumpp]

So, what they are saying again is that there are large reactions to small stick travel. Not that the plane was unstable.

Yes, they definately say there are large aceleration changes for a small amount of elevator travel.

The other part is that they do say the airplane is unstable. Neutral or unstable......

At a neutral or unstable condition, the Spitfire is not able to hold a constant aceleration in a turn.

One can run the math on Cm and see that too.

flight records from other airplanes show that a turn may be entered rapidly and the desired normal acceleration may be held constant by a single rearward motion of the stick provided the static stability of an airplane is sufficiently large.

At forward CG, the static stability is sufficiently large. At normal and aft CG the static margin is neutral or unstable.

[bongodriver]

At forward CG, the static stability is sufficiently large. At normal and aft CG the static margin is neutral or unstable.

But this applies to 'all' aircraft, it seems pretty odd to criticise the Spitfire for something that is universal, this is exactly the same problem the Mustang has with a full fuselage tank.

to determine how much of a problem this is for the Spitfire a decent weight and balance schedule is needed, from that it can be calculated how much fuel burn is required to put the CoG forward.

[Sternjaeger II]

I always thought that the "breaking up in the air" of early Spits was mainly caused by design flaws on the tail section (like in the early Typhoons) which emerged in high speed dives.

[Crumpp]

But this applies to 'all' aircraft

No it does not.

It depends on the static margin. The static margin will move as the CG changes but most aircraft are designed to have positive stick fixed stability at the most rearward position.

In fact, that point defines the rear CG limit.

[IvanK]

So then Mr Crumpp exactly what is wrong stability wise with the IL2 CLOD Spitfire MI I or II Ver 1.06.17582+Hot Fix

[macro]

Originally Posted by IvanK

So then Mr Crumpp exactly what is wrong stability wise with the IL2 CLOD Spitfire MI I or II Ver 1.06.17582+Hot Fix

Thats what i want to know.

[winny]

Originally Posted by IvanK

So then Mr Crumpp exactly what is wrong stability wise with the IL2 CLOD Spitfire MI I or II Ver 1.06.17582+Hot Fix

And this, gentlemen, is the 64,000 dollar question...

[fruitbat]

Originally Posted by IvanK

So then Mr Crumpp exactly what is wrong stability wise with the IL2 CLOD Spitfire MI I or II Ver 1.06.17582+Hot Fix

Yes, I'm curious to.

And how has it been tested?

[Sandstone]

Originally Posted by IvanK

So then Mr Crumpp exactly what is wrong stability wise with the IL2 CLOD Spitfire MI I or II Ver 1.06.17582+Hot Fix

Indeed.

Crumpp, you should answer this one.

[NZtyphoon]

Originally Posted by IvanK

So then Mr Crumpp exactly what is wrong stability wise with the IL2 CLOD Spitfire MI I or II Ver 1.06.17582+Hot Fix

According to Crumpp the Spitfire was dangerous:

http://forum.1cpublishing.eu/showpos...&postcount=245

"The solution for the unacceptable and dangerous longitudinal instability of the Spitfire was bob-weights." These were added not because the NACA made a mistake in some half baked theory on weight and balance calculations. They were added by the RAE to correct a serious stability and control issue with the design."

(No they weren't, they were added by Supermarine to control a truly dangerous instability problem caused by poor loading at squadron level, but we can let Crumpp away with his poor grasp of history - he's only an engineer. )

One solution to the "dangerous" instability exhibited by the Spitfire would be for the IL2 developers to add bob-weights - ASAP!