Stability and Control characteristics of the Early Mark Spitfires

[6S.Manu]

Originally Posted by TomcatViP

May I suggest that we open a new thread for that with precise suggestion to the devs based on our sim experiences/lifetime real flight and Math knowledge. Then they will only have to pick what suggestions fit their agenda regarding the Sim.

Manu, regarding your post for the visual acquisition range some months ago, I suggest you'd be the one opening that thread.

I'm going to open it under "Technical threads".

EDIT: http://forum.1cpublishing.eu/showthr...848#post447848
Sorry again for my bad english.

[bongodriver]

Originally Posted by CaptainDoggles

No matter how you set up your curves, you'd still need to reduce pressure on the stick to avoid the aircraft tightening up the turn by itself.

That right there would go a long way towards the correct "feel".

You just don't have the evidence that that is actually what happened for a start, and even if it did happen it only would have happened when the CoG was at the point it created the 'slight' instability i.e. with a full fuel tank, so the effect you talk about would be dependent on fuel burn, the less fuel in the tank the lesser the effect.

[TomcatViP]

no, the tank is frwd of the CG

[bongodriver]

Originally Posted by TomcatViP

no, the tank is frwd of the CG

it's rear of the next biggest mass (the engine) an according to at least 1 diagram it is 14 inches behind the datum point, when the tank is full the CoG comes back.

[CaptainDoggles]

Originally Posted by bongodriver

You just don't have the evidence that that is actually what happened for a start, and even if it did happen it only would have happened when the CoG was at the point it created the 'slight' instability i.e. with a full fuel tank, so the effect you talk about would be dependent on fuel burn, the less fuel in the tank the lesser the effect.

It's unstable unless the CG is in the forward position.

We just spent 46 pages hashing this out so I'm not going to get into it with you; don't bother replying.

Go back and read the thread; it's all there. This thread has devolved into fanboys re-interpreting the presented evidence into "merely a slight" instability because their egos can't handle it, so I'm not going to perpetuate it.

Ta ta

[bongodriver]

It's unstable unless the CG is in the forward position.

Which is pretty much what I said

it only would have happened when the CoG was at the point it created the 'slight' instability i.e. with a full fuel tank

A full fuel tank is what makes the CoG move back, as the fuel empties the CoG shifts forward and the aircraft becomes more stable, it's got nothing to do with fanboyism, it's just plain and simple facts, I do CoG calculations as part of my day job remember.

This thread has devolved into fanboys re-interpreting the presented evidence into "merely a slight" instability because their egos can't handle it

No the pilot's notes also say it is 'slightly' unstable

[robtek]

The fuel tank is right above the line between the first and the second third of the wing, thats where the cog usually lies, so if it gets lighter the cog doesn't move at all, afaik.

[bongodriver]

Originally Posted by robtek

The fuel tank is right above the cog, so if it gets lighter the cog doesn't move at all, afaik.

CoG is not a stationary datum, the CoG is dynamic and will shift with change in weight, the datum you are talking about is the AC aerodynamic centre, the point at which all the forces act, if the CoG is behind the AC then the aircraft is unstable and vice versa, so....given the Mass of the engine sits ahead of the AC and the fuel is sligtly behind then any reduction in the combined weight will bring the CoG forward.

Sorry my mistake, AC is where lift acts and CoG where weight acts, but the point is the same.

I meant to add, the reason I believe this is the effect is because the only Weight and balance diagrams I have seen of the Spitfire place the fuel tank moment just behind the datum point, as fuel reduces then the moment weight is offset by the constant moment weight of the engine which I think we can all agree is ahead of the datum.

[Glider]

I know this is going to sound rather foolish but can someone point me in the direction of the test report that mentions 3/4 in of travel for 3 G.

Its in here somewhere but I cannot find it, any hunts welcome

[bongodriver]

Originally Posted by Glider

I know this is going to sound rather foolish but can someone point me in the direction of the test report that mentions 3/4 in of travel for 3 G.

Its in here somewhere but I cannot find it, any hunts welcome

I can't find it either, I'm not as sure I ever saw it but I just assumed nobody was making it up.
Here is robteks first reference to it and it seems he was working from his own recollection of things, prior to this post I saw nothing with regards to that figure.

Originally Posted by robtek

The necessary Stick movement (elevator) to induce a 3 g load at cruise speed was three quarters of an inch in the Spitfire, afaik, very easy to get unintended reactions there if your arm isn't completely fixated.