Stability and Control characteristics of the Early Mark Spitfires

[macro]

i dont get the "stick free" comments here, why would you fly a plane without holding the stick?

and as someone posted before, can you (anybody) explain for my better understanding how what being discussed here is different than in game i.e what it should be doing compared to what it is doing now

[fruitbat]

A question for you all, can't find the answer myself, what was the first aircraft fitted with bob weights, and particuarly the first british plane?

Was it the Mk V Spit?

Thanks in advance.

[bongodriver]

Originally Posted by fruitbat

A question for you all, can't find the answer myself, what was the first aircraft fitted with bob weights, and particuarly the first british plane?

Was it the Mk V Spit?

Thanks in advance.

You could also search for 'inertia weight'

[CaptainDoggles]

Originally Posted by bongodriver

Really?.....are you sure?

You took that out of context. He's saying most aircraft do not have positive static but negative dynamic stability when stick free.

[JtD]

Originally Posted by Crumpp

Because I do disagree with you.

In that case you're disagreeing with NACA. Take it up with them.

[robtek]

No, JtD,
YOU are disagreeing with NACA, because YOU wrote that the long period oscillation is the only unstable oscillation for the Spitfire, where the NACA report ignored the long period oscillations as insignificant.

[JtD]

Maybe it helps if I sum it up:

A.&A.E.E. tested Spitfire K9788 (a Spitfire I) and it showed increasing long period oscillations, which means it is dynamically unstable.

NACA did not bother to investigate these, as "the well know long period oscillations have no correlation with the handling qualities of an airplane". NACA tested a Spitfire V. It evaluated short period oscillations, which all were damped satisfactory, and evaluated static stability, which was found to be neutral to positive flaps up, and negative flaps down.

Now I absolutely agree with NACA, in particular with the statement that the long period oscillations are irrelevant in terms of handling and in fact, dynamic instability was not atypical for fighter aircraft of the time. The Hurricane for instance, having gone through similar trials, proved to be far more dynamically unstable.

I've neglected the flaps down instability, which I consider irrelevant in air combat, because flaps down was no condition for combat.

As for the other qualities evaluated by NACA, be it good or bad, it sums up that there's nothing critical. Only characteristic, in that some points are rather weak, some excellent.

And all the hype about dangerously low elevator forces and changes to pilot notes - it was decided to add the part of the Mk II notes, which is repeatedly quoted here, after a total of 3 (three) Spitfire I's were lost due to mid air wing failures and investigation found that inexperienced pilots coming in fresh from training mostly in bi-planes needed an extra warning because they simple were not familiar with high speed pull outs and trimming in high speed dives.

The weakest point in terms of control were the fabric covered ailerons, whereas the overall control characteristics made the Spitfire an easy plane to fly, and an easy plane to fly to the limits. For a WW2 fighter aircraft.

[NZtyphoon]

Originally Posted by Crumpp

The RAE was not stupid. They measured the stick free behavior for a valid reason. You can quickly look at the those graphs to see the Spitfire has positive static and negative dynamic stability stick free. It shows the work load required of the pilot and the ability of the aircraft to maintain equilibrium. The Spitfire was neutral or divergent.

Yet the RAE were stupid enough not to have any standards, according to Crumpp.

Originally Posted by Crumpp

Everything is "absolute nonsense" to you, yet you confuse so many things. My advice is to look at the exact conditions and take each statement one at time. It is a scientific report and the language is specific.

I would recommend you do the same Crumpp, instead of layering your interpretations on straight-forward comments.

[Robo.]

Originally Posted by JtD

Maybe it helps if I sum it up:

A.&A.E.E. tested Spitfire K9788 (a Spitfire I) and it showed increasing long period oscillations, which means it is dynamically unstable.

NACA did not bother to investigate these, as "the well know long period oscillations have no correlation with the handling qualities of an airplane". NACA tested a Spitfire V. It evaluated short period oscillations, which all were damped satisfactory, and evaluated static stability, which was found to be neutral to positive flaps up, and negative flaps down.

Now I absolutely agree with NACA, in particular with the statement that the long period oscillations are irrelevant in terms of handling and in fact, dynamic instability was not atypical for fighter aircraft of the time. The Hurricane for instance, having gone through similar trials, proved to be far more dynamically unstable.

I've neglected the flaps down instability, which I consider irrelevant in air combat, because flaps down was no condition for combat.

As for the other qualities evaluated by NACA, be it good or bad, it sums up that there's nothing critical. Only characteristic, in that some points are rather weak, some excellent.

And all the hype about dangerously low elevator forces and changes to pilot notes - it was decided to add the part of the Mk II notes, which is repeatedly quoted here, after a total of 3 (three) Spitfire I's were lost due to mid air wing failures and investigation found that inexperienced pilots coming in fresh from training mostly in bi-planes needed an extra warning because they simple were not familiar with high speed pull outs and trimming in high speed dives.

The weakest point in terms of control were the fabric covered ailerons, whereas the overall control characteristics made the Spitfire an easy plane to fly, and an easy plane to fly to the limits. For a WW2 fighter aircraft.

Thank you JtD This is pretty much how I read the facts in this thread.

[robtek]

The instability in the NACA report is, that a constant stick input, say one inch back with 6lbs pressure, led to a ever increasing g-load, and that was the malus for the Spitfire controls.

The ideal reaction would have been i. e. pull the stick 3 inches back with 15 lbs pressure and get a constant 5 g pull up.