Spitfire Pitch up / Pitch down

[Blutaar]

You guys seem to have knowledge about the spit so i want to ask a question, sry if it not belongs here. I may have found a bug or at least some strange behavior, maybe you guys know more.

If you go inverted at ca 330 kph, the nose will not go down to the ground but up into the sky. If you go faster it will reverse but it holds the inverted attitude with little to no forward stick pressure. 

The Yak1 on the other hand will imediatly needs quite some forward stick pressure while inverted like any other plane im aware of. Is this normal in a spit or some kind of bug or has it to do with the new FM of the spit?

[unreasonable]

What I have found is that the Spitfire is nose heavy even with tail heavy trim. I am always flying with a little back pressure. When I do a slow roll I certainly noticed that I had to remove the back pressure - ie going inverted would have caused me to head towards the ground unless my stick was more forwards than when flying sunny side up.  So perhaps what you observed is also influenced by the trim effects.  Overall the elevator is very sensitive, so it certainly does not feel that I have to make such a crude forwards movement when inverted as I would in say a Yak, but that is true throughout the envelope.

[6./ZG26_5tuka]

What I have found is that the Spitfire is nose heavy even with tail heavy trim. I am always flying with a little back pressure. When I do a slow roll I certainly noticed that I had to remove the back pressure - ie going inverted would have caused me to head towards the ground unless my stick was more forwards than when flying sunny side up.  So perhaps what you observed is also influenced by the trim effects.  Overall the elevator is very sensitive, so it certainly does not feel that I have to make such a crude forwards movement when inverted as I would in say a Yak, but that is true throughout the envelope.

Is your trim centered according to the gauge? With centered trim the aircraft doesn't deviate when I turn it upside down thx to it's neutral stability.

[unreasonable]

Is your trim centered according to the gauge? With centered trim the aircraft doesn't deviate when I turn it upside down thx to it's neutral stability.

 

What I find is that the plane is nose heavy whatever trim I use: and it is working correctly according to the gauge - if I take my hands off the stick and release back pressure (which is very small) the nose will drop.  With the 109, for example, I can land virtually hands off once the correct trim, flaps and throttle position is reached. With the Spitfire this does not work (with my G940) - it has to be flown all the way.  (Which is just fine by me, this whole "stabilized approach" nonsense is just a massive misunderstanding anyway).

[Gavrick]

The Spitfire really had an interesting feature in longitudinal channel controlablity. As already mentioned, Spitfire was a statically neutral airplane. As one of the manifestations of this - during acceleration or braking, the balancing position of stick does not practically change with it (see the excerpt from the NACA report).

 

 

Unlike a conventional stable airplane, in which the lower the speed, the more you have to pull on yourself to maintain the balancing. That is, if you, for example, dive on the Spitfire - hold the stick the way it is set, the plane will accelerate and fly straight. But, at the same time, due to the peculiarities of the weight compensation of the elevator, force on the stick is changing, and strongly. And indeed, if you accelerate in a dive, then as the speed increases, stick will tend to go "on yourself", so the pilot has to push it away more and more from itself (that is, apply the same effort as on a stable aircraft), or twist the trimmer On the dive. Note - the forces applied to the stick vary, but the stick itself is practically stationary. Therefore, yes, indeed, as the speed increases, the aircraft must be trimmed to dive, and at the maximum permissible speed the trimmer must be twisted to a dive for the greater part of the stroke. By the way, on the indicator of the position of the trimmer, which is on the dashboard, the neutral trimmer on the handlebar is an arrow half a turn up from the neutral on the instrument. The range of the deviation for the dive is greater than for the trimming three times.

[ZachariasX]

Thanks for your explanation Gavrick!   Great to hear your position.

Edited July 10, 2017 by ZachariasX

[Finkeren]

It's so great to see Gavrick take the time to engage in these discussions. Saves us a lot of guesswork.