109 horizontal stabilizer

[71st_AH_Mastiff]

 

who's engineering brain is bigger, I guess..

Edited December 26, 2013 by 71st_Mastiff

[MiloMorai]

 

who's engineering brain is bigger, I guess..

 

One has to have an engineering brain in the first place.

[kestrel79]

Does anyone know if it's possible yet to adjust the trim or horz stabilizer to two keys? Similar to how the default keys for trim were the arrow keys in IL2? Right now it looks like they can only be assigned to an axis or trim wheel?

[dburne]

Does anyone know if it's possible yet to adjust the trim or horz stabilizer to two keys? Similar to how the default keys for trim were the arrow keys in IL2? Right now it looks like they can only be assigned to an axis or trim wheel?

 

I have mine set to the same two keys I have pitch trim set to - lalt+darrow and lalt+uarrow.

I believe these were the default keys for pitch trim?

Certainly can set them to whatever two keys you would like, unless I am not understanding completely?

[kestrel79]

Sounds good. I think I just didn't read the controls screen properly. Thanks!

[dburne]

Sounds good. I think I just didn't read the controls screen properly. Thanks!

 

Glad to help, let us know if this is not the case for you or if you have any more questions.

[DD_Squawk]

Managed to check a C185 after getting home from Christmas today.   Ran the tail trim full nose up, and full nose down, I measured the yoke pull from the instrument panel.    At full nose down trim, I gained 1 cm of travel on the yoke over full nose up.

 

 

So, length of pull does vary according to the varied incidence of the horizontal stab.     Now the questions are; how much of a difference is it in the 109?  And is it enough to make a difference?

Edited December 29, 2013 by =69.GIAP=GRACH

[JtD]

http://forum.il2sturmovik.com/topic/3235-109-horizontal-stabilizer/?p=70706

 

As stick - elevator relation is not changed, stick travel behaves the same way the elevator does.

[Crump]

Crump says:

 

You will not lose elevator authority due to the method of trim.  You will increase stick forces to the point it might seem that way.  Simply trim stall any airplane and you will notice that in the recovery.  Control authority is the same but it requires more input force to achieve it.

 

 

 

 

Managed to check a C185 after getting home from Christmas today.   Ran the tail trim full nose up, and full nose down, I measured the yoke pull from the instrument panel.    At full nose down trim, I gained 1 cm of travel on the yoke over full nose up.

 

You will not gain 1 cm of travel with an air load. 

[DD_Squawk]

Always need the last word?

 

And yes you could.

 

With an extreme aft CoG, you can have max nose down trim and still be within normal flight envelope.  The aircraft will fly like a rubber hose, but it is doable.  (just don't stall or you are likely boned)

[Crump]

 

With an extreme aft CoG, you can have max nose down trim and still be within normal flight envelope.

 

 

Exactly, with an air load, you are not losing any control authority.  While not entirely accurate, a good way to think of it is the 1cm of travel is being used by the trim system to hold trim speed.

[DD_Squawk]

Exactly, with an air load, you are not losing any control authority.  While not entirely accurate, a good way to think of it is the 1cm of travel is being used by the trim system to hold trim speed.

 

 

??? 

 

I don't see how that can be the case.   The variable angle incidence of the tail is what is holding the trim speed, not the elevator.

 

 

Mind you, at this point I think we are just arguing semantics and I'm not an engineering student, I just fly the damn things.

[Crump]

??? 

 

I don't see how that can be the case.   The variable angle incidence of the tail is what is holding the trim speed, not the elevator.

 

 

Mind you, at this point I think we are just arguing semantics and I'm not an engineering student, I just fly the damn things.

 

 

Well, it is the case and it is not "semantics".

 

By definition trim is the point there are not moments created about the CG.  From a stability and control standpoint, it does not make any difference if the moments are neutralized by the pilot holding control input or a mechanical trim system. 

 

For the comfort of the pilot, most designers put at least a longitudinal trim system as good design can eliminate the need on any other axis.

 

So, we trim to zero moments about the CG and we have lost that 1 cm of travel as it is creating the control pressure required to achieve trim. 

[DD_Squawk]

Up until your last statment, I followed you.

 

I put it to you this way. you cant 'lose' the extra travel as it is mechanical, and not aerodynamic. Even If you use it to maintain a trimed state, you still have used it.

 

While there are some instances where using mechanical trim mechanisims are insufficient and control inputs are needed, there are still others where you need no input what so ever on the column/stick so in those instances if we took your view at face value it would still not be entirely correct.

 

If i had a fixed horizontal stabilizer I would agree with you, any change in the mechanical trim system, would necessitate a change in position of the column/stick owing to th deflecton of the elevator due to the trim tab. But we are not discussing fixed horizontal stabs.

[Crump]

What I am saying is correct for any trim system. In fact it is the purpose of a trim system.

 

You seem stuck on mechanical movement that makes no difference outside of maintain trimmed flight.

 

Moment = coefficient of moment * reference area* dynamic pressure.

 

Trimmed flight:

 

Moment - Moment about the CG = 0

[DD_Squawk]

I agree with the concept of moment. 

 

 But we were not talking a 'trim system'.   We were talking about the physical movement of the column, which is mechanical.

 

If the 'trim system' is in ballance from the variable incidence horizontal stabilizer, I put to you that the control column is in the neutral position with no air load required to maintain level flight(ie. hands off).  Regardless of nose up/nose down application.

 

At this point, dependant on where the trim is set, you can gain or lose some column travel which will alter the amount of stick induced moment.

 

Whether or not you actualy gain or lose any total moment is irrelevant.  It was not the point I was making.

 

 

To go further in this discussion will serve no purpose, any advantage in the real world would need to occur at such rare extremes of the flight envelope, as to make it impractical and/or improbable to undertake by the pilot. (If not just plain reckless)