109 elevator trim

[Robo.]

Originally Posted by SlipBall

Could you post the reference material

Of course:

Lowering the flaps makes the ailerons feel heavier and slightly less effective, and causes a marked nose-down pitching moment, readily corrected owing to the juxtaposition of trim and flap operating wheels.

Longitudinal Trim
Five three-quarter turns of a 11.7 in diameter wheel on the pilot's left are needed to move the adjustable tailplane through its full 12-degrees range. The wheel rotation is in the natural sense. Tailplane and elevator angles to trim were measured at various speeds in various condition; the elevator angles were corrected to constant tail setting. The airplane is statically stable both stick fixed and stick free.

RAF Royal Aircraft Establishment (RAE) Farnborough handling trials,Bf.109E Wn: 1304. M.B. Morgan and R. Smelt of the RAE, 1944

I am aware that this are British tests of a battle-damaged airplane that was apparently not trimmed correctly, but the actual statemens are only re the actual operation and in agreement with the manual.

There were no movable trim tab controls on the ailerons or rudder, although both had fixed tabs that could be bent on the ground. Pitch trim was affected by changing the stabilizer incidence thrugh a range of 12 degrees. The design scheme was that both the flaps and the stabilizer were coordinated mechanically from two 12-inch wheels mounted concentrically on the left side of the pilot's seat. By twirling both wheels in the same direction the pilot could automatically compensate for the change of pitch trim due to lowering or raising the flaps. Differential coordination could be set by moving one wheel relative to the other.

A series of mock dogfights were conducted by the British in addition to the flight test and the following was revealed:
If the airplane was trimmed for level flight, a heavy push on the stick was needed to hold it in a dive at 400 mph. If it was trimmed into the dive, recovery was difficult unless the trim wheel was wound back, due to the excessive heaviness of the elevator forces.

both quotes above from 'The Best of the Breed by Col. "Kit" Carson Airpower, July 1976 Vol. 6 No. 4'

[SlipBall]

Originally Posted by Robo.

Of course:





RAF Royal Aircraft Establishment (RAE) Farnborough handling trials,Bf.109E Wn: 1304. M.B. Morgan and R. Smelt of the RAE, 1944

I am aware that this are British tests of a battle-damaged airplane that was apparently not trimmed correctly, but the actual statemens are only re the actual operation and in agreement with the manual.





both quotes above from 'The Best of the Breed by Col. "Kit" Carson Airpower, July 1976 Vol. 6 No. 4'

If in fact the wheel revolutions are correct as you presented, then I would agree the game model is wrong...but I think that you would need more proofs, other than an authored book as a reference.

[Robo.]

Originally Posted by SlipBall

If in fact the wheel revolutions are correct as you presented, then I would agree the game model is wrong...but I think that you would need more proofs, other than an authored book as a reference.

Yes they are correct and yes the game model is wrong I am afraid.

Why do you find the above reference (especially RAE tests) untrustworthy?

[Flanker35M]

S!

So the trim was used in Bf109 and other planes to compensate the changing flight conditions, like in any other plane. The extent to which pilot used elevator trim in a Bf109 can only be speculated, some might have used more than others.

Finns did use elevator trim to pull out from high speed dives as the controls went almost solid. But then we are talking about speeds excess 700km/h, not the usual 300-500km/h.

I also read from a P51D pilot's combat story that he did fiddled with trims even in combat to achieve best performance. And a Pony had more trims than Bf109 So the thing is that these pilots were so used to the controls and their location that could operate them blindfolded and quickly because of their training and experience. This is hard to model into a game as there is no absolute truth how it works. We have the travels, rotations etc. but the rest..?

In the end what we get is how the developer interprets these things and puts them in the game. A compromise of something hard to model otherwise IMHO.

[Robo.]

Originally Posted by Flanker35M

So the trim was used in Bf109 and other planes to compensate the changing flight conditions, like in any other plane. The extent to which pilot used elevator trim in a Bf109 can only be speculated, some might have used more than others.

Of course, but it is apparent that the 109 elevator trim was rather specific with the design and purpose. Feel free to google for French tests of the same captured Emil and what they state regarding elevator trim (when compared to D.520 iirc)

Originally Posted by Flanker35M

Finns did use elevator trim to pull out from high speed dives as the controls went almost solid. But then we are talking about speeds excess 700km/h, not the usual 300-500km/h.

Not just Finns but everybody There is specific paragraph regarding trim wheel use in a dive in the manual. (Sturzflug) You set it incorrectly and you can end up in very unpleasant crater situation. There is also factory test of the dive characteristics with different trim settings out there. This was overly important of course.

Originally Posted by Flanker35M

I also read from a P51D pilot's combat story that he did fiddled with trims even in combat to achieve best performance. And a Pony had more trims than Bf109

American a/c have had a bit different approach to trims. While we're at the Finns, have a look how they compared US made Brewsters and MTs regarding trims.

Originally Posted by Flanker35M

This is hard to model into a game as there is no absolute truth how it works. We have the travels, rotations etc. but the rest..?

It is hard to model, but still possible. What we have got at the moment is not good enough imho, hence this thread.

[robtek]

How long does the full travel from -3 to +8 degree take in game?

I only know for shure that the reaction is much slower than my trim axis.

I think 4 quarter turns a second is normal for a pilot familiar with the 109, that would make it 5 seconds for a full change, which never would happen.

So, to trim nose up one might need 2, max. 3 degree + on the elevator, as it is only needed to get the lead for a few seconds, taking 1 turn of the wheel or about 1 second and is easily feasible, imo.