109 elevator trim

[Robo.]

Originally Posted by 5./JG27.Farber

When Osprey was talking to me about it on Steam he said 109's where using it to out turn him.

Oh yes, you can outturn a Hurricane if you want, because you can apply nose-up trim very very fast. It is very useful and responsive in other manoevers, too - vertical or horizontal scissors etc... Do you need to hit a Spitfire that is breaking hard while you're diving on him at 450km/h? Apply full nose-up trim and you'll have plenty lead on him. This probably applies to all aircraft, and as you can do things no one could do in so called real life, this is certainly wrong. The 109 is specific because of the trim wheel design and purpose (e.g. pilot was not able to achieve full nose-up trim position so fast, which is more of a HW issue restricted via antropomorphic controls already.)

Originally Posted by 5./JG27.Farber

So... How long should it take? -Thats the real question. Bearing in mind you dont use all of it. Lets say half, how long does it take to roll out half of it?

I don't know. It took 4 complete revs (or cca 5 3/4 revs) of the wheel to get from full up to full down trim. (It took about 22-25 seconds to deploy flaps fully (see varratuu's video again, he was refering to the wheel operation))

I can only assume that it was full 2 revolutions from neutral position to full up. Now watch the animation (less than one rev) and the immediate effect we have got in game. Neutral position (0), +3 was nose down, -8 was full up - assuming the 0 is neutral for cruise flight, it would be even more than 2 full revs to get from neutral to full up, it would be more like 3 and half full revolutions. I would need to verify this and do some more research but I am sure someone will have that knowledge.

Now try to take a Hurricane and do the same, the trim wheel is very similar in fact as was typical for many aircraft of that era - and have a look at the trim indicator and wheel animation. Response is pretty similar. It's not too bad, there is even this small delay modelled, sort of.

[robtek]

I think there would only be a problem if the nose up trim gave the 109 the ability to outturn the spit/hurri in a sustained turn, which would be clearly wrong.
A "dynamic" turn is only limited by the pilot, the structural integrity of the ac and the effectivity of rudder, elevator and ailerons.

[5./JG27.Farber]

Robo, dont confuse the operation of the landing flaps with the operation of the trim wheel. They share a spindle but thats it, they are geared differently. So I dont think that video has any relevance.

[Robo.]

Originally Posted by 5./JG27.Farber

Robo, dont confuse the operation of the landing flaps with the operation of the trim wheel. They share a spindle but thats it, they are geared differently. So I dont think that video has any relevance.

I am not confusing anything, the relevance is in the position and access to the wheel control. 5 full turns (or 4 three-quarter turns) were required to adjust the full 12 degree range.

[SlipBall]

Originally Posted by Robo.

I am not confusing anything, the relevance is in the position and access to the wheel control. 5 full turns (or 4 three-quarter turns) were required to adjust the full 12 degree range.

Could you post the reference material

[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.

[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.

[Varrattu]

Originally Posted by SlipBall

Could you post the reference material

I'm not sure wether this is the report Robo referred to. Please have a look at page 7, last paragraph (4.23):


ME109 handling & manoeuvrability test



I bet it were actually 6 turns in newer machines. 1/2 turn corresponds to 1 degree ...

[Flanker35M]

S!

The thing in CoD is that if we trim the aircraft then the appropriate trim know/lever/wheel moves constantly until it reaches the desired position. This in all planes. So if you need 5 revolutions to fully deflect the trim in Bf109, for example, it will move nonstop that 5 seconds as the "grabs" are not simulated. Same goes to Bf109 flaps. It takes them pretty much the same time to deploy as stated in many reports EVEN the trim wheel moves nonstop in the game.

So I think Luthier and his team have taken in account the "grabs" on trimming to achieve historical results even the visual indication tells the movement is continuous.

I tested offline on Bf109E-4. The flaps take ~25sec to deploy/retract. Trimming the full deflection ~5-6sec. The movement of the trim axis does NOT affect trim speed in ANY way, always the same. So mapping to an axis does NOT give you an advantage. As reference on Spitfire Mk.Ia the elevator trim takes about the same 5-6sec for full deflection so not much difference there.