109 horizontal stabilizer

[VBF-12_Snake9]

I noticed that if you trim the nose down, one cannot get full deflection pulling the stick back.  Is this a control issue/bug or was it like that is reality.  Way to test, go into a dive with nose trimmed all the way down.  Yank stick fully back.  You get a smooth climb upward.  Then go into dive with no trim, yank the stick back.  Very sharp climb and even black out. 

[BeastyBaiter]

The stabilizer trim moves the entire stabilizer, that's why. The stabilizer at high speeds is actually a more effective means of dive recovery than the elevator is. Also, the default position is 1.5 degrees up instead of neutral.

Edited December 21, 2013 by =LD=King_Hrothgar

[VBF-12_Snake9]

cool as long as it's working correctly. 

[dburne]

Yeah you do not want to get into a dogfight with the stabilizer trim out of whack, it can cause problems - I already found that out...

[Uriah]

Just what is this stabilizer?  I know there is a key for it but I am unfamiliar with it.  And I understand there is no trims on this plane.

[Karost]

never use stabilizer in IL2 old day before

 

after learn in picture then I get the point

 

I remember from reading a book long time ,  LW pilot like to set nose up before get in to combat  but I forget which they use trim or stabilizer to set nose up   

[LukeFF]

Just what is this stabilizer?  I know there is a key for it but I am unfamiliar with it.  And I understand there is no trims on this plane.

 

Google it.

[kestrel79]

I didn't know what it was either, until I set a rotary for it and watched it physically move from an external view in the game. That's the best way to see everything moving and working.

[Jaws2002]

This is on FW-190, but it works the same on 109. You control the AOA of the horizontal stab. pretty clever way to trim the pitch. effective at very high speeds, when the effectiveness of elevator and normal trim tabs is reduced.

 

 

Edited December 22, 2013 by Jaws2002

[VBF-12_Snake9]

So will the 109 and 190 have elevator trim when it is placed into game or these planes didn't have that function?  In il2 1946 these planes always had elevator trim. 

[Jaws2002]

So will the 109 and 190 have elevator trim when it is placed into game or these planes didn't have that function?  In il2 1946 these planes always had elevator trim. 

 

 

The 109 and 190 used the control of the horizontal stabilizer as trim. Most planes had trim tabs on the elevator. Just two different ways of doing things. The 109 already has the H stab control working in game, so we are good. I just assigned the same rotary I use for elevator trim. Planes that have one system won't have the other, so it works perfect. Does the same thing.

[VBF-12_Snake9]

According to these post it's not exactly the same. 

 

 

I noticed that if you trim the nose down, one cannot get full deflection pulling the stick back

 

The stabilizer trim moves the entire stabilizer, that's why. The stabilizer at high speeds is actually a more effective means of dive recovery than the elevator is. Also, the default position is 1.5 degrees up instead of neutral.

 

Yeah you do not want to get into a dogfight with the stabilizer trim out of whack, it can cause problems - I already found that out...

 

 

 

Never had elevator trim screwing with the deflection of my stick. 

[SKG51_robtek]

As changing the aoa of the horizontal stabilizer doesn't changes the movement of the elevator there shouldn't be a feelable difference when using the elevator.

[Matt]

As changing the aoa of the horizontal stabilizer doesn't changes the movement of the elevator there shouldn't be a feelable difference when using the elevator.

Could you explain a bit why that should be true.

 

When you adjust the stabilizer, the AOA of the elvator already changes with it right? Why wouldn't you be able to feel a difference when using the elevator then?

 

Not trying to prove you wrong, but i just can't imagine how you can adjust the whole tailplane including the elevator and then still have the exact same elevator response.

[SKG51_robtek]

Simple explanation: when you change the AOA of the stabilizer the AOA of the plane changes also as a result.

The final result is that the air flows around the stabilsator again almost exactly as before the changes.

So when you change the stabilizer 1° up you create a lift there, the nose of the plane will go down until the air flows

again around the stabilisator without creating extra lift.

The elevator has all the time the same airflow, except during the AOA change.

[VBF-12_Snake9]

 but i just can't imagine how you can adjust the whole tailplane including the elevator and then still have the exact same elevator response

 

 

 

 

Could you explain a bit why that should be true.

 

When you adjust the stabilizer, the AOA of the elvator already changes with it right? Why wouldn't you be able to feel a difference when using the elevator then?

 

Not trying to prove you wrong, but i just can't imagine how you can adjust the whole tailplane including the elevator and then still have the exact same elevator response.

That's just it.  It will not be the same result.  If one does the test I wrote out in the first post, there are two very different results. 

[Matt]

That's just it.  It will not be the same result.  If one does the test I wrote out in the first post, there are two very different results. 

And, when talking about adjustable stabilizers (not trim tabs), i would say that is exactly as it should be.

 

I'm still not convinced by Robteks explanation, i would like to read some more input on this matter.

[Crump]

 

but i just can't imagine how you can adjust the whole tailplane including the elevator and then still have the exact same elevator response

 

 

Robtek is correct.  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.

 

Interesting fact is the pilots in JG 26 initially thought the electric trim on the FW-190 could be used to increase the level turning ability of the aircraft.  That is not true either.  Focke Wulf overcame this misconception with additional pilot training.

 

The huge advantage of the adjusting the horizontal stabilizer is immunity to mach effects.  All aircraft will experience a loss of control authority when the control surface is enveloped in the flow separation preceding a normal shock.  

 

An all moving tail will always have attached flow on its surface to maintain some degree of control authority.  The adjustable horizontal stabilizer trim system works in the same fashion if the pilot uses the trim control as a primary control in recovery.

 

From a design standpoint the adjustable stabilizer offers the designer the ability to reduce the tail size for the same trim power over a fixed horizontal stabilizer trim system or the larger moments created by the adjustable stabilizer can be used to widen the CG range of the design. 

[VBF-12_Snake9]

That's all well and good, but talking just about what is happening in this game and nothing else, if one "trims" the nose down in the 109 then a large amount of positive elevator control is lost.  Pulling the stick all the way back only gives a faction of bank compared to pulling the stick all the way back with no trim applied. 

[Furio]

As I understand it, and if I’m not mistaken, this is correct. To make it as simple as possible, we could say that changing the stabilizer AoA changes the neutral point of the whole tail. The elevator starts to push the tail down and the nose up from a displaced starting point, and runs out of available displacement earlier.

[Crump]

 

That's all well and good, but talking just about what is happening in this game and nothing else, if one "trims" the nose down in the 109 then a large amount of positive elevator control is lost.

 

 

It should not lose elevator control.

[Crump]

Raaid,

 

Read up on trim systems because as I understand it from both college and getting an Airframe & Powerplant certificate, your understanding is wrong. There is no loss of control in comparison to other trim system design.

[DD_bongodriver]

Trimming the horizontal stabilizer will not affect the ability to make full deflections on the elevator, but if the tailplane is trimmed fully nose down then a full elevator deflection for pitch up will have less effect, unlike with a trim tab there should be no appreciable increase in control force to full deflection.

[DD_Squawk]

(Disclaimer)

I am basing my post off of 50's civilian aircraft tech, and memory. I could well be wrong, but I am 900km from home and will have to wait until after Christmas to physically confirm my thoughts.

 

With a stabilator equipped aircraft you dont 'lose or gain' anything in elevator effectiveness because the elevator stops are attached to the fuselage and not the elevator. Therefore, as the pitch gets trimmed nose down, the front of the stabilator goes up, and the rear being past the pivot point, goes down. This translates into a greater distance between the elevator itself and the physical stop for nose up elevator, located on the fuselage.

 

With a full nose down trim angle, you would end up with greater aft travel available on the stick, but end up with an equal net effect. Conversely if you trim full nose up and pull the stick, you would not be able to pull as far back as normal before the elevator hit its stop limit.

 

That being said, trying to get full aft elevator with full nose down trim is a very tall order.

Side note, the faster you are traveling, the harder it appears to manually change the angle of incidence.

(at least on a C185)

 

In game we are limited in joystick throw, in the absence of "off centring" FFB we don't get this perceived 'extra' length of pull.

Edited December 24, 2013 by =69.GIAP=GRACH

[DD_bongodriver]

it's not a 'stabilator' on the 109, any input on the control column does not make the entire tailplane move, the tailplane stays fixed in whatever 'trimmed' position it is put.

[DD_Squawk]

Yes, yes. I should know better. Too much Christmas cheer mate. Couldnt think of the correct ruddy term.

Too late to edit now.

 

But yes, it is NOT a stabilator. As the technical name escapes me I shall call it a "variable incidence horizontal stabilizer."

(or Steve, for short )

 

Operating principal remains the same.

Edited December 24, 2013 by =69.GIAP=GRACH

[DD_bongodriver]

Steve....love it.....Steve it is...

 

Not sure how the 'Steve  ' has any effect on available elevator travel, the full stick deflection still translates to full physical elevator deflection no matter what position the 'Steve' is in, the physical 'stops' for the elevator in this case should be part of the 'Steve' and not the fuselage.

[DD_Squawk]

Should be or not, the stops are attached to the framework of the tail end of the fuselage.

 

The elevator itself uses some form of bell crank(dirctly attached to steve), and the crank butts up against the stops that are (screwed/bolted?) to the fuselage tail.

 

The stops look like bolts with oversized heads, and I think the elevator travel can be adjusted by screwing them in/out.

[Crow]

I think where Snake is coming from is not about elevator authority. I think it is agreed that the elevator will have the same travel and (approximately) the same authority regardless of the stabilizer position. However, that doesn't mean that the total moment of the tail isn't higher or lower based on trim position.

 

Take a simple case, the elevator is deflected fully up (stick pulled back all the way) and the stabilizer is set to nominal (1.5 deg) trim. Now compare that to a fully up elevator and the stabilizer is set to the maximum nose up trim position. What is the difference between the two? Will they produce the same moment? I say no. Without any actual aircraft maintenance or pilot manuals to confirm, I would guess that the overall pitching moment of the 109 is actually (in a very simplified way),

 

elevator moment + stabilizer moment = pitching moment

 

Another way to think about this is that if you look at the chord line of the stabilizer + elevator, case 1 would have a smaller angle of attack than case 2 which means they produce different magnitude forces. So changing either of the stabilizer or the elevator actually changes the pitching moment, which would lead to the behavior that Snake and others have mentioned.

 

(Obviously this would only apply to aircraft like the 109 with the variable horizontal stabilizer design.)

Edited December 24, 2013 by Crow

[DD_bongodriver]

Yep, that explains better what I'm seeing in my head.

 

But having looked at diagrams of the structure now it leaves me wondering on the actual operation, did the tailplane trim by moving the entire incidence of tailplane + elevator or did the tailplane move independently of the elevator therefore creating a camber? GRACH's explanation leaves me thinking it is the latter.

 

Anybody got some good engineering drawings on this?

Edited December 24, 2013 by DD_bongodriver

[DD_Squawk]

I think it is the former. Change the angle of incidence, you change the AoA, and change the lift.

 

The elevators are attached to the horizontal stab via hinges, they are actuated by way of a pulley/cable system.

Simply, camber is controlled by pilot input. ( not really camber but it is 4 am, close enough)

 

What I am trying to get at, is when the stab has a change in trim, the elevators ( being attached to trailing end of the stab) change their position in relation to the elevator stops which are fixed to the airframe, and you get varrying lengths of pull.

 

The pivot point for the horizontal stab should be close to the center of the chord.

Edited December 24, 2013 by =69.GIAP=GRACH

[DD_bongodriver]

Not so sure, my diagrams show the actuating mechanism is close to the leading edge, what my diagrams don't show clearly is where exactly the hinge point for the tailplane rotation is, if it is on the same axis as the elevators then the latter is more likely because the elevator bellcrank does seem to be completely independent of the tailplane.

[JtD]

Travel of 109G elevator according to handbook, given relative to stabiliser:

 

trim neutral (0°): push: 34°, pull: 33°

trim max nose down (2°): push: 35°20', pull: 31°40'

trim max nose up (-6°): push: 30°30', pull: 36°

 

Looking at the totals, the maximum nose down position of the elevator relative to 0° position is 37°20' with trim nose down, and 24°30' with trim nose up. Essentially adjusting the trim into a direction gives you larger elevator in the direction you've trimmed the 109 into. Figures for the 109F are fairly similar, but not 100% the same.

[VBF-12_Snake9]

Travel of 109G elevator according to handbook, given relative to stabiliser:

 

trim neutral (0°): push: 34°, pull: 33°

trim max nose down (2°): push: 35°20', pull: 31°40'

trim max nose up (-6°): push: 30°30', pull: 36°

 

Looking at the totals, the maximum nose down position of the elevator relative to 0° position is 37°20' with trim nose down, and 24°30' with trim nose up. Essentially adjusting the trim into a direction gives you larger elevator in the direction you've trimmed the 109 into. Figures for the 109F are fairly similar, but not 100% the same.

 

As long as the elevator/stabilizer throw is correctly modeled I have no problem, and with these numbers it looks like what I am feeling is proven correct.  With nose trimmed fully down you will not get same "pull" as nose trimmed neutral. 

[Crump]

As long as the elevator/stabilizer throw is correctly modeled I have no problem, and with these numbers it looks like what I am feeling is proven correct.  With nose trimmed fully down you will not get same "pull" as nose trimmed neutral.

 

 

Which is how all trim systems work......................

 

 

Does not have anything to do with control authority at trim speed.

[DD_bongodriver]

apart from standard trim tabs which do not alter the throw of a control surface at all.

[Crump]

No, some vary the surface area and all induce control pressure (movement) in the direction of trim. In other words, trimming nose down will reduce the control surface movement range in the nose up direction. Trimming nose down tells the airplane to increase dynamic pressure and the control authority remains.

 

Control authority will change with velocity and cg position irregardless if the trim system design.

The higher the dynamic pressure, the less surface area required to exert the same force.

 

If force remains constant and area is allowed to vary, dynamic pressure and area have an inverse relationship.

[DD_bongodriver]

But they do not physically alter the range of motion of the control surface.

[Crump]

So what??

[VBF-12_Snake9]

  Merry Christmas!