[CLOSED]Bf-109 Trim controls

I guess the problem (if it presents) is in the joysticks with hard center force like Thrustmaster... never like it especially for formation flying.

 

MSFF2 - our choice! :) Get the hand away and no trimmers required :)

Unfortunatelty Yo-Yo, these are no longer available commercially, and it's difficult to find a good one in 2nd hand, specially here in Portugal :-(

Being unable to use a good FF joystick with either of the flight simulators I use and am told would behave rather better if with a FF ( DCS, ROF and BOS ) I kinda feel frustrated :-(

In DCS I had to manually edit the picth, roll and yaw curves, even used saturation in pitch, to be able to successfully dogfight in the K4, and I increased the tension in my Rhino to it's bigger ( very noisy ) spring, so, it now feels closer to the TM COUGAR HOTAS I used for a while, and for me it's better than when I have the joystick feeling loose...

If one day you find some expedite way to simulate control forces for users of non-FF joysticks, that would be GREAT!

Having just tested the 109, I have to say it feels extremely tail heavy. To the point of being dangerously tail heavy and unstable.

 

I need full nose down trim for takeoff and even then it is very dangerous, with lift off being able to stall the aircraft as the nose pitches up viciously. In normal level flight I need full nose down trim.

 

It seems the centre of gravity is too far back, causing the extremely unstable pitch.

 

The P-51 flight model is beautiful, however the 109 feels as though its missing some forward weight causing an aft centre of gravity.

 

If this was really how the 109 handles, as a pilot I would be ordering the pit crew to attach weights to the nose to get it back into balance, because at the moment, its almost unflyable its so unstable.

Well... it certainly seems so, but when trim is applied the plane is very stable and no wierd stalling characteristics occur. Try it if you stall the plane noses down... meaning that the weight is on the nose.

I read some documents that said that the 109 had nose up attitude and up to a certain point the pilot had to push the nose down to keep it level... but never thought that was this much. Although, the faster you go the less pronounced it is and if I am right, the 109 starts to be nose heavy above 550kph... but don't take for granted... I haven't flown it long enough since the last patch.

I think it was Messerschmitt's style of design. Even G2 was out of trim with full tank and trimmer full nose-heavy as it is documented in NII WWS report.

 

Anyway, we asked Erich about trimmer setting and he told that he trimmed the plane only once for cruise and then did not touch the wheel.

Surely there is something wrong with the test data of Bf-109G2-R6 (with underwing gun pods cannons ) performed by the VVS in 1942, that YO-YO is commenting before.

Probably the airplane had an incorrect trim tabs settings, due to the Russians was not known the correct setting.

It is unquestionably that the trim setting of the DCS: Bf-109K4 is modeled incorrectly, because the airplane does not fly straight and level at cruising speed with Handwheel trim set in zero position as German Flight manuals says. (The trim setting remains wrong in version 1.2.15 published recently.)

Besides the above, there are many books that talk about the good stability in flight of the bf-109.

In the book "Messerschmitt Bf-109; Owners' Workshop Manual" of Haynes Publishing 2009.

There is some commentaries about trim settings of Bf-109 in operations and Bf-109G2 "Black-6", the last original "Made in Germany" werk nummber: 10639, restored to airworthy condition.

In that book, Dave Southwood the RAF test pitot, who flew the Bf-109G2 "Black-6", He says.

In page 96:

"" In the pre -take-off check, I set 20º flaps and 1º nose up tailplane trim. The original data said 0º trim, but 1º nose up was added after the propeller ground strike on the first sortie. ""

In the page 97 of same book Dave Southwood says:

""trim settings: The ailerons and rudder fixed trim tabs were adjusted to give centralized slip ball and wings level flight with cruise power (1.0ATA, 2000rpm) set in straight and level flight. If adjustments were needed, the rudder trim had to be adjusted first before the required aileron trim tab adjustments could be made. Note that if the ailerons trim was correct at these cruise conditions, it was correct throughout almost the entire required flight envelope. ""

This means the airplane is not tail heavy, and capable to straight and level flight with correct trim tabs set on ground, and with elevator trim handwheel set to zero.

What did German testing say about stab trim for cruise?

No, trim curves measured in NII VVS in the USSR shows that nose down elevator (stick) position was necessary to trim the plane for the most range of cruise speed with stab Phi=0.

what says the VVS about elevator trim tabs setting on ground? ...What angle they set to tab?

Do they performed the adjustment for straight and level flight that Dave Southwood the RAF test pilot say?

Yo-Yo Tell me, what is the procedure for trimming an airplane with the stick ?

..the trim handwheel is used for flight without stick forces, if you are pulling or pushing the stick all time of flight .. what kind of trimming are you doing?.

No, trim curves measured in NII VVS in the USSR shows that nose down elevator (stick) position was necessary to trim the plane for the most range of cruise speed with stab Phi=0.

Yo-Yo I would be very grateful to you, if you will can expand the information about adjusting elevator' trim tabs of the Bf-109K4.

I tried to retouch some settings in the file:

C:\..... \DCSWorld\Mods\aircraft\Bf-109K-4\FM\FMOptions.lua

aileronTrimTab = -0.045

elevatorTrimTab = 0.0

rudderTrimTab = 0.0

I tried to assign some positive and negative random values to the parameter "elevatortrimtab" but it does not work.

The plane still flying with a strong nose-up attitude with the handwheel set in zero position (neutral trim).

Somebody can help with this problem?

Nobody says that you must have straight and level flight exactly at "0 deg" stab position

 

By the way, did you notice that I did nod talk about FORCES but only about MOVEMENT that is independant to trim tab position.

I have read many books about Bf-109 and nowhere said anything about the need to trim the airplane full nose-down for cruising, with normal load in clean configuration.

however I have read many comments about adjusting elevator trim to zero or 1º (nose-up) for takeoff, and zero for cruise and trimming near to full nose-up for landing.

It is well known that with full flap and undercarriage deployed the Bf-109 has strong nose down tendency.

Clearly you have something wrong in the DCS FM of Bf-109K4.

Do you know that the handwheel trim indicator of the Bf-109 indicates positive values for tail-up contrary to American planes?, (for example)

Hi Yo-Yo, any word on trim working on axis? (Saitek trim wheel)

Are these trim positions final or are we going to get a little more down trim?

As it is now I trim full nose down for the whole flight and keep finding myself pressing the trim nose down button.

not working good on axe for me also .

It's all ok as it is done according real trim curves. The only thing is that in RL trim is mostly about FORCES and not about the elevator or stab angle, i.e. it means that it's a matter of free controls not fixed.

In simulators we can not use free controls conceptions untill at least all user has FFB device.

If I am not misinformed, you are using data and curves of a Bf-109G2-R6 (with underwing gunpods) captures in 1943. That is NOT a Bf-109K4 in clean configuration.

That configuration possibly need a special trimming in elevator trim tabs, due to gunpods are a extra weight that alters the CoG. If the VVS was removed the gunpods for test, the airplane need readjust the elevator trim tabs, for level flight,.. and this possibly they didn't.

Surely, by adjusting the trim tab it's possible to change stick forces for the certain stab inclination but you can not change the required trim elevator angle.

That is not true. if you set CERO in the elevator trim, and the elevator trim tabs are folded in the correct angle, the plane must be fly straight and levelled, by design.

For DCS 109 adjustment accurate and detailed curves from the flight tests were used. They contains accurate elevator angle values for the certain IAS and balance, both in clean and landing configuration, for power-on and power-off conditions.

Any anecdotal reference without exact balance, power settings, etc is only an anecdote... by the way, my anecdotal reference from Erich Brunotte states that there was no use for retrimming the plane and he only trimmed it once for cruise.

well, It seems that there are many anecdotes contrary to current DCS 109K4 FM with full nose-down trim for cruise.

I think it possible that the Bf-109 needs a little elevator trim setting, at cruising speed, but in any case would be 1º nose-up, according to comments from pilots who have flown. All comments of pilots who flying the Bf-109 say that the attitude of the airplane is nose-heavy, not tail-heavy.

Surely this problem is because the positive angles of the elevator trim are mistaken with nose attitude angles in data tests of the VVS, or in the FM, that angles are reversed and should be negative.

Anyway I will try to find more data, about elevator trim of Bf-109 to report the bug properly.

IIRC the Soviet trial of the captured 109G-2 Yo Yo has possibly used to get some idea on the trimming characteristics of the 109K has a picture of the "clean" 3-gun (no gondies) 109G-2 the Soviet forces have captured. There was also another G-2 in five gun condition (gondies) but that was not the subject of the Soviet stability report.

Its a bit difficult for me to make sense of the all Cyrillic report though, but if I have decoded it right it does shows a nose up tendency in all trim conditions and centre of gravity. I do find it odd that the plane allagedly can't (?) be trimmed to level flight but it seems thats what the report says...

Or maybe we are missing something.

I have full finnish G2 test report somewhere in the house, problem is that i have not seen it in last couple of years. I'll try to find it and check what it says about trimming. Because i have to agree with JG52 Otto, trimming as it's now in DCS 109 seems quite weird to say at least.

The data of this report has EXACT data for the balance. By the way,gunpods can not significantly change neither CoG position, as they are quite close to MAC, nor aerodynamic focus position.

 

The balance in DCS K4 is obtained form the documents for K, not G model. K model has normal aft CG position even more aft than G2 that was tested and measured in the USSR (26% vs 23%).

It was very useful that these flight tests were conducted up to initial 30% CG at TO, that gives wide range of trim characteristics.

 

So, using G balance curves is correct in this case.

As Yo-Yo relates, if the Neutral Point is the same and the CG limits are the same....the basic longitudinal stability is the same. The trim curves apply.

It is difficult to change a designs CG limits once it is built. There are only certain things that can be done to move the neutral point (aircraft's aerodynamic center). Those design changes are usually easy to spot.

Otto's is right. By adjusting the elevator trim tab you can change the trim point of a plane without changing the angle of the adjustable tail plane. So if the authority in pitch of the adjustable tailplane is insufficient even when the trim wheel is in the fully nose-heavy position with the tab in a particular setting, you could simply bend the balance tab to an appropriate angle. In the current DCS scenario you would bend the tab up a bit to move the angle of zero hinge moment for the elevator down somewhat which in turn will move the adjustable tailplane trim range towards a more nose heavy range.

This is pretty basic stuff on any plane with trim tabs and I'm sure this is also what the crew chiefs did on the real 109's as well. So an IRL pilot that flew a 109 and found that he could not trim his plane in pitch would simply instruct his crew chief to do this if he was not happy with the current trim range he was getting out of the adjustable tailplane.

The only thing to bear in mind here is that if you adjust the elevator trim tab in this way you will of course not be able to trim the plane as tail heavy as before but right now I don't see there is any problem here so I will definitely ask my crew chief to bend my trim tab before flying my K4 again. However the problem right now seems to be that my DCS crew chief is unable to comply since he is not allowed to do this.

So a good way to get a more realistic implementation in DCS would be to either make the elevator tab adjustable in settings or set the stick-free trim point to a more down elevator position so that the adjustable tail plane trim range also allows that we can trim to zero stick force also at high speeds. I would prefer the former but be willing to settle for the latter.:)

As Yo-Yo relates, if the Neutral Point is the same and the CG limits are the same....the basic longitudinal stability is the same. The trim curves apply.

 

It is difficult to change a designs CG limits once it is built. There are only certain things that can be done to move the neutral point (aircraft's aerodynamic center). Those design changes are usually easy to spot.

Yes but a competent "calculator" will certainly spot that the CG is not "fixed" by design but will change depending on the girth of the test pilot!

CG is not "fixed" by design

CG limits are the same.....

Limits are fixed by design.

:smilewink:

That one flew over your head did'nt it? :smilewink:

I have to add that pilot's notes on modern flying 109s must be added with actual balance for the trim they use and whether trim tabs were bend for their planes to get said trim.

 

Though NII VVS report has no direct mentioned neutral trim tab, the common engineering sense tells that as the trim tab is ADDITIONAL and secondary mean of trim, so, presumed neutral.

Exactly,

The fixed trim tab is there to overcome manufacturing tolerances. It's setting is adjusted by feel and flight experience.

The engineer would have no way of predicting each individual airframe fixed tab trim point.