[CLOSED]Bf-109 Trim controls

[IIIJG52_Otto_]

Otto,

 

my hat is off to you!!!

 

Thx for your post above - lot's of useful info on it!

 

It took me some time to show that that prop effects on the downwind wing of a DCS prop aircraft when taking off or landing in a crosswind were overdone / unplausible, but it eventually got sorted out... Let's hope the same happens with the pitch trim in the K4...

 

Thank you for your support, my friend :thumbup:

[IIIJG52_Otto_]

No one said it was from a K4.

It`s a joke? :music_whistling:

 

As well you still aren't showing anything that makes me doubt the current 109 we have and its performance. More so you confirmed that the trim tabs were for initial tweaking of a new plane and probably never touched again, the aircraft would be trimmed for best cruise performance, it doesnt mean it equals hands free 0 trim flight...

.

 

Do not forget that the flight controls were adjusted after repairs.

You know, battle damage, breakdowns, etc.etc. :joystick:

[NineLine]

It`s a joke? :music_whistling:

 

Do you have better data from a K4? Do you have a Luftwaffe pilot that flew most marks of the 109 to ask the differences?

 

Do not forget that the flight controls were adjusted after repairs.

You know, battle damage, breakdowns, etc.etc. :joystick:

 

Which I already stated above somewhere in this mess, that the tabs could be used to help an aircraft that might have been abused in some form, but still doesnt say anything about making it fly straight and level hands free trim at 0.

[Dirty Rotten Flieger]

I think Otto has made is absolutely clear how the K4 was designed to fly.

 

It appears what we have in the sim is how one particular captured, and possibly damaged/ repaired airframe performed in the hands of the Russians.

 

I for one would prefer the bf109K4 as it was designed to fly.

 

Well done Otto.

[NineLine]

I think Otto has made is absolutely clear how the K4 was designed to fly.

 

It appears what we have in the sim is how one particular captured, and possibly damaged/ repaired airframe performed in the hands of the Russians.

 

I for one would prefer the bf109K4 as it was designed to fly.

 

Well done Otto.

 

He has shown nothing of the sort, he showed one propped up on the ground. You guys are funny. Anyways, I wont engaged anymore, I talked for a long time with Yo-Yo on this subject, I am happy with his take on the issue.

[Yo-Yo]

In the better of all cases .. that curves chart, are not from a Bf-109K4 ..because..

 

 

 

In acordirng with the book of Thomas H. Hitchcock - "Bf 109 K Monogram Close-Up 16 -Monogram Aviation Publications- 1979 and with the book "Messerschmitt Bf-109 F to K Development, Testing and Production by W.Radinger & W.Otto -Schiffer Publishing Ltd.-1999-

 

The "Economical cruising speed" for BF-109K4 was 645 km/h(TAS) at an altitude of 8.4 km. and 477km/h(TAS) at Sea level.

open the spoiler for see a screenshoot of the data chart.

 

- "Bf 109 K Monogram Close-Up 16 by Thomas H. Hitchcock -Monogram Aviation Publications- 1979 data chart

 

 

 

I.A.W. kurfurst.org This cruise speed was obtained at engine regime of 2000 RPM@ 1.15ATA

Open the spoiler for see the DB-605DB performances chart.

 

 

Sparleistung = power in Economical mode.

 

 

 

I.A.W. Messerschmitt Bf-109 K-4 Werkschrift 2109 K-4 Teil 1,2,3,4, Flugzeug-Handbuch, 1944,

After reparations in the flight controls, was mandatory the control of the dimensions and angles of the tailplane. It was performed placing the fuselage at level flight position using some spirit levels and plumb bobs and the THS (Trimmable Horizontal Stabilizer) airfoil was setting to zero degrees, with zero tolerance. (see the chart below)

 

the angles of travel in the control surfaces were also checked in the different THS and elevator stops positions. (Note that the angles of travel in the elevator control surface are different, when the THS angle of incidence is different than zero)

Open de spoiler and see the figure and control chart:

 

 

Trim tabs were finally adjusted after a test flight. as you see in the picture.

 

 

 

Dear Otto... I always wonder (again - always wonder) how peolpe having (as you just showed us in this post) no attention to the details in engineering documents are trying to discuss on the matters of flight dynamics... I do not want to say that everyone must know what Sigma_P.B. (Руль Высоты or rul' vysoty or Hochrudder or elevator) in Russian aircraft engineering notation means, but the small circle always means DEGREES even in Africa...

Phi means EXACTLY the same Germans measured, and yes, positive angle means LEADING edge up direction of the stab inclination.

It corresponds with two clues at the graph: with the same stab position 2.4% CoG movement requires 1 degree of elevator movement or 0.417 degrees per 1% of CoG movement.

As the CPSU always taught us, around the small changes stability dependancies are linear, so if the stab is remained at +1.5 it would be necessary to deflect the elevator to -0.58 degree (pulll the stick). Instead of it we see that it is deflected to +2.5 to counteract stab angle change. It means that, indeed, changing the stab angle from +1.5 deg to zero we retrim the plane for tail-heavy.

Additionally, this school homework gives us the ratio of stab/aileron effectiveness on trim: one degree of the stab deflection is equivalent of 2.05 degrees of the elevator.

 

And the third question about level flight, diving or climbing: DOESN'T MATTER. Because of comaparatively low flightpath angle. Because the matter of discussion is only a trim, i.e. CL or AoA.

 

Regarding convenience of the flight test... 146% that it is climb, because otherwise the change of the speed is much faster to stabilise and record the state. Diving? Noway.

 

So, I think that your attempts to compromise flight tests results will not be successful...

 

 

P.S. The report contains pilot's notes on 109 stability, controlability, etc. The only issue that was mentioned was its longitudinal instability at power-on. No comments on inconvenient stick forces that makes the plane "not to fly".

Edited June 18, 2015 by Yo-Yo

[Yo-Yo]

It`s a joke? :music_whistling:

 

 

 

Do not forget that the flight controls were adjusted after repairs.

You know, battle damage, breakdowns, etc.etc. :joystick:

 

If you find the same type of German report on mint condition K4, please, let us know.

[Dirty Rotten Flieger]

Can anyone explain what the zero on the stabilizer is for if not for cruise. Why have 7down 2up if they could just have 9? If zero is meaningless. I suppose zero is stab in line with the airflow? Would it be possible to design plane so stab is trimmed at zero at cruise? It would seem this would give least drag and best range?

 

Was the Bf109 originally designed to trim at this zero setting but added weight of extra equipment to the rear fuselage as the plane grew heavier move COG rearward and meant the plane would no longer trim at zero?

 

I can imagine as the design grew heavier the original trim was no longer possible.

 

Also how much weight is in ammo? Of course Russians tested with hundreds of kilos of ammo in nose? maybe ammo wight would not account for such changes?

Edited June 18, 2015 by Dirty Rotten Flieger

[Yo-Yo]

Can anyone explain what the zero on the stabilizer is for if not for cruise. Why have 7down 2up if they could just have 9? If zero is meaningless. I suppose zero is stab in line with the airflow? Would it be possible to design plane so stab is trimmed at zero at cruise? It would seem this would give least drag and best range?

 

Was the Bf109 originally designed to trim at this zero setting but added weight of extra equipment to the rear fuselage as the plane grew heavier move COG rearward and meant the plane would no longer trim at zero?

 

I can imagine as the design grew heavier the original trim was no longer possible.

 

Also how much weight is in ammo? Of course Russians tested with hundreds of kilos of ammo in nose? maybe ammo wight would not account for such changes?

 

You can type any number you wish - for Dora the actual angle and the marking are different, for example.

And as I wrote before - for E, for example, F, and G/K the cruise IAS is about 240-320 kph where the trim works.

[Dirty Rotten Flieger]

Maybe engineers designed plane to cruise with stabilizer close to zero but added weight of MW50 tank and heavier radio, IFF in rear was too much to balance against heavier engine and armament armament in nose.

 

If this is the case and heavier equipment negatively affected the trim of the plane then what we have is historical accurate nuance, not bug. Even so if this was the case, the ground adjustable trim tab would surely be used to correct the nose up problem as much as was practical.

 

Please allow elevator trim tab. Is it so hard to do? Is there good reason not to enable?

[NineLine]

 

Please allow elevator trim tab. Is it so hard to do? Is there good reason not to enable?

 

If you read some of the reports on trim, and trimming for cruise, it adversely effected performance such as dive recovery. SO you set these fixed tabs so you can fly close to level, then get in a dive and die. Enjoy ;)

[Dirty Rotten Flieger]

I would enjoy very much to be able try this and experience this crash from using trim tab.

 

As I believe it would be the firs thing the real pilots would have done. Maybe the first ones to do it did crash. Lets try it and see.

 

I live in a nanny state. no speeding, drinking, smoking... not even allowed to crash my flight sim in case I get hurt! :P

[Supongo]

Dear Otto...

 

So, I think that your attempts to compromise flight tests results will not be successful...

 

 

What test Otto want to compromise? The G2 in a climb with emergency power or a test K4 have taught us?

 

Regards

 

Supongo

[gavagai]

I haven't been following this thread, but it has been popping up frequently.

 

Anyway, I just flew the 109 after some time away. It really feels like it has CoG problems, and the elevator becomes less effective at only 400km/h. What a pig it is to fly!:doh:

[Ala13_ManOWar]

Regarding Yo-yo posted graph, may be this graph is related to something similar? If I understand it says stick has to be pulled to keep level flight, with force in kilograms instead of elevator surface deflection degrees like Yo-yo. So, means that the need to pull stick to keep levelled the 109 at high speed is correct? :music_whistling:

 

 

 

 

 

S!

[NineLine]

Is it saying for level flight, I didn't get that anywhere? I can only get that its the results of speed on stick force (which we see), but I don't understand it all, so I will defer to Yo-Yo :)

[messermeister]

Regarding Yo-yo posted graph, may be this graph is related to something similar? If I understand it says stick has to be pulled to keep level flight, with force in kilograms instead of elevator surface deflection degrees like Yo-yo. So, means that the need to pull stick to keep levelled the 109 at high speed is correct? :music_whistling:

 

 

 

 

 

S!

 

Actually, very related, and it shows both stick force and elevator angle for several IAS and Mach numbers, albeit only for a single CoG position (the NII VVS report for W.Nr. 14513 wich has several CoGs).

 

BTW, 109 02 E 44 it's the only report that shows this kind of detailed data from german sources (either Mtt AG or DVL) for a late Bf 109.

 

PD: they dived the plane to get the high IAS measurements, and I guess the soviets did the same, as climbing at 500 km/h CAS it's too much for a 109 (it's max horizontal speed already at sea level) :smilewink:

[Ala13_ManOWar]

Is it saying for level flight, I didn't get that anywhere? I can only get that its the results of speed on stick force (which we see), but I don't understand it all, so I will defer to Yo-Yo :)

Well, I'm not an engineer, but I read forward stick forces in Kg needed at different airspeeds (not told IAS or TAS, I guess IAS because the numbers shown but) and different altitudes and it has to be to keep level flight because every curve shows constant altitudes. All in a single CoG configuration as messermeister says, 21,2%, and using +0,75º trim which is a short one.

 

Also shows deflection degrees needed of right rudder, I guess to keep ball centered, under same conditions. We don't know short or long tail.

 

 

 

But I don't talk German, may be someone can translate it better. Anyway I think it's pretty clear you have to push to keep nose levelled, and after further dive test paper reading I'm starting to think it was intentional to keep pilots alive in high speed dives because aircraft behaviour and design.

 

S!

[IIIJG52_Otto_]

Actually, very related, and it shows both stick force and elevator angle for several IAS and Mach numbers, albeit only for a single CoG position (the NII VVS report for W.Nr. 14513 wich has several CoGs).

 

BTW, 109 02 E 44 it's the only report that shows this kind of detailed data from german sources (either Mtt AG or DVL) for a late Bf 109.

 

PD: they dived the plane to get the high IAS measurements, and I guess the soviets did the same, as climbing at 500 km/h CAS it's too much for a 109 (it's max horizontal speed already at sea level) :smilewink:

 

Well, I'm not an engineer, but I read forward stick forces in Kg needed at different airspeeds (not told IAS or TAS, I guess IAS because the numbers shown but) and different altitudes and it has to be to keep level flight because every curve shows constant altitudes. All in a single CoG configuration as messermeister says, 21,2%, and using +0,75º trim which is a short one.

 

Also shows deflection degrees needed of right rudder, I guess to keep ball centered, under same conditions. We don't know short or long tail.

 

 

 

But I don't talk German, may be someone can translate it better. Anyway I think it's pretty clear you have to push to keep nose levelled, and after further dive test paper reading I'm starting to think it was intentional to keep pilots alive in high speed dives because aircraft behaviour and design.

 

S!

 

This that Messermeister says is what Supongo and I are trying to explain you, last night in TS when we show you this German tests chart.

 

The Russian test as Yo-Yo says is in climb attitude, NOT at leveled flight, and the CoG is displaced more rearward than the German test curves.

 

Dear Otto...

 

Regarding convenience of the flight test... 146% that it is climb, because otherwise the change of the speed is much faster to stabilise and record the state. Diving? Noway.

 

So, I think that your attempts to compromise flight tests results will not be successful...

 

Edited June 19, 2015 by III/JG52_Otto_+

[Ala13_ManOWar]

This that Messermeister says is what Supongo and I are trying to explain you, last night in TS when we show you this German tests chart.

 

The Russian test as Yo-Yo says is in climb attitude, NOT at leveled flight, and the CoG is displaced more rearward than the German test curves.

You didn't try to explain a thing so you didn't understood what graph said until I explained you both :smilewink:. Whatever, CoG doesn't change while climbing Otto... :thumbup: Climb or slight dive is only used to get the IAS quickly or when it's hardly or impossible to achieve by aircraft itself. You need to climb or dive to get data enough for the graph. In any case IAS is constant through the atmosphere so also it doesn't matters climb or dive as long as you have a certain IAS at a certain altitude as stated in graphs.

 

S!

[Echo38]

CoG doesn't change while climbing Otto...

 

That isn't what he said. He said that the Russian test had a more rear-ward CoG than the German test, not that the CoG changed while climbing.

[Ala13_ManOWar]

That isn't what he said. He said that the Russian test had a more rear-ward CoG than the German test, not that the CoG changed while climbing.

Oh, OK, I reread. So he just misread what messermeister said and then I misread his attepmt :lol:.

 

 

Well, so, messermeister don't say a thing about climbing Otto. Climbing still doesn't change tests results :smilewink:.

 

S!

[Dirty Rotten Flieger]

I still don't understand why the German mechanics would bother to put the plane up on blocks and hang plumbobs off the stabilizer to work out exactly where zero was on the trim, when it is never used and doesn't matter. Seems like a lot of wasted effort. Unless they thought it was important for some reason.

 

There are quite a few flying bf109's at airshows. of course they have no weapons and are not weighted the same but maybe it would still be useful to ask some of the pilots how the currently flying 109's trim out at cruise.

[Yo-Yo]

I still don't understand why the German mechanics would bother to put the plane up on blocks and hang plumbobs off the stabilizer to work out exactly where zero was on the trim, when it is never used and doesn't matter. Seems like a lot of wasted effort. Unless they thought it was important for some reason.

 

There are quite a few flying bf109's at airshows. of course they have no weapons and are not weighted the same but maybe it would still be useful to ask some of the pilots how the currently flying 109's trim out at cruise.

 

This efforts were only to be sure that the plane would behave at zero trim setting exactly as it was designed.

[Ala13_ManOWar]

I still don't understand why the German mechanics would bother to put the plane up on blocks and hang plumbobs off the stabilizer to work out exactly where zero was on the trim, when it is never used and doesn't matter. Seems like a lot of wasted effort. Unless they thought it was important for some reason.

It's said to be Take Off trim setting. And it's 0º AoA deflection for stabilizer. It's important since finding stabilizer position isn't as easy as regular trims just aligned 0º with elevator.

 

S!