[CLOSED]Bf-109 Trim controls

[Yo-Yo]

Trim problems...

 

.https://youtu.be/OMh-Js0KFFc

[Ala13_ManOWar]

I am reposting it again so you can read it. http://www.wwiiaircraftperformance.org/me109/Diving_Test_109F_W.Nr.9228_ger_eng.pdf

Further reading that paper, indeed tests looks like to say it was usual to fly holding stick forward, until you can't hold any more. It's said in many dive tests, they even aren't able to pass some diving angles because stick forces :music_whistling:, trim setting is showed, and the top trim we have now (2º forward) is never even reached... may be that says something about ED can be right even though it's true it's weird to us (using short sticks, don't forget that). And that also makes me think what I already said, fixed trim tabs will help a bit but they won't change SO much the available control. Indeed fixed trim tabs mostly helps in reducing force needed to move surfaces and that's not so easy to model without a FFB.

 

S!

[Yo-Yo]

Further reading that paper, indeed tests looks like to say it was usual to fly holding stick forward, until you can't hold any more. It's said in many dive tests, they even aren't able to pass some diving angles because stick forces :music_whistling:, trim setting is showed, and the top trim we have now (2º forward) is never even reached... may be that says something about ED can be right even though it's true it's weird to us (using short sticks, don't forget that). And that also makes me think what I already said, fixed trim tabs will help a bit but they won't change SO much the available control. Indeed fixed trim tabs mostly helps in reducing force needed to move surfaces and that's not so easy to model without a FFB.

 

S!

 

No problem with modelling like in p51 but their effectiveness is much less than for conventional trim tabs due to small area/chord and - the main problem - if they even are able to make hands-off level flight at high speed, you can not retrim it again to obtain proper positive g ability.

[Yo-Yo]

Further reading that paper, indeed tests looks like to say it was usual to fly holding stick forward, until you can't hold any more. It's said in many dive tests, they even aren't able to pass some diving angles because stick forces :music_whistling:, trim setting is showed, and the top trim we have now (2º forward) is never even reached... may be that says something about ED can be right even though it's true it's weird to us (using short sticks, don't forget that). And that also makes me think what I already said, fixed trim tabs will help a bit but they won't change SO much the available control. Indeed fixed trim tabs mostly helps in reducing force needed to move surfaces and that's not so easy to model without a FFB.

 

S!

 

No problem with modelling like in p51, but their effectiveness is much less than for conventional trim tabs due to small area and - the main problem - if they even are able to make hands-off level flight at high speed, you can not retrim it again to obtain proper positive g ability.

[Ala13_ManOWar]

No problem with modelling like in p51, but their effectiveness is much less than for conventional trim tabs due to small area and - the main problem - if they even are able to make hands-off level flight at high speed, you can not retrim it again to obtain proper positive g ability.

Yeah, that's what I guessed, if we are able to change so much trim stability with fixed trim tabs control surfaces movement will be reduced so will effectiveness because control stiffening already modelled. I guess that's the reason also to not use all available trim in dive tests as the paper shows. Trimming so much won't allow to recover a dive.

 

 

I see the best solution clear now, you all use a long stick like me :lol:.

 

S!

[NineLine]

 

I see the best solution clear now, you all use a long stick like me :lol:.

 

S!

 

yeah, I have been seriously thinking about modding an old stick I have just to try it out.

[Ala13_ManOWar]

yeah, I have been seriously thinking about modding an old stick I have just to try it out.

It's suuuuch a pleasure fly anything with it Sithspawn... I would recommend everyone. Mine is just an easy Warthog mod, but people out there have ideas to build any Joystick, you can do it mate :smilewink: . If we are here with just three WWII modules I'm glad to already have it looking upcoming modules :beer: .

 

S!

[Anatoli-Kagari9]

So... when it comes to stick, size matters!

 

Ok, I'll what I can do for mine .....

[Solty]

Yeah, that's what I guessed, if we are able to change so much trim stability with fixed trim tabs control surfaces movement will be reduced so will effectiveness because control stiffening already modelled. I guess that's the reason also to not use all available trim in dive tests as the paper shows. Trimming so much won't allow to recover a dive.

 

 

I see the best solution clear now, you all use a long stick like me :lol:.

 

S!

Exactly what I've said. The current behaviour is correct, if the standard cruise trim for the 109 is not applied.

 

And that is why we can read about combat pilots having to use stabiliser trim to get out of a dive. Dive tests are what they are, dive tests. Of course safety first during that part of flight, but that doesn't mean combat flying will be done the same. That is why this document states clearly at the begining that normally they were set for cruise setting.

 

That doesn't mean that the plane will fly hands off. 109 is not going to be a stable machine, but if we had that option or at least it would be pre-trimmed for standard cruise speed it would help a lot with the plane's inability to be trimmed down or up depending on the situation, instead of looping around on itself all the time, even with down trim applied (during high speed flight).

 

But I can't imagine beeing all the time trying to maintain level flight with a plane during combat flights and trying to stay in formation. And still we have 6 additional trim levels for upwards movment which are redundant as the plane pitches with 0 trim all the time.

 

Also, 109 had a very short stick for all the planes from WW2.

[NineLine]

What is standard cruise trim? What do you think you should be seeing and why (proof)?

 

Exactly what I've said. The current behaviour is correct, if the standard cruise trim for the 109 is not applied.

 

And that is why we can read about combat pilots having to use stabiliser trim to get out of a dive. Dive tests are what they are, dive tests. Of course safety first during that part of flight, but that doesn't mean combat flying will be done the same. That is why this document states clearly at the begining that normally they were set for cruise setting.

 

That doesn't mean that the plane will fly hands off. 109 is not going to be a stable machine, but if we had that option or at least it would be pre-trimmed for standard cruise speed it would help a lot with the plane's inability to be trimmed down or up depending on the situation, instead of looping around on itself all the time, even with down trim applied (during high speed flight).

 

But I can't imagine beeing all the time trying to maintain level flight with a plane during combat flights and trying to stay in formation. And still we have 6 additional trim levels for upwards movment which are redundant as the plane pitches with 0 trim all the time.

 

Also, 109 had a very short stick for all the planes from WW2.

[Solty]

What is standard cruise trim? What do you think you should be seeing and why (proof)?

Have you even opened the source I gave?

 

"These were fixed trim tabs and not movable by the pilot. They were bent by the ground crews at the first flights. So the Me109 was pre-trimmed for cruising "

I can only give you this one source for now. I am studying and can't check through all the internet. I am sure you will find more references there.

 

I would say that it was pre-trimmed for cruise speed at some altitude.

Wiki states 590 km/h (TAS?) for at 6,000 m. But that is not a good source is it?

Edited June 16, 2015 by Solty

[NineLine]

Have you even opened the source I gave?

 

"These were fixed trim tabs and not movable by the pilot. They were bent by the ground crews at the first flights. So the Me109 was pre-trimmed for cruising "

I can only give you this one source for now. I am studying and can't check through all the internet. I am sure you will find more references there.

 

I would say that it was pre-trimmed for cruise speed at some altitude.

Wiki states 590 km/h (TAS?) for at 6,000 m. But that is not a good source is it?

 

No its not a good source, it doesnt tell you anything about conditions, load, etc...in this case cruising is pretty vague, but keep trying. If you find anything, you know where this thread is, until then, I think Yo-Yo has a good handle on it.

[Ala13_ManOWar]

Have you even opened the source I gave?

 

"These were fixed trim tabs and not movable by the pilot. They were bent by the ground crews at the first flights. So the Me109 was pre-trimmed for cruising "

I can only give you this one source for now. I am studying and can't check through all the internet. I am sure you will find more references there.

 

I would say that it was pre-trimmed for cruise speed at some altitude.

Wiki states 590 km/h (TAS?) for at 6,000 m. But that is not a good source is it?

Problem is that's so vague we don't really know what that means. Cruising what speed, cruising what altitude, cruising what altitude, and pre-trimmed for cruising for what stabilizer trim setting?

 

 

I don't find this chart mentioned in the report, would be nice to take a look,

the development of forces in the dive is shown in flight report Nr. 901/274 chart sheet 2 in the addendum of the report

Luckily would be related to Yo-yo posted chart.

 

S!

[Supongo]

Ya me explicaréis que tiene que ver un test de control de fuerzas laterales en un 109F con un trimado en vuelo nivelado de un G2 (que es lo que nos pone Yo-Yo, con un K4.

 

Un saludo

 

Supongo

[Anatoli-Kagari9]

Guys,

 

I don't have the PDF of the Bf109 K4 manual here, but I am sure there are many sources over the Web can help.

 

A simple Wiki search will give you good info about what - cruising speed and Alt - are for the 109 G6 ...It reads somewhere:

 

Cruise Speed: 590km/h @ 6,000m

 

I would assume that, without carrying a bomb load, setting the trim to it's neutral ( "0" ) mark would most likely give the pilot an effortless flight regarding stick push / pull forces at this speed and alt ? Right ? Does that happen to the K4 in DCS ? I am asking, this is not a rhetorical question because I do no longer have DCS installed ( * ), and the data above can well be meant only for the G6 variant mentioned in that Wiki page, but I am sure some equivalent will exist for the K4, right ?

 

What I remember from my flights in DCS, specially in a cruising situation that comes with the module and I used to load for flight tests, the aircraft started aggressive pitch up as soon as the situation started, and I really had to push on the stick, and from there one, getting worse with increasing altitude, was a rather "strange" / "plastic" behavior of the aircraft regarding stability in pitch....

 

But there were other "problems", like the weird behavior regarding stalls and spins, specially spins and how the aircraft behaved when entering such a situation...

 

The K4 was, by far, my worst experience in DCS ww2 series.

 

( * ) I decided to give up on DCS because I am waiting for EDGE to be released, and see if it can run on my old rig, which I am not able to upgrade in the next years... I still find DCS as one of the two Masters in terms of flight dynamics I ever experienced in my long flight simmer experience, the other one being a sim which also covers ww2.

Edited June 17, 2015 by jcomm

[Ala13_ManOWar]

Cruise Speed: 590km/h @ 6,000m

 

I would assume that, without carrying a bomb load, setting the trim to it's neutral ( "0" ) mark would most likely give the pilot an effortless flight regarding stick push / pull forces at this speed and alt ? Right ? Does that happen to the K4 in DCS ? I am asking, this is not a rhetorical question because I do no longer have DCS installed ( * ), and the data above can well be meant only for the G6 variant mentioned in that Wiki page, but I am sure some equivalent will exist for the K4, right ?

Indeed the paper posted before says in a certain dive test, +1.0º trim (cruise setting). Of course it's a prototype, a F airframe "with G wings" and tall tail (like K) but still I think it's a quite interesting reading. All the paper looks like to mean pilots used to hold stick all the time instead of trimming in the USA design meaning we nowadays consider "normal" (P-51 being like that isn't any surprise...). With a long stick holding isn't any big deal, so it seems they used stabilizer trim and even trim tabs just to approach a comfortable zone of stick forces for the pilot and that's all. But still they held the stick, no hands off flying at all. So our main problem here IMHO is still using short sticks when you have an ultrarealistic simulator resembling that behaviour.

 

Paper states some interesting test data, I will make my own tests just to check DCS behaviour.

 

S!

Edited June 17, 2015 by Ala13_ManOWar

[NineLine]

 

I would assume that....

 

Stopped reading there...

[NineLine]

Indeed the paper posted before says in a certain dive test, +1.0º trim (cruise setting). Of course it's a prototype, a F airframe "with G wings" and tall tail (like K) but still I think it's a quite interesting reading. All the paper looks like to mean pilots used to hold stick all the time instead of trimming in the USA design meaning we nowadays consider "normal" (P-51 being like that isn't any surprise...). With a long stick holding isn't any big deal, so it seems they used stabilizer trim and even trim tabs just to approach a comfortable zone of stick forces for the pilot and that's all. But still they held the stick, no hands off flying at all. So our main problem here IMHO is still using short sticks when you have an ultrarealistic simulator resembling that behaviour.

 

Paper states some interesting test data, I will make my own tests just to check DCS behaviour.

 

S!

 

 

Yeah, still most references to cruise are somewhat vague compared to what we are looking for, seeing as Yo-Yo sat down and had lunch with a pilot who flew almost all marks of the 109, I am confident in what ED is presenting to us.

 

Funny enough, through this thread, I am starting to be less inclined to thing adjustable fixed trim tabs are as important as I once did as well (as an option to adjust), it seems like they might have been adjusted on the first few flights of an aircraft, and then not touched again, I would imagine the consistency in construction of a plane back then wasn't as good as it is now, and those tabs were used to 'trim' out any issues in a new aircraft. If that is the case, its very likely that captured fighters test by other countries could have had these set already, but no mention of them as they wouldnt have messed with them at all...

[MiloMorai]

Funny enough, through this thread, I am starting to be less inclined to thing adjustable fixed trim tabs are as important as I once did as well (as an option to adjust), it seems like they might have been adjusted on the first few flights of an aircraft, and then not touched again, I would imagine the consistency in construction of a plane back then wasn't as good as it is now, and those tabs were used to 'trim' out any issues in a new aircraft. If that is the case, its very likely that captured fighters test by other countries could have had these set already, but no mention of them as they wouldnt have messed with them at all...

 

Ding, ding, we have a winner. And, the fixed trim would be set on a 'clean' a/c as part of the a/c acceptance procedure.

[Ala13_ManOWar]

Funny enough, through this thread, I am starting to be less inclined to thing adjustable fixed trim tabs are as important as I once did as well (as an option to adjust), it seems like they might have been adjusted on the first few flights of an aircraft, and then not touched again, I would imagine the consistency in construction of a plane back then wasn't as good as it is now, and those tabs were used to 'trim' out any issues in a new aircraft. If that is the case, its very likely that captured fighters test by other countries could have had these set already, but no mention of them as they wouldnt have messed with them at all...

Exactly... It would be nice to have the option, may be as a tab in special features like TO assistance, but I don't think it's soooo important, it can't be when real adjustable stabilizer surface trim is not. I think now mostly fixed tab would change stick forces (and that can be modelled of course) than real trim nose position. I haven't flown any fighter aircraft like, but a couple long sticks I have really hadn't any "centre" of the stick, you almost felt nothing and no clues helped you to find that centre but the seat of your pants. If you use a short stick with a spring that's just unreal and that's why you look for that zero trimming position like mad.

 

S!

Edited June 17, 2015 by Ala13_ManOWar

[Yo-Yo]

Guys,

 

I don't have the PDF of the Bf109 K4 manual here, but I am sure there are many sources over the Web can help.

 

A simple Wiki search will give you good info about what - cruising speed and Alt - are for the 109 G6 ...It reads somewhere:

 

Cruise Speed: 590km/h @ 6,000m

 

 

I always wonder, where such figures bubble from... as you perform a small math you will see that max endurance IAS is about 250-260 for 109 and max distance IAS is about 310-330 kph. At 6000 m it means, by the way, not 590 kph TAS but 420-450 kph. So, if you want to fly cruise, you must be somewhere between 250-330 kph depending on the task.

Edited June 17, 2015 by Yo-Yo

[Dirty Rotten Flieger]

I just read this whole thread. Very entertaining! Almost as funny as watching Bosnians playing frisbee...

 

I just loaded the K4 up and tried it for myself and cruising at IAS450km/h @ 5km 1.2ata 2100rpm +2 stab trim the plane is almost hands free in level flight. Really quite nice.

 

It would be nice to have the trim tabs adjusted to give a little nose heavy so we can fly level like this at higher power settings but it is no where near as bad I was expecting after reading the thread. Surely it would not need much work to enable elevator trim tab to be adjusted as the ailerons and rudder are. Then everybody people would be happy.

 

Well some body will still not be happy. But even they would be hard to complain!

 

 

Also the original post was asking why the "elevator" trimmed down would give pitch up?

 

I guess he has realised by now that the trim wheel is not for elevator but is for stabiliser.

Edited June 17, 2015 by Dirty Rotten Flieger

[IIIJG52_Otto_]

Incongruous based on what?

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

 

Here is the issue, there is no good data on them, they were 'bent'? So it sounds like they were used to adjust a new aircraft and never touched again. You say they were trimmed to cruise. What is cruise? I know you have your idea of what is cruise, so does everyone else, but ED prefers facts.

 

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.

 

 

 

Edited June 18, 2015 by III/JG52_Otto_+

[Anatoli-Kagari9]

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...

[NineLine]

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

 

No one said it was from a K4. And I think Yo-Yo is quite capable of reading it as he has the full report, I am not going to question his understanding of this, certainly with some one trying to guess what it is showing.

 

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...

 

This ground tweaking you are showing I am sure was changed after a few flights if needed, so I am not sure what you think you are showing? I mean in those same books they talk about how different the K's were from different plants, so much so that it was hard to exchange parts and such. That again points to having the need to try and have something like these fixed tabs to make slight adjustments on initial flights.

Edited June 18, 2015 by NineLine