Bf 109 elevator trim

We're, slowly getting there @rel4y !!!

 

Thanks for not giving up !

 

I am sure Yo-Yo will, eventually, get the idea you're trying to pass, and we will, eventually, get a more harmonious control in pitch, or even ( ideally ) a way to set the ground adjustable elevator trim tabs...

Edited May 12, 2019 by jcomm

First of all, what is the point to decrease stabilisator autority to nose-down and after that INCREASE it again by using trim tab?

That is indeed a very good question. I could never figure out why people wanted to use trim tabs instead of the trim wheel. The argument for more nose down authority through the trim tabs seemed at least plausible, until I learned it was an engineering decision to limit nose down trim, to prevent unrecoverable dives... but to trim nose down with the wheel, to trim nose up, again with the trim tabs, sounds weird? :dunno:

That is indeed a very good question. I could never figure out why people wanted to use trim tabs instead of the trim wheel. The argument for more nose down authority through the trim tabs seemed at least plausible, until I learned it was an engineering decision to limit nose down trim, to prevent unrecoverable dives... but to trim nose down with the wheel, to trim nose up, again with the trim tabs, sounds weird? :dunno:

 

becouse trim tabs require a lot less force those whole system is much lighter i think :)

its easier to just add some trim tabs then changing production lines for trim mechanisms

becouse trim tabs require a lot less force those whole system is much lighter i think :)

its easier to just add some trim tabs then changing production lines for trim mechanisms

The question is why do some people want to adjust the trim tabs, rather than use the existing trim wheel, especially if the tabs would negate the trim wheel? E.g. why would you trim the tabs only to be required to counter the trim tabs with the wheel... honestly I think, Yo-Yo should consider adding the option to adjust elevator trim with the tabs, with a "use at your own risk, change of elevator trim not recommended" disclaimer and let people mess up the characteristics as much as they want to.

Depends on how much effort this is to implement, though...

The question is why do some people want to adjust the trim tabs, rather than use the existing trim wheel, especially if the tabs would negate the trim wheel? E.g. why would you trim the tabs only to be required to counter the trim tabs with the wheel... honestly I think, Yo-Yo should consider adding the option to adjust elevator trim with the tabs, with a "use at your own risk, change of elevator trim not recommended" disclaimer and let people mess up the characteristics as much as they want to.

Depends on how much effort this is to implement, though...

 

i know why becouse elevator trim wheel is out of range even when you crusing at 1.1ata bf109 likes to pitch up even with trim all way down

Edited May 12, 2019 by grafspee

i know why becouse elevator tim wheel is out of range even when you crusing at 1.1ata bf109 likes to pitch up even with trim all way down

Only if you do a start in midair with full fuel tanks front and aft. If you fly realistically it is pretty much ok. At least for me, that is...

Only if you do a start in midair with full fuel tanks front and aft. If you fly realistically it is pretty much ok. At least for me, that is...

 

mid air start i has trim set to 0 i know that . but even with trimm all way down at 1.1 ATA still climbs its ok nothing much but it is not level flight :P

mid air start i has trim set to 0 i know that . but even with trimm all way down at 1.1 ATA still climbs its ok nothing much but it is not level flight :P

No, I meant, your fuel tanks (center of gravity) when starting midair are full, as if you did never start from ground. If I start from ground, climb to 18.000 ft and have burned the fuel to do so, trim is already quite ok.

If you have a full tank behind the seat, you can't trim that away...

No, I meant, your fuel tanks (center of gravity) when starting midair are full, as if you did never start from ground. If I start from ground, climb to 18.000 ft and have burned the fuel to do so, trim is already quite ok.

If you have a full tank behind the seat, you can't trim that away...

 

OK

First of all, what is the point to decrease stabilisator autority to nose-down and after that INCREASE it again by using trim tab?

It's the easiest way to prevent excessive pitch rates without having to redesign the the entire stabilizer. While adjusting the stick free neutral point via the trim tabs.

It's the easiest way to prevent excessive pitch rates without having to redesign the the entire stabilizer. While adjusting the stick free neutral point via the trim tabs.

Yeah, but why not use the trim wheel for that? It is conveniently mounted in the cockpit, so you can even do it mid-flight.

Yeah, but why not use the trim wheel for that? It is conveniently mounted in the cockpit, so you can even do it mid-flight.

 

 

 

It would be possilbe to give 109 a more nose Down Attitude, even with the Trim Wheel fully foward it is nearly enough on the most Circumstances to fly level with this Trim Setting.

 

 

The hole Discussion around the Elevator Trim and Tabs is, from my Point of View when you meet some one in MP, he is not Flying like a AI.

 

 

He Flys upwards, before our 109 Pilot use both Hands on the Stick he is pushing negatives G again, after 109 moves likeswise not downwards you can sitt along time behind some Enemy, that somewhat realy Frustrating when you hamperd here by the Limitations where you not able to change the one Hand Flying or the Trim Tabs.

 

 

Other whise yes makes not sense to change the Trim Tabs..

It would be possilbe to give 109 a more nose Down Attitude, even with the Trim Wheel fully foward it is nearly enough on the most Circumstances to fly level with this Trim Setting.

 

 

The hole Discussion around the Elevator Trim and Tabs is, from my Point of View when you meet some one in MP, he is not Flying like a AI.

 

 

He Flys upwards, before our 109 Pilot use both Hands on the Stick he is pushing negatives G again, after 109 moves likeswise not downwards you can sitt along time behind some Enemy, that somewhat realy Frustrating when you hamperd here by the Limitations where you not able to change the one Hand Flying or the Trim Tabs.

 

 

Other whise yes makes not sense to change the Trim Tabs..

...and here we are full circle, back to where it started, because people don't read or don't want to understand, why the plane is designed(!) with limited nose down trim, as Yo-Yo explained, already.

The engineers, actually reduced(!) the elevator nose down authority to prevent pilots from crashing the plane.

As for the MP flying, ye shall not push negative GS in a plane for going after a bandit. use the flight characteristics of your plane to your advantage. Roll and pull, before prolonged push (nose down)...

I actually feel kind of frustrated, because I am going full circle with my answers. But let me address it once again.

 

...and here we are full circle, back to where it started, because people don't read or don't want to understand, why the plane is designed(!) with limited nose down trim, as Yo-Yo explained, already.

The engineers, actually reduced(!) the elevator nose down authority to prevent pilots from crashing the plane.

 

That statement is untrue and I adressed it twice in this thread already. The 109 was not limited in trim ability because of safety reasons, at least not in the way you make it sound! In the configuration our DCS 109 is at the moment, it is not trimmed for any specific speed at all. It simply has the trim tabs set to neutral. To that, the DCS K-4 stab range is artifically increased to ~+1,5°. That configuration doesnt allow for any dangerous dive anyway, as the paper I have cited clearly states. And in the paper the test plane at least was trimmed to level flight in the first place, aka nose down. So what we have currently is a "trim setting" no pilot in WWII flew with, other than the soviet test pilot of the G-2 report, with a stab range no K-4 ever had. The horizontal stab was limited in positive incidence because elevator reversal could occur at high Mach with double trim tabs set nose down and at stab +1,15° this was no problem anymore. So at +1,15° stab the plane is safe and trimmable at any trim tab setting.

 

So lets get to the answer why we would want trim tabs in addition to stab trim.

 

First and most bluntly, because its historical. Thats simply how the 109 was constructed and used operationally. In the late models they were doubled in size because they were important features of longitudinal stability. Could they have redesigned the elevator mechanism to be more reasonable? Surely, but changing the production lines most likely wasnt feasable, so they improved on what they could work with. I mean, what are we simulating here, our own personal opinion how the 109 should have been designed & operated, or the real deal?

 

Second, the effects of stab and trim tabs are not the same and I have already emphasized on this. I dont want to repeat myself, just take the fact that elevator reversal can occur at stab incidence of +1,45° with double trim tabs but not at stab +1,45° with single trim tabs, where even +2° is ok. Maybe the sim doesnt model these effects, but in real life the effects are not the same! To that you are suggesting that instead of trimming nose down by tabs, we should actually just use the stab at higher positive values for some unknown safety reason. This is the very setting that causes elevator reversal and makes the plane unsafe!

 

Third, the maximum trim range clearly increases and it would be possible to trim the aircraft at combat cruise. In german manuals combat cruise (in contested airspace) was considered to be maximum permissible continous rating (1,35 ata for K-4) and not maximum fuel efficiency. In air combat patrols you would want to go as fast as your motor possibly allows, since at any moment a P-51 or Yak could jump you. And I am sure pilots would not have liked their aircraft to pitch up constantly because the lazy mechanic has not set the trim tabs to anything but neutral.

Edited May 13, 2019 by rel4y

I actually feel kind of frustrated, because I am going full circle with my answers. But let me address it once again.

 

 

 

That statement is untrue and I adressed it twice in this thread already. The 109 was not limited in trim ability because of safety reasons, at least not in the way you make it sound! In the configuration our DCS 109 is at the moment, it is not trimmed for any specific speed at all. It simply has the trim tabs set to neutral. To that, the DCS K-4 stab range is artifically increased to ~+1,5°. That configuration doesnt allow for any dangerous dive anyway, as the paper I have cited clearly states. And in the paper the test plane at least was trimmed to level flight in the first place, aka nose down. So what we have currently is a "trim setting" no pilot in WWII flew with, other than the soviet test pilot of the G-2 report, with a stab range no K-4 ever had. The horizontal stab was limited in positive incidence because elevator reversal could occur at high Mach with double trim tabs set nose down and at stab +1,15° this was no problem anymore. So at +1,15° stab the plane is safe and trimmable at any trim tab setting.

 

So lets get to the answer why we would want trim tabs in addition to stab trim.

 

First and most bluntly, because its historical. Thats simply how the 109 was constructed and used operationally. In the late models they were doubled in size because they were important features of longitudinal stability. Could they have redesigned the elevator mechanism to be more reasonable? Surely, but changing the production lines most likely wasnt feasable, so they improved on what they could work with. I mean, what are we simulating here, our own personal opinion how the 109 should have been designed & operated, or the real deal?

 

Second, the effects of stab and trim tabs are not the same and I have already emphasized on this. I dont want to repeat myself, just take the fact that elevator reversal can occur at stab incidence of +1,45° with double trim tabs but not at stab +1,45° with single trim tabs, where even +2° is ok. Maybe the sim doesnt model these effects, but in real life the effects are not the same! To that you are suggesting that instead of trimming nose down by tabs, we should actually just use the stab at higher positive values for some unknown safety reason. This is the very setting that causes elevator reversal and makes the plane unsafe!

 

Third, the maximum trim range clearly increases and it would be possible to trim the aircraft at combat cruise. In german manuals combat cruise (in contested airspace) was considered to be maximum permissible continous rating (1,35 ata for K-4) and not maximum fuel efficiency. In air combat patrols you would want to go as fast as your motor possibly allows, since at any moment a P-51 or Yak could jump you. And I am sure pilots would not have liked their aircraft to pitch up constantly because the lazy mechanic has not set the trim tabs to anything but neutral.

I was referring Yo-Yo's answer. Anyway I trust his knowledge and sources more than the usual "could, should, would have" arguments...

We don't even know sure if the trim tabs are set to neutral in the flight model and only "neutral" in the visual model. Flying for prolonged times at 1.35 AtA requires pushing the stick, as far as I heard from pilot interviews and hearsay it was like that in the real plane.

And for my answer to Mad-MM, that was where we were back to "I want more elevator trim for dogfighting, because then I hope I can win"...

From my point of view, I would provide a trim tab setting with a disclaimer, that messing with it, asks for trouble, and be done with it, if I were Yo-Yo, but that is his decision to make, not mine.

I can confidently fly the Bf.109 K4 without trim tabs adjusted. In a combat area I don't trim nose down anyway, but that's just me.

I was referring Yo-Yo's answer. Anyway I trust his knowledge and sources more than the usual "could, should, would have" arguments...

We don't even know sure if the trim tabs are set to neutral in the flight model and only "neutral" in the visual model. Flying for prolonged times at 1.35 AtA requires pushing the stick, as far as I heard from pilot interviews and hearsay it was like that in the real plane.

And for my answer to Mad-MM, that was where we were back to "I want more elevator trim for dogfighting, because then I hope I can win"...

From my point of view, I would provide a trim tab setting with a disclaimer, that messing with it, asks for trouble, and be done with it, if I were Yo-Yo, but that is his decision to make, not mine.

I can confidently fly the Bf.109 K4 without trim tabs adjusted. In a combat area I don't trim nose down anyway, but that's just me.

 

That's the problem.. you trust someone more then the other, even if hard evidence were brought up here and taken point by point. Even a first grader understands..

It's not that Yo-Yo is not a good engineer, but sometimes, from lack of sources, or even wrong sources, mistakes can be made, and it takes a bit of courage to accept those mistakes and repair them.

We want, at least, the trim tabs that were on the K-4. If the effect of the trim tabs are calculated in the FM, they surely need to be corrected accordingly.

I was referring Yo-Yo's answer. Anyway I trust his knowledge and sources more than the usual "could, should, would have" arguments...

We don't even know sure if the trim tabs are set to neutral in the flight model and only "neutral" in the visual model. Flying for prolonged times at 1.35 AtA requires pushing the stick, as far as I heard from pilot interviews and hearsay it was like that in the real plane.

And for my answer to Mad-MM, that was where we were back to "I want more elevator trim for dogfighting, because then I hope I can win"...

From my point of view, I would provide a trim tab setting with a disclaimer, that messing with it, asks for trouble, and be done with it, if I were Yo-Yo, but that is his decision to make, not mine.

I can confidently fly the Bf.109 K4 without trim tabs adjusted. In a combat area I don't trim nose down anyway, but that's just me.

 

After having given up on asking for it, starting 2 yrs ago, I was tempted to believe it's actually some limitation in the DCS flight dynamics for these combination of elevator + stabilator + elevator trim tabs....

 

In another ww2 sim I use they're set, for nose heavy, and we can see the elevator deflect down just from propwash when we apply takeoff power... The aircraft also handles more plausibly / harmoniously IMO.

After having given up on asking for it, starting 2 yrs ago, I was tempted to believe it's actually some limitation in the DCS flight dynamics for these combination of elevator + stabilator + elevator trim tabs....

 

In another ww2 sim I use they're set, for nose heavy, and we can see the elevator deflect down just from propwash when we apply takeoff power... The aircraft also handles more plausibly / harmoniously IMO.

 

My thoughts exactly..

That's the problem.. you trust someone more then the other, even if hard evidence were brought up here and taken point by point. Even a first grader understands..

 

It's not that Yo-Yo is not a good engineer, but sometimes, from lack of sources, or even wrong sources, mistakes can be made, and it takes a bit of courage to accept those mistakes and repair them.

 

We want, at least, the trim tabs that were on the K-4. If the effect of the trim tabs are calculated in the FM, they surely need to be corrected accordingly.

Why would that be a problem for me?

re4ly did not even answer Yo-Yo's question, why you want to trim down, to trim up again,a question "even a first grader can understand" to keep the level of politeness.

And as I said, if I would be in the position to decide anything, I would give you the trim tabs to mess around, just with a big disclaimer.

Oh, come on.. See, thats the problem. Even though you guys know its wrong, the answer always is nothing to see here, please move on.

 

I trust his knowledge and sources more than the usual "could, should, would have" arguments...

 

Yes, I do also trust the sources. Thats why all my arguments are built around them. (Btw the same sources as Yo-Yo) And I trust YoYo in general, he seems to be a good & knowledgable engineer. Yet I know nobody is infallible. Even YoYo corrected several areas of the K-4 FM alone based on discussion/ documentation in the forums in the past

 

We don't even know sure if the trim tabs are set to neutral in the flight model and only "neutral" in the visual model.

 

Well, maybe you dont... I addressed it in one of my posts. Take the DCS K-4 to 4000m, MAC 23%, set the stab to 0°, turn the engine to idle, hit Ctrl + Z twice, observe. Finally compare to soviet test.

 

Flying for prolonged times at 1.35 AtA requires pushing the stick, as far as I heard from pilot interviews and hearsay it was like that in the real plane.

 

Aaah, the famous hearsay. Does it even make sense to ask you for sources here? Someone in this forum said feel, opinions and hearsay dont count a penny, or something like that.

 

re4ly did not even answer Yo-Yo's question, why you want to trim down, to trim up again,a question "even a first grader can understand" to keep the level of politeness.

 

Actually I did in all detail, you even quoted the post.

 

Honestly, why are we even still discussing this? Everybody makes mistakes and thats not a problem as long as you dont act like it never happened and everybody else is stupid. The mistakes in drag, roll rate, level speed all were corrected eventuelly and everybody was grateful to ED afterwards. Why is this matter such a religion?

Edited May 13, 2019 by rel4y

...and here we are full circle, back to where it started, because people don't read or don't want to understand, why the plane is designed(!) with limited nose down trim, as Yo-Yo explained, already.

The engineers, actually reduced(!) the elevator nose down authority to prevent pilots from crashing the plane.

 

 

 

 

Yes but this Problems does referring to different Problems, yes ofc was done in real Live to Prevent crashes, but i am say i can handle this Nose down Trim in DCS?

 

 

Because sometime ago, was added Pilots can not blacking out in the first few Seconds in a Instant Turn, for Example 8-10G as it should be, only limitation of the Airframe. With a few spilt seconds between you can go up and down to the Maximum as long you wish.

How long would this Kind of flying a Pilot survive in real live with extended Negative and Positive G?

And in real live, our Pilot would be also not starting with 1 Hand Pulling?

 

 

To be fair i thrust Yoyo's Work, and i read it, but the practical Appilication is somewhat difficult to do when the rest of the Envirmonet is not correct, or come out as expected?

 

 

 

But somewhat offtopic, better go back to read Relys Post..

...... Why is this matter such a religion?

Beats me too..

Yeah, but why not use the trim wheel for that? It is conveniently mounted in the cockpit, so you can even do it mid-flight.

 

This may excessively limit pitch rates as the elevator becomes biased either to far forward or aft. Or the position needed to establish stick free neutral position is beyond the capabilities of the trim system. Lastly, trimming the stabilizer forward may result in an uncomfortable stick position for the pilot.

 

The solution here being to add trim tabs, as the stick free natural point can remain in the centered position within the given range of motion of the controls. However the trim tabs increase the area of the elevator, which also increase it’s effectiveness. So with trim tabs installed the pitch rate for a given elevator deflection increase. To limit these pitch rates you limit the elevator deflection.