Bf 109 elevator trim

Well this doesn’t bode well for the p47 does it

The only thing that is really for sure is 30% difference in the gear ratio.

there is no clear evidences that 1) The dive in the last case was recovered without using trim wheel 2) or the same result could be achieved (or could not be achieved) by carefully setting somewhat between 1 15' and 1 45'.

For 1 you don't consider, the that report says "This trials started with idle dives to estimate an horizontal stabilizer trim setting that makes it possible to recover a dive with the stick. This setting was +1 degree 15 minutes ."

and that the report notes "the plane was pulled out of the dive with the stick alone."

or that the second chart with the 1 degree 15 minute does not have note stating that the craft was pulled out of the dive with the trim.

To be clear evidence that the craft was pulled out of a dive with a trim setting of 1 degree 15 minutes with the stick alone?

here's the entire page from the report I'm referencing.

THis is the translation, just to be sure we are see all the text and not we want to see:

I posted the complete translation of the entire report a few pages ago.

https://ww2aircraft.net/forum/attachments/diving_test_109f_w-nr-9228_ger_eng-pdf.81158/

What about it’s contents make you doubt that the aircraft was pulled out of the dive with the stick alone?

Yo-Yo,

I would really like to be able to play those tests too, in the DCS Simulator.

So, we need the elevator trim tabs to become adjustable, otherwise the tests will not be realistic according to that document.

I see the students's paphos. Please be not so arrogant or you would need to kick the ass of Ostoslavsky and Bushgens... and do not forget that only simplified approximations made F-117 possible.

 

(And, please, do not forget to make screenshots of our discussion... )

Guess you mean Pathos there, but dont worry I understood you anyway. Is having student pathos a bad thing btw? I would think the desire to learn and understand over our whole life span, is how it should be.

Dont get angry Yo-Yo, just as I choose to be very stoic about this discussion by now. I am sure we will agree eventually. I saved it on the wayback machine because sometimes admins get rather trigger happy about deleting stuff, just a precaution to not loose all this valuable discussion.

As far as I now the skunkworks development documents are still classified, even the -1 is still a national security asset. Are you saying you have access to them? Where did you get them from?

 

And, of course, I agree with two last facts that the trim tabs DO help to maintain dive as 1 15' stab alone was not able - there is nothing contradicting with the scientific approach.

Ok, so we are agreeing on this:

In this test the engineers set the trim tabs nose heavy and the stab to +1,15° to gain nose down authority, yes?

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

My answer was because it was done in real life and that it increases maximum nose down trim capability. That is also what the test report said. So we are in agreement now. Thats good progress I believe.

So now you are not sure they pulled out the dive with 1,15° stab fixed? Mmm, but that was the whole reason of the second test series, to find a stab setting at which pullout was possible with elevator only. So they steadily decreased stab from +1,45° to +1,15° in idle dives until they were sure they have found a good setting and tested +1,15° several times in a full power dive. I will compile a bunch of quotes from the report which will make it more clear, ok?

I posted the complete translation of the entire report a few pages ago.

 

 

 

https://ww2aircraft.net/forum/attachments/diving_test_109f_w-nr-9228_ger_eng-pdf.81158/

 

 

 

What about it’s contents make you doubt that the aircraft was pulled out of the dive with the stick alone?

(...)"They were bent by the ground crews at the first flights. So the Me 109 was pre-trimmed for cruising speed."(...)

As in "it was adjusted for trim for 0.9 to 1.15 and never touched again. At least that is my interpretation of the above.

..and basically, the first page is giving us the most important info?

(...)"They were bent by the ground crews at the first flights. So the Me 109 was pre-trimmed for cruising speed."(...)

As in "it was adjusted for trim for 0.9 to 1.15 and never touched again. At least that is my interpretation of the above.

Hey Shagrat,

I know you edited that part out by now, but I am glad you noticed that ground adjustable trim tabs are adjusted on the ground.

I think I found the problem with your approach, you only read the first page. If I may suggest, it always helps reading the full report, understanding it and then drawing conclusions. Several times it is described how trim tabs were adjusted, let me quote myself from one page ago about one of these incidences.

Bügelkante = trim tab

bügeln = describes the act of adjusting the trim tab

kopflastiger = more nose down attitude

So you are an ED translater and your "interpretation" is that they never adjust the trim tabs during these tests? If this is the state of ED members and how they handle documentation I am starting to realize why we are having this discussion in the first place.

@rel4y, I believe @shagrat has already acknowledged the use of the trim tabs, and in this post he's mentioning the part of the document where it's written that they're set by ground crew.

@shagrat also has suggested that the option for making the elevator trim tabs adjustment available in the special settings menu of DCS for the K-4 could be opened at "users's own risk". In this regard, being an element of the Team, even if as external colaborator, @shagrat, as he himself noted, is already going as far as he can go.

So, the question here for me turns out to be just one regarding the possible limitations of such an implementation.

Probably as it was created the K-4 flight dynamics model isn't ready for this aditional control, and making it available is too complex, or would require a lot of work that isn't compatible with the current development schedule - I believe new ww2 modules are in the making...

Yet, if this is the case then, I would like to see it clearly stated by the development team, since we all agree that:

a) there were 2 elevator trim tabs and their size was actually increased from that of previous models;

b) at least during the tests mentioned in that report these trim tabs were used and set away from neutral;

So, it would be more realistic to allow for the same settings in DCS, just as it is allowed to adjust the rudder and the aileron ground adjustable tabs.

@rel4y, I believe @shagrat has already acknowledged the use of the trim tabs, and in this post he's mentioning the part of the document where it's written that they're set by ground crew.

Ok, if it was ment like that I will apologize for being an asshole. His post before editing didnt make it sound like that to me though.

I thought it is common knowledge that ground adjustable trim tabs are adjusted on the ground and cant be changed in flight? Noone ever made it sound that way either. The aircraft mechanic set the trim tabs after a testflight for combat cruise with an instrument called Gradwaage.

I think our only difference here is what is considered cruise in German documentation. Combat cruise is used in contested airspace and always refers to Höchstzulässige Dauerleistung = maximum continous power. 1,15 ata is Sparleistung on the K-4 and only used if fuel is a problem. So let me address that quickly with a source.

Cruise G-2 is 1,15 ata for 595 kph

Cruise K-4 is 1,35 ata for 645 kph

In the following doc you see that Höchstzulässige Dauerleistung aka maximum continous power outputs around 1030 PS (horsepower) at 1,35 ata at rated altitude 7,7 km. V-Reise = cruise = 645 kph at 1030 PS.

Hey Shagrat,

I know you edited that part out by now, but I am glad you noticed that ground adjustable trim tabs are adjusted on the ground.

 

I think I found the problem with your approach, you only read the first page. If I may suggest, it always helps reading the full report, understanding it and then drawing conclusions. Several times it is described how trim tabs were adjusted, let me quote myself from one page ago about one of these incidences.

 

Bügelkante = trim tab

 

bügeln = describes the act of adjusting the trim tab

 

kopflastiger = more nose down attitude

 

 

 

So you are an ED translater and your "interpretation" is that they never adjust the trim tabs during these tests? If this is the state of ED members and how they handle documentation I am starting to realize why we are having this discussion in the first place.

Pilots on the other hand, as far as I understand, never touched or adjusted the elevator trim tabs, after they were set, unlike the rudder trim/aileron trim...

Did you see my above post? It addresses what cruise is. 109s don't have pilot adjustable aileron and rudder trim.

109s don't have pilot adjustable aileron and rudder trim.

That's why they asked the crews to adjust the trim, for long range flights earlier in the war... unlike the elevator trim tabs, which were adjusted only once, it seems.

As I said, I would love to see what happens if Yo-Yo adds the option to adjust the elevator trim tabs with a warning to do so at your own risk and how many people totally mess up their plane...

My guess is, they expect some wonderful advantage in dogfight to help them win, but only makes things "more interesting".

As I said, I would love to see what happens if Yo-Yo adds the option to adjust the elevator trim tabs with a warning to do so at your own risk and how many people totally mess up their plane...

My guess is, they expect some wonderful advantage in dogfight to help them win, but only makes things "more interesting".

In my case and since I do not play air combat, but use DCS just to enjoy the "feel of flight", as much as I use IL2 GB, I will be satisfied with being able to use the aircraft to fly around and perform some aerobatics, or formation flight with other online players feeling the same harmonious control I get in the G series and the K-4 in that other sim, where indeed the trim tabs, aileron, rudder and elevator, are all set for a cruise speed of around 450 - 500 km/h

Did you see my above post? It addresses what cruise is. 109s don't have pilot adjustable aileron and rudder trim.

Combat cruise is what you fly when time is pressing to e.g. intercept enemy bombers, but you don't require much fuel management, as the intercept is already near your location.

I guess whenever Yo-Yo and ED talk about "cruise" they actually mean "cruise" and not "combat cruise".

Actually that doesn't apply to the Spitfire or P-51 afaik, but may certainly be possible in some awkward way. Generally cruise is not equal to the economy setting and cruise and combat cruise can be used interchangeably. Economy setting means maximum range at minimal fuel consumption, while cruise means best range vs travel time.

Anyway, in Luftwaffe terms aircraft were trimmed for Reisegeschwindigkeit, which translates simply to cruise and is flown at maximum continous power. Depending on the theater, common combat altitude differed, so trim may have been slightly different. I just introduced the term combat cruise to describe what it meant in practice. I think the confusion stems from G-2 documents. G-2 cruise was set to 1,15 ata as that was it's maximum continous power.

Are we there yet? Have we reached the conclusion yet that these tabs are just there to set things up so the aircraft works as expected in a normal flight regime, rather than something that is constantly being adjusted? Hands up all aircraft riggers with flight line experience. The referral to the test results noted throughout the thread were I assume to determine the best settings to use for the above. Once that was determined, then surely the aircraft was rigged accordingly. No need to piss about with trim tabs by anyone unless the aircraft was a: damaged & required replacements, or b: in for a servicing that required the controls to be rigged.

Are we there yet? Have we reached the conclusion yet that these tabs are just there to set things up so the aircraft works as expected in a normal flight regime, rather than something that is constantly being adjusted? Hands up all aircraft riggers with flight line experience. The referral to the test results noted throughout the thread were I assume to determine the best settings to use for the above. Once that was determined, then surely the aircraft was rigged accordingly. No need to piss about with trim tabs by anyone unless the aircraft was a: damaged & required replacements, or b: in for a servicing that required the controls to be rigged.

and c) pull out of dives using hands only..

I read that as already being part of the "working as expected" - Once the testing was completed - and all parties had agreed on what was expected, then manuals would be amended, and procedures altered accordingly.

PS. Just found this online - very interesting anecdotal stuff - with mention of the K diving issue (search for "locked up"): http://www.virtualpilots.fi/feature/articles/109myths/

and c) pull out of dives using hands only..

You won't pull out of that dive, just overstress the plane and snap your wings... we have already been there in early access.

You mean this?

https://forums.eagle.ru/showpost.php?p=2353222&postcount=31

Thats makes not much sens, then should not climb in a Spitfire and Dive?

You mean this?

 

 

https://forums.eagle.ru/showpost.php?p=2353222&postcount=31

 

 

Thats makes not much sens, then should not climb in a Spitfire and Dive?

The change was taken back with the next patch.

I don't quite understand why people expect better elevator authority from trim tabs? They pretty much don't change anything at all in that respect, maybe the double sized trim tabs increased elevator area a bit, but that's it. They won't provide any advantage in pullouts or dogfights, neither will they mess up anything about the aircraft. Part of this discussion revolved exactly around that, because stab trim and trim tabs have pretty much the same effect at small deflections. All they do is trim the aircraft aka bias the elevator for a specific velocity. All that does is increase pilot comfort by increasing maximum nose down trim. What does help in a dogfight is that the elevator gearing factor changed on the K series (and G-10/U4 + some G-14 ASB/ ASC variants), which decreases stickforces.

What we have established so far is:

-K-4s had double sized trim tabs

-stab trim was limited to +1°10` = ~1,15° on late models

-stab trim was limited because double trim tabs set to nose down trim combined with high positive stab settings caused elevator force reversal* and goal was high speed pullout with the elevators only, at constant stab setting = basically safety reasons

-trim tabs were only adjusted on the ground, by the aircraft mechanic after a testflight and were not constantly readjusted (except in some test series obviously)

-we had a misconception of what cruise speed is supposed to be, Bf 109 Reisegeschwindigkeit corresponds to maximum continuous power

*elevator force reversal meaning that one needs to pull the elevator to stop the aircraft from increasing its dive angle at high Mach numbers. So at lower angles stick pull the aircraft would still nose down.

Based on this I would kindly ask ED to give us the option of elevator trim tabs in the menu or maybe trim the K-4 for a speed that more closely resembles Reisegeschwindigkeit. Based on the Soviet G-2 test about 3° elevator deflection nose heavy should be fine. But since we already have the one of a kind options in flight Sim history of trimming aileron and rudder tabs, I would be really happy about the addition of elevator trim tabs.