109 elevator effectiveness

[JG13_opcode]

The aircraft's air speed instrument measures IAS or TAS?

 

 

Vne is given in IAS because that's what's available to the pilot.  One of the primary determinants of setting Vne when you design an aircraft is aeroelastic flutter which is a function of TAS.

[Venturi]

Mach effects don't care about IAS. They only care about TAS. For this reason, dive speed limits are always based on TAS and as such, IAS speed limits should be quite low at high alts as compared to low alts (but TAS is actually the same for these limits).

Like everyone else is saying.

[Panthera]

From two modern 109 pilots:

 

Mark Hanna:

"When you maneuver above 500km/h, two hands are required for a more aggressive performance. Either that or get on the trimmer for help. Despite this heavying up, it is still quite easy to get 5 G's at these speeds"

 

Skip Holm:

"Pitch control is also delightful and very positive at 250 mph and below. As pitch and accompanying G is increased, the leading edge slats start to deploy.  I have not found either aircraft to have any problems with asymmetrical slat deployment, as we see in other aircraft such as an A-4 for instance.  The aircraft reacts very well to heavy maneuvering, and there is never any discomfort in pulling Gs, as wing separation and accompanying wing drop is mild, is easily noticed and dealt with by lightening up on the G.  Pitch force tends to get heavy at speeds above 300 mph, but is still easily managed with a little 2-hand pull or left hand re-trimming."

 

Doesn't get much more definite than that...

[JG13_opcode]

From two modern 109 pilots:

 

Mark Hanna:

"When you maneuver above 500km/h, two hands are required for a more aggressive performance. Either that or get on the trimmer for help. Despite this heavying up, it is still quite easy to get 5 G's at these speeds"

 

Skip Holm:

"Pitch control is also delightful and very positive at 250 mph and below. As pitch and accompanying G is increased, the leading edge slats start to deploy.  I have not found either aircraft to have any problems with asymmetrical slat deployment, as we see in other aircraft such as an A-4 for instance.  The aircraft reacts very well to heavy maneuvering, and there is never any discomfort in pulling Gs, as wing separation and accompanying wing drop is mild, is easily noticed and dealt with by lightening up on the G.  Pitch force tends to get heavy at speeds above 300 mph, but is still easily managed with a little 2-hand pull or left hand re-trimming."

 

Doesn't get much more definite than that...

So how do the developers program "delightful" or "quite easy to get 5G" into the sim? That's the problem with pilot quotes. Almost always useless.

Edited December 29, 2017 by JG13_opcode

[=RvE=Windmills]

Not to mention that 'above 500kph' or 300mph is not exactly a precise number. I suppose this would mean speeds within 25kph or so which sounds about right for what we have in the sim.

[=EXPEND=Tripwire]

Was there a German elevator stiffness vs speed test document that was used to derive the current levels we have in-game?

 

I've seen one dive test document with different stabilizer settings. Was that the source?

[CUJO_1970]

What is the correct relative stick force per G over 500kph for LaGG-3 and 109?

 

For La-5 and 109?

 

For Yak and 109?

 

For MiG and 109?

 

How did those aircraft perform historically relative to the 109 at speeds over 500kph?

[FTC_Riksen]

While I do agree the previous flight model for the 109 was just plain wrong and this one is by far better, I'm yet to see any data for the stick forces at high speed. People say that pilot accounts don't matter but I'm pretty sure that pilot accounts is what was used to make this new FM ... it would be nice to know which one though because, as you can see, they are plenty that say otherwise or at least minimize the stiffness. Maybe a middle ground could be reached to please everyone?

 

Note that I'm totally fine with this FM and would prefer this one over the previoud one any day

[=RvE=Windmills]

they are plenty that say otherwise or at least minimize the stiffness.

 

In what situation though? For us ingame not being able to pull lead on a manoeuvring plane while in a 800kph powerdive might be seen as unacceptable stiffness, while in reality simply maintaining enough elevator authority to not plow into the ground would likely be a much more common requirement. So what is 'controllable' or 'too much' stifness really depends on what situation you are talking about. Also, let's not forget about the pilots who lacked the elevator authority to recover from their dives, it's not like they were around anymore to add their anecdotes for context.

 

Anyway, whether it's correct or not ingame I don't see most anecdotes disagreeing that much with the representation we have.

Edited December 29, 2017 by Windmills

[Willy__]

Nobody said 800kph, the stiffening happens way before 800, more like 500kph, where the pilots accounts says it still Very maneuverable.

[=RvE=Windmills]

Nobody said 800kph, the stiffening happens way before 800, more like 500kph, where the pilots accounts says it still Very maneuverable.

 

Which anecdote in particular do you see as being irreconcilable with ingame behavior.

[ACG_Smokejumper]

Which anecdote in particular do you see as being irreconcilable with ingame behavior.

 I agree with that sentiment. We need some hard date then go in game with a stopwatch.

 

Where can I find this information on each model. I would need turn speed info at which speeds and altitudes.  Trim setting would also need to be known.

I think it might be a little off but I would need clear facts to test.

 

Any help there and I'll go make a video.

[Dave]

Was there a German elevator stiffness vs speed test document that was used to derive the current levels we have in-game?

 

I've seen one dive test document with different stabilizer settings. Was that the source?

 

You don't need one - an accurate enough model can be calculated using computational fluid dynamics.

There is even free software you can use to do this yourself if you already have a 3D model.

I recommend that everyone beating up the dev team about the FM have a read of everything linked to starting here: https://www.openfoam.com.

Then grab yourself a copy of this https://www.booktopia.com.au/low-speed-aerodynamics-joseph-katz/prod9780521665520.html

and become acquainted with flight modelling from the other side of the table.

Edited December 30, 2017 by Dave

[9./JG27DefaultFace]

There is a dive test document for the 109 around somewhere. Is usually thrown around in these discussions, both here and over in the ED forum.

[Inkophile]

 I agree with that sentiment. We need some hard date then go in game with a stopwatch.

 

Where can I find this information on each model. I would need turn speed info at which speeds and altitudes.  Trim setting would also need to be known.

I think it might be a little off but I would need clear facts to test.

 

Any help there and I'll go make a video.

 

Getting information per model will be extremely hard I think, unless there is a bunch of documents in non-digitized archives, for example in the Bundesarchiv. I do have one document though (got it on Aircraftperformance.org I think) and both linked to it in my dropbox-archive and wrote my thoughts around it in this post on page 2 in this thread.

Edited December 30, 2017 by Inkoslav

[CUJO_1970]

You don't need one - an accurate enough model can be calculated using computational fluid dynamics.

There is even free software you can use to do this yourself if you already have a 3D model.

I recommend that everyone beating up the dev team about the FM have a read of everything linked to starting here: https://www.openfoam.com.

Then grab yourself a copy of this https://www.booktopia.com.au/low-speed-aerodynamics-joseph-katz/prod9780521665520.html

and become acquainted with flight modelling from the other side of the table.

 

This is great news, Dave.

 

Can you use your openfoam program and low speed aerodynamics book and answer the following questions? :

 

What is the correct relative stick force per G over 500kph for LaGG-3 and 109?

 

For La-5 and 109?

 

For Yak and 109?

 

For MiG and 109?

 

How did those aircraft perform historically relative to the 109 at speeds over 500kph?

[ACG_KaiLae]

So how do the developers program "delightful" or "quite easy to get 5G" into the sim? That's the problem with pilot quotes. Almost always useless.

 

Which gets back to....is there any document that lists what these were on any model of the 109? If there isn't, how did we get to the levels seen in the FM?

[SCG_OpticFlow]

There is a dive test document for the 109 around somewhere. Is usually thrown around in these discussions, both here and over in the ED forum.

 

Here is a link to the report (in German):

 

https://www.dropbox.com/s/11f19ji7jf23mf9/V.B.%20109%2005%20E%2043%20-%20Hochgeschwindigkeitsversuche%20mit%20Me%20109%20%28April%2015%2C%201943%29.pdf

 

We were discussing it before the thread got derailed.

[9./JG27DefaultFace]

If you google it there’s even a translated version.

[JG1_Shadepiece]

If you could link the English version here that would be top!

[9./JG27DefaultFace]

http://www.wwiiaircraftperformance.org/me109/Diving_Test_109F_W.Nr.9228_ger_eng.pdf

 

109F with G wings. Not sure what the differences are though between F and early G wings. Other than maybe structural strengthening

??

Edited January 1, 2018 by 9./JG27DefaultFace

[ACG_KaiLae]

The translated version has some german and/or difficult to read parts. I'm not sure on some of the graphs what they are referencing, especially with regards to stick forces?

[Dave]

This is great news, Dave.

 

Can you use your openfoam program and low speed aerodynamics book and answer the following questions? :

I probably can - just not right now - I am spending all my available "spare" time working on my own FM and a BoX add-on which should have been released a year ago. It isn't clear why people care about relative forces rather than absolutes though.

 

Incidentally you don't use a book like this to answer such specific questions - only to educate yourself generally on the subject. There is also nothing magical about the book I referenced. It is simply a very good example of a highly regarded and yet accessible intro text on the subject of modelling complex continuous physical systems in discrete mathematical terms as the basis for computation. The reason I mentioned either of these things above is that the history of multiplayer air combat simulations (and games claiming to be so) has clearly demonstrated that no amount of historical documentation will satisfy most of the opponents and/or proponents of a particular FM claim. Every piece of supporting material put forth in support of a claim is in some way flawed: eg the purpose of the testing conducted; the accuracy of measurement; experimental procedural issues; specifics of the test environment; absence of experimental controls; subjective opinions of the tester; test regime coincidence with the issue at hand; and the list goes on. As a result every document supplied comes with about as much interpretation (and therefore inconsistency) as a religious text.

 

Frustrated by this, and having an employment background in software engineering, physics, and aeronautical engineering I figured the approach most satisfactory for me is to build a computational model that can be validated using more readily available test data for modern aircraft of similar configuration. Rest assured that as soon as that has been done the first historic aircraft on the list is the 109.

 

The most likely reaction to this might be "why would you build a computer model to validate another computer model?". The answer is that the game necessarily uses a real-time approximation which due to the limited capability of commodity consumer hardware must be considerable simplified compared to more accurate models which have the luxury of being run offline on powerful hardware over the course of several hours or days.

 

I was just throwing it out there in case anyone else was interested in learning more about computational fluid dynamics. If you are then the book and OSS project I linked are good places to start learning.

[unreasonable]

<snip>

 The reason I mentioned either of these things above is that the history of multiplayer air combat simulations (and games claiming to be so) has clearly demonstrated that no amount of historical documentation will satisfy most of the opponents and/or proponents of a particular FM claim. Every piece of supporting material put forth in support of a claim is in some way flawed: eg the purpose of the testing conducted; the accuracy of measurement; experimental procedural issues; specifics of the test environment; absence of experimental controls; subjective opinions of the tester; test regime coincidence with the issue at hand; and the list goes on. As a result every document supplied comes with about as much interpretation (and therefore inconsistency) as a religious text.

 

<snip>

 

Very true! I cannot help wondering if the quasi-religious belief in the supernatural qualities of German aircraft in particular is related to the fact that they are plastered with religious symbols!   

[FTC_Riksen]

Very true! I cannot help wondering if the quasi-religious belief in the supernatural qualities of German aircraft in particular is related to the fact that they are plastered with religious symbols!   

Way to go man! If you are trying to sabotage the topic and get it locked I think you did it

[SAS_Storebror]

The opening post's statement was...

 

Currently, if you go beyond a certain speed, the elevator stiffens up.

(...)

As it is now, it's somewhat hard to understand because it logically would have been noted as a design deficiency and corrected at some point, like the P-38's roll rate. 

 

Perhaps it's overdone? Is there data anywhere that shows what is accurate? Is there a way to check?

 

Report with date has been given: https://www.dropbox.com/s/11f19ji7jf23mf9/V.B.%20109%2005%20E%2043%20-%20Hochgeschwindigkeitsversuche%20mit%20Me%20109%20%28April%2015%2C%201943%29.pdf

 

The report not only shows that the effect apparently isn't overdone, it also shows that the germans actually did recognize the issue and they did change it, it's just that for the 109s currently available in IL-2 Great Battles, these changes weren't available (yet).

 

Cheers!

Mike

[SCG_OpticFlow]

The opening post's statement was...

 

 

Report with date has been given: https://www.dropbox.com/s/11f19ji7jf23mf9/V.B.%20109%2005%20E%2043%20-%20Hochgeschwindigkeitsversuche%20mit%20Me%20109%20%28April%2015%2C%201943%29.pdf

 

The report not only shows that the effect apparently isn't overdone, it also shows that the germans actually did recognize the issue and they did change it, it's just that for the 109s currently available in IL-2 Great Battles, these changes weren't available (yet).

 

Cheers!

Mike

 

No, read the report.

 

In the test on page 9, the pilot managed to reach 745 km/h indicated (880 true) airspeed at 3.8 km height at a 75-80 degree dive. At this height he managed to pull out of the dive using only the elevator in about 1 km height loss. Trim was set before the dive to 1 and 1/4 degrees nose heavy.

 

Why do you say they changed the elevator?

[SAS_Storebror]

No, read the report.

 

In the test on page 9, the pilot managed to reach 745 km/h indicated (880 true) airspeed at 3.8 km height at a 75-80 degree dive.

 

That was after applying the tail modifications. Re-read yourself 

Before that (Page 3 for instance) there was no stable flight above 650 km/h at all.

 

 

Why do you say they changed the elevator?

 

Where did I say so?

 

Cheers!

Mike

[Blutaar]

Stability has nothing to do with elevator effectiveness and the tail modification was just to counter the instability at high speed dives.

[SAS_Storebror]

Now that we seem to leave any factual talks, I leave the rest of this 100th 109 FM complaint thread to you guys.

What had to be said has been said and it seems you rather don't want to be disturbed while expressing condolences to each other 

 

Cheers!

Mike

[Panthera]

Will be interesting to see how they model the K-4 in bodenplatte considering it featured flettner tabs on the elevators, this would've greatly decreased the stick forces at high speeds, making the K-4 deadly responsive in pitch even in dives.

[Dave]

Will be interesting to see how they model the K-4 in bodenplatte considering it featured flettner tabs on the elevators, this would've greatly decreased the stick forces at high speeds, making the K-4 deadly responsive in pitch even in dives.

A servo tab on the elevator makes no sense for a variable incidence tailplane. I think it was only on the rudder and this had already been introduced to series production on the G6. The later G series also had aileron servo tabs, as did the K4 in limited numbers apparently. Perhaps you are thinking of the ailerons instead.

[Panthera]

A servo tab on the elevator makes no sense for a variable incidence tailplane. I think it was only on the rudder and this had already been introduced to series production on the G6. The later G series also had aileron servo tabs, as did the K4 in limited numbers apparently. Perhaps you are thinking of the ailerons instead.

 

Yes, you're right I misremembered, however according to the latest K-4 manual the elevators were modified for improved elevator control at high speeds.

 

"Servicing manual for Bf 109K-4, conditions as of October 1944, effective January 1945, authorized 25 January 1945.

 

 

 

It says:

 

3. Stabilisers and control surfaces.

 

Vertical stabilisers without horn balance, with Flettner tab; rudder with reduced area 

trail.

Cantilever variable incidence horizontal stabiliser, adjustable in flight; increased gearing compared to Bf 109 G.

Mechanical angle indicators for the horizontal stabiliser in the cocpit,

on the left side wall.

For reduction of the stick forcres, modified elevator kinematics. 

 

 

 

109K tail unit and elevator deflection angles, as of 30 December 1944:

 

"

Edited January 2, 2018 by Panthera

[MiloMorai]

Will be interesting to see how they model the K-4 in bodenplatte considering it featured flettner tabs on the elevators, this would've greatly decreased the stick forces at high speeds, making the K-4 deadly responsive in pitch even in dives.

 

Vertical stabilisers without horn balance, with Flettner tab; rudder with reduced area trail.

 

Vertical is not horizontal.

 

vertical = rudder

horizontal = elevator

[Panthera]

Vertical is not horizontal.

 

vertical = rudder

horizontal = elevator

 

Read my previous post.

 

It was the elevator kinematics that were improved to lower the stick forces. 

Edited January 2, 2018 by Panthera

[ZachariasX]

The changes in gearing of the elevator surfaces (-6* pull and -10* push) should reflect in less slow speed pich/turn authority on the 109K compared to the G series. I expect lot more trim work to follow good turning planes at lower speeds.

 

Edit: Servo tabs for the ailerons seem much more the exception than the rule and were installed only in very small batches of G and K types. I guess it would have to be a MOD for the plane rather than standard issue.

Edited January 2, 2018 by ZachariasX

[Panthera]

The changes in gearing of the elevator surfaces (-6* pull and -10* push) should reflect in less slow speed pich/turn authority on the 109K compared to the G series. I expect lot more trim work to follow good turning planes at lower speeds.

 

Not at all as you need to remember that you're always using much less than full stick deflection at slow speeds anyway, so there would still being a good margin left to ensure full controllability during take off and landing which is well below dogfighting speeds.

 

Also the -6* & -10* seems to be refering to the all moving horizontal stabilizer for trim, not the elevators.

Edited January 2, 2018 by Panthera

[ZachariasX]

Not at all as you need to remember that you're always using much less than full stick deflection at slow speeds anyway, so there would still being a good margin left to ensure full controllability during take off and landing which is well below dogfighting speeds.

 

Also the -6* & -10* seems to be refering to the all moving horizontal stabilizer for trim, not the elevators.

As I unserstand the document you posted it says: „Case I 33* will be changed for case II 27*“, and case I 34* will be changed for case II 24*“.

 

I doubt that 33* is not meant as trim deflection, but contol surface deflection. 6* and 10* are the reduction from the original deflection, reducing pull to almost 3/4 and push about to 2/3.

 

Of course, at high speeds this is way more than tolerable for the airframe, lest possible for the pilot to achieve.

 

At very slow speed (a frequent condition in MP fragging) this makes a difference. it is larger than the entire trim of the stabylo that already makes a huge impact in turning circles. You can pull the stick back all the way in such slow turns and you will notice the difference. The 109 hardly featured a stick travel that were never used, as it would come at the price of higher gearing of the stick.

Edited January 2, 2018 by ZachariasX

[Panthera]

As I unserstand the document you posted it says: „Case I 33* will be changed for case II 27*“, and case I 34* will be changed for case II 24*“.

 

I doubt that 33* is not meant as trim deflection, but contol surface deflection. 6* and 10* are the reduction from the original deflection, reducing pull to almost 3/4 and push about to 2/3.

 

Of course, at high speeds this is way more than tolerable for the airframe, lest possible for the pilot to achieve.

 

At very slow speed (a frequent condition in MP fragging) this makes a difference. it is larger than the entire trim of the stabylo that already makes a huge impact in turning circles. You can pull the stick back all the way in such slow turns and you will notice the difference. The 109 hardly featured a stick travel that were never used, as it would come at the price of higher gearing of the stick.

 

I sincerely doubt it will make any difference at anything but landing & take off speeds where a little extra trim will be needed. It should still be plenty for an accelerated stall.

[ZachariasX]

I sincerely doubt it will make any difference at anything but landing & take off speeds where a little extra trim will be needed. It should still be plenty for an accelerated stall.

One could try that. Just reduce axis movement in „settings“ and log in on Berloga, see how you‘re doing. A slow G-4 shouldn‘t be that different from a slow K-4.

 

In any way, it seems it was used only in few aircraft. So it maybe should be a mod as well, rather than standard. But if anyone has records showing otherwise, I‘d be happy to see it.