109 elevator trim

[Robo.]

Originally Posted by Kurfürst

It's mind dazzling, I agree.

http://kurfurst.org/Engine/DB60x/DB6...sheets_A1.html
http://kurfurst.org/Engine/DB60x/DB6...sheets_Aa.html

I did check my references. It seems that that Aa had the new type of Lader, it just had higher boosts, which can be maintained to lower altitudes only of course, and so seemingly the high altitude performance is worse than A-1 with new Lader.

However checking the power curves show that the A-1/new Lader has very similiar, practically the same altitude performance.

Quite complicated indeed. I have no knowledge of using different types of superchargers for A-1 engines (if you could point me to some reference that would be great!). Only tech. document I have is Betriebs- und Wartungsvorschrift for DB 601A (Aus. C, October '40), unfortunately, it's not going into further detail (obviously) and it does not distinguish between 601 subversions at all. Do you mean the A-0 by 'old Supercharger'?

http://kurfurst.org/Engine/DB60x/DB6...sheets_A0.html

I always thought Aa was basically slightly modified (re-designed head, reinforced valves allowing higher MFP, different supercharger gear ratio (I am not sure about exact details here) leading to slightly lower FTH traded for more power below FTH.

Originally Posted by Kurfürst

Essentially there is very little difference between these engines at the most common BoB fighting height, the 601A with the old lader is a bit poorer, the others are essentially the same. The Merlin XII is the best for these altitudes.

I agree. Plus it wasn't just the engine power but power to weight ratio which was in favour of the German design. Still very interesting discussion (although OT ). I find it difficult to compare the power of Merlins and DBs as British documents usually mention bHP (brake horse power). The data you posted are correct, of course.

Originally Posted by Kurfürst

The rare Merlin XII and 601N trump all the others, the 601N being the best engine at altitude by far.

The XII was not so rare during BoB, the XX and 601N were later designs and ones to be directly compared in my opinion.

Originally Posted by Kurfürst

I haven't seen the data files myself however, just one post on the board. Can you PM me how to extract these? Thx!

I also only seen it here and I remember the power of DB 601A-1 was set at 1020PS. I'll try to find that data, I have no idea how to extract anything from the game.

[VO101_Tom]

To the trimm topic. I know, it's G, but the trimm mechanics is the same:
(For those who doubt that the trim could be used at any time... )


"Sarantola recalled that the MT was a very stable plane, but not the most maneuverable. The stick forces were quite large and elevator trim was used quite frequently while maneuvering.
MT was easy to fly and overall a safe plane. Flying and landing was easy."
- Olli Sarantola, Finnish fighter pilot. Source: Blitz '01 - Meeting With The Veterans by Finnish Virtual Pilots Association.


Even more interesting is the fact that they tried different positions of the trimming. With the wrong trimset - the one for cruising at high altitude it was not possible to pull out of the dive just by using the stick. They needed to use the trimwheel to recover the plane from the dive. This happened in such violent manner that the testpilot had to push the stick foreward to be not blacked out...
If the trim was set to +1.15° it was possible to recover without using the trimwheel - both flightpaths, with and without the trimwheel, are very similar. So even with the concrete stick the limitating factor seems to be the pilot.
Also interesting in the dive the canopy iced, also the mechanism of the trim, so it was not possible to set it smooth, but in \"jumps\", but it was still adjustable...
- Source: Hochgeschwindigkeitsversusche mit Me 109, Messerschmitt AG, Augsburg.


Clarification of the escape dive: "It didn't stay (vertical) otherwise, it had to be kept with the stabilizer. I trimmed it so the plane was certainly nose down. Once I felt it didn't burn anymore and there was no black smoke in the mirror, then I began to straighten it up, and it wouldn't obey. The stick was so stiff it was useless. So a nudge at a time, (then straightening off with trims).
Then the wings came alive with the flutter effect, I was afraid it's coming apart and shut the throttle. Only then I began to level out. To a thousand meters. It was a long time - and the hard pull blacked me out."
- Edvald Estama, Finnish fighter pilot. Source: Recollections by Eino and Edvald Estama by Finnish Virtual Pilots Association.

[Robo.]

Tom I was already quoting this reference in this very thread.

Trim could be used at any time but not as it is in the sim now.

[VO101_Tom]

Originally Posted by Robo.

Tom I was already quoting this reference in this very thread.
Trim could be used at any time but not as it is in the sim now.

Ok then. I did not remember that.
Is not working as it should? This means that I lost the thread somewhere
There is ticket on the bugtracker about this issue?

[WTE_Galway]

Originally Posted by irR4tiOn4L

Actually, no idea. Could you explain please? Does that mean the controls DON'T get heavy at speed?

No, it means you have a null elevator. Regardless of holding the stick or letting it go, the aircraft is longitudinally stable and will tend to return to the trimmed position.

Though it may seem counter-intuitive, this is not always the case for all aircraft or for all loads in a given aircraft. In fact a statically unstable aircraft may offer some advantages. Modern fighters with computer assisted controls are often not statically stable.

[irR4tiOn4L]

Originally Posted by WTE_Galway

No, it means you have a null elevator. Regardless of holding the stick or letting it go, the aircraft is longitudinally stable and will tend to return to the trimmed position.

Though it may seem counter-intuitive, this is not always the case for all aircraft or for all loads in a given aircraft. In fact a statically unstable aircraft may offer some advantages. Modern fighters with computer assisted controls are often not statically stable.

Thanks for the explanation, but isn't it the case that such statically unstable aircraft are not flyable without modern fly by wire systems? Ie, of course the 109 is going to be statically stable if it is a workable pre-fly-by-wire design? (perhaps not at all loads though)

I guess I fail to see how that is particularly relevant to this discussion or the heaviness of the trim controls when the tail is subject to faster moving air.

[Igo kyu]

Originally Posted by irR4tiOn4L

Thanks for the explanation, but isn't it the case that such statically unstable aircraft are not flyable without modern fly by wire systems?

I suspect the I-16 was statically unstable.

[Osprey]

Originally Posted by VO101_Tom

Ok then. I did not remember that.
Is not working as it should? This means that I lost the thread somewhere
There is ticket on the bugtracker about this issue?

I don't think there is a ticket. The point of this thread, for me, was to clarify the issue. According to what has been discovered there certainly is an issue but I would leave it to a 109 driver to write it up as a bug to be fixed, this would obvious need to include details on what the setting should be and how it should behave.

You've done a few 109 issues Tom, is this one for you perhaps??

I also think that there needs to be some research into the Spitfire and Hurricane trims too, although perhaps nobody has complained really because they are already better turners so it isn't needed (exception of when the trim is used as per the original point of the thread)

[Crumpp]

Actually, no idea. Could you explain please? Does that mean the controls DON'T get heavy at speed?

It means the aircraft has precise trim control input. It is already stable.

The stability is one of the reasons for the higher control forces. The high elevator control forces is a function of the "stick force per G" of the control design. It is way beyond the scope of a gaming forum to adequately explain stability and control.

I will try and explain it so you get the basic idea.

There is a point in the aircraft's balance that is called the neutral point. If our center of gravity was placed at this point, the aircraft would have no tendency to return to last condition of trim. It would be neutral and continue in whatever direction we told it too. It would also require no force at all to move the stick, only the resistance from the hinge moments.

Do you know the law of levers; it is the basis for all Stability and control? It says that at the fulcrum, two moments or torque force of the levers will be equal.

Our basic formula for determing the torque force:

Moment = Arm x weight

Weight is the weight of the object or amount of force we place on the arm.

Arm is the distance from the Neutral Point in the case of stability.

Moment is the torque force required to move about the nuetral point.

The distance between our center of gravity and our neutral point determines the stability of the aircraft. The longer our arm or farther away we are from the neutral point, the more torque force we generate to return to last trimmed condition of flight. WTE_Galloway was correct in his explaination.
Understand?

Neutral stability, for the most part, is not good in an aircraft. Neutrally stable aircraft are "twitchy" and difficult to precisely control. Stable aircraft are easier to precisely manuver but come at the cost of higher input forces. The only axis Neutral stability is considered acceptable is lateral. Wings inhernetly have a considerable amount of roll stability.

Unstable is even worse and does require modern fly by wire controls to safely fly the aircraft. Most WWII fighters were just barely stable.

Now is above corner speed, you want a high stick force per G gradiant. It keeps the pilot safe by ensuring he does not destroy the airframe.

[Crumpp]

It means the aircraft has precise trim control input. It is already stable.

Just to clarify, trim forces will change over the range of an airfoils angle of attack. In general, for every speed there is a specific trim setting.

I am not saying the Bf-109 does not require trim input. There is a very tenious connection. It is entirely possible to have an unstable aircraft that trims very positively just as it is possible to have a stable aircraft that cannot be trimmed.