[CLOSED] K-4 module completely stops rolling at high speeds

Making a bug report of this.

I put the new version K-4 moduel through some brief trials today, personally I like the new "clipping" controls a lot more, even with the non-FFB joystick, it feels far more natural.

But there is one serious issue though, which is that during dive trials as ca 2-3 km altitude and at around 700 km/h indicated the ailerons suddenly stop working. Completely. Pitch is still controllable. I believe this may be down to odd clipping of the aileron control forces.

There is definietely something wrong with this, since its not that the roll rate would get reduced roll rate (with the increased stick forces), but the rolling ability is completely gone. The aircraft does not react to rolling inputs at all, not even slowl. It rolls to the right somewhat though, but I believe its entirely down to propeller torque.

The issue is that even if the pressure on the control surfaces is very great at low speeds and seriously limit deflection, you should still get some effect. This is shown on actual trials of Bf 109F-2 by DVL in 1944.

The guy behind the stick in a 109F-2 was still measuring about 0.6 radians (cc 34 degrees per sec) at 780 km/h TAS, there is no reason why our pilot couldn't do that. Perhaps the new "clipping stick" model prevents us from rolling. See attached graph.

The phenomenon I encountered in the DCS module appears at about 700 IAS. Now, 700 kph IAS, which at around 1500 meters would still work out as around only as cc. 770 TAS, so according to the graph, you should be still able to get a modest roll rate with the plane.

Thing is, the aileron reversal and "0 degrees of roll" point is far, far higher than that, even on this tested F-2 (and as an educated guess, even higher on the K, since wings were reinforced already on the G), at around 1000 km/h TAS.

Thank you Racoon. That was my impression too - as if the pilot's 'sideways hand force' would cease too early.

Any update on this..?

Thank you Sith!

Nice to hear that Sith, thanks for the feedback!

Is this normal for the K-4?

Hi gents,

is this the normal behavior for the K-4 in a dive?

What ever settings i use, diving with power, without power, rads closed, rads open or on automatic, 100% fuel or 20% fuel. When i hit 750 Km/H in a dive, she starts to roll right, even when i use full left rudder and full left aileron. No change to stop the rolling. So where is the sence in makeing it possible to dive with up to 850 Km/H, when i have from 750 Km/H no controll of the right rolling, but no problem with the elevator, there i have full controll and can bring the K-4 easy out of the dive without using trim.

Also she becomes between 250Km/H and 350 Km/H very wobbeling not nice, where the 190 flys like on rails at this speed, should not the 109 be better at low speed handling?

regards

Little_D

There is German Document where High Speed Tests are described.

Here small Passage:

At 750Km/h the Plane start rolling to the Right with counter force on the Aileron the Plane suddenly goes to the left was not possible to hold the Plane in Line anymore.

And the 750km/h are IAS Airspeed True Airspeed is around 850 Km/h.

That's very high Mustang was one of the best Dive Planes in WW2.

And the 109 behaves in low Speed far better but have to be very hard to work with your Rudder inputs and fly smooth also big influence by the PC Hardware you use.

big influence by the PC Hardware you use.

This and server lag seems to affect the stick forces as well. They appear to be much more pronounced around 300km/h when the server starts lagging. Notice this a lot on the ACG server unfortunately.

Why does it start to roll to the right in the first place? Even with power off etc?

Profile on rudder being the reason perhaps?

I think you reach the effects of air Compressibility, don't know this ever researched on the 109 like RAF did after the War with the Spit. Don't know how this affect the 109 Airframe and the Ailerons, Me-163 had near sound barrier strong pitch down movement should be happy 109 is only starting rolling :D

Why does it start to roll to the right in the first place? Even with power off etc?

Profile on rudder being the reason perhaps?

That's where I'd put my money. You can test for it in the DCS version: if the rudder is responsible the instruments should show a large amount of side slip when the uncontrollable roll appears.

Otherwise perhaps some detail asymmetry in the airframe might be responsible- what if, for example, Messerschmidt's wing jigs were slightly off-spec (though still within acceptable tolerances) and as a result the factory consistently produced wings with a slight twist in them?

rudder is not right, In my long held opinion of it

anyway, would be a good place to look, and possible eliminate as the culprit

Ailerons completely stop working above some speed in DCS. Kurfürst already has a Bug report open with quotes from the DVL report. (https://forums.eagle.ru/showthread.php?t=174867) I hope this gets fixed rather sooner than later. Even at Mach 0.8 the ailerons were effective in the high speed trials of 109 F with G wings. That was also around the Mach speed when compressibility caused artifacts in aileron control. Max speed reached was Mach .81 (at 4,5 km altitude).

In the same report with the "new" larger rudder (= K-4 rudder minus flettner tab) the pilot was able to compensate the yawing forces in all high speed dives up to the tested max Mach of .81. Even with the small "old" rudder only above 800 kph yaw forces could not be compensated. In DCS it is starting at about 700 kph with the "new" rudder and flettner tabs. This cant be right.

Why does it start to roll to the right in the first place? Even with power off etc?

Profile on rudder being the reason perhaps?

With increasing speed the "wing" shaped rudder produces more "lift" to the left, so that seems to be the answer. I am guessing "pilot strength" is the problem here in DCS, as the test pilot didnt seem to have a problem compensating the yaw.

I wrote a report in July (https://forums.eagle.ru/showthread.php?t=170388), but nothing has happened so far. I guess ED is busy with the Spit release. Hopefully afterwards some corrections will quickly find its way into the sim. But I think even while taxiing the rudder seems to lack authority. When I have RPM at 2600 and the rudder still has no effect I am always a bit confused.

^^i think, that this is also due to the stick forces which are probably too pronounced right now? our pilot is not able to pull full deflection on the controls on any of the flight surfaces at speeds of well below 300kph.

but yes, i agree, rudder and its effects are also in my opinion for the lack of a better word questionable. for example, you can hardly get the 109 into a proper sideslip, and i can hardly de-crab the aircraft at crosswinds even with full rudder...it will just roll into that direction, but hardly yaw.

I don't know how it is now, but from what I read, the 109 should be pleasant before 400kph, getting progressively stiffer and at 550 the pilot is not able to move the stick with one hand and needs two and considerable force. While at 700kph the force needed would be too much for an average man to move the ailerons but elevator would be operational but barely.

Conclusion is that, bellow 400kph stick should be easy to move around and deflect, at 400 and above person if doing it one handed would be able to move the stick but with more stenght with each kph gained. He would be able to deflect it fully, but slower due to overcoming the rising stick forces. G would also affect him as it has a great effect on a person.

I believe it's pretty much like that in as far as aileron goes, but we can still use rudder well above 750 kph IAS, and the elevator is also effective at higher speeds without the need for stabilator, unless you're really close to the ground...

I don't know how it is now, but from what I read, the 109 should be pleasant before 400kph, getting progressively stiffer and at 550 the pilot is not able to move the stick with one hand and needs two and considerable force. While at 700kph the force needed would be too much for an average man to move the ailerons but elevator would be operational but barely.

Test source? From test reports high speed aileron forces in the 109 are similar to the Spitfire eg.

Spitfire: (10000 ft alt = 3048 m)

50 lbs (22.7 kg) for 90 °/s at 300 mph (483 kph)

50 lbs (22.7 kg) for 60 °/s at 400 mph (644 kph)

109: (3000 m alt)

19 kg (41.9 lbs) for 79 °/s at 300 mph

18 kg (39.7 lbs) for 40 °/s at 400 mph

30 kg (66 lbs) for 30 °/s at 497 mph (800 kph)

Yes, but the stick length, available room and sitting position differ, which make for different results.

How do you think the testpilots pulled the 30 kgs to measure the graphs? Oh boy..

How do you think the testpilots pulled the 30 kgs to measure the graphs? Oh boy..

That doest mean it is easily and quickly achievable and especially during prollonged dogfights. Also show me a test at 800kph if the max safe speed for the 109 was 750kph

That doest mean it is easily and quickly achievable and especially during prollonged dogfights. Also show me a test at 800kph if the max safe speed for the 109 was 750kph

VNe is more of a guideline than a hard rule. The Spit was often dived to much faster than its VNe as well.

Also the VNe is 750 km/h IAS, whereas that test might have been 800 km/h TAS at an unspecified altitude.