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Aircraft roll to the left

Controlling your aircraft, using the autopilot etc.

Aircraft roll to the left

Postby TangoIndia078 » Sun Jul 08, 2007 4:15 pm

Hi,

I've just installed FG on my Linux machine.
I have a small problem though: every time I'm taking off, the airplane roll immediately to the left. (I swear I don't touch the Joystick)

I'm not sure if it's a problem with my Joystick calibration, or trimming configuration etc'...

I'm using by the way HOTAS Cougar (if it makes any different).

does anybody has some idea what to check/set/do?

Thanks

TI-078
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Postby Harald » Sun Jul 08, 2007 4:40 pm

Propeler torque is the main reason
To reduce this effect some aircraft have an aileron-trim property defined in their -set.xml file but the value is only good for cruise. When taking off your engine is at an higher rpm and then produce more torque. Reduce the rpm and see if that helps.

HJ.
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Postby TangoIndia078 » Sun Jul 08, 2007 4:46 pm

thanks but the problem is that my Simulator rolls with any Aircrafts.
I therefore assume, it's not a specific aircraft model related.

By the way, it rolls also when I'm trying to do straight and level (which is pretty hard to do right now :( )
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Postby HeliFlyer » Sun Jul 08, 2007 8:55 pm

Hi TI078,

I am pretty sure you used the jscal program or whatsoever to calibrate your joystick.
If so, use the Cessna C172p and press the "h" button. The HUD appears. With "h" you can cycle through the hud and with SHIFT+"h" you can change the intensity.
The HUD shows you the position of your controls. If they are neutral, the HUD control positions should be neutral. Easy test to do.

Regards
Georg EDDW
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Postby pauljs75 » Mon Jul 09, 2007 4:11 am

If your stick actually centers (is calibrated and centers on HUD), some aircraft still don't have the proper aileron trim for cruise. (Such as the C310.) You'll have to hunt for the aileron trim value of an aircraft in its .xml files.

But before altering an aircraft's aileron trim, use the "Browse internal properties", look for controls, then flight. In there you should be able to select the aileron trim and set it manually. Fine tune from there and write down the aileron trim that levels the aircraft at your desired flying (ideally cruise) speed. This will be the value that you'll need to enter into the .xml.

Also note that some aircraft (C172 and C310 are good examples) will not fly level at cruise speed without trimming the nose down. (Or constantly pushing the stick forward a bit.) However, elevator trim is provided in the standard flight controls, so this is easy to adjust for.
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Postby OldGrantonian » Thu Jul 12, 2007 3:15 pm

pauljs75 wrote:use the "Browse internal properties", look for controls, then flight. In there you should be able to select the aileron trim and set it manually.


I had the same problem and your instructions worked fine. Thanks.
.
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Postby simstick » Thu Jul 12, 2007 4:34 pm

And the obvious......wind. Your not using real weather are you? Start up with no wind and weather enabled.
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Postby powerin » Fri Jul 20, 2007 12:15 am

Flightgear aircraft roll to the left because that's what real propellor aircraft do and they require a bit of right rudder to compensate. The effect should cancel out when you reach cruise speed because aircraft are usually trimmed for straight and level flight at cruise.

There are two main forces that cause it from what I've read. Firstly the blast of air from the propellor does not travel in a straight line but spirals around the aeroplane. The air from the right side of the prop spirals under, and the air from the left spirals over the top and hits the vertical tail, blowing it slightly to the right and pushing the plane to the left. Secondly there is the P-Factor which at lower speeds (and therefore high angles of attack) causes the propellor blades to produce more thrust in the right half of their circle and less in the left.

Aircraft use various methods to counteract these forces (I think the tail of a C172 is at a slight angle for example). But since these forces vary according to the speed of the plane, they are designed to be cancelled out at cruise speed which is where an aeroplane spends most of its time.
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turning left issue

Postby robert » Fri Jan 04, 2008 8:12 pm

Hello I am new to flightgear and have also recognized the turning left issue which is already described several times in this forum.

First of all I Use Flightgear 1.0 on Mac osx 10.5

I am mainly interested into flying helicopters and to my surprise the turning left issue was there as well. I guess there can be some torque about the main axis of the rotor but I also had the helicopter "fall" to the left like if I would push the stick to the left. I know the stick is very sensitiv and that the helicopter has to be unfluenced all the time to hover or just even make a surviveavle lift off but there is a clear left tendency which I can not describe by any tropque :?:
For tests I selected the b1900d double engined aircraft again to my suprise I had the left tendency as well and also as hard as with the single engine aircrafts. Additionaly I tested different throttle positions and there seemed to be no direct influence to my "problem"
If I switch to the 2d Panel I check the neutral position of my controls and thy seem to be fine.

Any ideas what I am having here?

Regards

Robert
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Postby technobill » Sat Jan 05, 2008 1:33 am

Hurgh


This is a bit low tech, but maybe you hit delete, or some button which has toggled the autopilot...



I dunno
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Postby robert » Sat Jan 05, 2008 12:14 pm

That would be to funny to be true imaging that I always fly "against" the autopilot :shock: but I do not think so. I would have to hit the autopilot accidantly on every startup of flightgear and autopilot on the bo102?

But thanks for the idea anyway.

Robert
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new info

Postby robert » Mon Jan 07, 2008 11:53 am

Yesterday I launched Flightgear with the EC135 model and did leave the computer for a phonecall. The call took several minutes and when I came back the model had turned left almost 45 degrees on the ground no engine running. I tested that again and relaunched Flightgear with the EC135 Model. Waiting in front of the screen I recognized a slow but constant turn to the left of the helicopter with the engine still turned off. :?: Might that be a hint about the turning left behaviour of the aircrafts?

Other Question about the EC 135 is it normal that it is much more sensitive then the bo-102? Also I was confused that my Imac can handle flightgear when flying the bo-102 but not when using the EC 135 model. Is the performance influenced by the model that "extreme"

Thanks for input

Robert
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