View Full Version : Having trim problems!

03-18-2005, 08:32 PM
Are there any tutorials on the use of trim in PF? I'm having a terrible time trying to get my B-25 to fly level on a bomb run. I click aileron trim once and the plane leans one way, then I click the other way once and the plane promptly starts leaning the other way. There just doesn't seem to be a happy medium. Elevator trim is not much better, it takes too long for me to get the thing level and about then it's time to turn and I have to start over. I'm presently using hat switches on my X-45 to control the trim. I've heard you can program a rotary to control the elevator trim but haven't been able to figure out how this is done. Any help would be really appreciated!


03-18-2005, 10:23 PM
Basically, trim is performed to limit the effects of engine torque and speed.

Elevator trim is adjusted according to speed; nose down trim as the speed goes up (nose tends to rise), nose up trim as the speed goes down (nose tends to drop).

Rudder trim is applied to cancel out engine torque; as power & prop pitch increase and cause the aircraft to 'crab' in one direction, you apply the opposite rudder trim to center the 'ball'.

Aileron trim is applied to cancel out the tendency to roll in one direction or the other due to the interaction of the engine torque and rudder trim.

In the Controls Menu, you go down to the HOTAS section to designate your rotarys as rudder, elevator, and/or aileron trim in the same way as you designate throttle, elevator, aileron, and rudder inputs. These axis assignments tend to 'trump' the button inputs, so make sure you start your aircraft with the rotarys centered when you take off.



03-19-2005, 01:01 AM
You can use rudder trim to help keep from rolling and keep a straight hands off course. It works. Although for some (J8A example), to maintain straight course with rudder trim, your wings end up banked some.

I have rudder trim mapped to joystick throttle, smooth trimming, no clicking.

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If you have not tried it and you don't have Fancy Joystick, map elevator trim to mousewheel. It makes all the difference in the world for me.

03-19-2005, 05:50 AM
Yep, the main reason you're having trouble finding the 'sweet spot' in your aileron trim is that you are 'crabbing' slightly, your yaw is not compensated for. (Rudder trim is the most ignored trim function...it doesn't seem to have an obvious effect).

So trim your rudder until the ball is centred, and your are flying along relatively level. Then trim the aileron to roll the wings level. Early planes often lack one or more of these trim functions - some have no trim at all (p11c, I-153, I think)


03-19-2005, 07:45 AM
Make sure you map a key to "auto-stabilizer" or auto level or whatever it is (not autopilot). This will hold your plane straight and true for bomb runs.

03-19-2005, 12:26 PM
Thanks for the help, guys! I had wondered what I needed to do about rudder trim and now I plan to use it. I also like the idea of using the rotaries but I was under the impression that you couldn't program the rotaries like that with an X-45, but I'm going to try it now. I had turned on the level stabilizer but it didn't seem to keep me very level, I take it that it won't keep you from rolling if you're not trimmed right. Anyway, it looks like I have some work to do on my joystick profile, so if I have more problems I'll let you know.


03-19-2005, 04:03 PM
One,the rotaries on the x45 work great for trim, I know because I had them mapped before upgrading. 2 The level stabilizer once engaged will maintain present altitude and heading. You wont be able to change it until you turn it off, no matter how much control input you try to give it.