[Flightgear-users] Re: Rudder Trim

[RMcN]

On Tuesday 18 April 2006 23:00, barsalou wrote: > I have been trying to trim the rudder so that the plane doesn't go to > the left off the runway when trying to take off. > > Maybe this is normal airplane flight? > > > I have made attempts at setting the dead-band and other things, but am > not succeeding. > > I realize I probably haven't given enough info here...please help me > how you can. > > Mike B. As others have pointed out the torque is normal but here is a little more insight based on limited experience in real 172's.  Which is probably relevant for all tricycle gear aircraft in flightgear.  The torque is most pronounced at high RPM and low speed.  At higher speed the aircraft tail assembly, I think this is true for all aircrafts, act like a weather vane and help to point the nose into the relative wind, i.e. direction of flight.  Also at low speed the rudder is not effective since there is little wind over it and steering is done using the nose wheel.  You are probably taking off the way I started with flightgear.  Brakes locked at end of runway, some flaps, full throttle and release the brakes.  That's great for a soft runway and/or short field operation, or a 747,  but makes the torque problem worse.  The proper normal runway technique in the 172 is NO FLAPS, release the brake and smoothly increase the throttle to full power.  A slight nose down trim is also helpful in keeping the nose wheel on the runway and steering control until speed increases and the rudder is effective.  Use the nose wheel to counter the torque, LEFT PEDDLE, Mouse with left button down or the period key.  If set for auto coordination once you use the left or tight arrow keys or mouse without the left button down the wheel and rudder will jump to an almost centered position so be careful.  During maximum climb and slow fight with high RPM's you still have to use the right peddle to counter the torque.  That's why the standard pattern at an airport is to the left so the torque is pulling the plane in the proper direction your not fighting it.  My tail dragger experience is based solely on flightgear.  Since the steering is done with the tail wheel and it's friction on the ground tends to keep the tail from drifting as well, a nose up trim is desired.  I have found with high power aircraft, P51 especially, that take off flaps 10 degrees to increase lift, slow acceleration until the plane flies, not full throttle and steady nose up attitude to keep the tail wheel on the ground but not pitch the nose up too early.  Allows you to fly the plane with all three wheels coming off the ground at the same time and maintain control.  I'm sure that's not the real tail dragger technique but it works in flightgear.  Ray Mc