On Thursday 20 April 2006 09:24, [EMAIL PROTECTED] wrote: > 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.
In fact a flight instructor will tell you to increase the power slowly and smoothly. Aircraft with constant speed props (not the 172) need time for the prop governor to react to the increase in throttle so taking 4 to 6 seconds to open the throttle is about right for most GA aircraft. The more powerful the aircraft the more slowly you should increase power during takeoff. Not holding the breaks while increasing the power applies only to single engine and other (near) center line thrust (CLT) aircraft for the most part. Non-CTL twins are different in that you do hold the breaks while (slowly and smoothly) opening the throttles. The reason for this is to allow the engines to settle at or near takeoff RPM before you begin the talkoff roll to prevent the engines from spooling up at differrent rates during takeoff which would result in asymmetric thrust. My experience with FlightGear is that both engines spool up at exactly the same rate which is not realistic. But this may not be true for all multi-engine aircraft in FlightGear since of the twins I have only tried the C310 and the DC3. > 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. Normally this would be handled by applying rudder trim rather than holding pressure on the rudder pedals. But at least in 0.9.9 I have never been able to get the rudder trim to work. I need to try this with 0.9.10. > 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. My real world tail dragger experience is limited to a Super Decathlon which has more power (180 HP) than the J3 but not nearly as much as a P-51 or Spitfire. In general most tail draggers are setup so that when all three wheels are on the ground the plane is in about the same attitude as it would be when stalled. So taking off "with all three wheels coming off the ground at the same time" means you are taking off at a speed that is very close to stall. This is probably not a good idea. In fact the only real world case where this is done that I know of is with Reno unlimited race planes that have had larger engines with bigger props installed that prevent the aircraft from taking off in the normal way without a prop strike. You should accelerate with the tail wheel down (hold some back pressure on the stick) until you are gong fast enough that the rudder has enough authority and then bring the tail up slowly (2 to 3 seconds) until the aircraft is level. Then continue accelerating while adding more power to rotation and takeoff which should happen well above stall speed. You will also accelerate faster once the tail is up since there will be less drag. Hal ------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Flightgear-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/flightgear-users
