Wayne and netters, Precession will be greater, the greater the span of the propeller. For instance, a pilot flying a KR2 with a 48" prop will have a smaller area of gyro, hence less of a response from the aircraft. Typically most ultralights I have seen lean towards slower turning larger props. This is also true of KR drivers with larger Corvair, or Continental engines, especially if they replaced a VW engine with the larger engine, and stepped up to a longer prop. They typically run longer props to take advantage of the greater engine torque. This also creates a larger area for precession to occur, and with conventional gear, when raising the tail there effectively is a force applied to the "top" of the disc (prop), and the reaction comes not at the 12:00 position applied, but rather at the 3:00 position if clockwise rotation, or 9:00 position if VW or counterclockwise rotation. P-factor effectively disappears temporarily due to the aircraft's orientation into the relative wind is basically straight, giving both sides of the prop, descending and ascending, the same effective pitch. P-Factor will become more evident on rotation/climbout as the angle of attack is changed to climb from the level flight attitude during the takeoff run. Typically this precession combined with the torque twisting the aircraft causing more drag on that main tire, makes for very dramatic reactions if the aircraft is light, and good to high horsepower engine. In my KR with VW power, the precession at lifting the tail will cause a right turning tendency, along with the engine torque twisting the prop and reacting opposite, causing the right main to "dig in", also trying to turn the aircraft right. On rotation/climbout, the torque reaction will cause a mild rolling right, P-factor will cause a yawing right, and precession will cause a yawing left. After a few takeoff runs gradually adding power sooner, until you reach the edge of good control, should get you to the kind of performance you desire and takeoff technique you need, without being a hazard to yourself or others, whether in a KR or not. Colin & Bev Rainey KR2(td) crain...@cfl.rr.com Sanford, Florida FLY SAFE!!!!
