95% of the time the tire is out of balance and should be either changed or balanced, or occasionally if there are 2 nose wheels; a pressure difference
like a car with a shaky steering wheel
if you are using grease in the scissor links to take away shimmy it is past time to buy a new set of scissors, or shim/rebush them
rutan, you have never apparently dealt with an aircraft with a trailing link style landing nose gear, if the wheels are behind the leg then they have no option to go straight and follow it, admittedly the ones i work with have hydraulic NWS, but they are quite manageable with differential power and brakes to steer, and the other ones i work with have a vertical legs and work well when all the wheels balance weights are attached (they do fall off now and then) (i believe all boeings, emb 120, cessna 441, and metro have vertical legs, so the 'bicycle' theory needs work more to convince me)
my experience only
Last edited by Connaught; 16th May 2009 at 12:46.