raymondu999 wrote:Porpoising would/should happen under braking, not flat out on the straight.
True, but braking is not neccesary, see
here for an extreme case. Porpoising is the equivalent of torsion bending flutter that occurs when the energy being extracted by the structure from the air exceeds that disspated by the dampers & tyres (mostly the front dampers in this case). I think true to say that any aero vehicle will porpoise if the airspeed is sufficiently high (braking or not), but the "critical airspeed" can be reduced significantly if the dampers are not strong enough, or have been rendered ineffective with springs that are too stiff (the latter is sometimes the case during braking, courtesy of overenthusiastic bump rubbers).
