Eccentric Landing with Heavy Masses at the Wing Tips

Abstract

An eccentric landing of a conventional aircraft carrying heavy masses at the wing tips is investigated. The landing gears make contact with the ground one after the other, the second contact taking place before the shock absorbing process of the first gear is completed. The following results are of interest. (a) In eccentric landing with heavy tip masses the effective mass acting on (or the drop mass of) one shock absorbing unit may be larger than one half of the total mass of the aircraft. (b) The magnitude of this mass depends on the ratio, radius of gyration of the aircraft in roll to the undercarriage tread, on the initial roll angle, and on the roll velocity at the moment of the first contact. (c) Since the time span between two impacts and the magnitude of each impact depend on the initial roll angle and roll velocity and both can have any values, within certain statistical limits of course, an asymmetric wing vibration can be generated and have larger effects on wing stresses than the symmetric vibration due to the symmetric landing. (d) Parameters defining the landing gear strength are in general three: (1) sinking velocity, (2) roll angle, and (3) roll velocity. (e) Available information concerning the shock absorber characteristics is insufficient to bring the subject to a conclusion. I t appears, however, that for large tip masses the shock absorption capacity of the gear should be checked in two cases at least; (1) in the case corresponding to symmetric landing shock (small drop mass and large sinking velocity), and (2) in the case of eccentric landing shock (large drop mass and small sinking velocity).