Orbiter Tire Traction and Wear

The traction and wear problem for a main landing gear tire of the Space Shuttle Orbiter is considered. Side force acting on the tire during landing under yawed conditions, and the associated tire wear, are computed using analytical expressions derived from basic principles of physics. These equations relate side traction and wear to vertical contact load, slip angle, tire mechanical properties, footprint geometry, and rubber abradability. Numerical results in graphical form are presented for side force as a function of slip angle at various tire loads and compared with values obtained using the empirical formula of Dryden Flight Research Center (DFRC). Energy dissipated by the side force is used as a tire-wear index, forming the basis for deriving bilinear tire wear models for both the Kennedy Space Center (KSC) and Edwards AFB runways. The constants of these models are determined using Convair 990 (CV 990) Landing Systems Research Aircraft (LSRA) test data.