A Reliable Spline Coupling

Abstract

Involute spline couplings are commonly used in aircraft to transmit power to gearboxes, generators, pumps, and other engine driven accessories. Spline driven accessories which are cantilever mounted on an aircraft engine are of special concern to the user as these interface splines characteristically exhibit extremely poor reliability. To compound the problem, replacement of splines is difficult and costly due to their inaccessibility. Whereas the engine driven accessory may demonstrate a mean time between failures (MTBF) of 2000 hr., the spline coupling typically fails within 500 hr. Consequently, the degree of maintenance demanded by spline wear conflicts with the operational requirements of military or commercial aircraft. Failures can also compromise flight safety. This paper reviews recent spline research directed at understanding the characteristics and problems of conventional involute splines. It also discusses the design, development, and application of the circular spline coupling (MS14169) which was developed to solve spline wear problems being experienced in military aircraft.