Abstract: An aircraft disc stack (1) comprises a plurality of interleaved stator and rotor discs (3,4) keyed respectively to a torque tube (5) and a wheel hub (not shown). The stack (1) further comprises bi-functional friction/load-transmitting discs in the form of end stator discs (10,13). These discs (10,13) are subject to uneven loading because the non-friction surfaces (12,15) are in use compressed on areas less than the load bearing areas of the opposing friction faces (11,14). This can lead to premature disc failure and in the past load spreader plates have been used to distribute loading over these areas to minimize the risk of failure. In this invention portions of the load bearing areas of non-friction surfaces (12,15) are toughened ie: material underlying these surfaces is toughened, to increase their resistance to deformation, fracture and/or wear thereby removing the need for additional load spreader plates which were hitherto required.