Abstract: Detailed heat transfer distributions within a deep gap were measured with both a sharp leading edge flat plate and a flat cylinder at free-stream Mach numbers of 9.85,12.0,15.5 and corresponding unit Reynolds numbers of (1.0 × 107, 6.4 × 105, 3.2 × 105 )/m in CAS impulse tunnels. The gap was 2mm wide, 25mm deep and 100mm long. Attack angles α ranged from 0° to 90° and deflectionsβ from 0° to 90°. In this paper, typical heating distributions on the gap wall were presented; effects of Mach number, attack angle and deflection on heat transfer to the gap wall were discussed;and comparisons between measured and predicted gap heating were made.