Catalogue description Armstrong Siddeley Motors Experimental Department (Sapphire engines): Interim report concerning failure of engine B.7042/A.643502 in Hunter WP.143

Conclusions: All the evidence clearly indicates that the engine sustained severe compressor damage due to the entry of a foreign body when the aircraft was carrying out a low level gun firing exercise. The deposits of molten aluminium alloy on the turbine are consistent with the engine running at the time the compressor damage occurred. The rapid fall in rpm which occurred whilst the pilot was making a forced landing also indicates that the compressor was damaged prior to being involved in the forced landing