Blumlein was killed in the crash of an H2S-equipped Handley Page Halifax test aircraft while making a test flight for the Telecommunications Research Establishment (TRE) on 7 June 1942. During the flight from RAF Defford, whilst at an altitude of 500 ft the Halifax developed an engine fire which rapidly grew out of control. The aircraft was seen to lose altitude, then rolled inverted and struck the ground. The crash occurred near the village of Welsh Bicknor in Herefordshire. Two of Blumlein's colleagues, Cecil Oswald Browne and Frank Blythen also died in the crash.