The aircraft was engaged on a flight from Biggin Hill, Kent (BQH) to Pau, France (PUF). The commander called for start at 14:17 and, at 14:20, was cleared to taxi to holding point A1 for a departure from runway 21. At 14:24, ATC instructed the crew to hold at A1 and cleared them for a LYDD 2 departure. At 14:34, one minute after becoming airborne, the co-pilot transmitted: “And victor papa bravo golf echo er we’re making an immediate turn to return to the airport immediate turn to the airport.” The tower controller replied: “Victor golf echo join downwind right-hand runway two one, the biggin qnh one thousand, threshold elevation’s five one seven feet, what’s the nature of your problem?” The co-pilot replied: “ere we don’t know sir we’re getting er engine vibration we’ll come straight back.” The aircraft then manoeuvred to overhead the airfield at approximately 1,200 ft aal heading towards the end of the downwind leg for a left-hand circuit to runway 21. As the aircraft left the overhead it commenced a continuous descent and, at 13:36 hrs, the co-pilot transmitted: “And er victor golf echo we have major problem a major power problem it looks as though we’re er going in we’re going in!” The aircraft flew extremely low over the roofs of several houses before its left wing impacted the roof of a house at the end of a residential close adjacent to a small wood. After the initial impact the aircraft struck the ground and caught fire destroying the attached garage of a neighbouring dwelling. Examination of the wreckage, however, did not reveal any evidence of pre-impact restrictions in the flight control circuits and examination of the engines, after disassembly, revealed no evidence of either engine having suffered a bird strike or foreign object damage. Furthermore, no pre-impact damage or failures were found in any of the rotating assemblies or main bearings. CONTRIBUTORY FACTORS: 1. It is probable that a mechanical failure within the air cycle machine caused the vibration which led to the crew attempting to return to the departure airfield. 2. A missing rivet head on the left engine fuel shut-off lever may have led to an inadvertent shut-down of that engine. 3. Approximately 70 seconds prior to impact neither engine was producing any thrust. 4. A relight attempt on the second engine was probably started before the relit first engine had reached idle speed, resulting in insufficient time for enough thrust to be developed to arrest the aircraft’s rate of descent before ground impact.