Flight Details
The flight originated from Leavesden to Stansted, where the instructor filed an IFR flight plan for Stansted to Exeter at FL310. Departure from Stansted occurred at 1303. For 40 minutes, the aircraft conducted local flying in the Stansted zone, performing two ILS approaches followed by an overshoot. At 1345, the flight contacted London Centre. The climb to FL310 was normal.
Emergency Descent Exercise
At 1421, the pilot asked ATC if an emergency descent exercise could be performed before reaching Exeter, intending to begin after passing Dawlish. The controller agreed. At 1435, the aircraft was almost over Dawlish, and the crew announced readiness. They stated they would maintain a listening watch but could not transmit while donning oxygen masks. At 1436, ATC authorized descent to FL120. At 1438, the controller instructed a right turn towards Exeter, repeated at 1439. At 1443, noting a left turn, the controller authorized a left turn to Exeter. At 1444, a request for a transponder squawk went unanswered.
Loss of Contact
No replies were received from the aircraft after 1438. Beech G-BGHR began describing large circles to the left at FL310. Wind at that altitude caused a drift southward, passing over Guernsey, Jersey, Dinard, and Rennes. The aircraft's fuel endurance ended at 2020 (2220 local time), and it crashed near Nantes, 20 km east-southeast of the town. An RAF Nimrod escorted the Beechcraft during its progress to the vicinity of Nantes. Two Dassault Mirage III and three Mirage F1 of the French Air Force followed the aircraft from 1810 to 2010. The fighter pilots observed that the aircraft's external condition appeared normal: doors and emergency exits were in normal positions, cabin and cockpit illuminated, navigation lights operating. However, warning lights were noted on the control panel, and no contact could be established.
Official Findings
The immediate cause of the accident was the aircraft striking the ground at a steep angle. The underlying cause was depressurization of the cabin at high altitude, initiated by the pilot during the exercise. The oxygen masks were not connected, and the crew died in flight due to hypoxia. The investigation concluded that such exercises are too dangerous for this class of aircraft, given the limited useful consciousness time available in case of oxygen system failure.