DNK Aviation Services

De Havilland DHC-7 (Dash-7)

Prior to the flight the commander had filed a flight plan which indicated that after take off the aircraft would transit from Guernsey to the Berry Head VOR at FL 100. It was then planned to manoeuvre in the Plymouth area whilst conducting a performance related test flight. The commander called for start clearance at 0902 hrs and, after a short taxi, the aircraft was cleared for take off at 0918 hrs. After take off Guernsey ATC handed the aircraft over to the London Air Traffic Control Centre (LATCC) at 0930 hrs. As the aircraft approached Berry Head at FL 100 the commander requested FL 60. The aircraft was cleared for this descent and then handed over to Exeter ATC at 0943 hrs. Exeter ATC confirmed the aircraft requirements for a block of airspace between FL 60 and FL 100 and offered a radar advisory service. The aircraft was then vectored onto a northerly heading to keep it clear of departures from Plymouth Airport. As the aircraft approached FL 60 the commander requested further descent to FL 50, which was approved. The air traffic controller at Exeter then noticed that the altitude readout from the aircraft radar transponder indicated FL 47. He called the aircraft to confirm the local sector safe level of 3,500 feet but received no reply; this call was timed at 0947 hrs. From FDR timings the crew would not have heard this call. At the same time the transponder information disappeared from the radar screen and the primary radar return was no longer visible. The controller made repeated calls to the aircraft but received no reply. He arranged for LATCC to inform the Distress and Diversion cell whilst he notified the local emergency services. A large number of eye witnesses saw the aircraft in its final descent before impacting the ground; twenty two of these witnesses were interviewed. All agreed that the sky was clear and bright with only a few of them describing small amounts of light cumulus clouds. No one saw any other aircraft in the area and all were certain that there was no smoke or fire issuing from the aircraft or its engines whilst it was in the air. Most witnesses described the aircraft in a spin or a spiral descent, generally to the left, although some described the motion as like a falling leaf. Four witnesses, who all had a clear view of the aircraft throughout, described the aircraft completing a two or three turn spin/spiral to the left. Those witnesses who were in a position to hear clearly the sound of the engines confirmed that the engines were making a loud noise as if at a high power setting. The impact with the ground was followed immediately by a post crash fire. Both pilots were killed.