Flight Background
The accident occurred toward the end of a positioning flight from Stansted to Lyneham, prior to an intended freight flight from Lyneham to Singapore. Before departing Stansted, the captain telephoned the Meteorological Office at Lyneham and obtained the local weather situation. The en route flight to Lyneham was without incident.
Approach
On arrival overhead Lyneham, a Ground Controlled Approach (GCA) to Runway 07 was initiated. The aircraft intercepted the glide path at 2,000 feet and a normal talk-down approach was made until the 1/4-mile-from-touchdown position was reached. During the approach, a normal descent was maintained with variations of up to 50 feet above the glide path. At the 1/4-mile position, the aircraft's echo disappeared from the tracker's radar screen in a downward direction, indicating a high rate of descent.
Impact and Aftermath
At that moment, the captain, who was concentrating on the flight instruments, was suddenly warned by the co-pilot that there were trees ahead. The captain immediately pulled back the control column but was unable to prevent the aircraft from striking the upper branches of trees and the ridge of steeply sloping ground approximately 140 yards short of the touchdown point. The aircraft was severely damaged, and three of the crew were slightly injured. There was no fire.
Official Findings
The probable cause, as determined by the investigation, was that the captain allowed the aircraft to descend below critical height during the GCA without having visual reference to the ground. Contributory causes included: the captain was not warned by the talk-down controller that the aircraft was approaching break-off altitude; the visibility at the threshold of Runway 07 was less than the airfield visibility reported to the captain; and the aircraft was affected by a downdraught that caused it to sink below the glide path. Additionally, the glide path at Lyneham allowed for less obstacle clearance than is normal with a civil installation.