Flight and Initial Events
The pilot departed Cardiff (Rhoose) Airport at 0925 local time with one pilot and six passengers on a Visual Flight Rules flight plan to Eastleigh Airport, Southampton, with a planned continuation to Paris. The flight plan indicated an elapsed time of 35 minutes and a cruising altitude of 5,500 feet. Shortly after 0950, the pilot contacted London air traffic control requesting clearance to enter the Southampton Zone. He was instructed to contact Southampton Zone directly, which he acknowledged.
Engine Failure and Loss of Height
Following the radio exchange, the engines became unsynchronized and the aircraft began to vibrate. The port propeller stopped rotating, causing a loss of altitude. As the aircraft descended to approximately 200 feet, the pilot successfully restarted the port engine. The aircraft then flew at a very low altitude, passing over a line of high-tension cables. It continued at around 200 feet, flying at reduced speed with increased vibration over undulating terrain. After climbing slightly to clear a ridge, the aircraft descended into a densely wooded area.
Collision with Trees
As the aircraft neared the treetops, it banked to the left and the port wing tip struck a tree. The aircraft continued for approximately 400 yards, striking the tops of several trees before crashing. The accident resulted in the death of the pilot and serious injuries to four passengers.
Investigation Findings
Examination of the wreckage revealed that the starboard engine had sustained considerable impact damage. When dismantled, the crankshaft was found to have broken at the number 3 crankpin. The fracture was attributed to a fatigue crack that originated at a plugged hole in the rear web of that crankpin. Heavy scoring on the faces of the crankcase web and cap of the number 1 main bearing indicated that cylinders 1 and 2 had continued to operate after the crankshaft failure. The crankshaft had accumulated 1,205 hours of total running time since manufacture, including 619 hours since its last overhaul. During that overhaul, a modification designed to prevent such failures had been incorporated.
The probable cause, as determined by the investigation, is that the pilot mistakenly shut down the port engine instead of the starboard engine, which had developed a serious mechanical fault (the crankshaft fatigue failure). This error led to a rapid loss of height. Although the pilot later restarted the port engine, the starboard engine was not shut down.