Accident
A twin-engine cargo aircraft departed Southend Airport on a flight to Bergamo, Italy, carrying newspapers and magazines. Two minutes and 30 seconds after liftoff, while climbing in limited visibility due to night and low cloud cover, the airplane entered a dive and struck a garage, bursting into flames. The pilot, the only person on board, was killed.
Investigation
Examination of the propeller assemblies revealed differences between the two engines at the time of impact. The right-hand propeller appeared to have been at fine pitch and rotating at high revolutions. In contrast, the left-hand propeller was rotating much more slowly and appeared to have been at or near its fully feathered position.
The firewall shut-off fuel valve for the left-hand engine was found in the closed position, consistent with that engine having been shut down prior to impact. A strip examination of the left-hand engine showed no evidence of damage to its rotating assemblies before the collision. The only damage identified on that engine not consistent with the impact was a ruptured diaphragm within the low-pressure compressor bleed valve.
This rolling diaphragm is designed to keep the compressor bleed valve closed at high power settings and to allow smooth opening as compressor discharge pressure decreases.
Probable Cause
The official probable cause, as determined by the investigation, is as follows: Examination of the propeller assemblies indicated that, although the right-hand propeller appeared to have been at fine pitch and rotating at high revolutions at impact, the left-hand propeller had been rotating much more slowly and appeared to have been at, or close to, its fully feathered position. The firewall shut-off fuel valve for the left-hand engine was found in its closed position, consistent with the action of shutting down this engine at some point prior to the impact. A strip examination of the left-hand engine was conducted and showed no evidence of damage to its rotating assemblies prior to the impact with the garage. The only damage identified on this engine as not being consistent with the impact was a ruptured diaphragm within the low-pressure compressor bleed valve. This rolling diaphragm is designed to hold the compressor bleed valve closed at high power settings and to provide smooth opening of the compressor bleed valve with reduction of compressor discharge pressure.