What happened
On 2 April 2001, a Piper PA-34-220T, registration G-OMAR, was conducting a private flight from Shoreham, West Sussex, to Sheffield. After an uneventful outbound leg, the pilot began the return journey to Shoreham. As the aircraft approached the airfield for an overhead join at 2,000 feet, the pilot initiated pre-landing checks, which included advancing the propeller control levers toward the fully fine position.
Immediately following this adjustment, the left engine experienced a significant drop in manifold pressure, causing the aircraft to yaw and roll. Although the pilot managed to temporarily recover power by returning the lever to the cruise position, a subsequent attempt to move both levers to the fully fine position resulted in the complete failure of the left engine. Shortly thereafter, the right engine also failed.
With both engines inoperative, the pilot attempted several restarts using the electric starter and crossfeed settings but was unsuccessful. Realising the aircraft could not reach the runway, the pilot targeted a narrow grass strip between a railway line and a residential area. During the landing attempt, the left wing struck a house roof, and the right wing and tailplane collided with a tree. The pilot sustained one minor injury.
The investigation
The AAIB investigation focused on the simultaneous failure of two independent engines. Mechanical examinations of both engines, the fuel filters, and the ignition systems revealed no mechanical malfunctions or debris in the fuel system. Investigators also noted that the propellers were windmilling at impact in a fine pitch position.
Analysis of the fuel planning revealed that the pilot had used a 'rule of thumb' consumption rate of 20 USG per hour, whereas the actual flight speed required 23.3 USG per hour. Furthermore, a calculation error during refuelling at Shoreham meant the aircraft departed with approximately 54 US gallons, while the pilot had planned for 6/60 US gallons. The investigation also highlighted the difficulty in verifying fuel levels in the outboard tanks when levels are below 50%.
Findings
- The aircraft was operating with critically low fuel levels upon arrival at Shoreham.
- The deceleration caused by adjusting the propeller pitch to the fully fine position likely caused the remaining fuel to shift, uncovering the fuel lines and allowing air to enter the system.
- The initial failure of the left engine caused a yaw that further disturbed the remaining fuel in the right tank, leading to the subsequent failure of the right engine.
- The pilot's fuel planning was based on an underestimated consumption rate and contained errors regarding the volume of fuel uplifted.