What happened
On 31 October 2001, a Socata Rallye Commodore MS 892A-150, registration EI-BCH, departed Coonagh Airfield for a sightseeing flight near Lough Derg. The pilot was accompanied by two passengers, including his young son. The flight proceeded as planned, with the aircraft climbing to 1500 feet and flying northeast toward Garrykennedy before the pilot decided to return to the airfield.
During the descent toward Coonagh, the aircraft was positioned near Killaloe when the engine began to sputter. The RPM decayed, and the propeller eventually stopped rotating after a period of windmilling. The pilot identified a suitable landing field and initiated a forced landing. During the flare, the aircraft's belly struck a boulder located in a perimeter hedge, causing the nose undercarriage to be ripped from the airframe. Despite the impact, all three occupants exited the aircraft without assistance, and no fire occurred. One passenger sustained a minor nosebleed.
The investigation
The AAIU investigation focused on the cause of the engine failure and the accuracy of the aircraft's fuel monitoring. Investigators examined the fuel system, specifically the transparent sight gauge used to indicate fuel levels. Tests revealed that the plastic tube in the gauge had become discolored and aged, causing the internal float ball to stick. This prevented the gauge from accurately reflecting the actual fuel level, particularly when levels were between 60 and 80 litres.
Analysis of flight logs and fuel consumption indicated that the aircraft was significantly lower on fuel than the pilot believed. While the gauge indicated approximately 80 litres at takeoff, the actual remaining fuel was estimated to be only about 20 litres. This discrepancy was compounded by the fact that the high wing dihedral made it difficult for the pilot to visually verify the fuel level during pre-flight inspections.
Findings
- The primary cause of the engine failure was fuel starvation.
- The aircraft's fuel sight gauge was faulty, providing an erroneous reading that suggested much higher fuel levels than were actually present.
- The pilot was unable to effectively verify the actual fuel quantity against the gauge reading due to the aircraft's design and the discolored state of the sight tube.
- The engine stopped due to the lack of available fuel during the descent.