What happened
On the evening of 15 May 2000, a Socata-Aerospatiale Rallye 893E, registration EI-BFM, was performing a check flight at Coonagh Airfield, Co. Limerick. The flight was being conducted by a Class 1 instructor and a pilot-under-supervision. During the takeoff roll on Runway 28, the aircraft reached approximately 60 knots when the crew experienced a sudden and significant reduction in engine power.
Upon the loss of power, the instructor took control and attempted to abort the takeoff. However, the aircraft could not stop within the remaining runway length. The aircraft departed the paved surface, traveled 6/2 meters across a grass area, breached a wire fence, and crossed a public road before ultimately colliding with a stone wall. While the aircraft sustained extensive damage and was considered an economic write-off, there were no injuries to the two occupants.
The investigation
Investigators examined the engine, fuel systems, and environmental conditions at the time of the accident. Post-accident testing of the engine showed no mechanical defects; the engine performed normally during subsequent test runs, and the fuel was found to be clean and free of water. The investigation also reviewed the maintenance history, noting that the engine had been overhauled in 1998 and the propeller had recently been replaced.
Meteorological data from nearby Shannon Airport indicated an air temperature of 15°C and a dew point of 9°C. Investigators analyzed these figures against standard charts used to predict induction system icing. Additionally, the investigation noted that the aircraft had been moved to a hangar before the AAIU could perform an initial inspection, which presented a possibility of lost evidence.
Findings
- The primary cause of the power loss was determined to be carburettor icing.
- Atmospheric conditions, characterized by a relatively small spread between the air temperature and the dew point, were highly conducive to icing.
- While the crew had cycled the carburettor heat during the pre-flight check, the specific temperature and humidity levels at the time of takeoff created a high risk for ice formation in the induction system.
- No mechanical failures, fuel contamination, or pilot errors in handling the aircraft were identified as contributing factors.