What happened
On 4 August 2004, a private flight traveling from Clonbullogue, Co. Offaly, to Granard, Co. Longford, was interrupted by a sudden loss of power. While cruising at an altitude of 1,200 ft, the pilot of the X-AIR 582 microlight, registration G-CBFT, noticed the engine power dropping. Despite advancing the throttle to its maximum position, the engine's RPM failed to increase.
While the pilot monitored fuel pressure, magneto settings, and temperatures, the engine ceased functioning entirely once the aircraft descended to approximately 1,100 ft. Having already identified a suitable landing site in a freshly mowed field, the pilot executed an emergency landing near the shores of Lough Ennel. The aircraft touched down at 35 mph, coming to a stop within 50 metres. There were no injuries to the pilot or the passenger, and no damage was sustained by the aircraft or property.
The investigation
The AAIU examined the engine following the incident. Upon removal and teardown, investigators determined that the engine failure was caused by the failure of the No. 1 big-end bearing.
The investigation also reviewed the maintenance history of the Rotax 582 engine. At the time of the occurrence, the engine had only 172 hours of service, which was well within its 300-hour overhaul interval. The investigation noted that in two-stroke engines using Mogas, lubrication is provided via the fuel/oil mixture, and using incorrect oil types can lead to rapid bearing deterioration. Additionally, the investigation considered that running engines at high RPM during start-up before reaching operating temperature can contribute to bearing wear.
Findings
- The engine experienced a loss of power during the cruise phase of flight.
- The primary cause of the engine failure was a big-end bearing failure.