What happened
On August 9, 2009, a Stampe SV4A, registration EI-CJR, was conducting a private flight from a landing strip in Craughwell, Co. Galway. The flight began with a brief interruption when the pilot discovered the aircraft's radio was unserviceable, prompting a temporary return to the airfield to notify air traffic control. During this interval, the engine was left idling for approximately ten minutes.
Upon attempting a second take-off, the aircraft initially performed well. However, as the plane climbed to an altitude between 100 and 150 feet, the engine suddenly failed. The pilot attempted to use the throttle to recover power, but the engine remained non-functional. This necessitated an immediate forced landing into an agricultural field located just south of the airfield. While the aircraft sustained substantial damage upon impact, both occupants escaped the wreckage without injury.
The investigation
The AAIU investigation focused on the mechanical state of the engine and the environmental conditions at the time of the accident. Investigators confirmed that the aircraft was well-maintained and found no evidence of mechanical failure or pre-existing damage to the engine or airframe. The aircraft was operating on a 50/50 mixture of Avgas and Mogas.
Meteorological data indicated a warm front was approaching, with a surface temperature of 17°C and a dew point of 12°C. The investigation also noted that the aircraft was not equipped with a carburettor heating system. Furthermore, the investigators examined the implications of using Mogas, noting that its higher volatility increases the risk of temperature drops within the carburettor.
Findings
- The engine stoppage was likely caused by carburettor icing.
- The period of prolonged idling on the ground prior to take-off likely contributed to the formation of ice in the carburettor throat.
- The use of Mogas increased the aircraft's susceptibility to icing compared to standard Avgas.
- The standard carburettor icing charts used by pilots are not accurate for Mogas-blended fuels, as the risk areas are significantly larger.
Safety action
- The IAA should consider updating Aeronautical Notice A16 to include scientific and operational details regarding Mogas usage.
- The IAA should clarify the regulations regarding the use of Mogas in aircraft that lack carburettor heating systems.
- The IAA should explore additional methods to educate the general aviation community on the specific safety risks associated with Mogas.