What happened
On 2 September 2011, a Zenair CH 601UL Zodiac, registration G-CCVT, was conducting a private flight from a grass airstrip in Glenmavis, Lanarkshire. Following a light shower, the pilot performed standard pre-flight procedures, which included a water sediment check of the fuel. After completing engine power checks, the pilot released the brakes and accelerated down the runway.
As the aircraft reached an altitude of approximately 30 ft, the engine experienced a sudden change in tone, followed by a cough and a rapid decrease in RPM, leading to a total engine failure. To avoid overhead electrical cables and a road crossing the end of the runway, the pilot executed a steep right bank. During this maneuver, the right wing and landing gear impacted the ground, causing the aircraft to bounce and land heavily. The aircraft sustained extensive damage, though the pilot escaped without injury.
The investigation
Investigators examined the engine and the environmental conditions at the time of the incident. The aircraft was powered by a Rotax 912-S engine, which utilizes two carburettors positioned near the engine exhaust. The investigation considered two primary potential causes for the sudden loss of power: carburettor icing and fuel starvation.
While the high humidity (88%) and the temperature/dewpoint spread (14°C/12°C) created conditions conducive to icing, the investigators noted that the engine's design typically keeps the carburettor bodies warm. Furthermore, the sudden nature of the engine's failure was noted as being less characteristic of the gradual power loss typically associated with carburettor icing.
Findings
- The engine failure occurred shortly after takeoff during a period of high humidity.
- The sudden loss of RPM and engine stoppage were consistent with fuel starvation, though carburettor icing could not be entirely dismissed.
- The aircraft's damage was a result of the pilot's attempt to avoid obstacles during the power loss.