What happened
On August 25, 2011, a Cessna 150K, registration PT-LBT, operated by Escola de Aviação Civil Golden Wings Ltd, departed from the Anápolos Aerodrome in Goiás, Brazil, for a post-200-hour inspection test flight. The aircraft was operated by a single pilot.
Shortly after takeoff, upon reaching an altitude of approximately 400 feet, the pilot heard an unusual noise followed by a loss of power and a complete engine shutdown. Despite attempts to restart the engine, the pilot was unable to restore power. The pilot then attempted to perform an emergency landing in an unprepared field. During the approach to the intended landing site, the aircraft struck a fence, causing a sudden deceleration and a subsequent nose-over (pilonamento). The aircraft sustained substantial damage, but the pilot remained uninjured.
The investigation
CENIPA investigators confirmed that the aircraft had sufficient fuel at the time of the accident, and subsequent laboratory analysis by the National Agency of Petroleum, Natural Gas and Biofuels (ANP) verified that the fuel met all required specifications.
Technical analysis of the engine revealed excessive carbonization on the exhaust valves of all four cylinders. Specifically, the exhaust valve in cylinder 1 was found to be stuck in its guide due to the accumulation of carbon residues on the stem and seat, which prevented compression in that cylinder. Investigators determined that this buildup could have resulted from the use of non-specification oil, extended oil change intervals, improper mixture settings, or the use of low-quality fuel in previous flights.
Furthermore, the investigation examined the pilot's approach to the emergency landing. It was determined that the pilot inadequately managed the altitude-velocity relationship, arriving at the intended landing area with excessive altitude and speed, which necessitated a change in landing site and led to the collision with the fence.
Findings
- Carbonization of the exhaust valve in cylinder 1, caused by residue accumulation, which led to the engine failure;
- Inadequate pilot judgment regarding the altitude-velocity management during the emergency landing;
- Maintenance issues, potentially involving improper oil usage or delayed oil changes;
- Management oversight regarding maintenance and fueling procedures.