What happened
On June 29, 2021, at 11:48 UTC, a Cessna 172 M, registration TC-YUZ, was performing a VFR flight from Kocaeli Cengiz Topel Airport to Bursa Yunuseli Landing Strip. While approaching runway 09, the crew encountered heavy winds, prompting a decision to execute a go-around. During the go-around procedure, as the pilot applied power to climb, the engine failed at an altitude of approximately 500–600 feet. Realizing the aircraft could not reach the runway, the crew performed an emergency landing in an orchard located approximately 700 meters east of the Bursa Yunuseli landing strip. There were no fatalities or injuries among the two occupants, but the aircraft sustained total damage.
The investigation
The UEİM investigation examined the aircraft's maintenance records, fuel quality, and meteorological conditions. Investigators analyzed the fuel samples taken from the aircraft's tanks at the crash site. Laboratory testing conducted by METU Petroleum Research Center revealed that the fuel used was automotive gasoline with a Research Octane Number (RON) of 94.8 ± 0.5 and contained ethanol. The investigation also reviewed the pilot's licenses, the operator's manuals, and the meteorological forecasts (TAF) for the arrival airport. The investigation further looked into the regulatory compliance of the aircraft's insurance and the status of the safety pilot on board.
Findings
- The primary cause of the engine failure was the use of non-compliant automotive fuel containing ethanol, which did not meet the Lycoming engine manufacturer's service instruction requirements (minimum 98 RON/88 MON and ethanol-free).
- High ambient temperatures (30°C) likely contributed to fuel evaporation issues in the engine.
- The crew failed to evaluate the specific TAF for the arrival airport, which indicated significant wind gusts from the side (90-degree crosswind) during the arrival window.
- The safety pilot was not part of the operator's permanent staff, and there was no documented orientation or procedure within the company manuals regarding their role or authority during the flight.
- Several administrative discrepancies were noted, including discrepancies in the aircraft's insurance policy regarding crew capacity and the lack of a valid Aircraft Station License.
Safety action
- The investigation recommended that the Civil Aviation Authority (SHGM) take administrative action regarding the pilot's medical certification and the safety pilot's role.
- It was recommended that the operator ensure all future fuel usage strictly adheres to manufacturer specifications, specifically avoiding ethanol-blended automotive fuels.
- The operator was advised to implement formal procedures for reviewing NOTAMs and meteorological data prior to flight operations.