What happened
On March 21, 2010, an A-122-B aircraft, registration PP-GYK, departed from the Luziânia Aerodrome in Goiás, Brazil, for a proficiency check flight. The flight was being conducted by a civil aviation inspector acting as an examiner, accompanied by a student pilot undergoing an initial private pilot check.
After completing the required flight maneuvers at 5,000 feet, the crew returned to the aerodrome for an approach to runway 29. During a go-around maneuver, the engine failed at approximately 50 feet of altitude. The examiner took control of the aircraft and attempted to steer away from a nearby valley, eventually performing a forced landing in a wooded area approximately 200 meters from the runway threshold. The impact resulted in serious injuries to the examiner and minor injuries to the student pilot. The aircraft sustained major damage.
The investigation
CENIPA investigators examined the wreckage and the engine components. Fuel samples taken from the tanks and filters were found to be in full compliance with aviation gasoline specifications. Subsequent testing of the engine and ignition system at an authorized workshop showed that the engine functioned normally during tests, though investigators noted a drop in RPM when the left magneto was removed and a drop of 1-1.5 RPM when the right magneto was removed.
Crucially, the investigation revealed that during the pre-flight engine check at the holding point, the examiner had observed that the magneto drop was outside the manufacturer's specified limits. The aircraft manual explicitly states that if the RPM drop exceeds 175 RPM, the pilot should not take off. Despite recognizing this deviation, the examiner decided to proceed with the flight.
Findings
- The engine failure occurred during a go-around maneuver following a period of flight where the crew was aware of an ignition system irregularity.
- The decision to take off despite known engine magneto irregularities was the primary contributing factor.
- The crew's flight judgment and failure to adhere to the manufacturer's operational limits (flight indiscipline) contributed to the occurrence.
- The engine failure may have been caused by an electrical current leak due to improper torque on the igniter group connections.