What happened
On September 27, 1998, a PA-31P departed from Ourinhos, Brazil, en route to Congonhas. The flight was a return leg following an earlier flight from Congonhas to Ourinhos, which had been diverted due to adverse weather at the original destination of Assis.
Approximately 20 minutes after takeoff, while cruising at FL 090 under instrument flight conditions, the right engine failed suddenly. The crew attempted various restart procedures, including switching fuel tanks and activating electric pumps and cross-feed, but the engine could not be restarted. As the aircraft was unable to maintain level flight on a single engine, it began to lose altitude.
Upon reaching 1,500 feet, the crew gained visual contact with the ground and decided to perform an emergency landing on a plowed field. The crew extended the landing gear, believing it would assist in stopping the aircraft; however, the uneven terrain caused the gear to dig into the ground. The aircraft struck a depression in the terrain, causing it to nose-over and roll onto its back. The aircraft sustained severe damage, including the engines, propellers, and fuselage, while the pilot sustained minor injuries and the co-pilot was uninjured.
The investigation
CENIPA investigators examined the aircraft's fuel system, engines, and the crew's operational history. Testing of the right engine's fuel pumps, selectors, and mechanical components showed no mechanical failure capable of causing a sudden shutdown. While some discrepancies were noted in the mechanical fuel pump and servo-injector, these were not deemed sufficient to cause an immediate engine failure.
The investigation focused on the fuel management sequence. The crew had used the external tanks during the first leg of the flight, leaving approximately 10 minutes of fuel autonomy in those tanks upon arrival in Ourinhos. After departing Ourinhos, the crew switched back to the external tanks after leveling off. Investigators concluded that the engine failure was likely caused by fuel exhaustion in the active tank.
Findings
- Lack of fuel coordination: The crew failed to properly manage fuel consumption, leading to the right engine running out of fuel.
- Inadequate planning: The crew did not adequately plan for the necessary tank switches required to maintain fuel autonomy for the duration of the flight.
- Loss of engine performance: The aircraft was unable to maintain level flight on a single engine, leading to the descent.
- Improper landing technique: The decision to extend the landing gear on unpaved, irregular terrain contributed to the nose-over and subsequent rollover.
- Operational currency: Both pilots had not flown this specific aircraft type or performed IFR operations for approximately 90 days, which may have impacted their proficiency in engine restart procedures and single-engine flight control.