What happened
On September 9, 2002, at approximately 17:45 local time, a PIPER PA-28RT-201, registration EC-FDK, departed from Manises Airport for a scheduled test flight following a Type B maintenance inspection. The flight was conducted under an authorized IFR flight plan.
Approximately 10 to 15 minutes into the flight, while the crew was returning to the airport and roughly 5 kilometers from the runway, the pilot noticed abnormally low oil pressure accompanied by rising oil temperature. Recognizing the signs of an imminent engine failure, the pilot notified Air Traffic Control and attempted to return to the airport. However, the engine ceased functioning completely before the aircraft could land. The crew performed an emergency landing in an urban area within the municipality of Paterna. During the landing, the aircraft's right wing struck a tree, causing damage to the engine, engine mount, nose gear, and right wing. Both occupants were unharmed.
The investigation
Investigators examined the wreckage and found that the engine had seized due to a lack of oil. While a significant amount of clean oil was found in the rear lower fuselage, no leaks were identified other than at the oil drain valve located on the lower engine sump. The investigation revealed that the drain valve was stuck in the open position. The drain conduit was found bent, with marks suggesting it had been struck by a hard object.
Testing with an identical aircraft confirmed that during the retraction movement of the nose gear, a component of the gear assembly passes very close to the valve. On the accident aircraft, marks on the nose gear component were consistent with those found on the valve, indicating that the gear had struck the valve and forced it open.
Furthermore, the investigation highlighted that the aircraft was equipped with an incorrect type of drain valve. According to Piper Aircraft Corporation's Service Letter No. 910 and FAA Airworthiness Directive AD 81-11-02 R1, aircraft of this model should not use the valve installed on EC-FDK due to the risk of interference between the nose gear and the valve, which can lead to total oil loss.
Findings
- The engine seized because of oil depletion caused by the drain valve being forced into the open position.
- Mechanical interference occurred between the nose gear mechanism and the oil drain valve during the gear's movement.
- The aircraft was utilizing an unauthorized drain valve type that was susceptible to interference from the nose gear.
- The crew performed all required pre-flight checks, including fuel and oil level verifications, which were correct prior to departure.