Accident
On September 9, 2002, at approximately 17:45 local time, a Piper PA-28RT-201 aircraft, registration EC-FDK, departed from Manises airport for a test flight following a maintenance inspection. The flight was operated by a commercial pilot, age 29, with 1,600 total flight hours, and one other occupant. The aircraft was a 1979 model equipped with a Lycoming IO-360-C1C6 engine.
Between 10 and 15 minutes after takeoff, while returning to the airport and about 5 kilometers away, the pilot noted abnormally low oil pressure and rising oil temperature, indicating an imminent engine failure. The pilot decided to return immediately and notified air traffic control. Shortly thereafter, the engine stopped completely. The pilot conducted an emergency landing in an urban area within the municipality of Paterna, Valencia province. The aircraft sustained damage to the engine, engine mount, nose landing gear, and right wing. There was no fire. Both occupants were uninjured.
Investigation
According to the pilot's statement, the flight was planned as a test flight after the aircraft had undergone a B-type maintenance check. An IFR flight plan had been authorized by Valencia Air Traffic Control Center. Before the flight, the pilot performed all required ground checks, including fuel draining and level checks (both tanks full) and oil level verification (correct). After engine start, the pilot taxied to the holding point with the left tank selected, performed a power check, and switched to the right tank for takeoff. All indications were normal.
Approximately 10–15 minutes into the flight, the pilot observed low oil pressure and rising temperature, and decided to return. After the engine stopped, the pilot performed the emergency landing procedure. The aircraft came to a stop after the right wing struck a tree.
Inspection of the wreckage revealed that the engine had seized due to oil loss. A large quantity of clean oil was found in the lower rear fuselage, with oil stains on the lower engine cowling but none on the upper cowling. The oil drain valve, located on the engine crankcase, was found locked in the open position. The drain valve's outlet tube was bent rearward and to the right, with marks on its lower right side suggesting an object had struck it from below and slipped off to the left. No other oil leaks or pre-existing engine failures were found.
The valve functioned correctly when tested, moving easily between open and closed positions. However, when the valve was closed, pushing or striking its lower end (without excessive force) caused it to open and lock open. The crankcase drained completely in about 10 minutes with the valve open.
Further examination with a similar aircraft (same engine and nose gear geometry) showed that if the accident aircraft's valve were installed, a component of the nose landing gear would pass very close to the valve during retraction, with an upward movement. Marks on the corresponding nose gear component were consistent with those found on the valve.
Airworthiness Information
Piper Aircraft Corporation Service Letter No. 910, dated December 29, 1980, stated that aircraft models PA-28R-200, PA-28R-201, and PA-28RT-201 (including the accident aircraft) must not use the type of valve installed on the accident aircraft, due to potential interference with the nose gear causing total oil loss. Only valve part number Piper 492 172V was approved. Airworthiness Directive AD 81-11-02 R1, effective October 2, 1981, issued by the FAA, made these instructions mandatory.
Conclusions
The most probable cause of the accident was interference between the nose landing gear and the oil drain valve. During the final phase of gear retraction, a component of the gear mechanism struck the valve, leaving it open, resulting in oil loss and subsequent engine seizure.