What happened
On August 26, 2000, a PIPER PA-3-2RT-300T, registration EC-HNE, departed from Cuatro Vientos airport for a planned three-hour pleasure flight, intended to conclude at Casarrubios del Monte. The aircraft was carrying a pilot and two passengers.
Approximately 90 minutes into the flight, while climbing at 7,300 feet near the area between La Granja de San Ildefonso and El Paular, the pilot experienced intense abnormal vibrations accompanied by a significant loss of engine power. This was followed by a visible leak of fluid, believed to be oil, from the front of the engine, which obscured the pilot's view through the right windscreen. Shortly after, smoke and a strong burning odor entered the cabin.
Believing an engine fire was imminent, the pilot shut down the engine and cut the fuel supply. After notifying Valladolid tower of the emergency, the pilot performed an emergency landing with the landing gear retracted in a field parallel to the road between Revenga and Robledo. All three occupants were unharmed and evacuated the aircraft successfully.
The investigation
The investigation focused on the mechanical failure of the Lycoming TIO-540-S1AD engine. Post-accident inspection of the engine revealed extensive internal damage, including a crack through the entire thickness of the crankcase wall at the junction of the two semi-crankcases. This crack specifically affected the camshaft lubrication passage. Additionally, investigators found that at least two tappets and their respective housings were broken. Impact marks from flying debris were also identified on the interior walls of the crankcase, the bottom of the pistons, the connecting rods, and the crankshaft.
Findings
- The primary cause of the engine failure was the failure of a tappet, likely due to seizing.
- Fragments from the broken tappet traveled through the engine, causing secondary damage to internal components.
- The resulting crack in the crankcase wall led to the loss of oil through the camshaft lubrication passage, which caused the visible fluid leak and subsequent power loss.