What happened
On November 4, 2013, a Piper PA-25-235, registration PP-CTD, was performing local flight passes at the Lavras Aerodrome (SSOL) in Minas Gerais, Brazil. During the fourth circuit of the traffic pattern, while on the base leg of runway 05, the aircraft's engine suffered a failure. The pilot attempted an emergency landing in a nearby residential development (Loteamento Jardim Magnolia). Due to holes in the terrain, the aircraft'-s main landing gear collapsed, and the nose struck the ground. The aircraft sustained substantial damage to the engine block, engine cowling, landing gear, and the tip of the right wing. The pilot escaped the wreckage uninjured.
The investigation
CENIPA investigators examined the engine and fuel system following the accident. Initial inspections showed the engine rotated freely, with no evidence of internal component failure. While the spark plugs appeared to have been recently replaced, no maintenance records for this replacement were provided by the operator.
Investigators discovered that the fuel tank filler cap seals were dried and deteriorated. Subsequent fuel samples taken from the fuel filter base and the carburetor bowl confirmed the presence of water. The investigation noted that the aircraft had been parked outside, unprotected from the elements, for three days prior to the flight, during which time the region experienced heavy rainfall.
Furthermore, the investigation found that the pilot's pre-flight fuel drainage procedure was insufficient. The pilot only drained 200 ml of fuel from the filter drain, whereas the filter housing itself has a capacity of 400 ml. According to the Pilot's Operating Handbook (POH), the fuel system requires draining three separate points: two drains in the wing tanks and one at the filter. This incomplete procedure failed to identify the water contamination present in the tanks.
Findings
- Water contamination in the fuel system caused the engine failure.
- Inadequate fuel drainage procedure that did not follow the Pilot's Operating Handbook.
- Deteriorated fuel tank filler cap seals allowed moisture ingress.
- Exposure of the aircraft to rain while parked outdoors for three days.
- Pilot error regarding the omission of required drainage points.