What happened
On June 27, 2007, at approximately 19:55 local time, a PIPER PA-36-375, registration EC-EJY, was performing aerial spraying operations over a farm in Los Yébenes, Toledo. The aircraft was flying at a low altitude of approximately 10 meters as part of its routine work.
As the pilot completed a low pass and applied power to climb and continue the mission, the engine failed to respond, resulting in a simultaneous loss of power and altitude. Facing an ascending hill in the flight path, the pilot executed an emergency landing maneuver, turning left to attempt to pass between trees and avoid a head-on collision. During the descent, the aircraft's right wing struck a tree, causing the aircraft to veer and come to a stop on the ground. The impact caused significant damage to the airframe, including the separation of the engine from its mount and damage to the tail section. The pilot, who was wearing a safety harness, remained uninjured.
The investigation
The investigation focused on the engine's failure to respond to power increases. Physical examination of the fuel pump revealed that the diaphragm was perforated and contained debris near the rupture site. This failure caused a loss of fuel pressure to the engine.
Investigators also reviewed the aircraft's maintenance and inactivity records. The aircraft had experienced several periods of inactivity lasting several months between 2004 and 2007. While the engine and fuel pump had undergone recent overhauls, there was no documented evidence of specific preservation procedures being followed during these long periods of storage, despite manufacturer instructions recommending such actions for periods exceeding 30 days.
Findings
- The primary cause of the accident was the rupture of the fuel pump diaphragm, which prevented adequate fuel delivery to the engine when power was required.
- The most probable cause for the diaphragm failure was inadequate preservation of the engine and its components during periods of aircraft inactivity.
- The pilot's use of a safety harness contributed to the lack of injuries during the impact.