What happened
On June 19, 2007, a Cessna C-337-G (registration EC-HMC) was conducting a private demonstration flight near Moixent, Valencia. The aircraft was operating with its landing gear extended due to a known mechanical issue with a retraction door.
Approximately 20 minutes into the flight, the pilot observed fluctuations in the fuel flow indicator for the rear engine. In an attempt to stabilize the fuel supply, the pilot activated the auxiliary electric fuel pump, first in the 'LO' position and then in the 'HI' position. This action caused an excessive fuel-air mixture, leading to a loss of power and a decrease in RPM in the rear engine.
Because the pilot did not feather the propeller, the engine continued to windmill, creating significant drag. Combined with the extended landing gear, the aircraft could not maintain altitude. The pilot attempted to return to the departure airfield but was forced to execute an emergency landing in a nearby field. The aircraft struck trees on a slope before hitting the ground, at which point a fire broke to life. While the pilot and one passenger escaped, a second passenger died due to the post-impact fire.
The investigation
The CIAIAC investigation focused on the pilot's management of the fuel flow fluctuations and the subsequent engine failure. The investigation established that the aircraft was airworthy and that the pilot held valid commercial licenses, though his specific experience with the Cessna C-337-G was very limited, consisting of only theoretical instruction without flight training in the type.
Investigators examined the fuel system and determined that the primary issue was likely a faulty fuel flow indicator rather than an actual fuel starvation event. The investigation also reviewed the Pilot's Operating Handbook (POH), noting that the pilot failed to follow established emergency procedures for an engine failure, specifically the requirements to feather the propeller and secure the engine by disconnecting the ignition switches.
Findings
- The pilot incorrectly managed the fuel flow fluctuations by activating the auxiliary pump to the 'HI' position, which caused the engine to fail due to an overly rich mixture.
- The incorrect application of in-flight engine failure emergency procedures was the primary cause of the accident.
- The pilot failed to feather the propeller or secure the engine, which, when combined with the extended landing gear, created excessive drag and prevented the aircraft from maintaining altitude.
- The pilot's lack of practical experience and training in the specific aircraft type contributed to the improper response to the mechanical anomaly.
- The aircraft's landing gear was extended due to a known mechanical fault, which increased aerodynamic resistance during the emergency.