What happened
On October 31, 2023, a Robinson R44 II helicopter, registration F-HLOU, crashed in the Salazie region of La Réunion during a non-commercial sightseeing flight. The aircraft was carrying the pilot and three passengers.
Following an initial local flight, the pilot refueled the aircraft using a drum. During the second flight of the day, the pilot navigated the mountainous terrain, flying at altitudes between 3,000 and 3,600 feet. As the helicopter approached a mountain pass, the pilot radioed a warning of turbulence, followed by two "PAN PAN" emergency calls. Witnesses in a nearby aircraft observed the helicopter's main rotor speed decreasing and saw the aircraft enter a sudden, near-vertical descent, striking the mountainside and sliding down the slope.
The investigation
The BEA examined the wreckage at the crash site and performed detailed analyses of the engine and fuel system. Investigators found no mechanical anomalies in the engine, gearbox, or flight controls that would indicate a primary mechanical failure. However, the investigation focused on the refueling process and the pilot's actions following the rotor speed warning.
Analysis of the fuel samples from the wreckage and the refueling drum revealed high levels of dissolved water in the fuel. Furthermore, the investigation established that the pilot had not performed the required fuel tank draining procedure after refueling, which is a standard safety practice to check for water contamination.
Findings
- The pilot was flying at a low altitude over steep, densely vegetated terrain, which left almost no margin for error or time to react to an emergency.
- The pilot likely failed to take immediate, appropriate actions—such as lowering the collective pitch to initiate autorotation—following the drop in rotor speed.
- The pilot's failure to drain the fuel tanks after refueling prevented the detection of fuel contaminated with water.
- The ingestion of water-contaminated fuel likely caused an engine power loss or an in-flight shutdown, potentially triggered by the turbulence encountered near the terrain.