What happened
On November 10, 2004, at approximately 15:40, a Robinson R-22 helicopter, registration EC-GAU, was performing a dual-instruction flight at Cuatro Vientos Airport in Madrid. While the aircraft was on the downwind leg of the traffic pattern, the crew noticed a change in engine sound accompanied by a slight rightward yaw. The instructor took control and lowered the collective to manage the situation. Although the engine briefly appeared to recover as the main rotor RPM increased, it subsequently suffered a complete failure.
To avoid nearby power lines located to the left of the flight path, the instructor initiated an autorotation toward the right. During the landing sequence, the pilot performed a sharp flare to touchdown near a perimeter fence. The force of the vertical impact caused the landing skids to deform, and the sudden maneuver caused the main rotor blades to strike the tail boom, severing the tail cone. The two crew members were able to evacuate the aircraft safely after the rotor had stopped.
The investigation
The investigation focused on the engine failure and the aircraft's fuel state. Upon inspection of the fuel system, investigators found that the fuel tank contained only unusable fuel. While the aircraft's fuel gauge indicated "empty," the "fuel low" warning light had failed to activate. Further examination of the electrical system revealed that a disconnected wire had interrupted the circuit, preventing the warning light from illuminating the cockpit.
Investigators also reviewed the day's flight logs. The aircraft had completed several flights earlier in the day. The final flight, lasting approximately 13 minutes, began with a very low fuel volume. Although the flight plan had estimated a three-hour endurance, the actual capacity of the 19.2-gallon tank allows for only slightly more than two hours of flight time.
Findings
- The primary cause of the accident was fuel exhaustion, which led to the engine failure during the landing circuit.
- The "fuel low" warning light was non-functional due to a broken electrical connection in the wiring.
- The pilot's decision to flare aggressively to avoid a perimeter fence resulted in the main rotor blades striking the tail cone.
- The flight duration and refueling logs indicated the aircraft was operating with critically low fuel levels during the final flight segment.