What happened
On October 26, 2013, a Robinson R2-2 helicopter, registration F-GPKA, was conducting a scenic flight from the Torreilles ultralight airfield. The flight, which included the pilot and one passenger, proceeded normally for approximately fifteen minutes before the pilot initiated a return to the base.
During the approach, the pilot performed a tailwind leg at 85 knots at an altitude of roughly three meters, followed by a climb to execute a specific maneuver. While climbing through 200 feet at 70 knots, the pilot received a LOW RPM alarm. In an attempt to stabilize the aircraft and face the wind, the pilot turned right toward the runway threshold and initiated an autorotation. However, due to the low altitude, the pilot was unable to reach the runway. The aircraft struck a field covered in photovoltaic panels, causing the helicopter to capsize onto its left side. The pilot and passenger sustained slight injuries.
The investigation
The investigation focused on the mechanical state of the aircraft and the sequence of events during the climb. Investigators discovered that one of the two transmission belts connecting the engine to the main gearbox drive shaft had snapped, while the second belt had been displaced from its housing. Technical examinations of these belts showed no damage prior to the impact with the ground.
Video footage captured by a witness on the ground revealed that the engine was operating at 2,700 RPM during the tailwind leg. During the subsequent climb, a visible flash and a detonation were observed on both sides of the helicopter. While the engine RPM did not show significant fluctuations following this event, the cause of the detonation remained undetermined. The investigation also noted that the aircraft had undergone an annual inspection only three days prior to the accident and was within weight and balance limits.
Findings
- The aircraft was operating outside of its safe flight envelope during a low-altitude maneuver over an unsuitable environment.
- The climb maneuver placed excessive stress on both the engine and the rotor system.
- The rotor RPM decreased significantly, triggering the low RPM alarm.
- The observed detonation and flash were likely the result of excessive engine loading during the climb.
- The low altitude of the maneuver prevented the pilot from successfully executing a safe autorotation to a suitable landing site.