What happened
On December 6, 2006, a Bell 204B helicopter, registration OB-1835-P, operated by Servicios Aéreos de Los Andes S.A.C., was performing a transport flight for employees of the Camisea gas pipeline project. The flight was scheduled from the PS Nº 03 pumping station to Ayacucho.
During the takeoff sequence from the PS Nº 03 helipad, the pilot performed a vertical takeoff and maintained a hover at approximately 10 feet. As the aircraft transitioned to a higher altitude of 20 feet and moved laterally, the tail boom extended beyond the edge of the helipad platform. At this moment, the helicopter began an uncontrolled rightward rotation accompanied by lateral drift. As the rotation speed increased, the pilot was forced to execute an emergency landing in a nearby cornfield. The impact caused the main rotor blades to strike the terrain, leading to further damage when the fuselage struck a rock, rupturing the fuel tank.
There were 8 passengers and 1 pilot on board; all survived the impact, though the pilot sustained various contusions.
The investigation
The CIAA investigation examined the aircraft's maintenance records, the flight's weight and balance, and the environmental conditions at the time of the accident. Investigators analyzed the mechanical state of the engine, rotors, and fuel, finding the fuel quality to be satisfactory. The investigation also reviewed the operational procedures at the remote pumping station helipads and the pilot's response to the emergency.
Findings
- Loss of tail rotor effectiveness caused by gusty winds of moderate intensity, which disrupted the airflow over the tail rotor.
- The presence of obstacles at the PS Nº 03 helipad, which necessitated taking off with a tailwind.
- Inadequate meteorological monitoring at the remote pumping stations to alert pilots to unstable atmospheric conditions.
- A lack of specific performance charts for the aircraft's specific engine configuration.
- Deficiencies in the pilot's reaction to the sudden rotation during the transition from ground effect to out-of-ground effect flight.