What happened
On November 9, 2003, a Kazan Mi-8T helicopter, registration OB-1645, was performing a cargo and passenger transport flight from Pucallpa to the Taipiche camp in the Loreto region of Peru. The flight, operated by Helica del Oriente S.A., was carrying 10 passengers and a significant amount of cargo.
Upon arriving at the destination, the pilot identified that the primary approach path had a tailwind component and opted to use an alternative landing site. This site was a confined area surrounded by trees ranging from 40 to 50 meters in height. To navigate the confined space, the pilot initiated a high-performance approach. During the descent, the flight engineer warned that the tail rotor would likely strike the treetops. In response, the pilot reduced airspeed and increased the rate of descent.
As the aircraft reached approximately 25 meters of altitude, the pilot increased collective power to attempt a hover out of ground effect (HOGE). However, the aircraft was unable to stabilize, and the main rotor RPM dropped below operational limits. The helicopter descended into the terrain, where the main landing gear struck a log. This caused the aircraft to pivot, catching the nose gear on surface roots, which subsequently tore the nose gear from its mounts and caused damage to the right fuel tank and autopilot control block.
The investigation
The CIAA investigation focused on the aircraft's weight, performance calculations, and crew procedures. Investigators found that the crew had not weighed the cargo or passengers on a scale, relying instead on estimates. While the crew calculated a takeoff weight of 11,630 kg, the actual weight was determined to be 11,986 kg.
Furthermore, the investigation established that the crew failed to perform necessary performance calculations for both the takeoff from Pucallpa and the high-performance landing at the remote site. The investigation also noted that the crew did not submit a cargo and passenger manifest to CORPAC Pucallpa and failed to follow standard Crew Resource Management (CRM) procedures.
Findings
- The primary cause of the accident was an unstable approach during a high-performance landing at a confined remote helipad while the aircraft was in an overweight condition (exceeding performance tables by 692 kg).
- A lack of effective CRM prevented the crew from implementing timely corrections, leading the aircraft into a power settling (vortex ring state) phenomenon.
- The crew failed to plan the flight accurately, using estimated rather than verified weights and failing to calculate performance requirements.
- The landing site was a contributing factor, characterized by a confined area, unpaved and damp surface, and the presence of logs and roots.