What happened
On October 21, 1998, a BO-105 helicopter, registration PT-HXI, operated by Helivia Aero Táxi Ltda., was performing a passenger transport flight from Base ECUB in Guamaré, RN, to the Petrobras PA-26 platform. The aircraft was carrying one crew member and five passengers.
While cruising at 1,500 ft, approximately 10 nautical miles from the platform, the number 2 engine suffered an explosion, causing a sharp lateral yaw and triggering the engine failure alarm. The pilot initiated a left turn toward the coastline to approach the shore. During this maneuver, the aircraft lost 500 ft of altitude. Although the pilot momentarily leveled the aircraft at 1,000 ft, the helicopter continued to descend at an average rate of 100 ft/min.
Upon reaching 400 ft, the pilot executed an emergency water landing. The crew successfully deployed the floats, and the aircraft ditched in the sea. All six occupants were rescued unharmed by a passing boat 40 minutes later. However, the aircraft subsequently sank and was considered unrecoverable.
The investigation
The CENIPA investigation focused on the engine failure and the aircraft's performance during the single-engine emergency. Investigators examined the aircraft's weight and balance, maintenance records, and the pilot's flight parameters.
While the engine was recovered from the sea, investigators were unable to perform a definitive technical analysis of the failure. The engine had been stored improperly after recovery, and because seawater was not fully removed before crating, severe oxidation occurred, preventing a conclusive finding on the material cause of the engine failure.
Findings
- Inadequate airspeed: The pilot maintained a speed of 45 kt during the single-engine flight, whereas the manufacturer's manual recommended 60 kt for the aircraft's weight. This resulted in a loss of performance and a descent rate that prevented the aircraft from maintaining altitude.
- Operational weight: The aircraft departed with 2,470 kg, which was very close to its maximum takeoff weight of 2,500 kg. Although within limits, the high weight reduced the aircraft's performance margins.
- Failure to follow company procedures: The operator had a verbal policy instructing that the first flight of the day should carry a maximum of three passengers to ensure a safer weight margin; however, the pilot chose to depart with five passengers.
- Lack of supervision: The company lacked effective mechanisms to monitor and enforce its own weight-related operational instructions.
- Failure to attempt restart: Despite there being no immediate signs of fire or conditions precluding an engine restart, the pilot did not attempt to restart the engine for approximately seven minutes following the failure.