What happened
On December 15, 2005, a Bell 412 SP, registration PT-HUV, operated by Aeróleo Táxi Aéreo, departed Macaé, Brazil, for a personnel transport flight to the P-32 offshore platform. The aircraft was carrying two pilots and seven passengers.
Approximately 20 minutes into the flight, while cruising at 2,500 feet, the crew observed the "MASTER CAUTION" and "XMSN OIL PRESS" lights, with the main gearbox oil pressure gauge indicating zero. The pilots immediately initiated a descent to 500 feet and turned toward the coastline to prepare for an emergency landing. During the descent, a loud bang was heard in the cabin. Realizing a water landing was necessary, the crew deployed the emergency floats. The helicopter struck the water, and the occupants successfully evacuated using life rafts. The aircraft sustained severe damage and was a total loss.
Of the nine occupants, four were uninjured, two sustained minor injuries, and three suffered serious injuries.
The investigation
CENIPA investigators identified a hole in a return line (part number 412-0able-040-204-101) caused by friction between the tubing and the helicopter's airframe. Post-accident testing revealed that the oil leakage rate was approximately eight liters per minute. Given the reservoir capacity of 10.3 liters, the entire oil supply was depleted in roughly 77 seconds.
Because the failure occurred in the return line, the investigation found that pressure, temperature, and chip detector indications were delayed, as there was insufficient fluid to transport metal particles to the detectors. Furthermore, the investigation noted that the engines and main rotor had become disconnected during the descent, which caused a heavy impact with the water during the flare.
Findings
- Maintenance and Supervision: A recent Phase 3 inspection, conducted only 18 flight hours prior to the accident, failed to detect the wear on the tubing caused by friction.
- Design: The manufacturer's checklist for low oil pressure recommended landing "as soon as possible" rather than "immediately," a procedure that contributed to the severity of the event.
- Equipment: The Cockpit Voice Recorder (CVR) was found to be inoperable, and the investigation noted that the crew's method of testing the CVR was insufficient to ensure a proper diagnostic.
Safety action
Following the investigation, several safety recommendations were issued:
- ANAC directed Bell operators to inspect main gearbox lubrication lines and instructed maintenance sectors to enhance inspection rigor.
- CENIPA recommended that Bell Corp. modify emergency procedures for low oil pressure to mandate an immediate landing.
- Operators were advised to ensure pilots are aware that Bell-series transmissions are not certified for flight without lubrication.