Bell 206 N272M accident near High Island A-442A

Probable cause

A total loss of engine power due to maintenance personnel's failure to correctly torque the Pc line following removal and reinstallation of the turbine module.

NTSB analysis

The helicopter had landed on an off-shore oil platform and was refueled. It then took off with one passenger. Shortly after lifting off, the pilot "heard a loud pop as the nose of the aircraft passed over the edge of the helideck. The noise was simultaneously accompanied by illumination of the engine out warning light and a needle split indication was observed on the engine and rotor tachometer gauge. As the aircraft yawed and lost climb performance, the pilot lowered the collective pitch full down and activated the floats. Upon landing on the water, the aircraft rolled left until inverted. The helicopter was later recovered and the engine disassembled and examined. The only anomaly noted was a loose Pc line, which would cause a loss of fuel flow and subsequent loss of engine power down to or below idle. It was determined that the torque required to realign the B-nut would be between hand-tight and 27 inch-pounds. The required torque is 80 to 120 inch-pounds. Torque values on the other air line fittings between the power turbine governor and the fuel control were found to range from 55 to 85 inch-pounds. A review of the engine maintenance records revealed that 36.7 hours prior to the accident, the turbine module was completely disassembled and overhauled. This would have required the removal and re-installation of the Pc line.

Text from the NTSB. Open the NTSB docket for CEN10LA036 for the full record.