Bell 206B N806LA accident near Longboat Key, Florida

Probable cause

Unknown personnel's failure to comply with the engine manufacturer's engine fuel pump replacement guidance, which resulted in a total loss of engine power due to the engine fuel pump failure.

NTSB analysis

While enroute at 500 feet above ground level, the pilot experienced a total loss of engine of engine power. According to the pilot, the initial indication was a slight yaw followed by the engine out warning horn. He immediately lowered the collective and entered a power-off autorotational landing to the beach. Upon touch down, the helicopter's skids dug into the soft sand and the main rotor blades contacted the tail boom causing damage to the drive shaft cover and severing the tail rotor drive shaft. The pilot and passengers exited the helicopter as soon as the main rotor stopped. Examination of the helicopter structure and systems showed no evidence of failure or malfunction. The engine was removed from the helicopter and placed in a test cell. Attempts to start the engine were unsuccessful and the fuel put was determined to be inoperative. The fuel pump was replaced and the engine started and operated within all specifications. Examination of the engine fuel pump determined the main drive shaft splines and the internal drive gear splines were worn away to the point of no spline engagement.

This model of fuel pump was required to have spline inspections every 100 hours, and ultimately required upgrade as a result of spline wear observed on some pumps. Rolls-Royce (formerly Allison) commercial engine bulletin CEB A-1352, dated August 21, 1997, required 100-hour spline inspections with compliance within 25 hours of receipt of bulletin. Spline inspections were an interim safeguard while product improvements were developed and validated. Rolls-Royce (Allison) commercial engine bulletin CEB 1355, dated April 30, 1998 required pump upgrade with compliance no later than March 31, 1999. Upon compliance with upgrade bulletin, spline inspections mandated by CEB A-1352 were no longer required. The model number of the fuel pump installed indicated that the required upgrade had not been completed. Had the inspections and upgrade been completed, the pump would not have failed in the manner it did.

Text from the NTSB. Open the NTSB docket for ERA12LA366 for the full record.