Hughes 369 N28MP accident near Childress, Texas

Probable cause

The improper maintenance of the helicopter fuel system that resulted in erroneous fuel gauge indications and the pilot’s inadequate fuel management, both of which resulted in fuel exhaustion during a long-line hover. Also causal was the lack of company procedures to ensure adequate maintenance and fuel planning.

NTSB analysis

The helicopter was in a hover about 120-150 feet above the ground while a utility worker performing a long-line operation worked on a transmission tower. After the loss of power, the helicopter spun and descended during which the worker was pulled off the tower by the attached long line. The pilot performed an autorotation that resulted in a hard landing. The pilot sustained serious injuries and the worker sustained fatal injuries.

Postaccident examination of the helicopter revealed no usable fuel on board, and fuel quantities between the fuel tank and engine were consistent with fuel exhaustion. The examination revealed that the electrical wire to the start pump was not secured, which allowed for the possibility of it interfering with the fuel quantity transmitter float mechanism, thus providing erroneous cockpit fuel quantity indications to the pilot. The examination also revealed that the low fuel quantity annunciator was inoperative due to separation of the fuel quantity transmitter's low-level fuel whisker.

Recent maintenance of the helicopter's fuel system by the operator's maintenance personnel included the replacement of the start pump and testing of the low-level fuel light by electrically grounding the top of the fuel quantity transmitter using safety wire. A vacuum check of the fuel system was not performed after the fuel system had been opened. The method for testing the low-level fuel light and the lack of a vacuum check were not in accordance with the maintenance manual and the helicopter manufacturer's service bulletin relating to the start pump installation. Postaccident examination of the helicopter also revealed a nonstandard installation of an engine mounted fuel filter petcock drain valve.

No written company procedures and/or fueling records were available that required pilots to track fuel loading and time-based fuel consumption in order to determine time remaining for flights and their termination. The pilot stated that he would have the helicopter refueled when the fuel gauge indicated about 100 lbs. However, had the operator and/or pilot calculated the flight time remaining based on known fuel quantities that were independent of fuel gauge indications, then any fuel gauge inaccuracies would be have become apparent.

Text from the NTSB. Open the NTSB docket for CEN13FA075 for the full record.