Final Report: Space shuttle search helo crashed
Bell 407, Broadus, Texas, March 27, 2003–The NTSB said the probable cause of the 407 crash was “the partial loss of engine power due to erratic fuel flow metering to the engine resulting from the single-point failure of the PLA potentiometer in the hydro-mechanical fuel control unit.” A contributing factor was the lack of suitable terrain for a forced landing.
The crew of the 407 was part of an interagency mission to find and recover debris from space shuttle Columbia when the helicopter lost power and fell into a forest. The pilot and one crewmember were killed and three other crewmembers were seriously injured.
After investigators discovered anomalies with the actual position of the throttle position lever angle (PLA) and the readings from the electronic control unit the NTSB issued four safety recommendations (A-03-18 through -21) to the FAA that addressed the PLA potentiometer deficiencies. The PLA potentiometer was found to be faulty due to insulation breakdown between the rotor and shaft for undetermined reasons.