NTSB Identification: SEA03LA021.
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Accident occurred Tuesday, December 24, 2002 in Boise, ID
Probable Cause Approval Date: 11/25/2003
Aircraft: Hughes 369D, registration: N8366F
Injuries: 2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The commercial pilot, who had 900 hours PIC flight time in the make/model, and an FAA check pilot, who had 40 hours PIC flight time in the make/model, departed on a Part 135 check flight in the McDonnell Douglas (Hughes) 369D rotorcraft. After returning to the Boise airport, the commercial pilot (examinee in the left seat) transferred control of the aircraft to the check pilot (right seat) who then demonstrated a simulated 180-degree autorotation. After the check pilot rolled off power, the GEN OUT caution light illuminated followed by the ENG OUT warning light. The check pilot noted rotor RPM in the green but decelerating engine RPM, and the commercial pilot reported that he felt the check pilot's flare was premature. The rotorcraft landed hard during which time the main rotor blades flexed down impacting and severing the tailboom. Post-crash examination revealed that the left and right seat throttle/collective controls to the engine fuel control unit had been misrigged, and a test run of the engine confirmed a flameout condition when the right seat throttle was retarded to the idle position. A review of the rotorcraft's maintenance log showed that the right seat controls had been installed two days previous and signed off as "all rigging found to be within limits." The McDonnell Douglas MD500D Rotorcraft Flight Manual discusses throttle rigging in the Normal Procedures Section noting that a throttle rigging check must be performed prior to autorotation training, and the check must be performed on both left and right seat throttle controls if dual controls are installed. The Rotorcraft Flight Manual also provided a warning that "Misrigging of the throttle control may result in inadvertent flameout during rapid closing of the twistgrip to the ground idle position."
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The failure of the operator's maintenance personnel to properly rig the left/right seat twistgrip throttles to the engine fuel control, the pilot in command's failure to adhere to the rotorcraft flight manual, and the check pilot's premature flare during the autorotation resulting in a hard landing. Full narrative available
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