NTSB Identification: LAX02FA116.
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Accident occurred Tuesday, March 26, 2002 in Lakehead, CA
Probable Cause Approval Date: 09/01/2004
Aircraft: Sikorsky S-61A, registration: N318Y
Injuries: 1 Fatal,1 Serious.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The twin-engine helicopter impacted trees and terrain following a likely loss of power in the left engine while maneuvering. According to one witness, as the helicopter overflew his position, he observed the main rotor blades rotating very slowly to the point where they were coning and each blade could be viewed individually. This witness observed a tan smoke emanating from the transmission area. The helicopter then "fell like a rock," and impacted the ground. The witness indicated he heard the engines surging when he reached the accident site. Another witness did not hear any engine noise as the helicopter passed overhead. A post crash fire consumed the cabin, main transmission case, and, heavily damaged both engines. A post-accident examination of the helicopter revealed the main rotor and tail rotor blades sustained little to no leading edge damage though the helicopter fell through 150-foot pine trees. The number 1 engine displayed no rotational damage to its internal components. The number 2 engine sustained heat and tip rub damage to the 1st and 2nd stage gas turbine blades in a manner that suggested the damage occurred while the rotors were rotating. Numerous components from each engine were completely destroyed by the post-accident fire and could not be examined. The main rotor transmission case was nearly burned away. The exposed transmission gears displayed no signs of pre-existing anomalies; however, complete continuity of the transmission could not be established due to thermal damage. The number 1 and number 2 input free wheeling units were examined and displayed no signs of improper operation. The cockpit sustained severe fire damage; however, the left side triple tachometer and both left and right side torque indicators were examined. The torque indicators both displayed the number 1 engine torque at 13 percent, while the number 2 engine torque indication was only available on the left torque indicator, which displayed a number 2 engine torque reading of 140 percent.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A loss of engine power for undetermined reasons, and the flight crew's failure to maintain rotor rpm following a loss of engine power while maneuvering. Full narrative available
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