NTSB Identification: FTW98FA068.
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Nonscheduled 14 CFR
Accident occurred Sunday, December 14, 1997 in LITTLETON, CO
Probable Cause Approval Date: 08/20/1999
Aircraft: Bell 407, registration: N771AL
Injuries: 4 Fatal.
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.
On takeoff from an automobile accident site, with the patient on board, the air ambulance flight made a climbing right turn and flew into power lines. Witness marks on the helicopter provided evidence the helicopter struck the transmission line from below and impacted the ground in an inverted attitude below and to the west of the lines. Light conditions were a dark night with emergency response, construction, and emergency response vehicle lights illuminating the landing site area. The existence of the power lines was unknown to the fire rescue on-scene commander and the light conditions prevented the pilot from seeing anything outside the lighted area. The unmarked power lines were 622 feet apart and oriented northeast/southwest. The southern tower was 106 feet high and the northern tower 83.5 feet high. The towers and lines did not meet obstruction-marking criteria and were not marked. In addition, they were not depicted on sectional or topographic maps. Company policy, promulgated through documents and training, provided landing zone departure procedures which instructed the pilot to climb straight ahead in a near vertical climb to a minimum of 300 feet agl before turning. The horizontal distance from the helicopter's takeoff position to the power line was approximately 630 feet based on global positioning system (GPS) measurement.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's inability to maintain adequate visual lookout due to the lighting conditions and his failure to follow company procedures for departure from a landing zone. Factors were dark night conditions, bright lights in the landing zone which prevented vision beyond the zone, and the power line existence was not available on charts to either the pilot or ground personnel. Full narrative available
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