NTSB Identification: DEN90LA180.
The docket is stored on NTSB microfiche number 42632.
Accident occurred Sunday, September 02, 1990 in CANON CITY, CO
Probable Cause Approval Date: 12/14/1992
Aircraft: BELL 47G-3B1, registration: N73957
Injuries: 1 Minor.
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 HELICOPTER COLLIDED WITH POWER LINES WHILE ON A DOWNWIND TO THE HELIPAD. ACCORDING TO WITNESSES, THE HELICOPTER WAS TRAVELLING PERPENDICULAR TO AN ELECTRICAL TRANSMISSION LINE AT ABOUT 60 KNOTS WHEN IT COLLIDED WITH THE TOP OF A TWO WIRE SET AT ABOUT 30 FEET AGL. PAINT TRANSFER FROM THE T/R SKID WAS FOUND ON THE DAMAGED POWER LINE. AFTER STRIKING THE WIRE THE T/R SEPARATED AT THE GEAR BOX MOUNTING FLANGE; SMALL PIECES OF THE T/R BLADE WERE FOUND ON THE GROUND BELOW THE POINT OF INITIAL WIRE CONTACT. THE PILOT STATED THAT DURING THE DOWNWIND CLIMBING TURN AFTER TAKEOFF, AND WHILE PASSING OVER A GULLY NEAR A 6,200-FT RIDGE, HE HAD AN ENCOUNTER WITH WINDSHEAR AT 230 FEET AGL WHICH RESULTED IN LOSS OF 200 FEET AND THE SUBSEQUENT COLLISION. THE EXISTENCE OF THE REPORTED 'WINDSHEAR', OR POSSIBLE DOWNDRAFT COULD NOT BE VERIFIED.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: THE PILOT'S FAILURE TO MAINTAIN AN ADEQUATE PATTERN ALTITUDE AND THE POSSIBLE EXISTENCE OF ADVERSE WINDS DUE TO THE SURROUNDING TERRAIN.
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