Primary finding
Probable cause
the pilot's failure to maintain adequate rotor rpm which resulted in a loss of control and an uncontrolled descent.
Investigator assessment
Analysis narrative
The pilot was performing a normal approach when he noticed a slight "rotor droop." The tail of the helicopter then "snapped left," the helicopter began rotating clockwise, and the LOW ROTOR RPM warning activated. The pilot said he pushed the cyclic forward and applied "up collective" in an attempt to slow the descent rate. He said he was unable to apply further forward cyclic input due to other aircraft operating in the vicinity. The helicopter impacted the ramp in an upright attitude collapsing the right skid further than the left The tail rotor struck the ground and the tail boom cracked.
Source record
Factual narrative
On June 26, 2005, at 0842 mountain daylight time, a Schweizer 269C, N308BP, operated by Rotors of the Rockies, was substantially damaged when it struck terrain during landing at Jefferson County Airport (BJC), Broomfield, Colorado. Visual meteorological conditions prevailed at the time of the accident. The local aerial photography flight was being conducted under the provisions of 14 CFR Part 91 without a flight plan. The pilot and passenger were not injured. The flight originated at Broomfield, Colorado, approximately 0700 mountain daylight time. During a telephone interview, the pilot said that he was performing a normal approach when he noticed a slight "rotor droop." The helicopter was descending below the rooftop of a nearby hangar at the time the control was lost. The tail of the helicopter then "snapped left" and the helicopter began rotating clockwise. Shortly thereafter, approximately 10 feet AGL, the LOW ROTOR RPM warning activated. The pilot said he pushed the cyclic forward and applied "up collective" in an attempt to slow the descent rate. He said he was unable to apply further forward cyclic input due to other aircraft operating in the vicinity. According to the pilot, the helicopter impacted the ramp in an upright attitude collapsing the skids. The tail rotor struck the ground and the tail boom cracked. The winds at BJC 5 minutes before the accident were reported as 120 degrees at 4 knots.