Cody, WY, USA
C-GNSR
Agusta A119
The pilot said he was landing on top of an 11,900-foot mountain to allow his passengers to "stretch their legs." The approach was "normal" into a headwind of less than 10 knots. Indicated airspeed was 45 knots and main rotor rpm was 70 percent. The low rotor rpm warning horn sounded and he lowered the collective in an attempt to regain rotor rpm. As the helicopter descended from approximately 50 feet, he increased the collective to cushion the landing. The helicopter hit the mountain, spreading and fracturing both forward and aft skids. The engine was later functionally tested. Minor NF (power turbine speed) and NG (compressor turbine, or gas generator, speed) instability in MEC (mechanical mode) and EEC (engine electronic control) modes were noted. According to the engine manufacturer, this would point to the pressure regulator in the fuel control unit (FCU). Engine behavior and power response (slow and rapid acceleration and deceleration inputs) to CLP (collective pitch) inputs were within acceptable limits. The BOV (bleed off valve) closing point was also within limits. The FCU was tested and revealed indications of wear in the pressure regulator, which was reflected in the NF and NG instability. Analysis indicated that this instability would not have been detected by the pilot and would not have prevented the engine from achieving full rated power. According to the nearest weather reporting facility (elevation 5,102 feet msl) AWOS (Automated Weather Observation Station) 1255 observation, the temperature was 8 degrees Celsius (C.), and the altimeter setting was 30.12 inches of Mercury (Hg). The density altitude at the weather facility was computed to be 5,222 feet msl, and the estimated density altitude at the accident site was approximately 13,000 feet msl.
On November 6, 2007, approximately 1315 mountain standard time, an Agusta A119, Canadian registry C-GNSR, registered to and operated by Coordinates Capital Corporation of St, Johns, Newfoundland, and piloted by a commercial pilot, was substantially damaged during a hard landing on top of a mountain approximately 40 miles west of Cody (COD), Wyoming. Visual meteorological conditions (VMC) prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The pilot and two passengers were not injured, but one passenger sustained serious injuries. The cross-country flight originated approximately 1200 from Helena (HLN), Montana, and was en route to Riverton (RIV), Wyoming, and then to Colorado Springs (COS), Colorado. According to the pilot's accident report, he was landing on top of Ptarmigan Mountain (44 degrees, 21.315' north latitude, and 109 degrees, 35.371' west longitude, 11,900 feet msl) to allow his passengers to "stretch their legs." He said the approach was "normal" into a headwind of less than 10 knots. Indicated airspeed was 45 knots and main rotor rpm was 70 per cent. Suddenly, the low rotor rpm warning horn sounded, and he lowered the collective control in an attempt to regain rotor rpm. As the helicopter descended from approximately 50 feet agl (above ground level), he raised the collective control to cushion the touch down. The helicopter hit the ground hard, spreading and fracturing both forward and aft skids. One passenger sustained a compression fracture of the lumbar spine. On January 15, 2008, the engine was functionally tested at Pratt & Whitney Canada (P&WC), Montreal, under the supervision of the Transportation Safety Board (TSB) of Canada on behalf of NTSB. The test revealed some minor NF (power turbine speed) and NG (compressor turbine or gas generator, speed) instability in MEC (mechanical mode) and EEC (engine electronic control) modes. According to P&WC, suspicion was with the pressure regulator in the fuel control unit (FCU). Engine behavior and power response (slow and rapid acceleration and deceleration inputs) to CLP (collective pitch) inputs were within acceptable limits. The bleed off valve (BOV) was also within limits. On behalf of NTSB, the FCU was examined by Honeywell in Montreal under the supervision of TSB. The tests bore indications of wear in the pressure regulator, which was reflected in the NF and NG instability. Honeywell said this instability would not have been detected by the pilot, and would not have prevented the engine from achieving full rated power. According to the COD (elevation 5,102 feet msl) AWOS (Automated Weather Observation Station) 1255 observation, the temperature was 8 degrees Celsius (C.), and the altimeter setting was 30.12 inches of Mercury (Hg). The density altitude at COD was computed to be 5,222 feet msl, and the estimated density altitude at the accident site was approximately 13,000 feet msl.
A loss of engine power while on approach for undetermined reasons. Contributing to this accident was the high density altitude.
Source: NTSB Aviation Accident Database
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