Breckenridge, CO, USA
N38AZ
BELL HELICOPTER TEXTRON 206L-1
The helicopter was conducting external load operations at an estimated density altitude of 14,000 to 14,500 feet. While manuvering to the landing zone, the helicopter began to lose tail rotor effectiveness. The commercial pilot was unable to regain control of the helicopter prior to impacting sloping terrain. Substantial damaged was sustained to the helicopter's fuselage and the pilot was seriously injured. Using an estimate total gross weigh of 3,600 pounds (3,000 pounds for the helicopter plus internal load and 600 pounds for the external load), the helicopter would have been operating in the Area B section of the Out of Ground Effect (OGE) Hover Ceiling chart and is subject to the Critical Relative Wind Azimuth chart that lists a wind avoid area between 050-210°. This density altitude combined with the helicopter's weight placed the helicopter's performance in the "Critical Wind Azimuth Area." Convective activity in the area of the accident would have produced varying wind directions with gusts up to 30 knots.
On July 2, 2009, approximately 1515 mountain daylight time, a Bell 206L-1, N38AZ, owned and operated by Mile High Helicopters Incorporated, was substantially damaged after a hard landing near Breckenridge, Colorado. The rotorcraft external load flight operated under the provisions of Title 14 Code of Federal Regulations Part 133 without a flight plan. Visual meteorological conditions prevailed. The commercial pilot sustained serious injuries and one person on the ground sustained minor injuries. The flight was conducting local external load operations. According to a statement from the helicopter's operator, the helicopter was expecting to move an external load of 300 pounds slung by a 50 foot synthetic cable with a remote hook attachment to the cargo hook. Release functions were verified prior to the flight. The helicopter moved the external load to a landing zone at a higher elevation. The pilot reported making a shallow approach to the upper landing zone when the helicopter began an uncommanded rotation to the right. The pilot applied full left anti-torque pedal and released the external load. The helicopter was not recovered prior to landing hard on a sloping boulder field. The helicopter rolled before coming to rest on its right side. During the roll-over, one person on the ground was injured. The accident site was located at 12,925 feet mean sea level. The tailrotor section was found damaged and there was evidence of rotation throughout the tailrotor drive shaft. Substantial damage was sustained to the left, right, and aft sides of the fuselage. While recovering the wreckage by K-Max helicopter, the external load was estimated to weigh approximately 600 pounds (300 pounds more than expected by the pilot). A meteorological study was conducted of the mishap area to determine winds, temperature and density altitude. At the time of the accident, convective echoes were in the immediate vicinity southwest and north, which were capable of producing gusting winds to 30 knots. The density altitude based on temperatures of 50 to 52 degrees F, relatively humidity of 50 percent, produced density altitudes between 14,500 and 14,700 feet. The helicopter was equipped with a Rolls-Royce 250-C30P engine. According to technical manuals "[t]his upgrade will provide 206L3 performance for 206L1 helicopters." All calculations utilized the Bell 206L3 performance charts. Using an estimate total gross weigh of 3,600 pounds (3,000 pounds for the helicopter plus internal load and 600 pounds for the external load), the helicopter would have been operating in the Area B section of the Out of Ground Effect (OGE) Hover Ceiling chart and is subject to the Critical Relative Wind Azimuth chart that lists a wind avoid area between 050-210°. The manual states that "tail rotor control margin...may preclude operation in Area B of the hover ceiling charts when the relative wind is in the CRITICAL WIND AZIMUTH AREA". With the environmental conditions at the time of the accident, the Area B portion of the OGE Hover Ceiling chart is applicable down to a gross weight of 3,300 lbs. Of note, the helicopter would have still been operating in "Area B" of the performance chart with the 300 pound external load.
The pilot's failure to maintain directional control while maneuvering due to a loss of tail rotor effectiveness. Contributing to the accident was the pilot's failure to monitor wind direction while operating in the "Critical Wind Azimuth Area."
Source: NTSB Aviation Accident Database
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