Vernal, UT, USA
N265SH
Bell 206L
Prior to takeoff in conditions that resulted in a density altitude of over 10,000 feet, the pilot figured his takeoff/hover performance using the Hover Ceiling In Ground Effect chart, which indicated the helicopter could safely depart the landing zone (LZ). Because he was taking off over uneven, sloping, brush-covered terrain, he should have used the Hover Ceiling Out of Ground Effect chart, which indicated the helicopter did not have the performance to safely depart the LZ. After liftoff, the pilot started moving the aircraft forward, but it could not out-climb the up-sloping terrain, so he elected to make a precautionary landing on a nearby road. During the landing attempt, the helicopter's tail rotor lost its effectiveness, and the aircraft spun around once and descended into the terrain.
On June 15, 2006, approximately 1715, mountain daylight time, a Bell 206L, N265SH, impacted the terrain during a precautionary landing almost immediately after taking off from a remote landing zone (LZ) about 60 miles southeast of Vernal, Utah. The commercial pilot and his five passengers received minor injuries, and the helicopter, which is owned and operated by Silver State Helicopters, of North Las Vegas, Nevada, sustained substantial damage. No flight plan had been filed for the 14 CFR Part 135 passenger repositioning flight. The flight was being operated in visual meteorological conditions. According to the pilot, he had been using the same LZ for four or five days, and had been taking off into an upslope, because that allowed him to depart into a headwind. On the day of the accident, the wind was calm, but the pilot chose to takeoff in the same direction as he had on the previous days (into the upslope). The pilot lifted off into a hover, and then started moving forward toward the up-sloping terrain. In order to clear the brush growing on the up-sloping terrain, soon after starting to move forward, he increased power and applied a small amount of right anti-torque pedal in order to direct more lift to the main rotor blades. When he applied the right anti-torque pedal, the helicopter's heading rotated about 45 degrees to the right, but it did not climb any higher. Because he could see that he might not have the power to out-climb the up-sloping terrain, the pilot elected to try to put the helicopter down on a nearby road about 100 feet away. Just about the time he got to the road, the pilot heard a noise, and the helicopter spun rapidly to the right. Then the nose of the helicopter dropped, and the airframe impacted the terrain in a nose-down attitude, and then rolled onto its side. At the time of the accident, the helicopter was being operated at an altitude of 7,500 feet mean sea level (MSL) and an ambient temperature of 75 degrees Fahrenheit (approximate density altitude of 10,200 feet). According to the pilot's calculations, the weight of the aircraft at the time of the accident was 4,100 pounds, which is 50 pounds below its certified maximum gross internal operating weight. During the post-accident investigation, the FAA Inspector who interviewed the pilot and the operator, determined that for his pre-takeoff calculations, the pilot had used the "Hover Ceiling In Ground Effect" chart instead of the "Hover Ceiling Out of Ground Effect" chart, that he should have used. According to the FAA inspector, the "Hover Ceiling In Ground Effect" chart, which should only be used for calculating hover over level, flat terrain, without any significant growth of brush on it, indicated that the helicopter would have the performance to safely takeoff and depart the area. But his review of the "Hover Out of Ground Effect" chart, which should have been used for the takeoff over the uneven, brush-covered, sloping terrain, indicated that the the helicopter could not safely takeoff and depart the area. An inspection of the helicopter's engine, rotor drive, and flight control system by the FAA and the engine manufacturer (Rolls-Royce/Allison) did not find any anomaly that would have lead to the sequence of events that resulted in the aircraft impacting the terrain.
The loss of tail rotor effectiveness during an attempted precationary landing after a takeoff over uneven, sloping, brush-covered terrain. Factors include the pilot using the wrong performance chart while completing his preflight performance calculations, the uneven, sloping, brush-covered terrain, and a high density altitude.
Source: NTSB Aviation Accident Database
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