PIOCHE, NV, USA
N946L
Bell 206L-3
The pilot was approaching a narrow ridge. About 25 feet agl, he ran out of left pedal and the helicopter began an uncommanded right turn. The pilot reported that he attempted to gain altitude in order to remain on the ridge. He then entered an autorotation and the aircraft impacted the ground in a level attitude and rolled onto its left side. Review of the maintenance records revealed that on October 30, 1998, the maintenance facility had removed the tail rotor hub and blade assembly from the accident aircraft, and replaced it with the tail rotor hub and blade assembly from a Bell 206L-1. This was the first flight since the replacement. The Director of Maintenance reported that the maintenance technician did not perform a rigging check after installing the new assembly because he assumed that the same assembly did not require a check. According to the maintenance records, the tail rotor pitch links that were installed on the accident aircraft were Part Number 206-010-795-101. The maintenance manual states that the pitch links for a Bell 206L-3 should be Part Number 206-010-795-105. According to a representative from Bell Helicopter Textron, all the parts from the tail rotor hub and blade assembly are compatible from the Bell 206L-1 to the Bell 206L-3, except for the tail rotor pitch links. He further stated that the tail rotor pitch links on the Bell 206L-1 are smaller than those from the Bell 206L-3, and would give the pilot less tail rotor authority.
On November 3, 1998, at 0930 hours Pacific standard time, a Bell 206L-3, N946L, impacted the ground and rolled over on a mountain peak approximately 8 miles west of Pioche, Nevada. The helicopter sustained substantial damage. The commercial pilot received minor injuries and the two passengers were not injured. The helicopter was operated by Sundance Helicopters of Las Vegas, Nevada, under 14 CFR Part 135 of the Federal Aviation Regulations. The flight was contracted by Cubic Defense Systems of San Diego, California, who holds a government work contract with the United States Air Force for range instrumentation installation and maintenance. The flight originated at 0900 at Caliente, Nevada, and was to transport the crew to work on electrical equipment on the mountain peak. Visual meteorological conditions prevailed and a VFR company flight plan was filed. The pilot reported that he was approaching a ridge above a dirt road, which was oriented to the southwest approximately 9,300 feet msl. He stated that the ridge was very narrow, with sharp dropoffs on either side. He also stated that the winds were calm. The pilot reported that about 25 feet agl, he ran out of left pedal and the helicopter began an uncommanded right turn. He decreased power in an attempt to stop the turn and to regain airspeed. The pilot reported that he was unable to regain directional control before the aircraft had turned approximately 180 degrees. He then increased power, which increased his rate of turn, and attempted to gain altitude in order to remain on the ridge. At that time, the pilot reduced the throttle, entered an autorotation, and crashed on the top of the ridge. The aircraft impacted the ground in a level attitude and rolled onto its left side. The pilot stated that the helicopter had completed approximately three 360-degree right turns before impacting the ground. The maintenance records and daily flight logs were reviewed. On October 30, 1998, the accident aircraft was inspected in accordance with a 100-hour inspection, during which time the mechanic noticed an excessive vibration in the tail rotor pedals that had not been previously reported. The records indicate that the mechanics then removed the tail rotor hub and blade assembly from the accident aircraft and replaced it with a tail rotor hub and blade assembly from a Bell 206L-1. The work was signed off and the aircraft was not flown until the accident flight. The maintenance records revealed that the tail rotor pitch links that were installed onto the accident helicopter were Part Number 206-010-795-101. According to the manual, the correct part number for the pitch links for the Bell 206L-3 is Part Number 206-010-795-105. The Director of Maintenance reported that the maintenance technician did not perform a rigging check after installing the tail rotor and hub assembly because he assumed that the same assembly would not require a check. He stated that this error occurred "by not following the [maintenance] manual and by not having an adequate inspection system in place." According to a representative from Bell Helicopter Textron, all parts for the tail rotor hub and blade assembly are compatible from the Bell 206L-1 to the Bell 206L-3, except the tail rotor pitch links. He further reported that the pitch links for the Bell 206L-1are smaller and would give the pilot less tail rotor authority.
The loss of tail rotor effectiveness, due to the installation of incorrect pitch links by the maintenance facility. A factor in the accident was the lack of an adequate quality assurance program in the maintenance facility.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
