History of Flight
On May 25, 2018, about 0947 Pacific daylight time, a Bell UH-1H helicopter, registration N111DR, was substantially damaged when it crashed near Olympia, Washington. The pilot and sole passenger sustained serious injuries. The flight was conducted as a Title 14 Code of Federal Regulations Part 91 maintenance test flight.
The pilot arrived at Olympia Heliport (0WN4) about 0930. After a preflight walk-around, he received a briefing from the passenger/mechanic regarding the forward flight track and balance checks to be performed. The pilot noted that the preflight inspection appeared normal. The engine started and all indications were normal at idle and at 100% rpm.
The pilot lifted off and hover-taxied with a left pedal turn to the helipad. While hovering at about 10 ft skid height, the passenger/mechanic took hover measurements for track and balance, which were within limits for forward flight. About 0945, the pilot contacted the tower for takeoff clearance and departed to the south. Shortly after, he felt a “violent right yaw” and heard a “loud squeal” about 3 to 5 seconds later, while approximately 70 ft above ground level at about 20 knots. That was his last memory until the helicopter came to rest upright in a grass field within the airport boundary.
Upon ground impact, the pilot shut down the engine, checked on the passenger/mechanic, and egressed. There was no postcrash fire.
The owner of the company observed the helicopter take off, climb to about 200 ft, begin spinning, descend, and crash. He noted that the tail rotor did not appear to be turning.
Wreckage and Impact Information
The main wreckage came to rest on flat terrain about 657 ft west of the 0WN4 heliport. The tail boom had partially separated about 4 ft aft of the engine. Drive train continuity was established from the transmission to the 90° gearbox input quill. The 90° gearbox housing/output quill assembly, tail rotor hub, and tail rotor blade assembly separated from the tail boom mounted input quill.
Bolts, washers, castellated nuts, and cotter pins connecting the tail rotor crosshead to the slider were not found on the assembly. Cotter pins securing the attach bolt castellated nuts connecting the pitch link rod end bearing to the tail rotor grips were also missing; both nuts were finger tight. Shims between the retainer plate and the pitch change links separated and were recovered about 100 ft east of the wreckage, with intact bolt holes. During the on-site investigation, an FAA airworthiness inspector found both pitch change link bolts and the tail rotor pitch change horn finger tight, with no evidence of cotter pin installation. Three days later, the company chief inspector recovered one of the two crosshead bolts; it showed thread wear damage but was described as relatively complete.
Continuity of the tail rotor control system was verified from the left seat pedals to the tail rotor gearbox through the bell crank clevis. However, the crosshead bolts and pitch change link bolts were installed but not properly torqued—only finger tight—and cotter pins were absent.
Additional Information
The helicopter was operated by Northwest Helicopters. During the investigation, the company safety officer stated that, based on the condition of the wreckage parts, “it was reasonable to believe that the Crosshead Bolts and Pitch Change Link Bolts were installed but not torqued, nor were cotter pins installed to aid in the rigging process.” Northwest Helicopters could not determine who installed the tail rotor hub assembly or why the four bolts were not torqued.