Accident Overview
On February 22, 2022, about 1020 Hawaii-Aleutian Standard Time, a Sikorsky S-61N helicopter, registration N615CK, was destroyed when it crashed at the Pacific Missile Range Facility (PMRF) in Barking Sands, Kekaha, Hawaii, on the island of Kauai. The two pilots and two crewmembers on board were fatally injured. The helicopter was operated under Title 14 Code of Federal Regulations Part 133.
Operator and Mission
The helicopter was owned and operated by Croman Corporation under contract to the United States Navy. Its mission was to retrieve inert training torpedoes from the Pacific Ocean as part of Navy submarine training operations. According to the operator's director of operations, the accident flight involved locating a training torpedo in open waters, retrieving it using a recovery basket/cage system, and returning the torpedo to PMRF by sling load.
Flight History and Witness Accounts
The helicopter was one of two stationed at a hangar at PMRF Barking Sands, with three mechanics on site for maintenance. Equipped with ADS–B, the helicopter departed PMRF and proceeded north-northwest to an area about 44 miles away. After maneuvering, it returned south-southeast toward PMRF. As it approached the facility, it crossed the shoreline and began a shallow left turn into the prevailing wind. Near the ordnance recovery clear area (ORCA), the left turn stopped, and the helicopter proceeded in a northeasterly direction before the ADS-B data ended.
Multiple witnesses near the accident site reported that as the helicopter continued the left turn toward the ORCA, the turn stopped, and it began traveling northeast. At about 200 ft above ground level, it gradually pitched nose down and impacted nose first in a near-vertical attitude.
Wreckage and Examination
The helicopter came to rest on its left side on a heading of about 230° magnetic. Three ground scars consistent with main rotor blade impact marks were near the initial impact location. The nose bay door for avionics was found at the start of the debris trail, followed by cockpit structure and instruments, then the remainder of the helicopter. The initial impact mark and debris trail were oriented about 65° magnetic. A postcrash fire consumed most of the cockpit and cabin, though remnant frame sections remained near the main landing gear and transmission deck. The cockpit voice recorder was found near the forward end of the main wreckage.
The main transmission gearbox remained whole and installed on the airframe, coated in soot but not consumed by fire. The main rotor blades exhibited considerable fragmentation.
Examination of the wreckage revealed that the flight control fore/aft servo input link remained connected at its clevis end to the fore/aft bellcrank adjacent to the main gearbox. However, the rod end was partially connected to the fore/aft servo input clevises, with the attaching hardware mostly backed out and the bolt cocked. The bolt remained partially within the rod end bearing inner race, also cocked, exposing a portion of the bearing's rolling elements. The bolt head-side bushing and three washers were present between the bolt head and rod end. The nut, nut-side bushing, nut-side washers, and cotter pin were not present. A loose bushing was found on the main transmission deck within the right-side longitudinal beam. The bolt between the fore/aft servo input link and the servo input clevises was removed and showed no evidence of fractures or visible deformation of the bolt shank.
Maintenance History
According to maintenance records, multiple actions were performed from December 17–29, 2021. The director of maintenance and another mechanic traveled from the operator's base in Oregon to PMRF Barking Sands and worked with two additional mechanics based there. The fore/aft primary servo of the flight control system was installed on December 28, 2021. About 7.5 flight hours had elapsed from installation until the accident. Both the director of maintenance and a traveling mechanic stated that when the main gearbox assembly is removed, the primary servos typically remain installed on the gearbox housing and are disconnected at each servo input link's clevis connection to the main gearbox bellcranks. During a primary servo replacement, the servo input link would be removed from the old servo and transferred to the new one. The condition of hardware such as bolts and washers would be checked and replaced as needed, with one-time-use items like cotter pins and nylon-locking nuts discarded after removal. After all work was complete, a company certified inspector inspected all work performed.