Accident Overview
On September 1, 2022, about 0735 Pacific daylight time, a Sikorsky S-61N helicopter, registration N617CK, sustained substantial damage following an accident near White City, Oregon. The two pilots and a ground support team member sustained minor injuries. The helicopter was operating as a Title 14 Code of Federal Regulations Part 133 rotorcraft external load flight.
Pre-Accident Hot Start Event
Two days before the accident, on the morning of August 30, 2022, the flight crew—consisting of the pilot in command (PIC) and second in command (SIC)—intended to conduct timber logging operations. During the start sequence of the No. 2 engine, the SIC observed that the Ng took longer to rise, and the T5 temperature fluctuated between 630°C and 670°C before the starter was released. The temperature subsequently increased to 720°C, and the SIC alerted the PIC. The PIC told the SIC to “Hold,” and the digital T5 gauge eventually indicated 001°C. According to the T5 gauge manufacturer, 001°C is the maximum value the gauge will report, even if temperatures exceed 999°C. The No. 2 engine start was aborted after a maintenance technician outside the helicopter transmitted “It’s hot” over the intercom. The No. 1 engine was secured, and after about five minutes, both engines were started without anomaly. The crew flew multiple sorties that day, and the helicopter remained in service. No entries were annotated in the maintenance log regarding the hot start.
Accident Sequence
On September 1, 2022, the same PIC was assigned to N617CK with a different SIC. During climb out, a right pedal turn was accomplished. Shortly after, the crew heard a loud “bang” sound. All engine and flight instruments indicated normal operating limits, and the PIC continued the logging operation. Two additional sorties were accomplished, and the “bang” sound recurred. A precautionary landing was made, and maintenance personnel were unable to identify a definitive source of the sound. The PIC decided to continue. While departing a log landing site, another right pedal turn was followed by immediate and successive “bangs,” a grinding noise, and a degradation of the No. 2 engine torque value to zero. The Master Caution warning light illuminated, and the helicopter descended, landing hard on the main landing gear. It rolled to the right and came to rest on its right side.
Postaccident Examination
The accident site was a flat surface used for timber storage, surrounded by trees over 50 ft tall. All five main rotor blades separated from the fully articulated main rotor hub, which remained attached to the upper fuselage. The airframe sustained substantial damage to the right overhead, chin bubble, and windscreen. The lower fuselage showed substantial damage to tailwheel landing gear attachment points. The tail rotor remained attached, but the horizontal stabilizer sustained substantial damage.
Postaccident examination of the No. 2 engine revealed overtemperature distress on most gas generator turbine parts. All stage 1 turbine blades had severe overtemperature distress; four had separated at mid-span, and multiple blades had cracks. Metallurgical examination confirmed evidence of overtemperature exposure, including bulk deformation, coating cracking, and creep voiding. The fuel flow divider was tested and did not meet operational standards, though no discrepancies had been noted by the operator. The spindle bearings examination was inconclusive as they had been disassembled before arrival at the manufacturer.
The No. 2 engine, serial number 285036RC, was installed on July 14, 2022, and had about 18,646 hours time since new, about 311 hours since installation, and about 479 hours since light overhaul. It operated about 17 hours between the aborted hot start and the accident.