N388RA

HISTORY OF FLIGHTOn July 21, 2022, about 1642 mountain daylight time, a Columbia Helicopters CH-47D, N388RA, was destroyed when it was involved in an accident near North Fork, Idaho. The pilot and copilot were fatally injured. The helicopter was operated as a public aircraft.

The helicopter operator was contracted by the United States Forest Service (USFS) for firefighting operations related to the Moose fire. The helicopter was relocated to the area two days before the accident and began firefighting flights the day before the accident. The helicopter was equipped with a 2,600-gallon water bucket attached to the helicopter’s belly-mounted cargo hook via a 200-ft long line. On the day of the accident, the pilots had flown about 1.5 flight hours and dropped multiple bucket loads.

A 38-second video of the accident flight recorded by a local resident showed the helicopter setting up to dip the water bucket into the Salmon River. At the start of the video, the helicopter was hovering about 200 ft above ground level (agl) over the river with its empty water bucket, at the end of the long line, swinging close to the surface of the river. (See figure 1.) The helicopter then climbed to about 325 ft agl over a period of 8 to 9 seconds; its heading remained generally the same throughout the ascent. Next, the helicopter began to yaw to the left, and once it had turned about 180°, the helicopter suddenly pitched down, continued to yaw left, and descended. The left yaw continued through the descent until the helicopter impacted the river and riverbank.

Figure 1. This still image from the accident video shows the helicopter hovering above the river with the empty orange water bucket just above the water (source: witness video).

The pilots were rescued by nearby USFS firefighters who witnessed the accident and were transported to nearby hospitals, where they later succumbed to their injuries. PERSONNEL INFORMATIONAccording to the pilot’s USFS interagency helicopter pilot evaluation application, the interagency guidelines for vertical reference (VTR)/external load training required that the pilot demonstrate VTR knowledge and proficiency with a 150-ft long line. The pilot’s USFS VTR demonstration and proficiency check were completed June 27, 2022, during which a 200-ft long line was used. The pilot reported on the application that he had accumulated 38 hours of vertical reference flight experience, 18 of which were in a Boeing BV234 (the civilian variant of the CH-47D). A Federal Aviation Administration (FAA) letter of competency showed that the pilot satisfactorily met the requirements of 14 Code of Federal Regulations (CFR) Part 133.37 and was approved to conduct Class A, B, and C external loads in a CH-47D helicopter. Additionally, the pilot demonstrated proficiency in system and flight operations in 14 CFR Part 137 firefighting operations in the CH-47D.

On February 27, 2022, the copilot completed initial training for second-in-command (SIC) duties in the CH-47D, which was conducted by Columbia Helicopters. He had accumulated 6.6 hours as pilot-in-command (PIC) in the CH-47D during training and while repositioning the helicopter to various locations. The day before the accident, he had accumulated 3.5 hours as SIC, and on the day of the accident, he had accumulated about 1.5 hours as SIC, all involving firefighting flights related to the Moose fire. On the copilot’s most recent satisfactory proficiency check, he received company ground training, which included Part 133 and 137 operations and long line proficiency. AIRCRAFT INFORMATIONOriginally manufactured by Boeing for the United States Army, the Columbia Helicopters CH-47D is a surplus military helicopter that was type certificated under the restricted category. The CH-47D has two fully articulated, three-bladed rotor systems, in a tandem (forward and aft) configuration that provides helicopter lift, thrust, and attitude control.

Review of the accident helicopter’s maintenance records revealed that, as of July 20, 2022, the helicopter accumulated an aircraft total time of 7,735.9 hours and Hobbs time of 69.5 hours. The records showed that there were no unresolved maintenance discrepancies at the time of the accident and no anomalous trends. AIRPORT INFORMATIONOriginally manufactured by Boeing for the United States Army, the Columbia Helicopters CH-47D is a surplus military helicopter that was type certificated under the restricted category. The CH-47D has two fully articulated, three-bladed rotor systems, in a tandem (forward and aft) configuration that provides helicopter lift, thrust, and attitude control.

Review of the accident helicopter’s maintenance records revealed that, as of July 20, 2022, the helicopter accumulated an aircraft total time of 7,735.9 hours and Hobbs time of 69.5 hours. The records showed that there were no unresolved maintenance discrepancies at the time of the accident and no anomalous trends. WRECKAGE AND IMPACT INFORMATIONThe helicopter came to rest mostly upright in the Salmon River except for the aft fuselage and aft pylon. The aft pylon partially separated from the aft fuselage and came to rest on its right side and was partially submerged in the water. Both engines remained installed on the airframe. The lower portion of the airframe exhibited significant upward deformation and crushing due to ground impact. The cockpit floor and the ramp were submerged in the water while the cabin floor was deformed significantly upward. The two cockpit doors were separated from the airframe. The forward rotor blades remained attached to the forward rotor head, but exhibited fragmentation on their outboard ends due to impact. The aft rotor blades remained attached to the aft rotor head but exhibited fragmentation on their outboard ends due to impact.

The pilot (left seat) and copilot (right seat) cyclic controls remained attached and connected to their mounts. The copilot’s cyclic control was partially fractured at its base. Manual movement of the pilot’s cyclic control resulted in a corresponding movement of the copilot’s cyclic control in both lateral and longitudinal axes. Manual movement of the pilot’s cyclic control resulted in movement of the longitudinal control tubes that route to the transfer bellcranks, but the longitudinal control tubes were fractured near their aft end. However, the aft end of the longitudinal control tubes remained connected to the transfer bellcranks via their rod ends. Both the pilot’s and copilot’s cyclic control grips remained installed on their respective cyclic controls. Both thrust levers were present in the cockpit structure. The pilot’s thrust lever remained connected to its bellcranks; the bellcrank was impact separated from the airframe. The pilot’s thrust lever grip was whole, but its buttons were damaged during recovery of the wreckage. Manual movement of the pilot’s thrust lever resulted in a corresponding movement of the copilot’s thrust lever as well as movement of the longitudinal control rod going to the transfer bellcranks; however, the longitudinal control rod was fractured near its forward end as well as near its aft end, and the central portion of the longitudinal control rod was not present. The copilot’s thrust lever grip and switches were crushed downward. Note: in this report “control rod” and “control tube” are synonymous with “connecting link,” which is the terminology used in the CH-47D maintenance manual.

The pilot’s pedal set was present, but both pedals were disconnected from their respective pedal position adjustment plates; therefore, movement of the left and right pedals did not result in a corresponding movement of both pedal jackshafts. All pedal position adjustment plate stops were present on the pilot pedal set. The right pedal position lever had moved beyond its limit and was pointed left. The left pedal position lever had no anomalous damage. Both pedal return springs remained installed. Both left and right brake levers remained installed, and all brake lines remained attached. Movement of the pilot’s pedal position adjustment plates resulted in a corresponding movement of the copilot’s pedal set as well as the longitudinal control rod leading to the transfer bellcranks. The lateral interconnect control rod between the pilot’s and copilot’s pedals remained connected, but was deformed upward about mid-length.

The copilot’s pedal set was present, and both pedals remained connected to their respective position adjustment plates. The left pedal was in the forward-most “5” adjustment position and the right pedal was in the middle “3” adjustment position. The left pedal position lever was intact. The right pedal position lever was fractured near its base. The operator stated that the right pedal in the middle adjustment position was typical for that pilot; however, the position of the left pedal was unusual given the copilot’s height. Both left and right brake levers remained installed, and all brake lines remained attached. The right pedal shaft support attaching to the airframe had separated from the airframe but remained attached to the right pedal jackshaft, with all rivet heads present on the support. The left pedal control rod, connecting to the left side of the left pedal jackshaft, had separated from its control tube, the latter of which remained installed.

The yaw control rod was continuous from the left side bellcrank to its transfer bellcrank below the ILCAs. The thrust control rod was fractured in overload and the mid-section of the rod was not present, but the two rod ends remained connected between the cockpit bellcrank and the thrust transfer bellcrank. All four transfer bellcranks moved freely and were not seized. On the yaw/thrust pallet, the yaw magnetic brake, yaw viscous damper, and yaw centering control spring remained installed. Manual movement of the yaw centering spring revealed no evidence of restriction in both directions of travel. The yaw magn...