CEN22FA331

The failure of the flight crew to properly secure a company-issued iPad, leading to its migration into and jamming of the copilot’s left pedal, preventing the pilot from arresting a left yaw, and resulting in a loss of control.

The public firefighting helicopter was equipped with a 2,600-gallon water bucket attached via a 200-ft long line and a belly cargo hook. On the day of the accident, the pilots had flown about 1.5 flight hours and dropped multiple bucket loads. A witness video of the accident revealed that the helicopter was setting up to dip the water bucket in the river when it ascended and subsequently began a left yaw. Once it had turned about 180° the helicopter suddenly pitched nose down. The left yaw rate increased as the helicopter rapidly descended until it impacted the river. Postaccident examination of the wreckage revealed no evidence of malfunction or failure of the helicopter’s rotor systems, transmission and drive system, structures, and engines. The witness video corroborated that there was no structural failure before ground impact. Examination of the hydraulic system found no evidence of contamination, loss of fluid, or malfunction that would contribute to a loss of control inflight. Examination of the flight control system linkages showed no evidence of preimpact disconnection or separation. None of the hydraulic actuators of the flight control system exhibited functional hydraulic anomalies. The lee plugs that were found to be missing from the aft swiveling upper boost actuators (UBA) likely blew out from the actuator due to ground impact forces. The yaw integrated lower control actuator’s (ILCA) control rod and lever likely over-traveled upward due to ground impact, resulting in its impact with the yaw ILCA’s main control valve spool. While the jam indicators of multiple hydraulic actuators were extended, their extension was likely due to ground impact forces on the actuators rather than an actual jam of the control valves of multiple actuators during the accident flight. Therefore, no malfunction of the hydraulic system and flight control system was found. Analysis of the witness video showed no rotor speed anomalies throughout the accident flight. The video also showed the helicopter initially in a coordinated left yaw about the vertical axis as it remained in a mostly level attitude through the 180° turn. Because each UBA’s input is a result of the mixed pitch, roll, yaw, and thrust outputs, more erratic helicopter attitudes would have been expected with anomalous behavior of the UBAs. Therefore, malfunction of the UBAs was unlikely in this accident. A simulation study showed that the flight control inputs needed for the accident flight profile were not beyond the capability of a normally functioning flight control system. Additionally, the left pedal input was not at its forward limit stop until about 2 to 3 seconds after completion of the 180° left turn; therefore, it was likely that the initial 180° left turn was intentionally commanded by the pilot flying. Accordingly, investigators explored factors that could result in the flight crew’s inability to arrest the left yaw with the absence of a flight control system malfunction or failure. An iPad used by the flight crew was discovered in the river near the wreckage. The iPad displayed three distinct gouges on its long side and a bend from the back side. Testing with an exemplar helicopter and the iPad showed that it was possible to wedge the iPad between the airframe and the copilot’s pedals in a manner that would produce three distinct gouges corresponding to parts of the airframe and the copilot’s pedal heel slide. Additionally, as force was applied to the right pedal to bring the pedals to neutral, the jammed iPad would press against the copilot’s left pedal adjustment lever, which could result in unintended readjustment of the copilot’s left pedal position, and the iPad would remain jammed. In the wreckage, the copilot’s left pedal was found in the forward-most adjustment position, which was unusual given his height. Testing also found that, when the left pedal was pushed forward, the iPad became unjammed but could migrate further down between the left pedal and the airframe while still preventing the left pedal’s return back to its neutral position. Lastly, the position of the yaw magnetic brake clevis connection was found in a position consistent with the left pedal (in the cockpit controls) being forward of neutral. Based on the aggregate findings, it is likely that during the 180° left turn, the unsecured iPad migrated into the copilot’s left pedal and became jammed between his left pedal and the airframe, restricting the pedals from moving back to neutral. Testing showed that it would be difficult for the copilot to reach down to move the iPad, and possible for the copilot to bump the cyclic control forward when attempting to reach down, which would result in a sudden nose-down pitch, as seen in the accident video. The helicopter descent continued, likely due to a commanded reduction in the thrust lever. The reduction of thrust from both rotor systems would alleviate the increasing yaw rate as the left pedal could not be returned to neutral. The pilot likely pushed the left pedal further forward to assist the copilot in removing the jammed iPad, but the iPad likely migrated further down between the left pedal and the airframe, putting it further out of reach from the copilot while significantly increasing the helicopter’s left yaw rate. The operator stated that the flight crew’s use of the iPad was not required during the firefighting flight and that the copilot should have been monitoring the cargo hook load gauge during water pickups. However, it is plausible that the copilot was using the iPad before the water pickup and was holding onto it, allowing for its migration into the pedals during the accident flight. While the operator had a portable electronic device (PED) policy that prohibited the use of cell phones during an operation, it was ambiguous as to whether that policy extended to use of company-issued iPads. Regardless, the security of all items in the cockpit during an operation is necessary to ensure they do not adversely interact with critical systems, such as flight controls.

An autopsy of the pilot was performed by the Ada County Coroner’s Office, as authorized by the Lemhi County Coroner. According to the autopsy report, the pilot’s cause of death was multiple blunt force injuries. The autopsy did not identify any significant natural disease. The FAA Forensic Sciences Laboratory also performed toxicological testing of postmortem specimens from the pilot. No tested-for substances were detected. At the request of the Coroner’s Office, NMS Labs performed toxicological testing of postmortem femoral blood from the pilot, which detected caffeine. An autopsy of the copilot was performed by the State of Montana Department of Justice Forensic Science Division. According to the autopsy report, the copilot’s cause of death was multiple blunt force injuries, and his manner of death was accident. The autopsy did not identify significant natural disease. The FAA Forensic Sciences Laboratory performed toxicological testing of postmortem specimens from the copilot. According to the FAA toxicology report, the dissociative anesthetic medication ketamine was detected in the copilot’s femoral blood and urine, and the ketamine metabolite, norketamine, was detected in his femoral blood. Postaccident treatment records documented that the copilot had been given ketamine as part of his medical care after the accident, before arriving at the hospital. The copilot’s postmortem toxicological testing was otherwise negative for tested-for substances. Originally 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. According 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. On 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. The 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 n