Aircraft Accident/Incident Report

Camp Butler
Friday, July 17, 2009 8:30 UTC

The helicopter arrived at a military gunnery range with two pilots and two door gunners onboard. The gunnery range included an east-west track, approximately 1 mile long, with four targets just to the north of the track and three targets just to the south of it. Each target was to be engaged as it came into range, with gunfire coming from both sides of the helicopter. After engaging all of the targets along the track, the helicopter was to reverse course and commence another firing run. A total of eight tracks were flown prior to the accident: four in each direction. All of the eastbound tracks were flown by the copilot, seated in the left seat, and all the westbound tracks were flown by the pilot in command (PIC), seated in the right seat. After the completion of each track, the pilots transferred control of the helicopter and the new pilot at the controls executed the course reversal. After the copilot had completed the final eastbound track, he transferred the controls to the PIC. The PIC then began a left-turn course reversal approximately 100 feet above the ground. The next thing the PIC remembered was that, while in the turn and “like a hazy dream,” he saw the copilot’s finger moving toward the instrument panel and, after that, “being dragged, shaken, and bumped along the ground.” The PIC stated that despite his hazy recollection, he remembered that the helicopter was operating properly, with no warnings, cautions, or changes in sound. He further noted that even though the copilot appeared to be pointing at something, the copilot did not speak or otherwise indicate that anything was wrong. There was no indication of hostile fire. Observations at the accident site revealed that the helicopter was traveling westward at terrain impact. The initial impact point, at the eastern edge of a dried-up pond, was 17 meters in width, indicated by imprints of both skids. About 1 meter east feathered dirt indicated a spinning tail rotor. The second point of impact was on the western edge of the same dried-up pond. The distance between the first point of impact and the main wreckage was about 44 meters. The tail boom came to rest about 20 meters to the south, and about 24 meters east of that was the tail rotor. After the wreckage was secured, it was shipped to the United States where examination revealed that the helicopter had impacted the ground in a descending left turn. Main rotor blade damage indicated flailing at impact, at operational rpm. Tail rotor blade damage also indicated that the rotor was under power at impact. Flight control continuity could not be confirmed from the cockpit to the flight control surfaces; however, continuity was confirmed at the tail rotor pitch change mechanism. The engine did not exhibit any preimpact mechanical anomalies, and interior compressor blade scoring on the engine shroud indicated that it was operating at impact. The ENGINE OUT warning light was illuminated at some point during impact sequence; however, an expected RE-IGN P RST caution light was not concurrently illuminated for unknown reasons. It is possible that the ENGINE OUT warning light illuminated as the helicopter was decelerating while in ground contact. With no indication of mechanical failure or hostile fire, and with the PIC observing the copilot pointing to something on the instrument panel, it was possible that the PIC's attention was sufficiently diverted to allow the helicopter's inadvertent descent into terrain.

The pilot’s failure to maintain terrain clearance during a low-level course reversal.