ACCIDENT RECOVERY
The circle at left indicates the area where
the NTSB found pieces of plexiglass, the aft cap of the left skid, a tail-rotor blade segment, and green paint transfer onto a rock. (National Transportation Safety Board Photo)
confirmed by static impact marks that the impeller airfoils’ leading edges made on the impeller compressor housing, with no material transfer or significant rub damage. All compressor blades “were present and intact, with no rub, impact, or ingestion damage.” The rollers in the No. 2 bearing,
were not provided by the US National Transportation Safety Board (NTSB).
The Flight The UH-1B lifted off from 6L4 at about 16:30 on Jun. 22, 2022, on the last flight of the second day of the Huey reunion. In addition to the two pilots, four passengers were seated in the cabin. Fifteen minutes later, the aircraft hit power lines 180 ft. above a two-lane road, struck the adjacent rock face, and crashed onto the road, where it hit a guardrail. The impact ignited a fire that consumed the cockpit and canopy. All six on board perished at the scene. The helicopter wasn’t in radio con-
tact with the airport, and the NTSB was unable to find any witnesses to the accident itself. Someone, however, made a 911 emergency call to report the crash just minutes later, at 16:49. The accident site was about 2 miles beyond the easternmost section of the planned tour route. The reason for the diversion was never explained.
60 POWER UP DEC 2024
The Investigation The debris path stretched 542 ft. from a group of three power cables, two of which had been severed. Bits of plexi- glass, the aft cap of the left skid, and part of one tail-rotor blade were found on a ledge about 40 ft. above the main wreckage. Green paint transfer marks were also found on a rock there. Both main-rotor blades remained installed on the main gearbox, which had sepa- rated from the airframe. Examination of them found no evidence that they’d been turning under power at impact, suggesting that a total or at least par- tial loss of engine power had precipi- tated the crash. On-site examination of the engine’s
power turbine blades as seen through the exhaust diffuser showed that two had fractured near their roots and were missing; an intact blade remained between those two locations. The engine was taken to Ozark Aeroworks’ facility for a teardown examination. Engine stoppage before impact was
which supported the aft end of the gas turbine’s compressor shaft, were flattened, and the outer race “exhibited considerable material transfer.” The roller cage remained in good condition. Rub marks left by the power turbine blades indicated contact with the power turbine inner support and outer ring support, and damage to its front shaft was consistent with contact with the rear compressor stub shaft. Metallurgic analysis of the two frac-
tured blades confirmed that both failed from excess stress. Multiple cracks were found on each inner strut support flange for the exhaust diffuser’s outer cone; one inner strut had separated from the bearing housing. Extensive rubbing damage suggested the strut had separated before the accident and had been “operating in that condition for a considerable amount of time.” These findings led investigators to
reconstruct the failure sequence as fol- lows: Fatigue cracks in the spot welds attaching the inner cone to the exhaust diffuser’s bearing-housing support progressed around the cone’s circum- ference. The preexisting separation in the outer flange of the rear bearing cover reduced load transfer to the inner cone, increasing stresses that led to cracks in the inner and outer flanges of the exhaust diffuser’s inner struts.
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