What happened
On September 11, 2024, at approximately 1400 EDT, a Hughes 3ASS (Hughes 369D) helicopter, N8969F, was conducting a Part 133 rotorcraft external load operation near Canton, Michigan. The flight was part of a powerline maintenance mission, involving the delivery of Class B cargo to a powerline structure located roughly 300 yards from an off-airport landing zone.
During the low-level flight, the pilot noticed an intermittent and unusual vibration. In response, the pilot performed a precautionary landing at the landing zone and shut down the engine. The pilot was not injured.
The investigation
A postflight inspection of the main rotor system revealed a crack in the yellow-marked main rotor blade. The crack, which was located on a blade painted white, was a chordwise crack situated outboard of the root fitting near the doubler. The crack originated at the trailing edge and propagated through both the upper and lower skins, though it did not reach the leading-edge spar area.
The investigation noted that the yellow main rotor blade had accumulated 3,289.9 hours since new, with 12.4 hours elapsed since its last inspection. The aircraft, which had a total airframe time of 18,318.8 hours, sustained substantial damage to that specific blade, but no other damage to the helicopter was identified. The blade was sent to the NTSB Materials Laboratory in Washington, D.C., for examination. There was no evidence of bird strikes, object strikes, or terrain contact.