On April 25, 1987, a Bell 47D1 (registration N3575) was involved in an aviation accident near Ardmore, OK. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
Following an unusual engine noise, the pilot executed a precautionary autorotation. The helicopter landed hard on uneven terrain in a nose-low attitude, causing the main rotor blades to sever the tail rotor assembly.
Pilot Actions
After hearing an unusual noise from the engine, the pilot initiated a precautionary autorotation to land. The maneuver was performed to ensure a safe touchdown given the potential engine issue.
Landing Sequence
The helicopter touched down on uneven terrain in a nose-low attitude. The impact conditions resulted in the main rotor blades making contact with the tail boom. This contact chopped off the tail rotor assembly from the tail boom.
Post-Recovery Examination
Following recovery, the owner/operator examined the helicopter and reported finding no evidence of any pre-existing mechanical failure or anomaly. The owner/operator stated that the damage was consistent solely with a hard landing event, during which the main rotor blades contacted the tail boom, causing it to be severed in two.