On November 25, 1989, a Bell 47G-3B1 (registration N1358X) was involved in an aviation accident near Ewell, AL. Investigators recorded the probable cause as: THE LOSS OF ENGINE POWER, FOR UNDETERMINED REASONS, AT LOW ALTITUDE DURING A PRACTICE AUTOROTATION. CONTRIBUTING TO THE ACCIDENT WAS THE INSTRUCTOR'S FAILURE TO PROPERLY PLAN THE DEMONSTRATED AUTOROTATION SO AS TO PRECLUDE AN ACCIDENT, IN THE EVENT THAT POWER… This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter was substantially damaged after a hard landing during a practice autorotation. The instructor reported engine power loss, but subsequent examination found no discrepancies.
Accident Details
A private-rated pilot was conducting a practice 180-degree autorotation under instruction. The instructor aborted the first attempt due to improper alignment by the pilot. The instructor then performed a second autorotation to demonstrate the correct procedure. During the recovery phase, the instructor reported that the engine did not respond when he attempted to restore power. To avoid trees, he applied collective pitch, which resulted in low rotor RPM. The helicopter reached an open field but impacted the ground hard, causing substantial damage.
Investigation
A post-accident examination of the engine was conducted. The investigation did not reveal any mechanical discrepancies that would account for the reported loss of engine power.