What aircraft was involved and where did it happen?

The accident on 22 Feb 1989 involved an Aerospatiale AS-350D, registration N5793P, at Spring Valley, NY.

What was the probable cause of the accident?

FAILURE OF THE FAA FLIGHT EXAMINER (F/E) TO FOLLOW PROPER PROCEDURES CONCERNING THE AUTOROTATION, AND IMPROPER REMEDIAL ACTION BY THE PILOT-IN-COMMAND (PIC). FACTORS RELATED TO THE ACCIDENT WERE: LACK OF INFORMATION IN THE FLIGHT MANUAL CONCERNING AUTOROTATIONS, THE FLIGHT EXAMINER'S LACK OF EXPERIENCE IN THE…

Tail Rotor Strike During Training Autorotation (N5793P)

On February 22, 1989, an Aerospatiale AS-350D (registration N5793P) was involved in an aviation accident near Spring Valley, NY. Investigators recorded the probable cause as: FAILURE OF THE FAA FLIGHT EXAMINER (F/E) TO FOLLOW PROPER PROCEDURES CONCERNING THE AUTOROTATION, AND IMPROPER REMEDIAL ACTION BY THE PILOT-IN-COMMAND (PIC). This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

During a Part 135 check flight, an autorotation initiated for power recovery resulted in a tail rotor strike and rollover after the engine failed to respond to collective input.

Incident Overview

During a Part 135 check flight, the pilot in command (PIC) and an FAA examiner were conducting a check flight. At an altitude of approximately 900 to 1,000 feet above ground level (AGL), the examiner initiated an autorotation with the intention of performing a power recovery. However, no procedure for executing a power recovery from an autorotation was published in the flight manual.

Sequence of Events

The examiner initiated the autorotation by moving the fuel flow control/power lever (FFC) out of the full forward (power locked) position. At about 400 feet AGL and 65 knots, the FFC was repositioned back to the full forward (detent) position. At approximately 65 feet AGL, the PIC initiated a flare using collective pitch control, but the engine lacked response. The PIC continued the autorotation to touchdown on soft terrain.

Impact and Damage

During the landing, the tail rotor struck a mound of dirt. Both tail rotor blades separated, and the helicopter rolled onto its right side before coming to rest.

Investigation Findings

Investigation revealed that the governor anticipator would not have activated until collective pitch was applied, and the engine could take up to nine seconds to spool up. The flight manual addressed only full-stop autorotation landings. The manual for Aerospatiale instructors restricted power recovery to 200 feet AGL. Additionally, no mechanical stop was provided to prevent the engine from going below 50% during power reduction for autorotation.