NTSB Identification: FTW92GA160.
The docket is stored on NTSB microfiche number 47108.
Accident occurred Saturday, June 13, 1992 in YUKON, OK
Probable Cause Approval Date: 06/30/1993
Aircraft: MCDONNELL DOUGLAS 369E, registration: N684F
Injuries: 2 Uninjured.
: NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this public aircraft accident report.
THE MANUFACTURER'S TRAINING PILOT WAS CONDUCTING UNAPPROVED 'ZERO AIRSPEED' AUTOROTATION TRAINING IN CONJUNCTION WITH ANNUAL PROFICIENCY TRAINING FOR THE POLICE AVIATION SUPPORT UNIT. HE WAS NOT A CERTIFIED FLIGHT INSTRUCTOR. AFTER HE DEMONSTRATED THE MANEUVER, THE POLICE PILOT ATTEMPTED IT. THE HELICOPTER CONTACTED THE GROUND WITH LOW MAIN ROTOR RPM AND NOT IN A LEVEL ATTITUDE. THE MAIN ROTOR BLADES SEVERED THE TAIL OF THE HELICOPTER. THE POLICE PILOT STATED THAT THIS AND OTHER EMERGENCY PROCEDURE MANEUVERS WERE NOT COVERED IN THE BRIEFING CONDUCTED BEFORE THE FLIGHT.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: THE DUAL STUDENT'S FAILURE TO MAINTAIN ADEQUATE MAIN ROTOR RPM AND FAILURE TO LEVEL THE HELICOPTER AT TOUCHDOWN. FACTORS WERE THE MANUFACTURER'S TRAINING PILOT'S INADEQUATE SUPERVISION AND THE DUAL STUDENT PERFORMING THE MANEUVER.
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