NTSB Identification: DEN92LA036.
The docket is stored on NTSB microfiche number 45925.
Accident occurred Saturday, February 29, 1992 in LEADVILLE, CO
Probable Cause Approval Date: 07/23/1993
Aircraft: ENSTROM TH-28, registration: N8631E
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

THIS WAS ONE OF A SERIES OF EXPERIMENTAL TEST FLIGHTS LEADING TOWARDS FAA CERTIFICATION OF THE MODIFIED HELICOPTER. DATA POINTS FOR THE HEIGHT VELOCITY CURVE HAD BEEN COLLECTED AND THE PILOT WAS ATTEMPTING TO CONFIRM THEIR ACCURACY. AT 46 KNOTS AND 400 FEET AGL, THE PILOT MADE AN INTENTIONAL AUTOROTATION. HE SAID THE SINK RATE WAS HIGHER THAN PREVIOUSLY NOTED, AND HEAVY ROTOR BLADE STALL MADE THE FLARE INEFFECTIVE. THE PILOT SAID A DOWNDRAFT MAY HAVE PRECIPITATED THE ACCIDENT.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE PILOT MISJUDGING THE DESCENT RATE AND CONSEQUENTLY DELAYING THE FLARE. A FACTOR WAS: DOWNDRAFT.

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