NTSB Identification: FTW94FA044.
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Accident occurred Sunday, December 05, 1993 in GUTHRIE, OK
Probable Cause Approval Date: 09/13/1994
Aircraft: UPTON MUSTANG M-II, registration: N4YP
Injuries: 1 Fatal.

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 aircraft accident report.

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

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

WAS THE IN FLIGHT FAILURE OF THE LEFT AILERON FOR REASONS UNDETERMINED.

Full narrative available

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