NTSB Identification: ANC01LA055.
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Accident occurred Monday, May 07, 2001 in FAIRBANKS, AK
Probable Cause Approval Date: 02/20/2002
Aircraft: Cessna 170B, registration: N3143A
Injuries: 2 Uninjured.

NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The commercial certificated pilot/flight instructor was conducting a local area instructional flight with the student pilot/owner of the airplane. The flight instructor reported that he was doing wheel landings with the student to a gravel runway. During the touch down on the third or fourth landing, the tailwheel assembly suddenly broke off. An FAA airworthiness inspector examined the airplane after the accident and found a preexisting crack in the tailwheel spring assembly that was about 1/16 inch deep, and about 1/2 inch long. The spring failed at the crack. When the tail wheel departed the airplane, it struck the bottom of the rudder, and the rudder trim tab. The bottom and aft portion of the rudder assembly was torn open. The spring assembly had accrued 126 hours, and 65 hours since the last annual inspection.

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

A failure of the tailwheel spring assembly due to fatigue during touch and go landings. A factor in the accident was an inadequate annual inspection by maintenance personnel.

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