NTSB Identification: ANC91IA046.
The docket is stored on NTSB microfiche number 44656.
Incident occurred Wednesday, March 27, 1991 in ANCHORAGE, AK
Probable Cause Approval Date: 05/05/1993
Aircraft: NIHON YS-11A-600, registration: N173RV
Injuries: 4 Uninjured.

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

THE CREW OF FOUR WERE ON A TRAINING FLIGHT AND WERE PREPARING TO PERFORM APPROACH TO LANDING STALLS. DURING THE MANEUVER, THEY NOTICED THE NOSE GEAR WOULD NOT EXTEND. UNABLE TO EXTEND THE NOSE GEAR, THEY LANDED WITH THE NOSE GEAR UP CAUSING MINOR DAMAGE TO THE AIRPLANE. SUBSEQUENT EXAMINATION REVEALED THAT THE RIVETS WHICH RETAIN THE CENTERING CAM SHEAR PINS WERE SHEARED. THE SHEAR PINS WERE NOT SHEARED. AN EXAMINATION BY MITSUBISHI HEAVY INDUSTRIES, NAGOYA AIRPLANE WORKS, INDICATED THAT THE SHEAR PINS MAY HAVE BEEN INSTALLED IN REVERSE. THE OVERHAUL MANUAL ALSO CONTAINED AMBIGUOUS INFORMATION CONCERNING THE INFORMATION. THE GRAPHICAL DISPLAY SHOWED THE INSTALLATION INCORRECTLY, BUT THE TEXT EXPLAINED THE INSTALLATION CORRECTLY.

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

A JAMMED NOSE GEAR DUE TO INCORRECT INSTALLATION OF THE SHEAR PIN. CONTRIBUTING TO THE ACCIDENT WAS THE INSUFFICIENTLY DEFINED MAINTENANCE PROCEDURE.

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