NTSB Identification: CHI91IA120.
The docket is stored on NTSB microfiche number 44065.
Incident occurred Tuesday, April 02, 1991 in WEST CHICAGO, IL
Probable Cause Approval Date: 05/28/1993
Aircraft: CESSNA 172RG, registration: N9592B
Injuries: 2 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.

AFTER REPEATED ATTEMPTS TO LOWER THE LANDING GEAR, ONLY THE LEFT MAIN AND NOSE GEAR WOULD EXTEND. THE PILOTS ELECTED TO MAKE A WHEELS-UP LANDING. DURING THE LANDING, THE LOWER FUSELAGE AND PROPELLER TIPS RECEIVED MINOR DAMAGE. AN INVESTIGATION REVEALED THE RIGHT MAIN LANDING GEAR PIVOT ASSEMBLY (PN 2441100-1) HAD FAILED. A METALLURGICAL EXAMINATION DISCLOSED THE SPLINED SHAFT ON THE PIVOT ASSEMBLY HAD FRACTURED IN TORSIONAL OVERLOAD. AS A RESULT, MECHANICAL EXTENSION OF THE RIGHT MAIN LANDING GEAR WAS NOT POSSIBLE.

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

FAILURE OF THE SPLINED SHAFT ON THE RIGHT MAIN LANDING GEAR PIVOT ASSEMBLY. A FACTOR RELATED TO THE INCIDENT WAS INADEQUATE DESIGN OF THE LANDING GEAR PIVOT ASSEMBLY.

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