CHI82FA098

Factual narrative

THE PLT HEARD A GRINDING NOISE WHEN HE ATTEMPTED TO LOWER THE LANDING GEAR. THE GEAR WOULD NOT EXTEND WITH EITHER THE NORMAL OR EMERGENCY SYSTEMS. THE ACFT LANDED WITH THE GEAR IN THE PARTIALLY EXTENDED POSITION. SUBSEQUENT TO EXAMINATIONOF THE NOSE LANDING GEAR ACTUATOR BY THE MANUFACTURER, THE GEAR BOX FOR THE NOSE GEAR ACTUATOR WAS DISASSEMBLED. IT WAS STILL PACKED WITH GREASE. WHILE REMOVING THE MASS OF GREASE FROM AROUND THE DRIVE PINION GEAR, A SMALL NUT, FOREIGN TO THE INSIDE OF THE GEAR BOX, WAS FOUND BURIED, AND INVISIBLE, IN THE GREASE THAT WAS PACKED AROUND THE BEVELED GEARS. EXAMINATION OF THE NUT SHOWED INDENTATIONS OF TWO OPPOSITE SIDES. PLACEMENT OF THE NUT ON EITHER SIDE OF THE POINT WHEREBOTH BEVELED GEARS MET WOULD JAM THE ROTATION IN EITHER THE RETRACT OF EXTEND CYCLE. ON 12/23/77 THE GEAR ACTUATORS WEREREPLACED WITH REBUILT PARTS. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12