FTW04IA078 · Beech C90

The crew reported the landing gear would not completely retract after take off, and only the right main came up while the gear motor continued to run. The left main and nose gear did not retract. The landing gear handle was cycled to the down position and the gear motor stopped running, but the right main landing gear failed to extend. The landing gear handle was cycled again, and the right main still would not extend. The crew used the emergency checklist, but the emergency gear extension handle was very hard to move, then it seemed to not catch anything at all. The crew made an emergency landing with the right main gear retracted. During the recovery process, a bolt, which attached the clutch shaft and nose gear drive sprocket, was found laying in the belly of the airplane. Examination of aircraft and maintenance records revealed the airplane underwent a phase inspection about a month prior to the event that included the replacement of the landing gear retraction gear box and clutch. The records indicated that this item was removed and an overhauled unit was reinstalled in accordance with the manufacturer's maintenance manual. According to the maintenance technician that performed the work, he used the manufacturer's maintenance manual as a step-by-step guide, and "all parts, nuts, bolts, cotter pin, etc, were intact when the final inspection was completed. New cotter pins were used to safety these items." After installation, the assembly and operational checks were inspected by his lead mechanic and an inspector. The gear was cycled approximately 12-15 times, and the "cavity" was vacuumed before the final inspection and the floor panels reinstalled. At the time of the incident, the airplane had flown a total of 21.9 hours, which included a total of 35 landings, after the phase inspection was completed. Nine days prior to the emergency landing, another flight crew reported that they were unable to retract all three landing gear while executing a go-around procedure. An examination revealed that a mechanic had removed the center and right floor boards and visually inspected the landing gear limit switches and engagement of the emergency extension disconnect assembly. Inspection of the limit switches consisted of visually inspecting the mount bracket and security of the switches and wiring. The mechanic also made a visual inspection of the wiring to the gear motor and engagement of the emergency extension disconnect, and engaged and disengaged "J" hook several times and found it operated normally. The visible portion of the nose gear chain was also examined for general condition. The floorboard panels were reinstalled, and the gear were cycled three times in five minutes, followed by four more cycles. All functional tests were normal and the airplane was returned to service. At the time of this inspection, the airplane had flown 11 hours since the phase 4 inspection, which included 17 landings.

Verbatim NTSB analysis and probable cause from the NTSB dataset