Mooney M20F N9387V accident near Leesburg, Florida

Probable cause

The incorrect rigging of the landing gear emergency extension system by unknown maintenance personnel, which resulted in a failure of the emergency extension cable, and jamming of the normal extension gear motor.

NTSB analysis

The pilot reported that when he attempted to extend the landing gear, he heard a "snap," and the landing gear did not extend. He then cycled the landing gear and attempted the emergency (manual) landing gear extension procedure with no success. The pilot subsequently performed a gear-up landing to a grassy area at an airport. Examination of the airplane revealed that the emergency gear extension cable terminated with a spline drive at the landing gear actuator. The emergency cable was separated from the spline drive, which was seized. The emergency gear extension cable was also misrigged, which allowed it to contact the landing gear actuator arm and engage the cable during normal gear operations. Subsequently, with a seized spline engaged to the electric landing gear motor via the actuator, during normal gear operations, the electric landing gear motor would not be able to overcome the seized spline to actuate the landing gear.

The airplane had been operated about 60 hours since its most recent annual inspection, which was completed about 10 months before the accident. Review of the airplane's most recent airframe logbook (dating back 7 years) revealed that the landing gear actuator was removed and replaced about 4 years before the accident. During reinstallation of the actuator, an emergency (manual) gear extension was successfully completed. There were no other entries pertaining to emergency (manual) gear extension in the airframe logbook; however, the entry for the most recent 100 hour inspection noted three landing gear retraction cycles. The mechanic that recorded that entry stated it was a standard entry and typically more than three cycles are completed with the first one being the emergency (manual) extension. While it was likely that a mechanic checked the rigging of the emergency gear extension cable following the actuator replacement, the investigation was unable to determine if the rigging of the emergency gear extension cable was affected by any subsequent maintenance. Additionally, the cable routing and rigging wouldn't typically be inspected if the landing gear manual extension was successfully accomplished during the 100-hour or annual inspections.

Text from the NTSB. Open the NTSB docket for ERA13LA175 for the full record.