Piper PA-30 N8458Y accident near Concord, California

Probable cause

The failure of the main landing gear to extend and lock for reasons that could not be determined based on the available information. Contributing to the accident was a mechanical failure of the manual landing gear release mechanism due to inadequate clearance between the release linkage and side structure and maintenance personnel’s failure to identify the interference during previous annual inspections.

NTSB analysis

The pilot was cleared for landing at the destination airport. After extending the landing gear, he performed a pre-landing check and noticed that the landing gear switch was in the down position, while the annunciator showed the gear in the retracted position. The pilot attempted to cycle the landing gear multiple times, but was unsuccessful in extending the gear. He then overflew the runway and the tower controller noted that the landing gear was only partially extended.

The pilot cycled the landing gear again, attempted to shake the gear loose with abrupt maneuvers, and attempted to manually extend the gear, but remained unsuccessful. The pilot elected to land with the gear partially extended, which resulted in substantial damage to the fuselage.

The landing gear was cycled multiple times during a postaccident examination, but the landing gear failure could not be reproduced. Functional testing of the manual gear extension revealed that the system did not function as designed. During tests, the gear release arm was moved in accordance with the pilot’s operating handbook instructions, yet the manual extension failed to release the landing gear. Further examination found that inadequate clearance between the push/pull rod clevis and lightening hole resulted in resistance that inhibited the release tube and torque tube from decoupling. The landing gear would manually extend when the release arm and clevis were pushed away from the lightening hole. The binding and damage to the side wall from its interaction with the push/pull rod clevis was indicative of long-term wear; however, when this interference began could not be determined based on the available information.

The airplane had accrued a total of 36 flight hours in the 8 years before the accident and had received only two annual inspections during that time. Both annual inspections required a visual inspection of the side wall and push/pull clevis, which should have identified the binding between the two components.

Text from the NTSB. Open the NTSB docket for WPR24LA275 for the full record.