Beech 60 N167U accident near Chino, California

Probable cause

Corrosion on a landing gear retract rod assembly which precluded an extension of the gear and resulted in a gear-up landing.

NTSB analysis

After an uneventful flight, the pilot attempted to extend the landing gear in preparation for landing and observed that the left main landing gear green light annunciator was extinguished. He cycled the landing gear, changed the annunciator light bulb, and attempted to manually extend the landing gear; however, the pilot was unable to extend the landing gear or prompt a green light on the instrument panel to indicate the left main landing gear was down. The pilot then landed with the left main gear retracted, which resulted in substantial damage to the left wing.

Postaccident examination of the landing gear system revealed that the gear motor functioned normally. Both manual and automatic extension of the left main landing gear failed due to a separation in the retraction rod assembly. The main gear retract system includes a pressure boot that is attached to a bushing on the retract rod assembly that extends and retracts the landing gear.

A metallurgical examination of the landing gear retract rod found that the rod fractured due to buckling from compression overload during the landing gear extension. The primer on the rod was worn where the bushing for the pressure boot slides along the rod during extension and retraction operations, which exposed the underlying steel surfaces to oxidation. The bushing likely seized on the corroded (oxidized) rod near the retracted position due to increased friction from the accumulation of corrosion products. The rod then buckled during normal extension operations due to constraint from the pressure boot and the seized bushing. With the rod segment outboard of the bushing held in place near the retracted position by the pressure boot and seized bushing, the left main landing gear would not have been able to extend when the main landing gear actuator rotated to extend the gear.

The maintenance logbooks indicated that the retract rod would have been inspected during the annual inspection seven months before the accident; however, it is unknown if a visual inspection would have found the wear on the retract rod.

Text from the NTSB. Open the NTSB docket for WPR24LA110 for the full record.