Cessna 210 N9443T accident near Louisville, Kentucky

Probable cause

A malfunction of the landing gear extension system due to a fractured hydraulic line. Contributing to the accident was the inadequate inspection and maintenance of the hydraulic line.

NTSB analysis

During a flight review, the commercial pilot attempted to lower the landing gear but, after the gear-up light extinguished, the gear down light would not illuminate. After multiple attempts to lower the landing gear, the flight instructor declared an emergency, took control of the airplane, and prepared for a gear-up landing. During touchdown, the airplane left the paved portion of the runway, and was substantially damaged.

A postaccident examination of the landing gear system revealed that the hydraulic nose gear door actuator line on the right side of the aircraft failed due to fatigue at the flared end of the line. Review of maintenance records revealed that a high pressure electric fuel pump had been installed in close proximity to the failed line. No identification information or manufacturer information was present on the line and the straight sections of the tubing were not completely straight indicating that it had been bent by hand. A wear mark corresponding to significant contact with another object was observed on the aft side of the upper horizontal portion of the line which was covered by a plastic sleeve wrapped in electrical tape. It was likely that contact at that location produced excessive bending loads on the hydraulic line at the flare which lead to the fatigue fracture. Removal of the plastic sleeve which appeared to have been installed as a chaff guard revealed the existence of two other wear marks on the hydraulic line, one of which was approximately 50 percent of the wall thickness deep. The location of the wear marks corresponded to the location of the electric pump that had been installed and its fuel line fittings.

According to the Federal Aviation Administration, tubing should not be nicked, cut, dented, collapsed, or twisted beyond approved limits. When inspection shows a line to be damaged or defective, the entire line should be replaced or, if the damaged section is localized, a repair section may be inserted. Minor dents and scratches in tubing may be repaired. Scratches or nicks not deeper than 10 percent of the wall thickness in aluminum alloy tubing, that are not in the heel of a bend, may be repaired by burnishing with hand tools. Lines with severe die marks, seams, or splits should be replaced. Any crack or deformity in a flare is unacceptable and cause for rejection. A dent less than 20 percent of the tube diameter is not objectionable unless it is in the heel of a bend.

Text from the NTSB. Open the NTSB docket for ERA10LA005 for the full record.