Bombardier CL-600-2B19 N407AW incident near Philadelphia, Pennsylvania

Probable cause

the failure of the maintenance personnel to properly complete the installation, and the inspection personnel to conduct the proper functional test, of the left main landing gear uplock assembly.

NTSB analysis

The flight crew had indications of a landing gear problem during approach. After unsuccessfully attempting to lower the gear, the flight crew elected to make an emergency landing with only the nose gear and right main landing gear "down and locked". After touch down, the airplane came to rest on its right main landing gear, nose gear and the left wingtip and flaps, resulting in minor damage. Post-incident examination of the maintenance records and airplane revealed that the left and right main landing gear (MLG) uplock assemblies had been replaced prior to the incident flight. No anomalies were found with the installation of the right MLG uplock assembly; however, the upper attachment bolt in the left MLG uplock assembly was improperly installed and had not properly been inspected. As installed, the upper attachment bolt did not engage the uplock assembly, which allowed the uplock assembly to pivot inboard about the lower attachment bolt and the uplock release cable no longer allowed the lever full travel to release the uplock. The left and right uplock assemblies had been replaced by two different mechanics and neither mechanic witnessed the gear swing test, but each signed the work package off as being completed after making a verbal turnover to the day shift supervisor. This was inconsistent with company policies and procedures. The installation was inspected and there were several discrepancies noted concerning the left gear assembly installation. Although the discrepancies were corrected, they were not properly documented. Additionally, the inspector did not use a mirror to examine the components in the darkened gear well and used an abbreviated functional check procedure instead of the manual gear extend test procedure specified in the maintenance manual. The mechanic who replaced the right uplock assembly stated that he had replaced uplocks on other airplanes but not the accident type airplane. The inspector stated that he had no experience inspecting uplock assemblies, nor did he recall ever having removed or replaced a gear uplock assembly as a mechanic. Based upon findings of the investigation, the NTSB issued Safety Recommendation A-10-96 and -97, dated May 28, 2010.

Text from the NTSB. Open the NTSB docket for DCA09IA017 for the full record.