Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Bombardier Model DHC-7- 100, -101, -102, and -103 series airplanes. This proposal would require inspecting the endcaps of the main landing gear selector valve for leaks of hydraulic oil and, if leaks are detected, replacing the leaking endcaps or the entire selector valve. This proposal would also require eventual replacement or rework of certain selector valves, which would terminate the repetitive inspections. This action is prompted by a report of the collapse of the main landing gear due to an external leak of hydraulic oil in the landing gear selector valve, resulting from a fracture of the endcap. This action is intended to prevent leaks of hydraulic oil from the main landing gear selector valve, which could result in the collapse of the main landing gear.