Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Jetstream Model ATP airplanes. This proposal would require modification of the hydraulic system, and a revision to the Airplane Flight Manual (AFM) to include revised procedures for lowering the landing gear. This proposal is prompted by a report of uncommanded application of the brakes when the direct current (DC) hydraulic pump was selected ON with the main hydraulic system operative; this situation was caused by build-up of back pressure in the brake supply and hydraulic return systems. The actions specified by the proposed AD are intended to prevent uncommanded application of the brakes during landing, as a result of the build-up of back pressure.