Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain CASA Model CN-235 series airplanes. This proposal would require disabling the brake control valve of the propeller. This proposal also would require that, prior to restoring propeller brake operation, the propeller brake control unit be replaced with a certain new propeller brake control unit. This proposal is prompted by reports of uncommanded activation of the propeller brake system on in-service airplanes during flight, due to the existing design of the brake control valve. The actions specified by the proposed AD are intended to prevent in-flight uncommanded activation of the propeller brake system, which could result in in-flight shutdown of the engine.