Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Fokker Model F27 Mark 050, 200, 500, and 600 series airplanes. This proposal would require installation of certain components, and revisions of the Airplane Flight Manual. This action is necessary to prevent undetected failures of the horizontal and vertical stabilizer de-icing system, which could result in reduced controllability of the airplane. This action is intended to address the identified unsafe condition.