Summary
This document proposes the adoption of a new airworthiness directive (AD) this is applicable to certain Fokker Model F.28 Mark 0070 and 0100 series airplanes. This proposal would require repetitive operational tests for discrepancies of the heating system of pitot tube #1, and replacement of the pilot tube, if necessary. This proposal also would require eventual modification of the alternating current sensing circuit for pitot tube #1, which would terminate the repetitive operational test requirement. This action is necessary to prevent failure of the heating system of pitot tube #1 due to a short circuit, which may go undetected and lead to the pilot receiving erroneous airspeed indications, resulting in reduced control of the airplane. The action is intended to address the identified unsafe condition.