Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain Fokker Model F28 Mark 0070 and 0100 series airplanes, that would have required a one-time operational test of the pitot heating system, and repair or replacement of failed elements. That action also proposed to require the replacement of the pitot heating system with a new improved system. This new action would revise the proposal by adding a requirement to install power supply wiring with increased gauge thickness and a circuit breaker with an increased amperage rating. This action also would add additional airplanes to the applicability of the rule. The actions specified by this proposed AD are intended to prevent icing of the No. 1 pitot tube, which could result in failure of the No. 1 Air Data Computer, or output of erroneous airspeed data to all on-side subsidiary systems, including the Automatic Flight Control and Augmentation System.