Summary
This document proposes to revise an earlier proposed airworthiness directive (AD) that would have required replacing certain AlliedSignal Inc. VN 411B VHF navigation receivers installed on aircraft if the receivers do not have Modification 20 incorporated. The proposed AD was the result of a report of navigation receiver interference during landing operations. The actions specified by the proposed AD are intended to prevent VHF navigation receiver interference from frequency modulation (FM) radio station broadcasts, which could cause distortion of the navigation audio and deflection of the desired flight path of the airplane during landing operations with possible loss of control of the airplane. Since issuing the NPRM, the applicable service information has been revised to incorporate additional procedures for modifying the affected navigation receivers (Modification 21). The Federal Aviation Administration (FAA) has determined that these procedures are necessary to correct the unsafe condition; that the revised service information should be incorporated into the proposed AD; and that the comment period for the proposal should be reopened and the public should have additional time to comment.