Airworthiness Directives; Various Transport Category Airplanes Equipped with Mode “C” Transponder(s) with Single Gillham Code Altitude Input

This amendment rescinds Airworthiness Directive (AD) 99-23-22 R1, which is applicable to various transport category airplanes equipped with Mode "C" transponder(s) with single Gillham code altitude input. That AD requires repetitive tests to detect discrepancies of the Mode "C" transponder(s), air data computer, and certain wiring connections; and corrective actions, if necessary. The requirements of that AD were intended to prevent false advisories that direct the flightcrew to change course and either climb or descend, which could result in the flightcrew deviating the airplane from its assigned flight path, and a possible mid-air collision. Since the issuance of that AD, test data have been collected that demonstrate that the repetitive tests are unnecessary.