Summary
This document proposes to rescind an existing airworthiness directive (AD), applicable to all Cessna Model 750 Citation X series airplanes, that currently requires repetitive in-flight functional tests to verify proper operation of the secondary horizontal stabilizer pitch trim system, and repair, if necessary. The actions specified by that AD are intended to detect and correct such contamination and damage, which could result in simultaneous failure of both primary and secondary pitch trim systems, and consequent reduced controllability of the airplane. Since the issuance of that AD, an improved part has been developed, which, if installed, would terminate the repetitive tests; that improved part has been installed on all affected airplanes or is being installed in production. Therefore, the identified unsafe condition no longer exists.