Airworthiness Directives; Boeing Model 747-400 Series Airplanes Equipped with Pratt & Whitney PW4000 Series Engines

This document corrects information in an existing airworthiness directive (AD) that applies to certain Boeing Model 747- 400 series airplanes. That AD currently requires installation of a modification of the thrust reverser control and indication system and wiring on each engine; and repetitive functional tests of that installation to detect discrepancies, and repair, if necessary. This document publishes Appendix 1, which was referenced in, but inadvertently omitted from, the existing AD. Appendix 1 describes procedures for a functional test to detect discrepancies of the additional locking system on each engine thrust reverser. This correction is necessary to ensure that operators have the procedures necessary to perform the required functional test.