Airworthiness DirectiveEASA AD US-2023-21-09

Flight Controls - Trailing Edge Flap Transmission and Gearbox Assemblies - Inspection

Published: Nov 20, 2023
Effective: Dec 18, 2023
Deadline: Dec 18, 2023

Boeing 777 200 200LR 300 300ER

AI-generated summary of the official EASA document. Verify against the PDF before acting.

What to do

Operators of affected Boeing 777 aircraft must inspect or review records to identify the serial numbers of the trailing edge flap transmission and gearbox assemblies by December 18, 2023. If affected parts are found, they must perform the required corrective actions as specified in the Boeing Alert Requirements Bulletin 777-27A0123 RB. Installation of affected assemblies is prohibited unless they have been inspected and corrected according to the directive before the effective date.

Summary

Airworthiness Directive 2023-21-09 is a final rule issued by the Federal Aviation Administration (FAA) addressing all Boeing 777-200, 777-200LR, 777-300, 777-300ER, and 777F series airplanes. It mandates inspection or records review of the trailing edge flap transmission and gearbox assemblies to identify affected serial numbers and requires corrective actions if necessary. The directive also restricts the installation of certain parts to prevent unsafe conditions related to flap control failures.

What changed

This new airworthiness directive introduces mandatory inspections or records reviews to determine the serial numbers of the trailing edge flap transmission and gearbox assemblies on specified Boeing 777 models. It requires on-condition corrective actions, including replacement or repair of assemblies with damaged ratchet pawls or torque tube disconnects. Additionally, it limits the installation of affected parts unless they have been inspected and corrected per Boeing Alert Requirements Bulletin 777-27A0123 RB.

Why it matters

This directive is critical for aviation professionals because it addresses a safety issue that could lead to asymmetric lift loss and jeopardize safe flight and landing. Operators and maintenance organizations must ensure compliance to prevent in-flight flap drive failures that have previously caused air turn-backs. Proper tracking and inspection of parts are essential to maintain airworthiness and avoid operational disruptions.

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