EASA AD US-2021-01-07
Air Conditioning - Environmental Control System / Equipment Cooling System - Inspection / Installation / Modification
Summary
Airworthiness Directive 2021-01-07 is a final rule issued by the Federal Aviation Administration (FAA) addressing certain Boeing 737-700 series airplanes. It mandates repetitive testing of the smoke clearance mode of the equipment cooling system and low pressure environmental control system, installation of new relays, and wiring changes to the environmental control system. This directive aims to prevent latent failures that could lead to smoke in the flight deck or cabin and potential loss of aircraft control.
What Changed
This new Airworthiness Directive introduces repetitive operational tests and corrective actions for specific Boeing 737-700 airplanes with certain air distribution system configurations. It also requires installing new relays and modifying wiring in the environmental control system. Unlike previous AD 2016-04-06, this AD applies to seven specific 737-700 airplanes and does not supersede the earlier AD but terminates its requirements for those aircraft.
Why It Matters
This AD is critical for aviation professionals because it addresses latent failures in the equipment cooling and environmental control systems that could compromise smoke clearance during a cargo fire event. Operators and maintenance organizations must ensure compliance to maintain aircraft safety and prevent smoke ingress into the flight deck or cabin. The directive also clarifies compliance responsibilities for specific aircraft not covered under previous regulations.
What To Do
Operators of affected Boeing 737-700 airplanes must perform repetitive tests to verify proper operation of the smoke clearance mode and carry out any necessary corrective actions. They must also install new relays and modify wiring as specified in the Boeing Alert Service Bulletins. Compliance with these actions is required by March 9, 2021, and comments on the AD are invited until April 8, 2021.
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