Federal Register #FAA-2026-4668

FAA Proposed Airworthiness Directive for Boeing 747-400 Series: Water Leak Inspections and Corrective Actions

The Federal Aviation Administration (FAA), through its Airworthiness Products Section, Operational Safety Branch, is proposing a new airworthiness directive (AD) for Boeing 747-400 series airplanes. - Government Buyer: - Federal Aviation Administration (FAA), Airworthiness Products Section, Operational Safety Branch - OEM Highlight: - The Boeing Company is the only OEM referenced - Products/Services Requested: - Repetitive inspections of potable and waste water lines on the upper and main decks for leaks and clogs - On-condition corrective actions if leaks or clogs are found, including rendering systems inoperable or checking the engine indication crew alert system (EICAS) - Procedures are specified in Boeing Message TBCTBC25669401B - Quantities: - 4 U.S.-registered Boeing 747-400 series airplanes affected - Unique/Notable Requirements: - Inspections must occur within 1,000 flight hours of the directive's effective date and recur at intervals not exceeding 1,000 flight hours - On-condition actions must be performed before further flight if issues are found - The directive is considered an interim action pending a future modification - No specific part numbers or product procurement; the requirement is for inspection and maintenance services

Description

The FAA proposes a new airworthiness directive (AD) for certain Boeing Model 747-400 series airplanes due to reports of potable water leaking into the electrical equipment bay cooling air inlet. The AD requires repetitive inspections of potential water sources from the upper and main decks, including potable and waste water lines, to detect leaks and clogs, along with applicable on-condition actions. This action aims to address the unsafe condition that could impact essential electronics and result in loss of safe flight and landing. The FAA invites comments on this proposed AD by August 14, 2026.

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