The US FAA is urging airlines to conduct “repetitive” inspections of the area under all lavatory washbasins on board their Boeing 787s, after fielding reports of undetected water leaks that could harm electronics and create an unsafe condition.
If adopted, the agency’s proposed airworthiness directive (AD) would cover Boeing 787-8, 787-9, and 787-10 twinjets and affect 140 airplanes of US registry.
“The FAA received reports of undetected water leaks from the faucet control module (FCM) migrating below the passenger floor in multiple lavatory locations during flight, and into the electronic equipment bay(s), which could damage flight critical equipment,” it explains in a notice of proposed rulemaking.
“This condition, if not addressed, could result in loss of multiple line replaceable units (LRUs) and subsequent loss of continued safe flight and landing,” it warns.
Among the reports received by the agency, one 787 operator found wet carpet around the flight deck which led to an inspection of its fleet.
“After inspecting their fleet, multiple airplanes had water leaking from the FCMs. The FCMs are located under the sinks in each lavatory and have an O-ring seal at the top of the FCM mixing chamber, which has been identified as the source of the leak,” explains the FAA.
“When the FCM is activated and the lavatory faucet is in use, a small amount of water can leak past the O-ring. The leak path is out of the lavatory module and through the airplane floor. Intermittent leakage will have a slow leak rate (approximately 8 ounces per hour) but a long latency period because it is difficult to detect.”
As a result, the FAA is calling on operators to conduct “repetitive general visual inspections of the area under all lavatory washbasins for evidence of intermittent and active leaks at the FCM and applicable on-condition actions”.
Labor and parts to replace each product are estimated to cost roughly $6106, but the FAA notes: “The agency has no way of determining the number of aircraft that might need these replacements.” Comments will be received for 45 days (PDF).
Featured image credited to Jason Rabinowitz
