Posts about: "The Federal Register (USA)" [Posts: 10 Page: 1 of 1]¶

https://www.federalregister.gov/docu...pany-airplanes

Do we know what electronics / avionics have been leaked onto previously that ended up resulting in this AD and its previous iteration?

Would anyone know whether this AD is relevant?

FAA Orders Boeing 787 Inspections to Fix Water Leak Issues

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I add this note: the background on this AD is here:
https://www.federalregister.gov/docu...pany-airplanes
T28B

Water ingress into the E/E bay is a serious issue. The B744 had this issue in the past causing serious problems, one of which was fortunate to not lead to a loss of the aircraft, on a B744F. The B744 pax aircraft had a number of water problems related to the toilets and the galley. The forward galley on the B742/3s had many issues.

Any large aircraft going through maintenance is interesting to observe the extent of corrosion that occurs near toilets and galleys, and from water lines.

The B777 was not immune to this either. The potable water tank failing caused one of our aircraft to have 6.5 tons of ice accumulating in the underfloor area of the aft cargo hold, which we detected on a preflight walk around as a series of water streams from the drain holes in one area of the aircraft. This was an interesting item for CG, a note on weight, but only affected the electrical services related to the aft cargo systems.

Water accumulations on the B744 came to light at rotate, and took out a lot of electrical services.

My suspicion is some cause such as this will come to light shortly.

The water leak issues with the B787 go back to in service reports in 2014 and before, considered an unsafe condition in 2016, and were covered by AD 2016-14-04. This latest AD is curious as it stems from an administrative oversight in the drawings of the aircraft, that arose on aircraft manufactured from 2018 onwards. 2025-09-12 stands alone related to missing sealant, following the drawing oversight in production. It did not affect all aircraft. The earlier AD, 2016-14-04 was related to water line coupling issues, and is in Service Bulletin B787-81205-SB380009-00 WATER/WASTE - Water System- Potable Water System - Couplings Replacement. It notes on page 21 of 229 the reason for the work

The latest AD and the earlier AD highlight that problems can occur, and have done so in the past. Both of the E/E bays contain stuff that is nice to keep dry and operating, and prior events have shown that multiple system failures can and have occurred when a flood is added to all the black boxes sitting innocently on their racks.

The ADs are not necessarily directly related to the specific cause, they highlight the potential for water damage and that bad stuff happens. In two cases I investigated, the event occurred at rotate. Both were B744's one pax, one F.

Compound, unrelated system failures at rotate? Single cause? Water in the E/E bay.

The amount of flooding that occurs in the toilet cubicles is unfortunate, apparently towels still fit well into toilet bowls, signs are disregarded etc. Coffee grounds block galley drains with monotonous regularity, the planes are only as good as we care for them, and passengers seem to have odd ways of treating the conveniences.

The type of switch being discussed is the specific type reported as being liable to problems. The SAIB is here https://ad.easa.europa.eu/blob/NM-18...SIB_NM-18-33_1 and specifies a part number for the B788 as 4TL837-3D

That's a TL series switch with 4 poles (the "4" in "4TL"), a "type D" lock (meaning locked out of centre position per the Honeywell data sheet - the "D" in "3D." This is a photo of one:


You can find the manufacturer's datasheet here: https://octopart.com/datasheet/4tl83...ywell-25749542

Problems with critical switches aren't new on 787-8s. For instance, in addition to the SAIB above, there's this AD: https://www.federalregister.gov/docu...pany-airplanes

Looking at the photo above, it isn't just wear that's potentially an issue, but foreign object impingement. There don't appear to be gaitors fitted to these switches in the 788, so the locking mechanisms are potentially susceptible to a build-up of material if not kept clean. There are a range of other failure modes possible, whilst the SAIB specifically describes found-in-the-field problems with these switches.

Yes, they're chunky, and very positive when new. That doesn't mean they shouldn't be discussed.

This switch thing is a nothing burger. If you\x92ve ever operated these switches you\x92d know how they feel. They require a very distinct pull and are most definitely either on or off. There is no impossibly balanced in between position.

On this matter, your numbers fall within the range I earlier calculated from doppler shift on the rooftop video's audio, so yes the numbers make sense and, given the circumstances, are reasonably close together.

I also placed the relevant positional data (last ADSB, video source, resting site) into a GIS application and used this along with the audio stream duration to calculate average speed. Obviously it is necessary to correct the speed of sound for environmental conditions but even with this I wasn't happy with the early results I got. At about this time I came to a view that this information wasn't really going to help anyone much so didn't go any further.

From detail that may be retrieved here the FAA noted that Boeing made the following 'Request for correction' (my bolding to highlight why I quote this):

"Boeing explained that the RAT will remain operational as the airplane decelerates through the minimum RAT design speed of 120 knots, not 130 knots. Boeing expressed that the performance of the RAT was shown to meet the Boeing Model 787 requirement that specifies 120 knots as the minimum RAT design speed. We agree that the RAT will remain operational as the airplane decelerates through the minimum RAT design speed of 120 knots, not 130 knots..."

Again I'm not sure this is of any particular utility now, but is included here in the interests of ensuring as much factual data is available as possible.

FP.

In response to removed posted video link about drifting ADs since 2022, not finished yet but remarkably, seems to be 100% accurate:

https://www.federalregister.gov/docu...pany-airplanes

https://www.federalregister.gov/docu...pany-airplanes

Actually, I have a little experience with this too. More commonly a male-related problem, but that "water" that could seep through from the lav floors into the EE Bay(s) is often highly conductive, if ya get my drift? Water has an absolutely amazing ability to track and seek. Add some electrolytes and it's often even better.

Agreed. But the FAA itself does speculate - on what basis, I have no idea. They use the word "may", see here, last sentence (and in other ADs in the sequence):

https://www.federalregister.gov/d/2022-26933/p-18

This paragraph (and one before) is/are also worth a read - they see no rush to fix, obviously. https://www.federalregister.gov/d/2025-08346/p-20

100% Agree: any suggestion that it's in any way related to 171 is pure speculation. Sounds like these ADs apply only to small numbers of 787s. Don't even know if 171 was one of them.

But installing lavatories directly above EE Bays? Who's the genius...? .

Anyway, I make a point of not going 'there' during the last half of any long flight. They are frequently "awash" and unpleasant places to be. The washbasins themselves are also prone to the ejecting of water onto the floors. Agreed, it's a ####ty problem.

The requirements I have seen indicate that RIPS is applicable only to CVR or the CVR function of an EAFD. If you are aware of any requirement for RIPS to support flight data recording would you please provide a reference.

FAA requirements and the discussion/changes that resulted from the initial NPRM here -

https://www.federalregister.gov/docu...er-regulations

Yes, possible electric failure on the eafr is of course a totally different story concerning voice recording