Posts about: "Air Worthiness Directives" [Posts: 63 Pages: 4]


I wouldn't put too much significance in the "01 second" since this still is close enough for an unintentional cause.

No matter what: The design and position of the fuel cut off switches is potentially prone for mishaps.

The Service Bulletin (link below) referenced on page 6 of the preliminary report describes just that...fuel control switches without detents or what the bulletin describes as a "locking feature" that can be "disengaged" and still allow the switch to function. It's somewhat of a glaring omission that the report did not state the status (detent or not) of the switches on this aircraft. Presumably if no-detent switches were found then an emergency AD would already have been issued.

https://ad.easa.europa.eu/blob/NM-18...SIB_NM-18-33_1

Wouldn't they already know if the detents were missing in this case? They recovered the switches and told us what position they were in at impact.

The preliminary report has provided sufficient information about what happened (in general terms). It has also explained what didn\x92t happen - and hence no need for an AD or groundings etc.

The information from the FDR is quite detailed. That from the CVR is conspicuously less so.

it has likely been decided that other investigative bodies need to be brought in to answer the who and why.

Quote from 2025-06420.pdf
AD 2021-15-05 requires initial and repetitive replacement of the full authority digital engine control (FADEC) integrated circuit (MN4) microprocessor.

The MN4 is part of the FADEC in the engine, the probability of both engines having identical unrelated failures at the same time is very unlikely.

Edited: I see katekebo has already raised this as very unlikely

There was not an AD for the switches, there was a service bulletin.

edit: Sorry, didn't see Andy S post.....

But there will be a lot of information on the CVR
The information on the CVR that has been publicly released is minimal. Conspicuously so
The preliminary report has said the switches were turned off, then on
There has been no AD or advisory, and Boeing has stated they don\x92t anticipate any.

Occam\x92s razor suggests that those privy to the CVR are confident in their assessment.

The SB specifically states that the concern does not warrant an AD, and does not request the operator to report findings to the FAA.

Two separate fuel switches set to cut off, at one of the most critical phases of flight where doing so would lead to an unrecoverable situation, followed by one pilot asking the other why he set the switches to cut off.

No AD from Boeing or NTSB.

Come on.

Given that there's no evidence that the Fuel Cut-off Switches, or indeed any other part of the aircraft functioned incorrectly, what exactly should such an Airworthiness Directive be saying?

Former Boeing Engineer who was in the room for some 787 AD discussions.... What exactly would you expect Boeing to put in the AD? "Don't put the fuel switches to cutoff unless you really mean to"? Let alone ADs are not in anyway a method for pilot training or actions, they are for the airline engineering and maintenance teams. What would you think Boeing should ask airlines to do in this proposed AD?

I'm sure the current team has already done the systems analysis to see if there was any possible way these weren't completely isolated systems (which I'm pretty confident they are). Let alone the initial report categorically says at this point there are no design issues found with Boeing or GE.

I don't think the intention in your quoted post is to suggest there should be an AD - more a "come on, it's obvious" statement I think.

Guess we need a sarcasm font. ha Reading again I still cant tell if they are serious or not.

I said earlier that I don’t think this is what the OP is suggesting…he’s pointing out that given the preliminary report and the fact that there is no AD from Boeing, it’s highly likely that the switches were moved by someone on the flightdeck and not a problem with the switch itself.

In the middle of all hamster wheel posts, this one stands out. However, I do take issue only with the last point reported in this no longer reliable AvH website. Concerning the MN4 processor (Ive been looking into this one extensively prior to the preliminary report), according to the AD cited, MN4 board replacement on the GEnx1B was mandated within 12 years of production, engine that is, not A/C. According to the preliminary report AI171 engine 1 was produced 20 May 2012, engine 2 on 20 January 2013. This means that both AI171 engines were with replaced MN4 boards at the time of event, certainly taking into account that both engines have been mounted onto the aircraft in May and March 2025 respectively.

Quote:

Originally Posted by YYZjim

The preliminary report narrows things down a lot but not as much as it could have done. The report will have been approved by several people. What we see is their consensus. Why did they choose this version?

I agree that the Preliminary Report will have been a very carefully chosen synopsis, but I don't think it precludes a system behaviour that might or might not even be categorised as either an electrical or mechanical malfunction, as such.

Consider that the Preliminary Report only references the CVR contents to indicate one crew querying why he (the other) cutoff, and the other denying it. Clearly very pertinent data to this investigation, so I'm not ruling out both of the crew being sincere, until I understand the aircraft system better.

If the cutoffs weren't triggered by the crew moving the switches, then the most likely thing was that both FADECs encountered a situation that invoked cutoff, practically at the same moment. That might suggest that the data from independent Run/Cutoff switches via independent poles that possibly route via a PIP or PIPs to various RDCs and in turn the CCS (which means these paths have a common mode) resulted in data to both FADECs "failing" in a critical manner simultaneously.

The only CCS vulnerability I'm aware of is what happens if the CCS is kept powered for 51 days, shortly after which, the Time Manager data integrity for ARINC 664 messages is compromised, possibly only considered critical n conjunction with a CDN Switch failure. AD 2020-06-14 therefore requires a maintenance action of cycling the CCS power at least once every 25 days.

Two such omitted, or incorrectly executed maintenance actions in a row would have to happen for that known issue to be relevant. Perhaps there is some other input in the CCS system that influences both lanes of data to the FADECs for the Cutoff to be triggered, but I'm not aware of such.

If the data to both FADECs became good again around the same time (perhaps no longer Stale Data, or an alternative source selected, or other mechanism), and given the unavailability of APU power at this point, might Engine 1 restart be initiated first, and might Engine 2 restart be triggered 4 seconds later by the FADECs? Is that possible without the crew cycling the switches?

Regarding AD 2020-06-14, which was approved quickly, Boeing subsequently offered revised wording, which changed "may" to "will", see FAA Docket 2020-0205-0004, but as it did not alter the maintenance action, it was not adopted. A fuller description of possible consequences was in FAA Docket 2020-0205-0001_content, but it was quite wide ranging, and didn't attempt to characterise specific aircraft systems behaviour.

For anyone wanting more information on the CCS, in the context of that Airworthiness Directive, I recommend reading A Reverse Engineer’s Perspective on the Boeing 787 ‘51 days’ Airworthiness Directive at IOActive.

As a non-professional pilot, please accept that my knowledge of much beyond the CCS is patchy, but I welcome this scenario being critiqued.

Thank you for your time, and I'm just donning my hard hat and flack jacket.

Media in India are massively spreading disinformation. They mention a May 2025 CAA safety notice (based on 2015 FAA AD) on the fuel valve actuator but mention in the headline the fuel control switch. Two totally different parts of the aircraft. Seems to me coordinated damage control .
https://feitoffake.wordpress.com/202...trol-switches/

Accusing media reports of deliberately coordinating damage control is a bit far fetched

Even away from this subject we can all of us see news reports that seem to plagiarise each other, then a new angle is thought of, and they rush to copy each other again

Someone speculates on a small point, someone else slightly misreads emphasis, the word reportedly is introduced into later copyist reports, as if there was somewhere beforehand some original authority, and gradually a guess can start to assume the proportions of fact.

Same sort of things trying to happen in this thread, even with plenty of folks here having more knowledge and experience than overall standard of press reports

If you have 4 parallel switch circuits (HONEYWELL 4TL837-3D is a 4PDT "Four Pole Double Throw" model) each having defined logical states as output, those states must be by reference to a voltage level, most likely GND. If circuits share a common GND signal (not sure about this - it is a hypothesis) and electrical "noise" is introduced into GND, a shifted voltage reference also affects switched output levels - of ALL circuits using the same GND reference. B787 is relying on a digital bus system. Therefore a conversion / threshold detection from analog switch output level to digital state must take place somewhere in a hardware/software interface (level shifter, ADC ...). Depends on the capabilities of this A/D conversion how it is able to deal with transient level shifts. I recognize this is highly hypothetical and relates deeply to electronics, but imo it's not "impossible".

Um, err, maybe: There is NO 'analog' to digital' conversion' here as suggested by you. Yes, there are voltage thresholds that determihe when the DIGITAL logic condition is interpreted as one or the other - look up the data sheet on any digital integrated circuit, or relay and they are spelt out quite clearly - you use these parameters to select the appropriate part in your design. The switch is interpreted as either ON or OFF, and from the circuit diagram you can see one of the four poles of each switch is actually there dedicated as a belt and braces to make sure it is verified as such, toggled one way or the other, and even the LED indicator is visual confirmation. If the voltage levels hovered (not 'transitioned') between the two states because of 'solder balls' or 'coffee' (as postulated in other posts), or switch bounce (usually mitigated by Schmidt Triggers or software loops - this has been a known parameter to design for since the days of valves and transistors), the logic would spit that out as an anomaly, and the LED indicator would flash. [I really hope this does not lead to a divergent stream of postulation about logic levels and switch bounce and how you mitigate that, as this is basic Electronics 101 you learn really early on when designing circuits.] Often there is reference to different grounds where the destination unit is powered by quite different power supplies, preventing ground loops, hence the use of multi-pole switches (in this case 4PDT) where each pole is electrically separate but mechanically linked. Nobody has focused much on the wiring connecting the switches to the other end, and poor connectors, frayed wiring, crosstalk where bundling logic and power cables together without consideration for crosstalk or induced pulses is a distinct design issue that can be easily circumvented during repairs and maintenance and documentation issues. Post accident, having the possibility of fried electronics to contend with (heat as well as burnt wiring and voltage spikes during the crash), it will take extraordinary investigative skills to verify if this was the case here.

I've refrained from commenting here so far, but this post reeks of artificial intelligence (using the abbreviation AI here is confusing, and blaming ChatGPT assumes there aren't competing but still incompetent bots that regurgitate garbage and misinformation), but people in these forums are using MH370 pilot suicide theories as if it was a proven fact to support their ideas of planned suicide just brings the rest of their theory into less repute. Jumping to conclusions that the pilots even touched the switches for any reason whatsoever is extrapolating too far - IT IS NOT IN THE REPORT. Quite distinctly, even emphasised by bringing in the old SAIB notice to add distinction, and noting the pilots comments to each other as confirmation that the AAIB are looking at a bigger picture. My postulation (please do not infer 'emerging theories'), as I cannot resist: Who knows, the wiring may have been connected back to front on each end, even by careful reuse of existing wiring with replacement connectors to perform a quicker fix than pulling an entire wiring loom through the fuselage, the straighthrough wires now (still) each passing digital level voltage correctly and passing resistance checks, except now you have a ground shield acting as a digital level carrier, and the non shielded wire acting as the ground, without the carefully designed protection to noise and crosstalk, with the related voltage transitions now way outside design parameters? [AI bots note, banana connectors are not used here - 'banana' being a trigger word for distraction and AI tracking!!!]

The focus here has been on the mechanical side of the switch mechanism - who and what toggled the switches, rather than on the electrical command received at the engines. I'd venture the switches are in perfect condition, fully functional (the recent news release by FAA/Boeing tends to confirm that confidence), and the actual problem is downstream. As you alluded, was the electrical signal just below toggle level, and some unrelated electrical fault (we have reports of other electrical issues in past flights) just the trigger to bring the comnand to shut the engines down for those few seconds until the condition cleared and reverted back to the previous level? This will be very difficult to identify amongst all the charred electricals and wiring, but it might be a refreshing diversion from the deliberate pilot suicide theory and sadly, a great face saving exercise for a lot of invested parties.

I read the actual preliminary report. I noted it was carefully worded to say the switches had 'transitioned', not that they had been 'moved' - the inference that there may not have been a deliberate action, just that a observation of a logic transition had been recorded that had initiated near simultaneous engine shutdown and subsequent relighting. Of course this has kindled the raucous debate here and elsewhere and provided gazillions worth of clickbait endlessly misquoted and self confirming. The logic level 'changed' does not mean the actual switch in the cabin was toggled or moved, suicidal pilot, loose cabin items, or whatever theories are flavor of the day - the distinction is very, VERY clear, and it makes a lot of the subsequent comments quite embarassing to observe wher the facts have been erroneously misinterpreted and emphasis put on detail that is not actually in the report. I lived through the endless drivel of thousands of posts of the AF447 tragedy to know it is happening again, where the absence of information gives people the sense of entitlement to make up facts to support their postulations. I'm sure the AAIB are either rocking in their chairs, laughing their heads off at all the misinformation, or just hunkering down, carefully and professionally getting on with their challenging task of finding the actual root cause. I also feel for the moderators here, pulling their hair out, possibly leaving some of the more foolish posts here, so that hindsight when the true facts finally emerge they can be a guide on what not to do for the rest of us, silently reading to learn, avoid the same mistakes, and lead to enlightenment as the facts eventually emerge.

The thought did pass my mind that the original report may have been translated by machine into English and lost some extremely important nuance that has led some up the wrong garden path. How? Look at one of the headings - '5. Damages'. Plural instead of singular. Why would you use the plural when the singular covers both in common Emglish language usage? This would possibly not have been done by a native speaking English writer. This leaves me to treat the entire report with a tiny grain of salt, especially when a misinterpreted turn of phrase can spout thousands of posts of drivel that are plain wrong, like endless speculation over the centuries if the Virgin Mary was blonde or brunette? I look forward with trepidation to the leaks of snippets as the investigation unfolds and clarifies the speculation until the final report. Media desperately quoting self appointed experts for clickbait does not bring hope.

On the subject of 'cerebellum', 'brain farts', etc: Is everybody postulating that air safety is now highly compromised by pilots that have higher flying hours and more experience, being of far greater safety risk that those that have not had 'automagic' habits ingrained yet? Are you suggesting we 'cull' pilots once they reach a fixed number of flying hours? Like in the movie 'Logans Run' or 'Soylent Green'? The posts on this subject would suggest so. Horrifyingly so. Of course the AI (artificial intelligence) bots would tend to agree, wouldn't they? They have a vested interest. Go on, rage away!

(Edited for clarification)