Do you stand by your previous assertion :-

a) 🤷‍♂️
b) Wouldn\x92t it capture the Alt rather than descending thru it?

It took much more than a few days for the 737 Max to be grounded

Maybe you should have kept sitting on your hands, theory a) in particular is about as risable as the last one you posted. Do you still think engine failure takes 30 seconds for the plane to react?! Thanks to rkenyon for alerting us not to take your post seriously. You still don't believe the RAT was out despite the in depth audio analysis done by an expert in the field. You still think its a motorbike?!

Given they took off at a perfectly normal point, at a perfectly normal speed, I don't see how you come to incorrect derate and low v speeds, or how on earth that would lead to a normal takeoff followed by sinking?

It isn't. It's essentially just a CVR and FDR in the same box. The main USP is that you now have two of each, about as far apart from each other as possible on the aircraft.

Each is downloaded separately in pretty much the same way as always.

I was referring to CVR/FDRs in general being specialist equipment requiring specialist facilities to process. In any case, I would be very interested to find out where those from this accident are read. It appears from a post upthread there are new facilities in New Dehli that could be used. Having said that, for the EK 521 accident in Dubai the recorders were sent to the UK for analysis, despite a "flight data recorder centre" in Abu Dhabi being opened (again with much fanfare) by the UAE GCAA five years before the occurrence.

The Indian AAIB successfully downloaded both FDR and CVR data from an Air India 787's EAFR relating to an incident in 2018, so your misgivings on that account are unfounded.

And they do have a new lab, as of this past April:

AAIB sets up flight recorders laboratory

More at linked site. The lab opening is also featured in the slide show on the top page of the AAIB website, following a series of slides for International Yoga Day.

I have no misgivings, I\x92m just challenging the assertion that because the recorders have been found, they have already been read. There\x92s any number of reasons why they may not have been read yet, in India or anywhere else.

If they had, we would still be looking at potato cam footage as we would only get to see it together with the (cleaned up) FDR readouts and paraphrased CVR protocol in a report +12 months from last week.

Absolutely.

If the aft EAFR ceased recording at the point (just short of the runway end) where the ADS-B and likely everything else went dark, then the extra 30 seconds of CVR recording from the forward recorder could well be crucial to the investigation.

Could the fellow who was cited as having heard the CVR and commended the pilot's actions.... because he trained under the Captain, and would be familiar with his speech, have been bought in to validate who was speaking on the transcript?

Given the number of times I reviewed DFDR data supplied by an operator after some sort of event/incident, I think most major operators have access to the equipment needed to download a healthy data recorder. So I'd be a bit surprised if Air India does not have this capability. OldnGrounded has also posted that the Indian AAIB also has that ability.

Usually when I hear of data recorders going back to the US NTSB or the recorder manufacturer, it's because the crash damage is such that specialized equipment is needed to download the data. The recorder in the tail would likely have little damage.
While the AAIB may have held off on downloading the recorders until all the major players are present, it's been several days - I'd expect everyone who matters is already there. So I think it is reasonable to believe that the investigators have done a download and have had at least a preliminary look at the data. If there is a smoking gun, they probably already know (and the longer we don't hear something regarding the rest of the 787 fleet, or at least the GEnx powered fleet, the less likely it is that they suspect a systemic problem with the aircraft and/or engine). However the proviso that I posted earlier about potential data loss/corruption due to a sudden shutdown still applies - so maybe the data simply isn't on the recorder.

As has already been posted, EMI is highly unlikely - the current cert requirements for HIRF are quite high, and due to the composite airframe construction of the 787, the lighting requirements are much higher than for conventional aluminum aircraft (the higher resistance of the composite airframe results is higher lightning induced currents).

FDR has suggested a large slug of water hitting critical aircraft electronics at rotation - it is possible that resultant electrical short circuits could falsely signal the engines that the switches are in cutoff. Highly unlikely that it would do that to both engines, but possible.
Then again, all the other plausible explanations are highly unlikely, so...

BTW, I do have a life outside PPRuNe - and I'm going to be traveling the next several days, with limited to non-existent internet access. So don't be surprised if I'm not responding posts or PMs.

I (and I think everyone else here) have been assuming that the FADEC does in fact have a dedicated permanent-magnet alternator, as is the case on the Airbuses (confirmed by FCOM) and surely the 737.

I have been told elsewhere that this is not the case. A read of the draft FCOM available online for the 777 & 787 makes no mention of a FADEC generator, but then neither does the 737 manuals. Is this simply a case of "Boeing thinks you don't need to know"?

It has been proposed that the primary source of power for the FADECs is actually the flight control PMGs, mounted on the engine gearbox, but that this power goes to the avionics bay, has failover switching gear, and comes back to the EEC.

Can anyone shed concrete light on this (e.g. a source that clearly states there is both an EEC alternator and a flight control PMG on the accessory gearbox)?

Alternator and generator seem to be used interchangeably in this context.

It's not quite that, but there is a list of received channels for a GEnx 787 in the FDR report into one of the original battery fires . Unfortunately, it is only a list of parameters that they used and verified in the investigation - the only ones listed for the engines are N1 and cutoff switch. Other accident/incident FDR reports might be more focused on engines and include a similar table.

I don't think you'll find an actual wire list for it (or it won't be useful) as apparently most/all of the data is via an ARINC bus.

I attempted to PM this but your inbox is full.

[SLF with an electrical background and some exposure to ground-side critical facilities power]

The details don't really matter, but this is the certification requirement:

​​​​​​​ https://www.easa.europa.eu/en/docume...s-engines-cs-e

Think about this accident from 100,000 feet. In other words, DON\x92T think about the specific root cause. We have almost no factual information to ponder at the moment but we can still ask a larger question: How did an experienced crew in a modern aircraft find themselves in a situation from which there apparently was no escape? Given the redundancies, fault tolerances, crew training, and engineering and operational controls present in modern aviation, how could it be that they happily took off in an airplane and flew it into an unsurvivable event just moments later?

This isn\x92t the first one either. On February 9, 2024 a Challenger 600 manuevering to final at Naples FL, (APF) lost both engines simultaneously and crashed on a highway short of the runway. The NTSB final report isn\x92t out yet so we don\x92t know that cause either, but the situation was the same. SOMEhow, a highly experienced crew found themselves in a situation from which there was apparently no escape. Whatever the cause was, how did it go un-detected until it produced an accident? (It\x92s NTSB accident number ERA24FA110. You can find that thread on PPRUNE by searching on Challenger 600. The preliminary NTSB report contains interesting readouts from the FDR. Yes, they lost both fans simultaneously.) I\x92m not suggesting these two accidents have related causes, I\x92m only observing that both crews apparently had no way out.

I\x92m asking, \x93Whatever the flaw was that initiated these events, how did it remain un-known *until* it produced an accident?\x94 We test and re-test modern aircraft for every imaginable failure mode during the design, certification, and production process. We train and re-train techs, mechanics, flight crew, and everybody else that touches the airplane to be sure a high level of performance and safety is not compromised. Think bigger. Think about \x93the system\x94 as a whole. Apparently the system missed something. What are we not seeing?

My condolences to all who were lost. Please keep in mind that except by the grace of God it could have been any one of us on that terrible day.

NASA retired, licensed since 1971.

I didn't read that thread, but having flown the aircraft (challenger 600 type), I believe the consensus is that the Captain reaching underneath the thrust levers to actuate the flaps can (and has) resulted in the "triggers" on the back of the thrust levers being engaged- if this is done while the FO is bringing the thrust to idle, it can result in going below the idle stop to cutoff. In other words, the engines were inadvertently shut down.

But I agree that the complete, simultaneous loss of thrust on both engines has to be an astronomical probability, and the cause is going to be interesting to say the least.

I also agree that any one of us could be put in a horrible position within seconds that would be very hard to recover from- the older I get and the more hours I spend in the air, this starts to spend more time in one's consciousness, unfortunately.

BTW calling the crew " highly experienced" is a bit of a stretch IMO, the Captain certainly was, but 1100 hours isn't even enough for an ATP in most countries. For all we know it was not a factor, of course.

PS, what is an SLF??

There seem to be issues with the evaluation due to damages. Cannot assess the reliability of the source.

https://weeklyvoice.com/damaged-blac...medium=twitter

The forward installed EAFR along with the Cockpit Area Microphone and Preamplifier are typically connected to the Recorder Independent Power Supply (RIPS), providing a backup power source for 10 minutes in the event of power interruptions.

https://www.geaerospace.com/sites/de...rder-3254F.pdf

The rear EAFR doesn't have power backup. So it will only record data (both CVR and FDR) while it has normal electrical power. At what point before impact that power was lost, we do not know.

Software Engineer here. IMO software glitches are more likely than mechanical failures and pilot error, and I would say increasingly more so, particularly with Boeings. I have good reasons, experience and expertise for saying this that I\x92m not going to get into here because it\x92s too long winded and will no doubt upset some people who will mistake facts for rule and let it hurt their feelings.

In 2019 I think it was, an ANA 787 had a TMCA dual engine shutdown just after landing. There was also a bug that shut down all AC power on 787s powered on for 248+ days (integer overflow causing GCU failsafe) that was supposed to be remedied on 2019. Can\x92t find any information confirming that it was implemented on all 787s. These are just two examples of software bugs. There are placed of others, and it\x92s highly likely there are ones we don\x92t know about, either in the original software or in the updates.