Posts about: "NTSB" [Posts: 12 Page: 1 of 1]¶

Originally Posted by Spunky Monkey

For an aircraft that will likely have TOGA pressed and be at a high power setting (plus the RAT deployed) it sounds awfully quiet.
Perhaps the gear was down because they knew they were going to force land due to lack of thrust.
(Only a 738 driver), but the electric pumps to drive the hydraulics is much slower than the engine driven pumps and so flap selection / re-selection could be not as expected.

RIP to all involved.

Originally Posted by The Brigadier

Assuming we're not facing a repeat of the Boeing 737‑800 crash at Muan International Airport when loss of loss of both engines apparently also cut power to Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR)

Originally Posted by Sriajuda

Also, what is this discussion about the RAT? Unless someone has extremely quickly faked the audio on the video, it is pretty clear that the engines were running. (Both of them, there is some slight interference pattern I (maybe imagine) to hear.

Originally Posted by Lead Balloon

Could someone post an authoritative list of the inputs to the EAFR’s?

By “authoritative”, I mean the actual wiring diagram excerpt of the aircraft model and engine configuration (and hopefully mod state...), that labels each input.
[snip]

Originally Posted by Someone Somewhere

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 .

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]

Originally Posted by JustusW

In reverse order, and the first one being very speculative: The type of battery will likely be highly specific for the usecase, here rugged before anything else. Likely specialized chemistry or one of those hybrid solid state ones. Commonly they trade capacity for other features.

Regarding the recording feature, there's three types of microphone commonly used nowadays: Condenser and Ribbon type are somewhat fragile and require power to record audio while Dynamic type is basically a reverse speaker and is considered rugged. There's an off chance that a Piezzo microphone would be used here as they are basically indestructible but usually reserved for recording while in contact with a large sound transducer. My guess based on that is that we're looking at a dynamic microphone with a run of the mill preamp.
Depending on the actual electric setup this would yield a handful of different possible installations:
1) The "Cockpit Area Microphone" (hereby christened CAM because I like abbreviations) is a self contained unit consisting of a Microphone, a preamp and AD converter. This would mean while provided power the digital recording could be passed to either EAFR.
2) The CAM is a self contained unit consisting of a Microphone and a preamp. This would mean while provided power it could send an analog audio signal to the forward EAFR no problem, but would potentially struggle generating enough of a signal to be picked up by the rear EAFR.
3) The CAM is just a Microphone. This would mean it requires either no or very little power (even Condenser Mics usually require only Milliwatts) but the signal would be very hard to send over long distances and would require the EAFR to have a preamp.

In general it is audio engineering 101 to place a preamp as close to the source as possible to avoid noise. Thus I would rule out 3. It has both ups and downs to convert the analog signal to a digital signal, and there is a possibility they'd do both. In either case I am confused from an audio engineering standpoint why the rear EAFR would not pickup audio from the CAM if the forward EAFR does. Unless the rear EAFR is fed (audio) data only via BUS, which would be an interesting choice.
Also keep in mind that historically the CVR was also located in the tail section and very much received an analog signal over the entire distance. There's really no technical reason this wouldn't be possible, I routinely use far longer cables when running audio signals at concerts and those can't use compression because it would dumpster sound quality.

So, yeah, I don't understand why there would be a mismatch between the recordings of either EAFR, unless there was something else preventing all signal transmission towards the rear EAFR. The CVR in the rear has been a thing for 80 years now.

Regards,
Justus

Originally Posted by Semreh

SLF here. Mods - please delete summarily if this does not contribute to the discussion, I have no wish to waste anyones time. No 'AI' was used in the preparation of this post.

My understanding is that, as you say, the CAM has a preamp. That preamp can be powered by the RIPS that accompanies the forward EAFR.
In addition, I believe there is a single analogue connection from the CAM+preamp to the aft EAFR in addition to the analogue connection from the CAM+preamp to the forward EAFR. I believe, but am not sure,that the other flight-deck audio (headsets) is carried digitally over the fibre-optic network to the aft EAFR. The network may or may not be in operation in the event of an electrical failure: I simply don't know.

The publicly available information I can find is not stunningly clear about this.

AEROSAFETY WORLD, January 2008 - https://flightsafety.org/asw/jan08/a...47-48.pdf?dl=1



GE Aviation: Consolidate and increase recording power with the 3254F EAFR. - https://www.geaerospace.com/sites/de...rder-3254F.pdf



As for power, this NTSB document describes the power set-up for the EAFRs

https://data.ntsb.gov/Docket/Documen...ort-Master.PDF



So the forward EAFR is powered from the left 28V DC bus with the possibility of being powered by the RIPS, and the aft EAFR is powered from the right 28 V DC bus.

What I have been unable to determine is whether the right and/or left 28 V DC buses are powered from the main battery in case of failure of the AC power supply. To my untrained eye, it looks like the Captain's flight displays are powered from the main battery in extremis (28 V DC - C1), but that there are various circuit breakers, that could be automated, that may or may not allow or prevent other loads (such as the F/O's flight displays (28 V DC - C2), or the aft EAFR, being supplied by the main battery, (See link to diagram). There could well be very drastic automated load shedding.

https://kb.skyhightex.com/wp-content...l-1024x640.png

If the right 28 V DC bus was unpowered for any period, it follows that the aft EAFR was not recording for that period. This would make the forward EAFR important in case of a power failure that prevented the right 28 V DC bus from providing power.

All the information that is unclear to me will be transparently clear to the crash investigators. But it seems to me that the aft EAFR will not hold data for any period that the right 28 V DC bus is not operating. Whether that applies to this incident is an open question.

Originally Posted by D Bru

That's exactly why I would really recommend reading through the NTSB FDR report on the 2013 JA829J Boston incident helpfully posted by EDLB . There's potentially a wealth of data concerning a to me at least surprisingly number of 2000 of parameters written on a 787 EAFR, that is that at least if there's elec power. Even the 10 min RIPS is useless if there's no data sent from electrically shut off systems.

Originally Posted by GroundedSpanner

Switching off the engines would cut power. (the RAT deployed before they overflew the end of the runway) The HUD would go blank. As would most of the display units. The lighting would change. The hissing of conditioned air would stop. Various 'noises' would cease. The engines sound would change dramatically, and they would feel the deceleration. The one EICAS screen remaining would be generating all sorts of messages. It would be obvious that power was lost.
I cant speak for how long it would take to connect the dots though.

Originally Posted by Chiefttp

After 1400 posts, why hasn’t anyone suggested this? EARLY ONSET ALZHEIMERS OR DEMENTIA. . I’ve shared my experience in an earlier post concerning a pilot whose confusion during a sim event was very apparent. This can be a possibility as opposed to the suicide theory.

Originally Posted by Pilot DAR

Not necessarily. I do not speak for how accident investigators do their job, and what information they choose to make public or not,