Posts about: "CVR" [Posts: 96 Pages: 5]

HumbleDeer
2025-06-14T19:54:00
permalink
Post: 11901774
Originally Posted by Tech Guy
Could the pilot in his last moments have been trying to avoid that scenario?
The pilot is dead, hence, we cannot ascertain that without the pilot having reported or spoken about it. If the CVR has no word on it, then anything the FDR shows in manouvring that suggests this, will forever be speculation.
That suggests to me myself, ethically, that we limit speculation on the intent of the pilots when it comes to things this ethically charged unless there's good evidence on the FDR. Rest in peace.

2 users liked this post.

BugBear
2025-06-14T20:16:00
permalink
Post: 11901796
Originally Posted by dbenj
I agree. It is intriguing that we have none of the radio communication released. As a result, we do not have confirmation of what was actually said during the Mayday call, and no ability to deduce who was the PF and PM.
Unless the mics are closed, it's in the CVR
For me, I don't need to know.
Gupeg
2025-06-15T02:11:00
permalink
Post: 11902052
Re FDR and CVR, remember the 787 uses EAFR(s) instead - one in tail and one in nose.

Comments above "they will already have been read" - suggest search and read India press links, and the (new) India AAIB lab ability to read data recorders, e.g. one timed at June 15, 2025 00:08 IST. It may well be the first 'political' issue about this accident in where the recorders are sent. If India is chosen, maybe they will take their time with a new lab, and watched over by the world and other AIB representatives? I believe the investigating state 'controls the release of information' (or not). Whilst the UK AAIB are there, as their website says they have 'expert' status, which I suspect means not a lot of involvement in the politics.

2 users liked this post.

Someone Somewhere
2025-06-15T02:36:00
permalink
Post: 11902060
Originally Posted by BugBear
Difficult!? Maybe not. If very late the flaps were tagged stowed, and there was a simultaneous gear up command, with FlapDown command, the overload could have failed a GCS. Then it becomes a switching exercise. (Automatics).

Alarms Warnings Impacted EICAS, ETC. it happened long ago, but we know what happens when an engine driven generator quits ..first it bangs for awhile, then it burns itself up, then ...
Originally Posted by MaybeItIs
Thanks for answering the question I hadn't yet asked but wanted to confirm!

I'm still sticking with "Major Electrical Fault" as my most likely cause, and this adds to my suspicions.

As I understand it, the landing gear is raised / retracted by electric motor-driven hydraulic pump (pumps?). This/these would create a significant electrical load.

If the plane's multi-redundant electrical system has a fault which is intermittent (the worst kind of electrical issue to diagnose), and which causes the redundancy controls to go haywire (as there are, of course, electronic controls to detect failures and drive the switching over of primary and backup electrical supplies), then this fault could to triggered by a large load coming on-line. It could even be as simple as a high current cable lug not having been tightened when a part was being replaced at some stage. The relevant bolt might be only finger-tight. Enough to work 99.99% of the time between then and now... But a little bit more oxidation, and particularly, a bit more heat (it was a hot day), and suddenly, a fault.

Having worked in electronics for years, I know that semi-conductors (and lots of other components, especially capacitors [and batteries]) can also degrade instead of failing completely. Electro-static discharges are great for causing computer chips to die, or go meta-stable - meaning they can get all knotted up and cease working correctly - until they are powered off for a while. They can also degrade in a way that means they work normally a low temperatures, but don't above a certain temperature.

Anyway, there MUST be ways that the redundant power supplies can be brought down, simply because, to have a critical bus powered from a number of independent sources, there must be "controls" of some sort. I don't know how it's done in the 787, but that's where I'd be looking.

As there is a lot of discussion already about how the bogies are hanging the wrong way suggesting a started but failed retraction operation, and it's now confirmed that the retraction would normally have taken place at about the point where the flight went "pear shaped", I'm going to suggest that the two things are connected. More than that: I'll suggest that the Gear Up command triggered the fault that caused both engines to shut down in very short succession. Nothing the pilots did wrong, and no way they could have known and prevented it.

It's going to be difficult to prove though.
Gear and flaps are both hydraulic, and the hydraulic pumps typically act as effective fault-containment - a hydraulic failure or excess load doesn't result in excess demand on the electric side; the pump just starts to run out of output flow/pressure.

In addition, the 787 has four main generators and I believe the switching is segregated into at least two controllers, on top of the four separate generator control units.

And again, electrical failure should not cause engine failure - consider QF32 where the wiring to the engine was mostly severed and they had to drown it with a fire truck.

Originally Posted by ILS27LEFT
Best post until now in my view. We will find out very soon I think. Gear up command triggered the instant lack of fuel to both engines. I'm not sure on how the fuel flow is dependant on the power supplies on the 787 but I genuinely believe you are very very close to what might have happened here.
It's not. Boost pumps should be more-or-less unnecessary at sea level.

Originally Posted by MaybeItIs
Yes, thanks, I've seen a few comments to this effect, and I have to accept most of what you say. I understand that they have their own dedicated generators and local independent FADECs (or EECs), but I'm trying to use what I do know to attempt to figure this out. I know that there are Fuel Cutoff switches in the cockpit. Somehow, if switched to Off, these will cut off the fuel to the engines, "no matter what". Of course, even that's not true, as the Qantas A380 engine burst apparently (comment in this thread) showed.

Anyway, the thing I'm looking at is how the fuel cutoff switch function could have been activated in some other way. To me, it seems obvious that there are wires that run between the engine fuel shutoff valves and the cockpit / flight control panel (no doubt with relays etc in between). I don't know where those shutoff valves are located, but logic says they should be located in the fuselage, not out at the engines. I also don't know how those valves operate - are they solenoid valves or electro-mechanically driven? Nor do I know where the power to activate those valves comes from, but using my logic, if those valves close when powered off, such as solenoid valves typically do, then the power cannot exclusively come from the engine-dedicated generators. If it did, you'd never be able to start the engines so they could supply their own power to hold those valves open. So, there must be some power (appropriately) fed from the main aircraft control bus to activate those valves - if the rest of what I'm assuming is correct. Anyway, like I say, I don't know enough about the details at this point, but there are many more ways to activate or deactivate a circuit than by flicking a switch. Killing the relevant power supply, for example. A screwdriver across some contacts (for example), another. Shorting a wire to Chassis, maybe. Just trying to contribute what I can.

You raise another interesting point: "TCMA notwithstanding". Could you elaborate, please? What will happen if the TCMA system, which apparently also has some degree of engine control, loses power? The problem with interlinked circuits and systems is that sometimes, unexpected things can happen when events that were not considered actually happen. If one module, reporting to another, loses power or fails, sometimes it can "tell" the surviving module something that isn't true... My concern is where does the power to the Fuel Cutoff switches come from? Are there relays or solid-state switches (or what?) between the Panel Switches and the valves? If so, is the valve power derived from a different source, and if so, where? Are the valves solenoids, open when power applied, or something else? What is the logic involved, between switch and valve?

Would you mind answering these questions so I can ponder it all further, please? If I'm wrong, I'll happily say so.
I believe the valves are almost all bi-stable power-open power-close. When not powered, they remain in the last commanded position.

The valves are located in the spar (hence being called 'spar valves'. The fuel tank is immediately above the engine so it is a very short pipe for suction feeding. Tail mount engines are potentially a different story...

Originally Posted by lucille
What\x92s the usual time frame for the release of preliminary data and report from the FDR and CVR? Is it around 6 months?

I guess if no directives come from Boeing or the FAA in the next 2 weeks, it can be presumed that a systems failure from which recovery was impossible was unlikely.
A Prelimnary Report must be prepared within 30 days, but does not need to be public. May or may not have CVR/FDR data.

1 user liked this post.

V1... Ooops
2025-06-15T03:40:00
permalink
Post: 11902077
Originally Posted by lucille
...I guess if no directives come from Boeing or the FAA in the next 2 weeks, it can be presumed that a systems failure from which recovery was impossible was unlikely.
I agree. The subject aircraft was fitted with two Enhanced Airborne Flight Recorders (EAFRs), one of which is located forward and one in the rear. These recorders capture both voice (traditional CVR) and data (traditional FDR), and provide redundancy. One - presumably the one in the rear - has already been recovered.

Two weeks is likely long enough for the investigators to determine if a systems failure might, in any way, have been a possible cause. I am sure that if there is any reason to suspect that a systems failure may have been a probable cause, or even contributed in any way to the accident, Boeing, GE, the FAA, or the Indian DGAC will promptly advise 787 operators.

4 users liked this post.

Icarus2001
2025-06-15T13:25:00
permalink
Post: 11902471
I don't see how they'd be able to say so with confidence after just a few days. Surely they'd need to review logs, do some lab analysis, etc for that?
Nope. I think they will know by now what happened, they may not know the why but they will already be able to see what was going on as well as hear the CVR.

​​​​​​​The rest is now narrative management, damage control and pass the liability parcel.

4 users liked this post.

nachtmusak
2025-06-15T14:35:00
permalink
Post: 11902510
Originally Posted by Icarus2001
Nope. I think they will know by now what happened, they may not know the why but they will already be able to see what was going on as well as hear the CVR.

​​​​​​​The rest is now narrative management, damage control and pass the liability parcel.
I must admit I'm confused. If there was a maintenance error involved in this accident (which is what I said would take some time to uncover), how exactly would either flight data or cockpit voice recordings tell the investigators this? Please correct me if I'm wrong but every maintenance screw-up leading to an accident that I can think of was surfaced by actually examining the wreckage and logs, the former sometimes using quite sophisticated lab methods.

Pilot error still seems to me like the only thing that could be conclusively ruled in after only a few days, and it may well be the case here, I'm not contesting that. But that does not mean that other factors can be ruled out after a few days - absence of evidence is not evidence of absence and all that.

Last edited by Saab Dastard; 15th Jun 2025 at 21:53 . Reason: unwarranted speculation removed

2 users liked this post.

Callisthenes
2025-06-15T15:33:00
permalink
Post: 11902561
Originally Posted by Iron Duck
A flight recorder was found 28 hours after the accident, so it's been in the AAIB's possession for nearly 2 days, but not a word has been said about its physical condition. I recall in other recent accidents that the physical condition has been publicised quickly, perhaps not least to manage the public's hunger for information.

This leads me to suspect that it is in good condition, has already been downloaded, what happened (if not why) is clear, and it is embarrassing.
This is assuming too much. There are legal and technical reasons why the CVR may not have been downloaded yet or, if it has, why no information has been released.

In an ICAO Annex 13 investigation, interested states and experts are invited to participate. In this investigation, investigators from the US and UK are participating (there may be others as well), and experts from Boeing (and possibly component manufacturers) have also been invited. The lead investigators will often hold off on recovering data from the CVR and FDR, or examining the data, until there's agreement between the interested parties on how to go about doing it. With the distances involved, travel logistics could easily delay examining the data by a couple of days.

In some cases, the board leading the investigation doesn't have the internal expertise to recover data from the CVR and FDR. In these cases, agreement needs to be reached on which technical experts are going to take the lead on recovery. I don't know if the Indian AAIB has internal expertise or if they need to find external expertise to recover the data.

In some cases the CVR and FDR can be damaged and technical experts need time to come up with a plan to repair the recorders and recover the data.

Annex 13, Article 5.12 prohibits the release of CVRs and analysis/opinions from FDRs, unless the investigators decide that the benefits of the disclosure would outweigh the adverse impact that release would have on future investigations. This rule exists to encourage full cooperation in investigations from participants in the industry, including pilots and operators. India's accident investigation rules are consistent with Annex 13: see section 17 of the Aircraft Investigation of Accidents and Incidents Rules, 2017. So even if the CVR and FDR have been analyzed, it may well be that information isn't being disclosed to the public because they haven't reached any definitive conclusions yet that they're confident will end up in the final report.




17 users liked this post.

EXDAC
2025-06-15T20:56:00
permalink
Post: 11902827
Originally Posted by DaveReidUK
One of the two recorders on the 787 is equipped with RIPS (Recorder Independent Power Supply), which will give a minimum of 10 minutes' operation in the event of a power supply failure.
But as previously posted a recorder is only as good as the systems that provide the data to it. If those systems, or some of those systems, are not powered the data is simply not available to be recorded. You need the DFDAU (or equivalent) to be powered and you need the systems that feed data to the DFDAU (or equivalent) to be powered and operational.

Edit to add - RIPS will likely maintain CVR function.

1 user liked this post.

DaveReidUK
2025-06-15T21:05:00
permalink
Post: 11902840
Originally Posted by EXDAC
But as previously posted a recorder is only as good as the systems that provide the data to it. If those systems, or some of those systems, are not powered the data is simply not available to be recorded. You need the DFDAU (or equivalent) to be powered and you need the systems that feed data to the DFDAU (or equivalent) to be powered and operational.

Edit to add - RIPS will likely maintain CVR function.
Correct, on the 787 it's the forward EARF that has the RIPS, and it will continue to record inputs from the CAM.
Icarus2001
2025-06-16T00:29:00
permalink
Post: 11903005
AFAIK the 787 DFDRs have an internal battery but if the power is off to the rest of the aeroplane, what data, if any, is going to make its way to the units?
You answered your own question. The units would have had power. One pilot made a radio call so electrical power was available at the very least at emergency level.

It has been established that the B787 utilises a EAFR, a combined CVR and DFDR.

1 user liked this post.

DIBO
2025-06-16T00:47:00
permalink
Post: 11903013
Originally Posted by FullWings
AFAIK the 787 DFDRs have an internal battery but if the power is off to the rest of the aeroplane, what data, if any, is going to make its way to the units? Is anything recorded while on battery power?
from the little I know:
* only the forward EAFR (Enhanced airborne flight recorder) has an (external) RIPS (Recorder independent power supply)
* and this RIPS provides, in addition to the forward EAFR, the cockpit area microphone and the preamplifier for this microphone with 10 minutes of backup power

Pretty recently, Indian media was reporting that the forward "CVR" has been recovered. Pure speculation..but one might interpret the use of this incorrect terminology and the continued search for this second 'black box' while the rear EAFR should have been easily recovered from the mostly intact tail-section, as an indication that things aren't going as well as expected regarding FDR/CVR data-extracting (as in rear EAFR lacking the last x crucial seconds, and forward EAFR now essential for recovery of the last x-seconds of area-CVR recordings, thanks to RIPS)

4 users liked this post.

Lord Bracken
2025-06-16T09:34:00
permalink
Post: 11903315
Originally Posted by Icarus2001
My information differs to yours, We do know the EAFR was recovered on Saturday. Are you suggesting that it sat in a room for three days?
My expectation is that at the very least the AAIB (India) would want to open / read in the presence of the AAIB (UK) and the manufacturer. They might even want to read it at a location with specialist equipment (NTSB in Washington, BEA in France, AAIB in UK). None of this would be unprecedented when looking at previous accident investigations particularly for those that took place in developing countries.

Quick example, EK 521 accident in DXB:

1.11 Flight Recorders The Aircraft was equipped with a Honeywell sold-state flight data recorder (SSFDR) and an L-3 Communication cockpit voice recorder (CVR). Both flight recorders were found mounted in their original locations on the Aircraft, with external signs of prolonged exposure to elevated temperatures. However, temperature indicators within each crash-survivable memory unit indicated that the memory components themselves had not been exposed to significantly elevated temperatures. The flight recorders were sent to the Air Accidents Investigation Branch (AAIB) facility in the United Kingdom for data retrieval in the presence of the Investigation Committee.
Pakistan A320 accident Karachi:

1.11. Flight Recorders 1.11.1. The aircraft was equipped with solid-state DFDR and solid-state CVR. DFDR and CVR were recovered from the accident site and taken to BEA, France by Investigator In-charge (IIC) from AAIB, Pakistan on 1st June, 2020. Despite having crash and heat effects, both recorders were successfully downloaded by BEA experts.
(1st June was 10 days after the accident).

4 users liked this post.

Icarus2001
2025-06-16T00:29:00
permalink
Post: 11903729
AFAIK the 787 DFDRs have an internal battery but if the power is off to the rest of the aeroplane, what data, if any, is going to make its way to the units?
You answered your own question. The units would have had power. One pilot made a radio call so electrical power was available at the very least at emergency level.

It has been established that the B787 utilises a EAFR, a combined CVR and DFDR.
DIBO
2025-06-16T00:47:00
permalink
Post: 11903732
Originally Posted by FullWings
AFAIK the 787 DFDRs have an internal battery but if the power is off to the rest of the aeroplane, what data, if any, is going to make its way to the units? Is anything recorded while on battery power?
from the little I know:
* only the forward EAFR (Enhanced airborne flight recorder) has an (external) RIPS (Recorder independent power supply)
* and this RIPS provides, in addition to the forward EAFR, the cockpit area microphone and the preamplifier for this microphone with 10 minutes of backup power

Pretty recently, Indian media was reporting that the forward "CVR" has been recovered. Pure speculation..but one might interpret the use of this incorrect terminology and the continued search for this second 'black box' while the rear EAFR should have been easily recovered from the mostly intact tail-section, as an indication that things aren't going as well as expected regarding FDR/CVR data-extracting (as in rear EAFR lacking the last x crucial seconds, and forward EAFR now essential for recovery of the last x-seconds of area-CVR recordings, thanks to RIPS)
fdr
2025-06-16T22:32:00
permalink
Post: 11903843
Originally Posted by tdracer
Something that occurred to me after I went to bed last night: My assumption that the FDR readouts would rapidly reveal the cause may be flawed.

Let me explain.

The consensus is that both engines quit shortly after liftoff (that assumes that the RAT did in fact deploy). At least one of the data recorders has battery backup, so it should have kept functioning when all aircraft power was lost.

However...

Over the years, I've looked at lots and lots of digital flight data recorder outputs when investigating some sort of incident or other engine anomaly, So I have become rather familiar with some of the interesting characteristics of DFDR data.

On the 767 and 747-400, when you shutdown an engine and the IDG goes offline, there is a momentary 'glitch' in the electrical power system as it reconfigures for the available power source - this is why you see the flight deck displays flicker and return, and the cabin lights momentarily flicker. As a result, most of the avionics boxes 'reset' - this is quick, but it's not instantaneous. This shows up in the FDR data - sometimes as 'no valid data' for a few seconds, or as garbage readings of zero or 'full scale'. Now, looking at the FDR data, it's easy to simply disregard the data, so normally no big deal.

Starting with the 777 (and on the 787 and 747-8), this electrical power glitch was 'fixed' - there is slight delay (~quarter of a second IIRC) before the fuel cutoff signal is sent to the engine - during which the electrical system reconfiguration takes place so no more 'glitch' during a normal engine shutdown...Except whatever happened to these engines wasn't 'normal'.

If there is a fuel cut at high power, the engine spools down incredibly rapidly - a second or two from max power to sub-idle. Assuming the fuel cut wasn't commanded by the flight deck fuel switches, the electrical system won't know it's coming, so it can't reconfigure until after the engine generators drop offline - and you're going to get that power glitch. Nearly every avionics box on the aircraft will reset due to this electrical glitch, and the FDR isn't going to get useful data for a few seconds (and then, only from the stuff that's on the battery bus).

Whatever happened, happened quickly - it's quite possible that whatever initiated the high-power fuel cut didn't get recorded.
True, I would bet that the voltage regulating architecture of the voice recorder at least will give useful information for a short time around the loss of power, as it did for the Lockerbie CVR using far less sophisticated recorder systems. That was sufficient to show the pressure pulse in the fuselage and to give a fairly good idea of where the explosion had emanated from. TWA was similar, a bigger bang though. Would be listening for any mechanical noises related to the fuel switches, and frankly I doubt that they existed, but they would be recorded.

If the cause is what I have suggested it will dificult to get direct evidence of that case, as it was for the QFA072 event as well. Like icing cases, a water ingress into the avionics is going to be a tough investigation, water would have been sprayed all over the wreckage in the aftermath. Dousing the E/E bay with 20 or 30 gallons of water will be an expensive investigative exercise to do in a real plane, with engines running. Would not want to be observing up close.

1 user liked this post.

katekebo
2025-06-16T22:45:00
permalink
Post: 11903852
Not a pilot, but an engineer with some experience in accident / incident investigation.
One thing that strikes me in this and the previous closed threads is the lengthy back-and-forth discussion about potential technical faults that could lead to this accident.

However, there has been relatively little discussion about the #1 cause of all airplane accident - pilots' mistakes.

Except for the initial conversation about mistakenly retracting flaps instead of landing gear, which eventually was dismissed in favor of engine failure as there has been an almost unanimous agreement that even if such mistake was made, it was recoverable.

But what if the pilots made more than one consecutive mistakes?

Mis-diagnosing the first abnormal behavior and making things worse by performing another action that instead of correcting the first mistake, turned the situation unrecoverable. The history of aircraft accidents is full of examples when a first, relatively benign issue was made much worse and eventually tragic by pilots' subsequent actions.

Frankly, I think it is much more likely that the pilots made several consecutive mistakes than eventually led to the crash than a 1-in-a-billion unrecoverable mechanic failure. I'm looking forward to the CVR and FDR transcripts and I suspect that we will learn that after whatever happened first (pilot's mistake or minor technical failure), it was subsequent pilot's action that turned a manageable situation into a tragic accident.

2 users liked this post.

gearlever
2025-06-17T08:27:00
permalink
Post: 11904073
"On Jun 17th 2025 an official, a former Air India Captain trained by the Captain of the accident flight, stated, that the CVR has been successfully read out, the voices on the CVR are very clear. It is becoming gradually clear from the newly emerging evidence that there was probably zero negligence in the cockpit, the crew did not give up until the very last moment. The probability of a technical cause is high. A preliminary report by India's AAIB can be expected in a few days."

AvH

10 users liked this post.

geo10
2025-06-17T08:42:00
permalink
Post: 11904093
Originally Posted by gearlever
"On Jun 17th 2025 an official, a former Air India Captain trained by the Captain of the accident flight, stated, that the CVR has been successfully read out, the voices on the CVR are very clear. It is becoming gradually clear from the newly emerging evidence that there was probably zero negligence in the cockpit, the crew did not give up until the very last moment. The probability of a technical cause is high. A preliminary report by India's AAIB can be expected in a few days."

AvH
Where is this quote from? a link perhaps 👍
SLF3
2025-06-17T09:24:00
permalink
Post: 11904134
AH report on the CVR is Quite nuanced for hearsay. Is clear the source is conflicted, does not (totally) rule out pilot error, explicitly rules out suicide. If the CVR has been read a lot of people will know what\x92s on it.

1 user liked this post.