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| Musician
June 22, 2025, 16:20:00 GMT permalink Post: 11908657 |
Whilst we wait for any announcements from the crash investigators can anybody suggest the logic behind providing the front mounted Enhanced Airborne Flight Recorders (EAFR) with a
Recorder Independent Power Supply (RIPS) but not giving the identical aft mounted EAFR unit the same protection where it is less likely to suffer damage?
Can you point to a single incident where this would have made a difference?
Another debate that should now be had is real time telemetry. Given the number of airlines contracting with Starlink for internet services onboard their fleets uploading the data stream fed to FDR's wouldn't put a dent on the available bandwidth and the search and recovery process for FDR's would be a thing of the past.
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| Semreh
June 22, 2025, 16:37:00 GMT permalink Post: 11908670 |
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 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
In the 787, the EAFRs store within their CVR-function memory partitions two hours of data from four audio channels and all data link messages. \x93The CVR function receives audio from three digital audio crew channels provided by the flight deck audio system and one analog audio channel from the cockpit area microphone and preamplifier,\x94 Elliott said.( Jim Elliott, a systems/applications engineer for the manufacturer. )
The Cockpit Voice Recorder function records the flight deck communications between crew members and also captures the general acoustical sound environment of the flight deck. The CVR function receives three analog audio crew channels provided by the Flight Deck Audio System and one analog audio channel from the cockpit Area Microphone and Preamplifier (AMP). The cockpit area audio and the three audio crew channels are recorded in both the forward and the aft installed EAFR recorders. The CVR recording duration is two hours minimum. Recorded audio can only be downloaded when the EAFR is off the aircraft.
https://data.ntsb.gov/Docket/Documen...ort-Master.PDF
Two EAFRs are installed on Boeing 787 aircraft, one forward and one aft. The forward and aft recorders are powered by the left and right 28V DC buses respectively. The forward recorder is equipped with a recorder independent power supply (RIPS) to provide backup power to the recorder for approximately 10 minutes once left DC bus power is lost. Both recorders record the same set of flight data independent of each other.
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. |
| QA1
June 22, 2025, 17:01:00 GMT permalink Post: 11908688 |
From a presentation I was given when the 787 came into service, it states that the RIPS only supplies the CVR section of the fwd EAFRs. IIRC this was stated in an earlier response. If both fwd and aft EAFRs have lost power with the RAT in operation, am I correct in thinking there is no flight data to record \x96 hence only the CVR is powered?
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| syseng68k
June 22, 2025, 17:53:00 GMT permalink Post: 11908716 |
Musician: CVR Data
I think you will find that the cvr data is digitised before reachng the recorder, so that could be starlink as well. Can see that happening in the future, but the main obstacle to that is the cost of bandwidth and data storage. Significant to include all a/c in the sky at any given time, though the data could be compressed into packets, sent in batches. |
| Musician
June 22, 2025, 18:23:00 GMT permalink Post: 11908738 |
Musician: CVR Data
I think you will find that the cvr data is digitised before reachng the recorder, so that could be starlink as well. Can see that happening in the future, but the main obstacle to that is the cost of bandwidth and data storage. Significant to include all a/c in the sky at any given time, though the data could be compressed into packets, sent in batches. |
| Senior Pilot
June 26, 2025, 16:01:00 GMT permalink Post: 11911339 |
https://www.pib.gov.in/PressReleseDe...x?PRID=2139785
Status Report on recovery and examination of data from Black Boxes – Air India Flight AI-171
On the evening of 24 June 2025, the team led by DG AAIB with technical members from AAIB and NTSB began the data extraction process. The Crash Protection Module (CPM) from the front black box was safely retrieved, and on 25 June, 2025, the memory module was successfully accessed and its data downloaded at the AAIB Lab.The analysis of CVR and FDR data is underway. These efforts aim to reconstruct the sequence of events leading to the accident and identify contributing factors to enhance aviation safety and prevent future occurrences.
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| D Bru
June 26, 2025, 21:39:00 GMT permalink Post: 11911519 |
https://www.pib.gov.in/PressReleseDe...x?PRID=2139785
Status Report on recovery and examination of data from Black Boxes \x96 Air India Flight AI-171 Note the front EAFR is the one with RIPS battery backup. 1. The investigation's reliance on the front RIPS battery backuped EAFR indicates a confirmation of a total electrical power loss; 2. Earlier reports (i.e. AVH, now removed) of successful readout of and observations from CVR have proven outright fake. Regards, D Bru |
| grumpyoldgeek
June 26, 2025, 21:58:00 GMT permalink Post: 11911531 |
Thx, this indicates at least two issues:
1. The investigation's reliance on the front RIPS battery backuped EAFR indicates a confirmation of a total electrical power loss; 2. Earlier reports (i.e. AVH, now removed) of successful readout of and observations from CVR have proven outright fake. Regards, D Bru |
| jolihokistix
June 27, 2025, 11:36:00 GMT permalink Post: 11911913 |
This paragraph from the BBC article above contains wording which suggests a secondary but important angle:
Quote: "The analysis of CVR and FDR [flight data recorder] data is underway. These efforts aim to reconstruct the sequence of events leading to the accident and identify contributing factors to enhance aviation safety and prevent future occurrences," the ministry said in a statement. These 'contributing factors' will surely be what is taking time to pin down. |
| First_Principal
June 28, 2025, 05:47:00 GMT permalink Post: 11912344 |
In keeping with PilotDAR's request, here is some possibly useful information regarding the type of Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) likely installed in the Air India B787 (using long names etc for those who may be unfamiliar with various acronyms).
The B787 was one of the first aircraft to receive a new type of FDR/CVR, known as an Enhanced Airborne Flight Recorder (EAFR). Some detail of the time may be found here: https://www.flightglobal.com/boeing-.../67970.article https://www.militaryaerospace.com/po...for-boeing-787 I don't believe it's absolutely confirmed yet but earlier posts (thank you V1... Ooops et al ) indicated that the unit in question may be a GE Aviation Model 3254F, the document here gives some good detail, along with another doc from Skybrary that has some relevant information. And this one discusses more on the 'new' ARINC-767 protocol in use with these later units. Some broader background into ARINC's role in determining the standards applicable to aviation can be seen in this video. While it doesn't specifically cover ARINC-767 (used by the B787 EAFR) the history and associated detail is interesting and may give a little useful background: In terms of actual data recovery I had a look around but couldn't find any video that showed this from an EAFR, however this NTSB YT link gives insight into how data was recovered from an earlier FDR unit (mounted in a Bombardier CRJ700 ). While it's different to that installed in the 787 the nature of the work and how it's carefully carried out may give some insight. Finally, this is a link to a short report re data recovered from an EAFR in a B787-9: https://data.ntsb.gov/Docket/Documen...ort-Master.PDF I claim no specific knowledge here, just providing references to detail I read while trying to learn more about these newer units. FP. |
| AAKEE
June 28, 2025, 13:13:00 GMT permalink Post: 11912486 |
I suspect both recorders will contain the same data. Given the radio transmission after the loss of thrust the aircraft still had at least the emergency electrical bus powered. This should have kept both recorders online. It is however possible given the 10 minute battery backup that Boeing chose to put the the recorders on another bus but that\x92s not the norm.
CVR and FDR, och combined such is not needed for survival. I would state that in general the CVR/FDR is shedded when on emergency electricity. Its clear from earlier posts that the front EAFR have a battery backup for this reason and the aft has not. |
| EXDAC
June 28, 2025, 18:53:00 GMT permalink Post: 11912625 |
FAA requirements and the discussion/changes that resulted from the initial NPRM here - https://www.federalregister.gov/docu...er-regulations |
| DaveReidUK
June 28, 2025, 19:10:00 GMT permalink Post: 11912632 |
However you are correct in that the requirements only specify that the CVR functions and the CAM must continue to operate. |
| D Bru
June 28, 2025, 19:17:00 GMT permalink Post: 11912637 |
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 |
| EXDAC
June 28, 2025, 19:40:00 GMT permalink Post: 11912643 |
"The front panel contains one connector, J1, and a grounding stud. • J1 provides the main EAFR power supply, Aircraft Data Network, Ethernet Channels A and B, analog audio input, input and output discretes, and other miscellaneous signals." If RIPS is external and the GE EAFD only has a "main power supply" pin then I agree it seems likely that the flight data function is powered by RIPS. For RIPS to power only the CVR function I would have expected to see separate main power and RIPS power input pins. I could not find any data except the two page marketing brochure which is not definitive. |
| nnc0
June 29, 2025, 15:01:00 GMT permalink Post: 11913074 |
By the time you're down to EMER GEN you usually know what the problem is and most systems with parameters that could be recorded on the FDR are unpowered so what's the point of trying. The CVR with a RIPS at least helps us to try understand how or why the events to regain control after that failed.
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| Musician
July 09, 2025, 15:09:00 GMT permalink Post: 11918452 |
If the switches were operated before the power went out, that's logged on the flight recorder. It's possible that the CVR would record a pilot calling out as he operated the switches, though. Last edited by Musician; 9th July 2025 at 15:48 . |
| AirScotia
July 09, 2025, 18:40:00 GMT permalink Post: 11918572 |
Theory alert : If you don\x92t have, or delete the cruise altitude in the FMC the aircraft will command a level off at 400ft, with the thrust levers reducing thrust significantly (I\x92ve seen it in the sim and happened at least once for real to my operator). It\x92s easy to do when loading the descent winds if you hit the wrong button. Could this have been confused with a loss of thrust?
And I would say the cut off switches do make a fairly unique click when being moved - I can hear it in my head as I write this! |
| DIBO
July 09, 2025, 21:49:00 GMT permalink Post: 11918656 |
I can add that a few weeks ago, I saw a video from the local media (don't remember the source and/or link), paying tribute to the 12 crew-members with a short bio/a few pictures of each individual, and it were 2 cockpit crew and 12 cabin crew (with a few very junior/trainee CC's). But that in itself, does not prove anything regarding possible jumpseaters. |
| KSINGH
July 11, 2025, 20:40:00 GMT permalink Post: 11919771 |
- fuel cut offs were found in the RUN position
- on take off roll both engines lost power as the fuel cut offs went from RUN to cutoff - CVR recorded one pilot asking why they had gone to CUTOFF - within 10 seconds the fuel cutoff was moved back to RUN -RAT was deployed, APU had begun auto start - 32 seconds after Vr the MAYDAY was called This should also dispel a lot of the comments about AAIB-India, Indian culture in general and general competence. For a preliminary report this is far more thorough and extensive than what would normally be expected and they\x92ve kept Boeing, GE, FAA and investigators from US, UK, Canada and Portugal in the loop from the start They have also clarified why it took so long to do the EAFR download- because of the extensive damage they had to source specialist equipment from the NTSB that only arrived on the 23rd of June (they downloaded on the 24th) so all that talk of a \x91coverup\x92 is pretty embarrassing now of course the big question is why/how those switches were commanded into cutoff in the first place the exact sequence at Vr is the most critical, there hasn\x92t been much scrutiny at all that I can see in the Indian/international media of the personal background of the flight deck crew which has happened in other suspected pilot initiated disasters in the past, I guess this is an avenue investigators will have been doing themselves |
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