Posts about: "DFDR" [Posts: 56 Pages: 3]

Reuters :

The TCMA runs on the FADECs (Full Authority Digital Engine Control). There is one per engine, located inside the nacelle. Each one has a dual channel design inside, to compare computations, inputs etc. and generally provide redundancy (but I don\x92t know further details on the design/logic).

The sensors and actuators related to that engine (pressure, temperature sensors, various valves etc.) are most likely directly connected to it. The two throttle position sensors per engine are also directly cabled to it according to tdracer. No idea how other inputs like WoW and RADALT are connected. The FADECs don\x92t necessarily need much else, as apparently Autopilot etc. always move the actual thrust lever.

There must also be a communication channel back to the flight recorders. No idea if it gets thrown into a comms bus or there is direct wiring.

In terms of power, each FADEC has its own alternator driven by the engine. But there\x92s a failover connection to the AC bus of the plane. Not sure if there\x92s a physical relay keeping it disconnected in normal operations.

slf/ppl here - with a respectable amount of experience in software delivery for real-time/embedded/safety critical systems. Software development in this area really is an engineering discipline and bears no resemblance to common practice in other areas. Couple that with the requirements for function duplication/triplication, harness separation et al then IMHO the chances of FADEC etc software errors are effectively zero.


I'm commenting to make that point but also to link the videos and the FR-24 dataset - (below with my deltas for height/time added)



Extract from FR24 csv dataset


As noted in both threads to date everything was normal until it wasn't - the two values for fpm above are subject to FR24 variance of +/- 25' so even these suggest a normal climb at this stage of flight ca 2,000fpm. FR24 Lat/Longs all follow the centre line.


On this data the climb stops at around 70' AGL and electrical failure around 2s later. Again, as noted in the threads, this aligns with when gear up might have been expected. If the climb stopped because of fuel shutoff then 2s for spool down to electrical failure isn't out of the question.


Looking at the two videos.

The CCTV video indicates a total flight time, from rotation, of about 32s, subjectively levelling off ~14s after rotation.

The rooftop video has a flight time ~14s suggesting the video starts ~18s after rotation.


The rooftop video evidences the RAT as deployed from the beginning - meaning it must have been deployed by at least 16s after rotation - which aligns with the ADS-B indicated electrical failure.


If the forward flight recorder really is being sent to the US for recovery then it's reasonable to assume that the rear recorder contains nothing after the electrical failure and they are hoping the forward recorder captured something from the cockpit in the final 16s.


I don't have any experience of flight deck CRM but I don't see how those timings allow problem identification/misidentification and subsequent action - ie it wasn't down to the crew.


However:

The maximum aircraft height in the CCTV video, as judged by wingspan, appears higher than 71' - though it is certainly less than a wingspan height at the beginning of the rooftop video.


I haven't seen, in the threads, any statement of what happens on the flight deck with a total electrical failure - is it a 4s blackout whilst the RAT deploys and systems restart? - or are there batteries that keep something alive?

Background info from "The Hindu", Ahmedabad plane crash: Aircraft Accident Investigation Bureau yet to decide where black box data will be decoded

Black Boxes
Preliminary Report

The situation with reading the flight recorders seem increasingly suspicious to me. As of yesterday, they're still dithering about whether to send them to the USA? Is this about India not wanting to reveal their smart new facility can't do the job? Or unwillingness to trust the US/Boeing? Or some other kind of argument? It seems ridiculous to me that no decision has been made about the boxes nine days after the crash and the rapidly discovered recorders.

India to decide on overseas analysis of Air India crash flight recorders

I am not from India, nor associated with this investigation.
Note this excerpt from your linked article:
I will defend their investigating team, and the release of information time line, based on at least these points:
1. They'd rather do things deliberately, and get it right, than to make a slight rush and get something wrong (even a little bit wrong)
2. The political leadership are sensitive to how the information age, and social media, amplifies even the slightest misstatement.
3. If they can do it in house then why not do it in house? Why add further delay by transferring the recorder and risk accidents in handling during transit?
4. They are under a timeline set by ICAO, not the time line that your, or my, or "the public's" hunger for information and impatience sets.

Let's give them the benefit of the doubt.

The Enhanced Airborne Flight Recorder (EAFR) fitted in the forward and aft locations are interchangeable and appear to be able to record video.

As their power requirements are 28 VDC and just 20.5 watts it seems strange that only the forward mounted unit should have a battery backup.

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

VHF L is on emergency power, the EAFR are not ( see Air India Ahmedabad accident 12th June 2025 Part 2 ). The front EAFR has its own battery (RIPS) for that reason, the back EAFR has not. (The number of 787 events where this mattered is zero so far.)
Different (older) aircraft, the flight recorders there did not have backup power iirc.

I had thought consideration for the preservation of truth might underlie India's reluctance to send the flight recorders across the Pacific Ocean. But it could simply be that the foreign accident boards and India have different opinions on how trustworthy India's flight recorder lab is. Negotiations ensue? Anyway, this is idle speculation on my part.

While impatient media might lament the delay, I think it is right that some time is spent on ensuring that the end result of the investigation is trustworthy. Even if that involves diplomacy.

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?

The RIPS unit is a certificated device that just has to supply 20.5 watts for ten minutes so cost cannot be a consideration.

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.

The RIPS provides power to both the recorder and to the microphones in the cockpit.... If there's no power to the microphones, there is nothing to hear. If there's no power for systems in the aircraft.... then there's not going to be much for any recorder to record.

Can you point to a single incident where this would have made a difference?

Quote:

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.

You'd still have to search for the CVR, so...

Two minor points regarding competence and who gets the task of data extraction from the data recorders: Firstly, that it's the AAIB (India) which will decide where and when to hand over the data recorders, and secondly, the supposed comment attributed to the Ministry of Civil Aviation in the press release dated June 19 ( https://www.pib.gov.in/PressReleaseP...x?PRID=2137718 ), that "t he decision regarding the location for decoding the flight recorders will be taken by the AAIB after due assessment of all technical, safety, and security considerations " would likely have been phrased rather differently if the lab in India were not considered capable of the work involved.

On edit:
And mods, apologies, this is getting rather more tangential to the incident than I intended!

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.

I don't see any direct confirmation that the flight recorder(s) have been read and their data determined, just that the AAIB have them in their custody, and they aren't going anywhere else.

To be honest, I don't see any detail in this reported conversation that tells me the Minister has any actual knowledge of the state of play in the investigation itself, just the process and a general round-up of what we basically already know.

My guess is that the investigation has not provided any feedback yet - or at least none that the Minister is able to pass on.

Then why didn't that happen on the previous flight from Deli to Ahmedabad, or any of the previous flights since that engine install in March?
Thanks for the update, and in particular that bolded bit.