Posts about: "FDR" [Posts: 192 Pages: 10]

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

Note the front EAFR is the one with RIPS battery backup.

The aircraft from the time they lost thrust to impact was probably less than 20 seconds. At a low energy state the best the crew could do was try and break the rate of descent. There was no opportunity to try and maneuver to the best landing site. As far as the FDR’s it appears they functioned exactly as designed. The intense fire would badly damage the FDR boxes and associated electronics. The chip which is the component that is heavily protected so far seems just fine.

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.

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 didn\x92t really find a clear reference for other posts (trying to avoid the hamster wheel to over-rev) but in general the emergency busses only support equipment needed for survival.
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.

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.

I believe the GE EAFR continues to function as both FDR and CVR for a minimum of 10 minutes following a power failure.

However you are correct in that the requirements only specify that the CVR functions and the CAM must continue to operate.

Link to the NTSB Report to which D Bru refers, (@EDLB goes to member’s profile):
Auxiliary Power Unit Battery Fire Japan Airlines Boeing 787-8, JA829J Boston, Massachusetts January 7, 2013

I was looking for connector pin data but only found this:

"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.

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.

One thing they said is that the accident site was 'cleaned up, short order', suggesting that this might make it difficult to check physical state against what the FDR has recorded, eg if the FDR says the flaps are down, but the physical evidence says the flaps are not down. They show video of a digger scooping up wreckage.

As I said, I've been out of the loop for a few days. Do we know if the wreckage is being reconstructed in a warehouse, or whatever? I appreciate there may not have been that much left to reassemble, but the was at least one wing, a tail section, and the wing box section that the chap managed to escape from.

There's two points here: Firstly, whether anyone outside the investigation has any credible data they are able to disclose, and secondly, whether anyone outside the investigation can report with any knowledge, what the plans are for furthering the investigation. The answer to both is no. This will also go to the question previously posed as to whether politicians are likely to have been briefed.

One has to wonder why people might suggest otherwise, but the (probable) reality is that the authorities in India are doing what they think is needed in a situation where they know more than we do. If, for example, they are clearing the accident site after two weeks, they may think they have retrieved all the information from it that they can, and nobody else can really say otherwise.

As to reconstructing the wreckage, who knows (as yet), though my experience of a fire on board a fully fueled aircraft that has crashed on takeoff is that there may not be much to reconstruct. Certain parts, such as wings and the tail section for example, if in coherent condition, could be recovered and removed - and I seriously doubt anyone other than on the scene at the time, would be able to know.

All in all, the supposition that this is being done 'in haste' is nonsense. It suggests there's an attempt at a cover up of some kind, which is rather silly in a situation where an airliner crashes in a very public place, thousands witness it, it's filmed and put on TV, there are investigators from local authorities, the US and UK all present - all with different and contentious interests, plus the glare of media and others is on them. But 3 guys in the US on YouTube have uncovered the truth... Yeah, I doubt it.

Searching the web, I found out that regulations concerning new FDR require parameter 35g "fuel cut-off lever position" to be recorded. I also found that for a 2003 event with a 757, this was recorded (as was fuel flow).

I expect that this is also true for the 787. Can anyone confirm this?

I asked because if the FDR indicates that the switches were pulled, but there's no sound on the CVR, that might be giving them pause.

A very cursory review of the FDR data will indicate if the fuel switches were cycled as a response to an engine rundown, or if the engine rundown was in response to the fuel switches being cycled.

The phrase in the report is "switches transitioned from RUN to CUTOFF position".
Does the FDR actually have some input of the physical position of the switches or is it just measuring the output signal voltage
which might be changed by a momentary short from liquid or swarf.
Both signals go to cutoff within 1 second but then one recovers four seconds after the other.
Surely a pilot discovering a turned off switch would have both back on in less than four seconds.

That's a very good question.

The fact that one of the pilots verbally asked why they were off, presumably from visually observing this (?), would seem to rule out a short?

A douple-pole switch. One pole used for FDR signal for the physcial switch position. The other pole for the electrical switching circuit.

That would only make a duplicate, wouldn\x92t it.
And indeed they are 4 pole on-on switches, but one set of poles signals the spar valve directly while the other goes to the digital systems.