Posts about: "EAFR" [Posts: 153 Pages: 8]

The Jeju Air recorders survived the crash, and their data was successfully downloaded. They simply stopped recording when the power failed. (And those recorders were also much damaged.)

Here, at least one EAFR has its own power source, and we're likely to see a record of the engine failures if those caused the power loss on AI171, so that's going to be more helpful.

Regarding the Recorders, obviously nothing to do with the cause, but still:

Given:
There were 2 recorders:
1/in the tail, likely to not be overly damaged, but might have stopped being powered at the moment the thrust was lost. Due to digital delay, it might not have catched interesting transient data of the cause.
It is too far removed from the cockpit to have independent analog feeds from microphones or other equipment.

2/ The one in the front, much more likely to have been damaged, and also more likely to be useful because it had an independent area microphone cockpit source.

I have 2 questions and a speculation:
Speculation: The front recorder also lost all data because the systems powered down, except it independently, and by analog direct means, powers the cockpit area microphone w/micpre and could continue recording that for a good amount of time on a small battery.

This then might be the recorder recieving special treatment and delayed read out, because of the damage, and because it contains audio from the cockpit, (while the other one, might already have been read by conventional means, but doesn't contain anything of use because this was a sudden event and digital latency. Or as I assume some might speculate, the tail recoder hinted to information leaving the decision on whether to read the front recorder abroad to someone much higher up)

Questions:
1/Would the recorders lose access to aircraft data streams when engine power is lost, at least temporarely making the cockpit area mic recorded by battery power on the front recorder the only source of information ?
2/The recorders only draw 20W, why is it the front have reserves only for 10 minutes? Can you even buy a battery that small giving 28VDC? Why is such a limited solution selected?
(And since they have a microphone input, and the units are interchangeable why don't they just stick a few grams worth of microphone in the back of the aircraft as well, just to catch mechanical noises that could help when data input is missing. Audio sensors seems underrated.)
( For reference, This battery could power the whole recorder for an hour: https://www.batteryspace.com/custom-nimh-battery-28-8v-800mah-23wh-with-tabs.aspx )

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

The recorder data sheet specifies it is an analog input for the area mic, and that it and its pre-amp are powered by the recorder.
It is likely a mems-type microphone, moving coil, ribbon or traditional condenser microphones aren’t really used outside the stage or vintage recording studios these days. But something along these lines: https://pdf.aeroexpo.online/pdf/l3-t...html#open64169

Note the dual analog and arinc digital outputs.

One reason for not doing an analog line all the way to the tail would be weight, as you mention, quality or noise wouldn’t be an issue due common mode rejection.

That's a very useful document, and it answered some questions for me.


The area microphone connects to both EAFRs. The EAFR are normally powered via the left and right main 28v buses.

The RAT powers the backup bus.

The main L and R 28v buses do not receive backup power.

After electric power is lost, the aft EAFR is unpowered, and the front EAFR has 10 minutes power off its internal supply.

I am not sure that is the case.

Under ICAO rules the AAIB has lead on this. It was an Indian registered aircraft that crashed in India, how could they not be?

The aviation minister ordered a “high level” investigation in to the accident. This is politics only.

This will make the minister feel he has control of the investigation and the narrative, in reality the EAFR data will be leaked by whichever party is in the clear.
If the aviation minister understood his portfolio he would know that the AAIB and DGCA are the accountable and responsible agencies here.

Watch carefully.

Just to summarize. There appears to be fairly wide consensus as to what happened:

1. Up to V1 it appeared normal and the pilots did not abort.
2. Loss of thrust very close to V2 rotate or shortly thereafter.
3. Loss of electrical and hydraulics resulting in deployment of RAT seconds after being airborne.
4. Mayday transmission seconds after takeoff (although it may have occurred around V2, the timing has not been established).
5. Gear tilted forward suggesting gear retraction was initiated but not completed.
6. All followed by glide to impact from AGL of little more than 100 feet.

Why the above happened is rather less clear. In my opinion, fuel contamination/starvation, water, additive, vapour or otherwise, may have affected thrust during takeoff before resulting in total loss of thrust and electrical power. On the other hand, software/electrical fault would more likely have resulted in a sudden loss of the engines.

On that basis, there is still some mileage in establishing the aircraft speed in the last moments before takeoff. There is definitely mileage in identifying a single point of failure that would cause the engines to shut down; other than fuel contamination/vapour issues. I suspect that the official investigation is not all that further ahead of this thread. Without useful data from the EAFR they have to rely on forensics and history. Enough has been leaked to know the engines were no more than windmilling at impact.

A high level of interest will continue given there are still remaining questions whether the reliability of Boeing machinery is implicated. That is not to mention the hundreds of people closely affected by this tragedy that are looking for reasons why it happened. Perhaps an interim report is now overdue?

Please note that the EAFR used on the B787 has got at least 2h audio recording for the CVR part as well:

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

This has been very briefly mentioned - inside a "quote" from an "official" - uptread, but I don't think has been specifically discussed here.

It "seems" that the Gujerati Anti-Terrorism Squad (ATS) have recovered a DVR (digital video recorder) from the accident aircraft:

https://www.financialexpress.com/ind...dence/3879001/

As I understand it, the ATS were there to assist as necessary, not because of any posited terrorism link. The article posits that:

The DVR in aviation settings records footage from CCTV cameras installed throughout the aircraft, including the cockpit, passenger cabin and entry/exit points. This footage is crucial for investigators as it provides visual evidence of activities before and during the flight, such as passenger boarding and ground operations.

I'd not hear that Air India had such devices installed (the EAFR combo black box on the accident aircraft does have a "growth function" for adding video recordings at some future date). What's more the DVR seen carried by a "ATS Agent" in the picture and linked videos looks to me first undamaged and second like a domestic DVD player.....

Anyway, anyone know more of a DVR fitted to Air India aircraft for investigative purposes?

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

The available video and trajectory information are quite conclusive that both engines stopped producing thrust within 12 seconds of the main wheels leaving the ground. Had partial power of any level remained, the aircraft impact would have been further away from the departure end of the runway. The NE end camera shows by using transit sightings against identifiable structures, that the failure occurred while the aircraft was still within the airport boundary area. The energy state of the aircraft at that time trades off to impact at the correct time and place.

On departure at these weights the aircraft would have some assumed temperature thrust reduction from max available on the GEnx -1B70, Unless they were carrying lead, they were around 30,000 or more below the limit weight for a flaps 5 TO. At that weight, around 440k lbs, they would have had a fair OEI climb gradient on one engine, certainly a positive gradient with the gear down, so they lost more than 50% of total thrust. There is no yaw or roll, or inputs to counter a yaw or roll moment so the aircraft was symmetrical at all times, that means losing absolutely no less than 50% of total available thrust at that point on each engine. At 50% reduction. the aircraft would have continued a positive gradient with the gear down and the flaps at the TO setting. It did not, it decelerated at around 1meter sec, or 0.1g deceleration for just maintaining level flight, but it also had to descend and that was worth around 0.05g as well. Instead of having any positive thrust margin, the guys were needing to descend to balance the decrement in thrust of around 0.15g, and that means it has negligible to no thrust from the engines. The full analysis takes more effort as the AOA has increased over the 15-20 seconds to impact, which is increasing the drag of the aircraft rapidly towards the end. For the first 5-10 seconds however, it is not such a great change, but it is still increasing.

In level flight, the aircraft would accelerate level at around 0.3-0.4g gear down with both engines running at max chuff. Lose one, and you are back to 0.05-0.1g or so. These guys had far less than one engine remaining, gravity was all that they had going for them.

To that end, there is no requirement to have the EAFR readout of the N1, N2, FF, or EGT, the video shows they had no puff going worth a darn. That is basic back of the envelope physics and anyone who does aircraft performance testing would be able to get that answer straight from the video without using a calculator, by the time they had watched the video a couple of times in replay.

I have no qualms on stating that the engines are not operating, the RAT, gear tilt are consistent with the dynamics of the aircraft. This is far simpler to determine the energy state than that of the B738W at Muan, the lack of early video required a couple of iterations of the kinetic energy of the aircraft at Muan to end up with a probable flight path, and most likely estimate of the thrust remaining for those most unfortunate souls.

regards,


FDR

Constructing ever more unlikely cascading failures to fit the very few known facts is unproductive.

Of more interest to me is the lack of word on the plan to interrogate the EAFR units. Where and when?

Also that the DGCA wants THREE managers removed from their positions at Air India. Unconnected to this accident however.


Imagine Qantas being told by CASA to do a similar thing, or BA by the CAA, amazing stuff.

Always possible, however since a pilot made a radio call there was some emergency leve l power available, which suggests the EAFR would be powered.

The Jeju recorders were okay if I recall correctly, they just had no input, was that the case?

Somoeone made a good point above about the German Wings FDR/CVR being available the next day after the aircraft was aimed at the ground like a missile. These things are built tough, as you know, this may be type specific but….

India is the first country to put a lander and a rover on the south pole of the moon. I'm sure they can get the data from the EAFR!

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.

The equipment on RAT/battery is limited:


(from the online 2010 FCOM)


(from the maintenance training )

The 787 battery fire report says the two recorders are on the left and right 28VDC buses. I don't think those get powered on RAT by the looks of it. I would wager you get whatever is on the 235VAC 'backup bus', plus the captain's and F/O's instrument buses via C1/C2 TRUs. You won't get all of that (like the F/O's screens) because the 787 energises/de-energises specific bits of equipment, not just whole buses.

Losing recorder power looks entirely expected.


400VAC/540VDC (+-270V) is not really known for blowing past input protection in the same way as actual HV or lightning. I would expect some optocouplers and/or transformers to be both present and adequate. There's definitely some big MOVs scattered around the main 235VAC buses.

Weight on wheels appears to go into data concentrators that go into the common core system (i.e. data network).

Presumably there is a set of comms buses between the FADECs and the CCS to allow all the pretty indicators and EICAS alerts in the cockpit to work. The WoW sensors might flow back via that, or via dedicated digital inputs from whatever the reverse of a data concentrator is called (surely they have need for field actuators other than big motors?). Either way, left and right engine data should come from completely different computers, that are in the fwd e/e bay (or concentrators/repeaters in the wings, maybe) rather than in with the big power stuff in the aft e/e bay.

At least one previous investigation report by the Indian AAIB has used CVR and FDR data downloaded from an (intact) EAFR.

With 'intact' being the crucial part of these recent posts. It is my understanding that a suitably equipped LAME can simply download the FDR data from an installed EAFR (CVR requires dismounting). So downloading as such, isn't the issue.

However more importantly, as implied by another poster 'patience' is of the essence in this thread ...

Actually download of an undamaged recorder can be done using a notebook with an ethernet interface. The EAFR even has an integrated webserver to browse through the recorded data. - At least that\x92s what GE promises.

But has AAIB India ever had to get data directly from the memory chips due to a badly damaged data recorder? I think it would have the capability.