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Musician
2025-06-20T09:25:00 permalink Post: 11906769 |
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. 1 user liked this post. |
Kraftstoffvondesibel
2025-06-20T16:36:00 permalink Post: 11907117 |
Regarding the Recorders, obviously nothing to do with the cause, but still:
Given:
"The forward installed EAFR along with theCockpit Area Microphone and Preamplifier are typically connected to the Recorder Independent Power Supply (RIPS), providing a backup power source for 10 minutes in the event of power interruptions."
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 ) Last edited by T28B; 20th Jun 2025 at 18:25 . Reason: formatting 5 users liked this post. |
JustusW
2025-06-20T17:45:00 permalink Post: 11907155 |
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 with reserves only for 10 minutes? Can you even buy a battery that small giving 28VDC? Why is such a limited solution selected? ( For reference, This battery gives about 9 times that: <url removed> ) 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 2 users liked this post. |
Kraftstoffvondesibel
2025-06-20T19:10:00 permalink Post: 11907217 |
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 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. Last edited by T28B; 20th Jun 2025 at 19:11 . Reason: punctuation and grammar assist 3 users liked this post. |
Musician
2025-06-20T19:44:00 permalink Post: 11907252 |
electric circuits
To explore the electrical system further see p. 86 of this document. I decided to trace out some electrical paths to equipment and do a few simple calculations.
https://fliphtml5.com/quwam/qhdw/Boo...cs_Electrical/ ![]() 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. 4 users liked this post. |
Icarus2001
2025-06-21T01:15:00 permalink Post: 11907429 |
so it's not clear who has primacy in the investigation any more.
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.
NEW DELHI, June 15 (Xinhua) -- India's federal civil aviation minister Ram Mohan Naidu Kinjarapu Saturday said keeping in view the utmost seriousness of the incident, another high-level committee has been formed to probe the deadly plane crash in the western state of Gujarat.
The committee, according to Kinjarapu, will be headed by the home secretary and will submit its report in three months. If the aviation minister understood his portfolio he would know that the AAIB and DGCA are the accountable and responsible agencies here. Watch carefully. 3 users liked this post. |
wheelsright
2025-06-21T04:06:00 permalink Post: 11907468 |
Just to summarize. There appears to be fairly wide consensus as to what happened:
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? Last edited by wheelsright; 21st Jun 2025 at 04:24 . 4 users liked this post. |
EDML
2025-06-21T11:52:00 permalink Post: 11907686 |
It is a battery, not a supercapacitor. Most commonly nickel-cadmium, because that chemistry has been used in aircraft for decades. They're safe and readily accepted by regulators. Li-ion can be used, but a "special condition" from the regulators is needed, plus the weight savings would be negligible.
The 10-minute limit has nothing to do with the battery capacity. It's to prevent the recorder from continuing to operate after an accident and thus overwriting the audio of interest. There's a timer in the RIPS module. It will stop providing power after exactly 10 minutes, regardless of state of charge. https://www.geaerospace.com/sites/de...rder-3254F.pdf 2 users liked this post. |
Gary Brown
2025-06-21T12:27:00 permalink Post: 11907703 |
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? 1 user liked this post. |
OPENDOOR
2025-06-21T15:29:00 permalink Post: 11907844 |
787 EAFR unit
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.
T he Image Recorder growth function is used to record visual images of the flight deck instruments, flight deck, the aircraft structures, and engines as required. The Image Recorder function is capable of receiving a digital 10/100 Mbit Ethernet data stream of cockpit images and stores this data in the Crash Protected Memory in a separate partition. Even though the image recording duration will be governed by regulations, the EAFR Crash Protected Memory capacity has the storage capacity for two hours of image data recording per EUROCAE ED-112 requirements. Data in the Image Recording Crash Protected Memory partition can only be downloaded when the EAFR is off the aircraft.
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fdr
2025-06-22T00:10:00 permalink Post: 11908171 |
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 Last edited by fdr; 22nd Jun 2025 at 15:01 . 17 users liked this post. |
Icarus2001
2025-06-22T06:23:00 permalink Post: 11908302 |
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. |
Icarus2001
2025-06-22T09:42:00 permalink Post: 11908389 |
I wouldn't be surprised the recorders are stuffed eg Jeju; possibly the rear one "died" on the power interrupt and the front one got smashed up in the crash
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….
2 users liked this post. |
MarineEngineer
2025-06-22T10:22:00 permalink Post: 11908417 |
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!
2 users liked this post. |
Musician
2025-06-22T10:34:00 permalink Post: 11908427 |
The Jeju recorders were okay if I recall correctly, they just had no input, was that the case?
Last edited by Musician; 22nd Jun 2025 at 11:12 . 3 users liked this post. |
Someone Somewhere
2025-06-22T11:01:00 permalink Post: 11908441 |
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…. ![]() (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.
SLF Engineer (electrical - not aerospace) so no special knowledge
Perceived wisdom may be applicable in normal circumstances but not when all the holes line up. For example I've seen it quoted many times that the engine FADECs are self powered by the engines, the TCMAs-whether part of the FADEC or a separate unit, similarly self contained within the engine. The perceived wisdom seems to be that there is no common single fault which can take out both engines. And yet we're also told that the TCMA function can only function in ground mode and receives ground-air signals from a combination of inputs from Rad Alts and WOW sensors. There is therefore a connection from the central EE bay to the engine. Yes I'm sure the Rad/Alt and WOW sensor processing will use different sensors for each side and powered from different low voltage buses. However as an analogy, in your house your toaster in the kitchen may be on a separate circuit from the water heater in the bathroom, each protected by a fuse at the main switchboard. In normal operation a fault in one cannot affect the other. However a lightning strike outside the house can send much higher voltages than normal operation throughout the entire system and trash every electrical appliance not physically disconnected at the time. Now I'm not suggesting the aircraft was hit by lightning but FDR has proposed a single event, buildup from a water leak entering one of the EE bays at rotate. It would be possible for one or more of the HV electrical buses to short so that all the low voltage buses go high voltage. I have no knowledge of how the FADEC / TCMA systems connect to or process the Ground-Air signals but there is a single fault mechanism whereby high voltage could be simultaneously and inappropriately applied to both engine control systems. It would be unfortunate if this failure mechanism did cause power to be applied to drive the fuel shut off valve closed. Since the likelihood is that we're looking at a low probability event then perceived wisdom about normal operations and fault modes might not be applicable. 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. 8 users liked this post. |
DaveReidUK
2025-06-22T11:25:00 permalink Post: 11908461 |
4 users liked this post. |
DIBO
2025-06-22T11:56:00 permalink Post: 11908486 |
However more importantly, as implied by another poster 'patience' is of the essence in this thread ... 1 user liked this post. |
EDML
2025-06-22T12:15:00 permalink Post: 11908493 |
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 ... 6 users liked this post. |
MarineEngineer
2025-06-22T12:26:00 permalink Post: 11908502 |
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.
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