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BrogulT
June 15, 2025, 14:21:00 GMT permalink Post: 11902500 |
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MarineEngineer
June 15, 2025, 14:25:00 GMT permalink Post: 11902503 |
Correct. That was the original purpose of the calculation. In addition to the sound itself having the measurable harmonic signature from other rat videos.
What this plot also does however is tell you the speed if you know the height or height if you know the speed. The iphone used to film this were pictured somewhere, knowing the iphone model, and thus the characteristics of the camera, and the dimensions of the airplane it wouldn't be impossible to calculate height from the video imo. Just throwing it out there if anyone sees the use and feels the call. My personal amateur speculation still centers around the cut off switches. Doesn't need to be a suicidal jump-seater, I have spilled coffee and sweet tea over complex electro/mechanical switches/panels before(large format audio consoles with 8000 buttons) and seen unexpected things happen. I am sure the switches are spectacularly well built, but they are in close proximity and thus prone to the same external factors. Does anyone know if these two cut-off switches in such close proximity has the exact same installation, or they differentiated in some way that makes a freak failure mode in one not neccesarily affect the other the same way? |
adfad
June 15, 2025, 16:31:00 GMT permalink Post: 11902614 |
Can anyone help with my theory - I'm an electronics and software engineer, but not a pilot.
My understanding of the infamous and previously fixed 787 issue was that the PCU software would trigger a shutdown of all AC generators (or rather their respective control units) after 248 days of continuous power due to an overflow of a software counter, and that this was fixed in software alone. Hypothetically , if the PCU software triggered this state during takeoff, what would happen? I know the engines may continue running with engine-driven fuel pumps, but I also understand this doesn't work in all situations and perhaps during rotation with a high fuel demand and fuel tanks not horizontal this could be an issue? What does everyone here think it would look like if all AC generators were shut down, in terms of engine performance - would you expect there to be a reduction in thrust? With the gear stuck down would that be serious enough? |
Engineless
June 15, 2025, 17:15:00 GMT permalink Post: 11902643 |
I think it needs to be said again that pretty much anything can happen to the aircraft systems and the engines will carry on running - this is by design as they have independent FADEC and power supplies and at sea level fuel will get through without boost pumps. You could almost saw the wing off the fuselage and the engine would still produce thrust, TCMA notwithstanding.
We don\x92t know yet what actually triggered the RAT from the relatively short list but every item on it means there is a serious/critical failure(s). The flight path suggests that it was a double engine failure or shutdown (commanded or uncommanded) as anything else should have left the aeroplane in a poor state but able to climb away . Secondly, as a (now ex) glider pilot who remains extremely interested in aviation in most of its forms, this discussion has been an education and thought-provoking, as it so frequently is whenever I lurk here (usually without logging in). Thank you all for sharing your knowledge, expertise and thoughts. To my mind the above post (especially the sentence I highlighted) is amongst the best (and most succinct) summary of what the pilots likely faced, with little to no time to resolve the situation. I cannot imagine those last few seconds and my heart goes out to them, the passengers and the many loved ones left behind. If there is any good that can come of this, it is that the cause is found quickly, with no bias, and steps are taken to ensure the same holes in the cheese cannot happen again. |
adfad
June 15, 2025, 17:16:00 GMT permalink Post: 11902645 |
When we see the video, the airplane is still climbing / flying straight and level (not losing altitude), yet we hear what we think might be the RAT, I can't imagine that they had the kinetic energy to do this with no engines. if they had dual engine failure, they would have been a brick, Hot and High, no thrust, flaps 5, zero chance.
The original mobile video (not the copy from someones phone screen) clearly sounds like a RAT but what does the engine itself sound like - is it idle or reduced in some way? What is the minimum amount of thrust that would need to be lost to stop climbing and sink back down - it took 30 seconds from leaving the ground to impact from the CCTV and the first 15 was climbing. I would look carefully at the fact that the PCU still has the technical ability to tell all AC generator control units to turn off via software, as proven in the documented and fixed 248-day software issue. |
fdr
June 15, 2025, 18:58:00 GMT permalink Post: 11902721 |
The biggest news site in Greece claims to have the results of a kind of preliminary report from India AAIB which say that as the plane rotated, the pilot's seat malfunctioned (broken pin) and went suddenly far back forcing the captain to accidentally lower the thrust lever as he already had his hand on it and despite the co-pilots effort to help increase the thrust it was already to late to avoid the stall. I dont believe they would have posted something as serious as this without any credible source cause they are supposed to be a serious news outlet but you never know when stupidity takes over validity. Source is the protothema dot gr site
The proposition that is floated is that the pilot does not pull back on the control column, which he is holding onto with both hands as his seat slides backwards like a caricature of a bad Cessna 180 seat rail, that is plainly obvious from the pitch attitude of the aircraft, yet grabs lustily a double handful of thrust levers and holds onto those until meeting Ganesh in the next life? Greek papers appear to be as rigorous and incisive in their cognition as the Daily Telegraph. Golly. Seats: electric. RAT deployment... presumably the hapless pilot doesn't grab the control column, or the thrust levers, just grabs both fuel control switches instead???? Do any reporters bother to read what they write? |
Stivo
June 15, 2025, 19:23:00 GMT permalink Post: 11902745 |
I will wager that this is absolute nonsense. The effect of pulling the power levers back to idle at rotate would be readily countered by pushing them back up again. The engines are still delivering thrust, it is a function of N1, not the lever. The lever commands where the thrust level will end up, the N1 gives the thrust output. The acceleration/thrust characteristics of these engines is not like a J52 or JT3D etc.
The proposition that is floated is that the pilot does not pull back on the control column, which he is holding onto with both hands as his seat slides backwards like a caricature of a bad Cessna 180 seat rail, that is plainly obvious from the pitch attitude of the aircraft, yet grabs lustily a double handful of thrust levers and holds onto those until meeting Ganesh in the next life? Greek papers appear to be as rigorous and incisive in their cognition as the Daily Telegraph. Golly. Seats: electric. RAT deployment... presumably the hapless pilot doesn't grab the control column, or the thrust levers, just grabs both fuel control switches instead???? Do any reporters bother to read what they write? |
C2H5OH
June 15, 2025, 20:06:00 GMT permalink Post: 11902782 |
As I've noted previously, a complete loss of aircraft electrical power would not cause the engines to flameout (or even lose meaningful thrust) during takeoff. In the takeoff altitude envelope, 'suction feed' (I think Airbus calls it 'gravity feed') is more than sufficient to supply the engine driven fuel pumps. It's only when you get up to ~20k ft. that suction feed can become an issue - and this event happened near sea level.
So I wouldn't vouch for the FADECs if there was catastrophic problem with the power distribution in the aircraft. |
Alty7x7
June 15, 2025, 20:23:00 GMT permalink Post: 11902791 |
Engine failure with electrical power loss
We agree that there was a lack of thrust. Possibly caused by a dual engine failure. But the sharpest frames in the video do NOT show the RAT and this is counter evidence to the RAT theory. If there were substantial technical failures who knows what sounds could be generated. I find the evidence weak at best. And we immediately get into a chicken-egg problem: did some power issue of unknown nature cause an engine failure or did a dual engine failure occur, resulting in a power loss? Both are extremely unlikely and need to be backed by quality evidence. The video is not it, in my opinion. I don't know the APU intake mechanism and whether it could open after the impact.
Tdracer earlier confirmed that an airplane electrical power loss would allow engines to keep running , because 1) engines are fully-capable of suction feed operation in takeoff envelope (if boost pumps lost), and 2) the EECs are powered by their own PMAs when running and to substantially below idle (I recall roughly 10% N2). Airplane powers the EEC for ground starts, prior to PMA coming online, and as backup to the PMA after that. Related: Engine igniters are powered by the aircraft. So theoretical full loss of aircraft power would disable Autorelight upon a flameout. Ignitors typically don't make the cut for most-essential battery-only loads because it would also take an engine flameout, and the airplane past V1 in ground roll can fly fine on one engine that can achieve takeoff thrust. Autorelight is relevant - if there was a single-engine failure post V1, autorelight will attempt to relight the engine, so there is no need for a pilot to try to cycle the fuel switch to reset the EEC (potentially grabbing the wrong one), or to otherwise intervene. In such a circumstance, they need to trust their training. I've heard accounts that the most likely pilot instinct in such a situation would be to push the throttle(s) forward. Finally - there was talk earlier about accidentally cutting the fuel switches - and it was duly noted that they have to be pulled out over the detent, so very unlikely. The same cutoff effect could be achieved with the engine fire handle(s), right behind the fuel switches on the pedestal - though they are an upward pull, so also not subject to inadvertent or accidental engagement. |
adfad
June 15, 2025, 21:51:00 GMT permalink Post: 11902879 |
It is similar to the 248-day continuous power software bug on the 787. In both cases a counter in the software would overflow after an amount of time that would be proportional to something like the number of seconds, milliseconds or other unit.
The 248 day bug would cause the PCU to trigger ALL 4 AC generator control units to shut down. The fact that this is even possible in software alone is remarkable and should make any engineer concerned. The fact that this was only fixed in software with no redundant physical system (e.g. 1 or more AC units being independent of this system) is concerning. The fact that Boeing had a second software overflow error causing the 51 day directive should really have everyone discussing software as a possible cause for this crash. People may say that the engine driven pumps / suction feed / gravity feed would continue to power the engines but my understanding is the aircraft attitude and high fuel flow at takeoff could potentially mean less thrust than was needed if all 4 AC generators disconnected and stopped all AC fuel pumps during rotation. |
Captain Fishy
June 15, 2025, 21:56:00 GMT permalink Post: 11902882 |
Do not discount the mistaken early flap retraction scenario too easily. Mull on this:
PF commanded gear up on attaining positive rate of climb, fixating on the HUD. PM mistakenly raise flap lever from 5 to Flap 1 gate. Thrust reduced to Climb Thrust. Landing gear remained deployed. Massive loss of lift misidentified as loss of thrust. If any one pilot just had a dual engine failure scenario on a recent sim ride, brain and muscle memory would jump to loss of thrust in dual engine, prompting them to accomplish the recall memory items which called for both engine fuel control switches to CUTOFF and then RUN, and physically deployed the RAT. There would be immediate loss of thrust with the engine taking time to recover , if at all, at such low airspeed! The rest is left for Ppruners\x92 imagination.😖🥴😬 A loss of lift AND thrust at this critical juncture could have had caused this awful disaster. I think the data recorders have already revealed the cause but If it's this, then I don't think we will hear much anytime soon. |
Kraftstoffvondesibel
June 15, 2025, 23:36:00 GMT permalink Post: 11902967 |
Maybe you should describe your analysis then and present the data? I'm a physicist so chances are I might actually not be so unfamiliar. Please include an analysis of raw data quality, spectral resolution and binning as well. And don't state it is the 'exact same' as this is statistically impossible.
The latest techniques let us separate such things as reverbration from the source, when superimposing the reverberation/ambience and background noise of the AI crash urban environment on the clean, dead open field recording of the known B787 w/rat, they do indeed sound exactly the same to this very skilled and experienced listener. Although this is not courtesy of the computer analysis. It is just another angle of confirmation. All in all, i think this source audio is excellent. The source is an iphone, their mems based microphones, although noisy shows great spectral balance and is comparable to basic measurement microphones of professional application. There is plenty of information to analyse from in this sample. And again, I can't see it in the video either, and until I put on some really expensive headphones and fired up the software I was of a different opinion. I bowed to the science. Edit: I took an extra look, I am prepared to say the fall off at slightly above 16kHz is from the original recording, this is probably a limitation in the microphone, as it is not a hard cut-off before a 16kHz Nyquist frequency as it would be with a 32kHz sampling rate, there is dither noise from 16-20kHz fitting with the source being 16 bit. Last edited by Kraftstoffvondesibel; 15th June 2025 at 23:54 . |
F-flyer
June 15, 2025, 23:39:00 GMT permalink Post: 11902970 |
Water ingress into the E/E bay is a serious issue. The B744 had this issue in the past causing serious problems, one of which was fortunate to not lead to a loss of the aircraft, on a B744F. The B744 pax aircraft had a number of water problems related to the toilets and the galley. The forward galley on the B742/3s had many issues.
Any large aircraft going through maintenance is interesting to observe the extent of corrosion that occurs near toilets and galleys, and from water lines. Water accumulations on the B744 came to light at rotate, and took out a lot of electrical services. My suspicion is some cause such as this will come to light shortly. Both of the E/E bays contain stuff that is nice to keep dry and operating, and prior events have shown that multiple system failures can and have occurred when a flood is added to all the black boxes sitting innocently on their racks. The ADs are not necessarily directly related to the specific cause, they highlight the potential for water damage and that bad stuff happens. In two cases I investigated, the event occurred at rotate. Both were B744's one pax, one F. Compound, unrelated system failures at rotate? Single cause? Water in the E/E bay. "System malfunctions Between 0846 and 0852, 4 after passing FL 100 and when the aircraft was turning onto an extended left downwind leg for runway 01 Right (01R), the EICAS, flight displays and automated systems showed faults of numerous electrical and other aircraft systems, including: \x95 AC buses 1, 2 and 3 not powered \x95 autothrottle disconnected \x95 autopilot disengaged \x95 some fuel pumps not operating \x95 weather radar not operating \x95 automatic cabin air conditioning and pressurisation system not operating \x95 right (FO\x92s) displays blanked \x95 between three and five pages of messages on the EICAS display \x95 lower EICAS display blanked. The CSM contacted the flight crew and advised that the cabin lighting had failed." "Origin of Generator Control Unit (GCU) faults Post-incident examination of the GCUs revealed corrosion of the internal circuit boards in all three of the GCUs that shut down. Analysis of the corrosion materials observed in GCU 3 showed evidence of long-term exposure to water, including evidence of acids and carbohydrates that are present in beverages such as coffee, fruit juice and soft drinks. Those findings indicated a fluid source originating from the aircraft\x92s galley drains or from spilt liquids in the cabin, and also suggested that liquid ingress had been occurring over an unknown, but extended period of time." https://www.atsb.gov.au/sites/defaul.../ao2008003.pdf This link to the report includes diagrams of where the 747 forward galley was located, directly above the Main Equipment Centre and the E1/E2 racks. The phtographs show how ineffective the dripshield was in protecting the electrical equipment and the extent of corrosion and damage. The aircraft was 17 years old at the time of the incident and had completed a C-check approximately three months before the incident. As FDR notes, this issue seems to have carried over to the 787-8 with Airworthiness Directive AD 2016-14-04 ( https://drs.faa.gov/browse/excelExte...A0058AF6B.0001 ) "We are issuing this AD 2016-14-04 to prevent a water leak from an improperly installed potable water system coupling, or main cabin water source, which could cause the equipment in the EE bays to become wet, resulting in an electrical short and potential loss of system functions essential for safe flight" AD 2016-14-04 mirrors precisely what occurred to the Qantas 747 on 7 January 2008. It is possible something similar may have occurred on take-off of AI171, with water causing the equipment in the EE bays to become wet resulting in electrical short and potential loss of system functions |
Muon71
June 16, 2025, 00:42:00 GMT permalink Post: 11903011 |
...
All in all, i think this source audio is excellent. The source is an iphone, their mems based microphones, although noisy shows great spectral balance and is comparable to basic measurement microphones of professional application. There is plenty of information to analyse from in this sample. And again, I can't see it in the video either, and until I put on some really expensive headphones and fired up the software I was of a different opinion. I bowed to the science. Edit: I took an extra look, I am prepared to say the fall off at slightly above 16kHz is from the original recording, this is probably a limitation in the microphone, as it is not a hard cut-off before a 16kHz Nyquist frequency as it would be with a 32kHz sampling rate, there is dither noise from 16-20kHz fitting with the source being 16 bit. The cut-off at 16 kHz is typically caused by lossy audio compressions (AAC), not the microphone. In this case, the audio was compressed two times (first the iPhone, then the Twitter). A microphone does not simply cut all frequencies above the certain point. Also, this audio content is Mono (the same signal on both channels) - an additional loss of information, if the original recording was Stereo. |
mechpowi
June 16, 2025, 06:11:00 GMT permalink Post: 11903125 |
Without any 787 knowledge, I would assume two discreet signals from respective Engine Fuel Switch to each FADEC channel, possibly with other redundancies. Or other solution that is at least as robust. |
bakutteh
June 16, 2025, 06:41:00 GMT permalink Post: 11903143 |
Fuel Cavitation/Vapour block?
If decrease in thrust not by transition to climb thrust due to early inadvertent flap retraction and pilot action on fuel control switches from accomplishing dual engine failure memory items, then fuel cavitation /fuel fumes lock may be a cause. Just saying.
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lighttwin2
June 16, 2025, 08:51:00 GMT permalink Post: 11903270 |
If TCMA cut fuel flow while still on the runway the aircraft would have been decelerating from the moment it lifted off, which is not what the ADS-B data indicates. The kinetic energy in the rotating parts of the engine wouldn't add much speed to the aircraft as the engines run down with no more energy being added via fuel.
In no particular order, here are some more thoughts on TCMA having caught up on the thread: If you cut the fuel from two big engines at take-off power, there must be some delay before n2 decays below the threshold for generation (below idle n2), the generators disconnect and RAT deploys. GEnx have relatively long spool up/down times as the fan is so large (and would be exposed to 170+kts of ram air). Perhaps someone has a view on how long this would be, but I imagine it could easily be 10s or more between fuel cut off and RAT deployment. On AI171 the RAT appears to be already deployed at the beginning of the bystander video. That starts c. 13s before impact and around 17s after rotation. This does not prove anything except that the supposed shut down must have happened very close to rotation and could have happened just before rotation while the a/c was on the ground. As a thought experiment, imagine if ANA985 in 2019 had decided to go around. The a/c rotates and is ~50 ft above the runway, suddenly both engines spooling down, very little runway left to land on and no reverse thrust available. I am struck by how similar this scenario is to AI171. This theory would require there to have been unexpected thrust lever movement in the moments before rotation - but plausibly one pilot moving to reject, followed by an overrule or change of heart - or even a simple human error such as the recent BA incident at LGW - could achieve this. This is perhaps more likely that any sensor fault that you would expect to only impact a single engine given the redundancy of systems. Tdracer writes that a key requirement of TCMA is to identify an engine runaway in the event of an RTO, in order to allow the a/c to stop on the runway. This will have been tested extensively - it is a big leap to imagine a false activation could be triggered. It did happen on ANA985 but through a very unusual set of inputs including application of reverse (albeit this latter point may not be relevant if TCMA logic does not distinguish between the reverser being deployed or not). Incidentally there is an assumption the TCMA software version in place on the ANA flight had already been patched and fixed on AI171. That probably is the case but I am not sure it is a known fact. In summary I remain baffled by this tragic accident. I have not yet read anything that explicitly rules out TCMA activation and it remains a possibility due to the vanishingly small number of factors that could shut down two engines at apparently the exact same moment when they have fully redundant systems. Fuel contamination, for example, has typically impacted each engine a few minutes (at least) apart. I am also cautious (as others have pointed out) of a form of confirmation bias about Boeing software systems with four-letter acronyms. In my mind the cause could equally well be something completely different to anything suggested on this thread, that will only become clear with more evidence. All of the above also incorporates a number of theories, i.e. that there was an engine shutdown - that are not conclusively known. Thank you to the mods for an excellent job. |
Pinkman
June 16, 2025, 09:17:00 GMT permalink Post: 11903301 |
With the information we have accumulated so far, is the following a possible scenario? Normal departure up to VR, then a total electrical failure at lift off (possibly as the ground/air logic switches to air.) All hydraulics lost and cabin lights flicker plus RAT deploys. All fuel boost pumps fail so engines only have suction feed. Engines roll back. The aircraft seems to me to have gone too far to have suffered a total loss of thrust at lift off. There must have been some energy being provided by the engines? Such a system failure "can't happen", of course but nothing is impossible!
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pampel
June 16, 2025, 09:39:00 GMT permalink Post: 11903323 |
I'm not convinced the RAT is deployed. If it has deployed it could've been a last ditch effort for the crew to bring the fuel control switches from RUN to CUTOFF & back to RUN believing they've had a dual engine failure. This would account for the RAT if it did deploy.
There just isn't enough time for the RAT to be deployed as a result of any action by the crew, IMHO. And to demonstrate how long 7 seconds is - that's enough to say 20 words, assuming no interruptions . |
Compton3fox
June 16, 2025, 09:41:00 GMT permalink Post: 11903328 |
The PF could've been task focused flying manually, following the FD's and not expecting the sinking feeling of losing the lift. The PM has made the mistake without knowing. ie. he/she has selected the flaps all the way to UP believing that the gear was now retracting. Both pilots now think the gear is retracting, they have full thrust but are sinking into the ground. "Professional crews" like Air France for eg. have made way worse decisions. Slats are extended because they are the last to retract. I'm not convinced the RAT is deployed. If it has deployed it could've been a last ditch effort for the crew to bring the fuel control switches from RUN to CUTOFF & back to RUN believing they've had a dual engine failure. This would account for the RAT if it did deploy. The APU inlet door could've been open as well because they were carrying out an APU to Pack takeoff.
Once the aircraft is airborne and the
weight-on-wheels (WOW) switches indicate air mode
, the main gear
bogies automatically tilt to the neutral position
before retraction. Also when the flaps passed the last takeoff position on the quadrant, the Landing gear configuration warning horn would've sounded further confusing the pilots.
The RAT was almost certainly deployed. 4 different sources. The Flaps were not retracted. Visible at the accident site plus many other sources agreeing they were indeed down. APU will autostart when all engine power is lost. Potentially explaining why the inlet door was open or partially open at the accident site. Mentioned in several previous posts On a 787-8, the main bogies tilt as the 1st action of the gear retract sequence. As stated in previous posts. I don't think this happens unless gear is selected up. So the conclusion was, gear was selected up. One caveat, IIRC, there was some discussion around a failure could have caused the bogies to tilt without Gear up being selected but I don't recall the outcome. As for the Air France remark, un-necessary IMHO. Let's respect the crews please. |
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