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604driver
2025-06-17T18:54:00 permalink Post: 11904568 |
One would hope, but, whilst there has been confirmation that the EAFRs have been recovered, nothing has been reported about their state or whether they have been downloaded or examined.
If the data is readable there may be a lot of politics and reputation on how that data may be interpreted. Behind the veneer of international cooperation vested interests will be being considered, advocated and agreed. It, unfortunately, is naive to think that politics will not have a silent presence in agreeing a press release. Boeing and GE are flagship USA companies. Air India is the flagship carrier of India. Investigations of all types first establish what happened, then how and why, before recommendations and actions. There is a possibility that they know the what, but the how and why incur liability. Investigators will try to establish a single source or truth. For them, that\x92s an ideal outcome. But due to the nature of investigations, the aim gets derailed as established facts versus possible/potential scenarios based on missing links of the chain are pieced together. But for sure, commercial considerations and liability wont enter into a proper investigation. The task of the investigators is to determine the how and why. Theres a saying, and it may even have been the title of a book\x85 Lift is a gift but Thrust is a must. In this case, certainly one or both were absent. For 2 (maybe 3 if it was a training flight) professional people, the day started with waking up, getting ready, saying goodbye to loved ones, who they believed they would see again soon in 2-3 days. Sadly, that won\x92t happen, and it\x92s the job of the investigators to find out why and liability isn\x92t a hindrance to them. They will look at every piece of evidence and recreate the events. But it will take time. information worthy of note is: A) The gear was still down. B) It would appear (due to some work by amazing members) that the RAT was indeed deployed. Other observances: 1. Bits flying off the aircraft. (From experience of operating in this area, they like to fly kites, and waste thermals and floats around, notably plastic bags) I have no idea if that la what we see or not. 2. Generally in India, they love using their horns. So whilst you can compare the frequencies of a potential RAT to a motorbike, appreciate there would be a million horns going off too. 3. Some posters have spoken of the \x93startle effect\x94 like they know what they are talking about. The most startling effect of a professional flight deck during an emergency is how calm it is. There aren\x92t hands flying around everywhere. In fact: V1 > Rotate > Positive Rate > Gear Up > Confirm FD/AP Modes is adjusted to: V1 > Rotate > Positive Rate > Gear Up > Silence the bell (Or your SOP Variation) FD/AP modes and the PF flies the aircraft. the next step is to identify the problem, agree on it and then perform the actions. That won\x92t happen below 400\x92. 4. There\x92s no company in the world where Pilots are being fed and watered between V1 and 1000\x92 so spilling drinks on run switches isn\x92t a thing on this departure. 5. Temperature inversion. Yes it\x92s possible and it degrades performance. However, if it\x92s present, it\x92s usually announced on the ATIS. IF other aircraft have reported it. 6. Fuel contamination. Without knowing the systems, yes it\x92s potentially possible, but it would appear no other aircraft have reported being affected by it. I think, this accident is especially interesting to Professional Aviators and Engineers because I think none of us would ever believe that it could happen. The aircraft is highly automated, the crew have been properly trained and the operation was a regular or possibly training flight. A query I have is, do later Gen aircraft like the 777/787/747 A330/A350/A380 constantly send Airframe/Engine data home to ops/engineering/oem\x92s. Is it likely the data is out there? Anyway, I just wanted to post this to reassure the travelling public that Pilots don\x92t try to shut down engines before they raise the gear. 8 users liked this post. |
Aerospace101
2025-06-17T19:01:00 permalink Post: 11904572 |
1. The hydraulic failure happened exactly when the truck had tilted forward but the split-second before the gear doors could open. That exact timing seems too coincidental. 2. The crew selected Gear Up. We have no proof of this. I speculate the crew never got as far as "Positive Rate...Gear Up" because they were already engrossed in flying the aircraft and processing their thrust problem. If an electrical problem had developed (as evidenced by the RAT deployment) the flight instrumentation would have been flickering and a flurry of silent master caution alerts would be very distracting. I suggest it's more likely that the truck remained in a forward tilt from the takeoff run because the hydraulic failure happened prior to rotation, therefore keeping it in this unusual position. This answer does not rely on the gear lever position either. It also insinuates that their hydraulic problems occurred probably between V1 and VR. See my earlier post . 3 users liked this post. |
D Bru
2025-06-17T22:37:00 permalink Post: 11904725 |
EEC MN4 - TMCA
Without a doubt one is looking at a very, very rare event, most likely the result of an unlikely/unlucky combination of issues, the grim gravity realised by the F/C (mayday) immediately after T/O. As a very, very FF/retired EU bureaucrat/economist/lawyer with an as ever staunch penchant for data/facts, I'm therefore wondering whether VT-ANB engines had already their EEC MN4 microprocessors replaced as mandated within 11000 cycles or 12 years per AD 2021-21-05
https://www.govinfo.gov/content/pkg/...2021-25491.pdf
. This AD was prompted by in-service occurrences of loss of GEnX engines thrust control resulting in uncommanded high thrust. Uncommanded high trust on (at least one of) the engines during the TO-roll, in particular past V1, resulting in a discrepancy with the actual (likely derated)thrust settings, could have triggered TMCA on or just before lift-off.
3 users liked this post. |
EXDAC
2025-06-17T22:42:00 permalink Post: 11904731 |
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EDML
2025-06-17T22:43:00 permalink Post: 11904732 |
That is not what the TCMA logic is supposed to do. Only high thrust with the thrust lever idle should trigger the TCMA.
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framer
2025-06-18T00:19:00 permalink Post: 11904793 |
Regarding the momentum: As the first seconds of the climb were normal compared to previous T/Os of the same flight (speed & altitude, confirmed by comparison of the RAW ADS-B data) I don't believe the engine failure happened before or on lift-off.
PM: “ V1 ….Rotate” The PF then begins to rotate the aircraft up to a pre determined attitude which is normally between 13 and 15 degrees. They do this at a rate of between 2 and 3 degrees per second so about 5 or 6 seconds later the aircraft is at its climb out attitude. The PM is then looking at their instruments to confirm that the aircraft has a positive rate of climb, this takes a moment, maybe 1 to 3 seconds then; PM “ positive rate” PF: “ gear up”. So minimum 8 seconds but probably longer between the PM calling “rotate” and the gear being selected up. The relevance of all that is to say that if you suspect that the gear up cycle has been interrupted by a dual engine failure, then the engines may well have been producing thrust up to an altitude of 50-100ft or so, which ties in nicely with the max height reached, distance travelled etc. Mods this is clearly not a theory, just info for those who don’t fly airliners to aid understanding. 11 users liked this post. |
Sailvi767
2025-06-18T02:49:00 permalink Post: 11904851 |
Yes, while there were other complications in play, this accident was caused by a single- throttle rollback after takeoff that wasn't detected by the crew:
https://en.wikipedia.org/wiki/TAROM_Flight_371 To my way of thinking, if you are in the habit of having your hand on the TLs, you're more likely to push them up when needed. 1 user liked this post. |
Capn Bloggs
2025-06-18T02:59:00 permalink Post: 11904858 |
Originally Posted by
Sailvi767
I will however point out that many airlines train to remove hands from the throttles at V1. This is supposed to reduce the chances of an inappropriate high speed abort.
2 users liked this post. |
Roo
2025-06-18T09:44:00 permalink Post: 11905074 |
Yep numerous times in the sim over the years. Typically when overly exuberantly trying to get AP in after a V1 cut. RA is right in your face on the HUD & if you don't wait til 200' RA, AP will not not engage.
3 users liked this post. |
FullWings
2025-06-18T10:26:00 permalink Post: 11905114 |
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mechpowi
2025-06-18T12:13:00 permalink Post: 11905186 |
Hi all,
Disclaimer: I read this thread from hour 1, still scratching my head regarding perf though. I know sound analysis points to higher odds being a dual engine failure with RAT deployed, however I still have some questions if anyone is available to enlighten. So, my questions is related to T/O performance. Is it possible on the 787 to calculate perf in the OPT for F15/20 T/O, and to enter F5 T/O speed on the FMC ? By that I mean do normal procedure, but at the point where you are suppose to enter flaps, CG speed ect\x85. You, out of habit (if F5 is indeed a habit on the 787) enter F5, but F15/20 speeds ? Or would there be a warning that you have manually inputed speeds that are not correct for the selected flaps and conditions inputed in the FMC ? Thanks for the help ! |
Bap7788
2025-06-18T12:26:00 permalink Post: 11905199 |
I think this has been answered for 76 and 77 on the first thread but I can\x92t recall an answer for 78. Can anyone confirm if you have inputed F15 in the FMC but selected F5 you would have some sort of FMC message displayed ? |
Xeptu
2025-06-18T23:09:00 permalink Post: 11905607 |
I need to correct one of my previous posts, I was going down the path of a mismanaged engine failure after V1, however it's been demonstrated to me that this aircraft will fly away on one engine even with the gear down with better than minimum climb gradient requirement. Quite astonishing actually.
That just leaves deliberate act not necessarily intentional, fuel vapour lock and automatically commanded engine shutdown. I hope the rat is found soon so we know for sure if both engines were in fact lost. 3 users liked this post. |
Magplug
2025-06-19T08:38:00 permalink Post: 11905832 |
Originally Posted by
Capn Bloggs
Come on, people. If it went into altitude hold, yes, the power probably would come off, but only to maintain the current airspeed. It would very quickly start powering back up as the aircraft attempted to sink and was countered by the PF. But the power didn't come back up, that being obvious from the increasing AOA during the descent.
In any case, there wouldn't be a sudden level-off because the PF is still l hand flying below 200ft. Do you think he'd blindly just jam the stick forward to follow the FD at such a low altitude? As stated before, if even only one of those engines was running, there's no way it would have descended, slowing down, as it did. Just after rotate is a very busy time for your scan. The FMA modes are in the HUD for both pilots to see, however did they have time to read and digest rapidly changing autoflight modes? I have way more experience flying the B744 than the B788 but I can see this happening on either type. How many times were you reminded to RTF FMA! 2 users liked this post. |
brokenenglish
2025-06-19T10:19:00 permalink Post: 11905890 |
Except that the PF does not immediately get the cue that the power is backing off, because he removed his hand from the power levers at V1.
If he sees the Flight Directors indicating down after take off.... of course he will ignore that command and maintain the normal 14deg NU +/- for the expected all-engines climb.
However when the speed starts to decay he starts to get the message all is not well and tries to salvage the situation. If the FD goes into altitude capture then the autothrottle becomes speed-on-throttle. Unfortunately the AT logic presumes you are following the FD. If you are now NOT following FD commands then the results become unpredictable. On correct speed but above FCU selected altitude = throttles close.
EK231 had thrust but no pitch. AI171 had pitch but no thrust. There's less information about the Air NZ low level altitude capture, I don't know how it compares. To be clear, I don't presume that AI171 had a low level ALT capture. It appears to have had a loss of thrust for an undetermined reason. Last edited by brokenenglish; 19th Jun 2025 at 11:14 . 2 users liked this post. |
LGB
2025-06-19T11:18:00 permalink Post: 11905939 |
THR REF/VNAV SPD
Does a Boeing 787 go from HOLD TO/GA to THR REF/VNAV SPD at 400' AGL/AAE, like older versions of the Boeing?
If so, what if the WoW stayed in ground mode, for whatever reason, how would that affect 1) Retraction of the landing gear (it didn't retract, as obvious in videos released) 2) The transition from HOLD to THR/REF at 400' (they reached just barely over 400' AGL before leveling, then descending) I am also thinking that Air India would follow Boeing procedures in that the left seat pilot will move their right hand away from the thrust levers at V1, and thus, at 400', the thrust levers are not guarded or monitored? Even if thrust levers were pushed forward, is there some kind of logic related to FMC and-or FADEC or other involved systems, which regardless of thrust lever position commands IDLE thrust to the engine? Remember that Airbus accident where the aircraft thought it was landing, while the pilots wanted full thrust, and they crashed into a small forest because some kind of idle is all they were afforded by the system? If the engines of this 787 thought it was in the rollout or final part of the flare, it might also command thrust levers to idle? This does not explain the RAT, though, unless there is some weird combination of software working against each others logic. Had the engines failed by some really random, odd reason, like birds, fuel contamination-vapor-starvation or such, wouldn't there be at least a slight bit of roll or yaw visible? Even with TAC or whatever they have on the 787, I would think even a 1 second difference in thrust reduction between the engines, a hint of yaw or roll should be visible ... Thoughts, especially by someone who flies the 787? Last edited by LGB; 19th Jun 2025 at 11:36 . Reason: Updates and more thinking .. 1 user liked this post. |
Capn Bloggs
2025-06-19T12:25:00 permalink Post: 11905982 |
Here we go again.
Originally Posted by
LGB
I am also thinking that Air India would follow Boeing procedures in that the left seat pilot will move their right hand away from the thrust levers at V1, and thus, at 400', the thrust levers are not guarded or monitored?
Originally Posted by
LGB
Even if thrust levers were pushed forward, is there some kind of logic related to FMC and-or FADEC or other involved systems, which regardless of thrust lever position commands IDLE thrust to the engine?
.
Originally Posted by
LGB
​​​​​​​
Remember that Airbus accident where the aircraft thought it was landing, while the pilots wanted full thrust, and they crashed into a small forest because some kind of idle is all they were afforded by the system?
Originally Posted by
LGB
​​​​​​​
If the engines of this 787 thought it was in the rollout or final part of the flare, it might also command thrust levers to idle?
Last edited by T28B; 19th Jun 2025 at 14:33 . Reason: formatting assistance 6 users liked this post. |
nachtmusak
2025-06-19T14:15:00 permalink Post: 11906057 |
Except that the PF does not immediately get the cue that the power is backing off, because he removed his hand from the power levers at V1. If he sees the Flight Directors indicating down after take off.... of course he will ignore that command and maintain the normal 14deg NU +/- for the expected all-engines climb. However when the speed starts to decay he starts to get the message all is not well and tries to salvage the situation. If the FD goes into altitude capture then the autothrottle becomes speed-on-throttle. Unfortunately the AT logic presumes you are following the FD. If you are now NOT following FD commands then the results become unpredictable. On correct speed but above FCU selected altitude = throttles close.
Just after rotate is a very busy time for your scan. The FMA modes are in the HUD for both pilots to see, however did they have time to read and digest rapidly changing autoflight modes? I have way more experience flying the B744 than the B788 but I can see this happening on either type. How many times were you reminded to RTF FMA! My understanding (and others have corroborated this) is that in a standard departure the autothrottle is armed and starts the takeoff roll in THR REF mode. It goes into HOLD mode when the IAS passes 80 knots (obviously still on the ground). While it is in HOLD mode, the autothrottle is physically inhibited from moving the thrust levers. It then automatically re-engages at 400ft AGL (though I am not sure how the altitude is measured), and begins to operate as requested by various human and computer systems. If something about my explanation is wrong, please let me know - but if it is correct, then how would the autothrottle roll back thrust drastically in what looks like the first few seconds of the flight? I do understand that what you describe is how the autothrottle would behave when it is active, but it sounds to me like it is by design not supposed to actually be active during the critical time that we are looking at no matter what automations are armed to be activated once the aircraft is safely away from the ground. Unless the crew did something to cause it to engage - and I'm not sure what that would even be. What would they plausibly be doing before even retracting the landing gear? My only guess was that depending on how the altitude is measured to determine whether the 400ft gate has been passed (radio altimeter? pressure altitude?), the autothrottle might have come out of HOLD mode (along with VNAV if armed) at a lower altitude than it was supposed to due to some mechanical fault or crew error. But that's already a bigger kettle of fish than just altitude capture... |
sabenaboy
2025-06-19T14:51:00 permalink Post: 11906087 |
OK, I promised some
informed speculation
when I got back, so here goes:
Disclaimer: never worked the 787, so my detailed knowledge is a bit lacking. First off, this is perplexing - especially if the RAT was deployed. There is no 'simple' explanation that I can come up with. GEnx-1B engines have been exceptionally reliable, and the GE carbon composite fan blades are very robust and resistant to bird strike damage (about 15 years after the GE90 entry into service, I remember a GE boast that no GE90 (carbon composite) fan blades had needed to be scrapped due to damage (birdstrike, FOD, etc. - now that was roughly another 15 years ago, so is probably no longer true, but it shows just how robust the carbon composite blades are - far better than the more conventional titanium fan blades). Not saying it wasn't somehow birdstrike related, just that is very unlikely (then again, all the other explanations I can come up with are also very unlikely ![]() Using improper temp when calculating TO performance - after some near misses, Boeing added logic that cross-compares multiple total temp probes - aircraft TAT (I think the 787 uses a single, dual element probe for aircraft TAT, but stand to be corrected) and the temp measured by the engine inlet probes - and puts up a message if they disagree by more than a few degree tolerance - so very, very unlikely. N1 power setting is somewhat less prone to measurement and power setting errors than EPR (N1 is a much simpler measurement than Rolls EPR) - although even with EPR, problems on both engines at the same time is almost unheard of. The Auto Thrust (autothrottle) function 'falls asleep' at 60 knots - and doesn't unlock until one of several things happens - 250 knots, a set altitude AGL is exceeded (I'm thinking 3,000 ft. but the memory is fuzzy), thrust levers are moved more than a couple of degrees, or the mode select is changed (memory says that last one is inhibited below 400 ft. AGL). So an Auto Thrust malfunction is also extremely unlikely. Further, a premature thrust lever retard would not explain a RAT deployment. TO does seem to be very late in the takeoff role - even with a big derate, you still must accelerate fast enough to reach V1 with enough runway to stop - so there is still considerable margin if both engines are operating normally. That makes me wonder if they had the correct TO power setting - but I'm at a loss to explain how they could have fouled that up with all the protections that the 787 puts on that. If one engine did fail after V1, it's conceivable that they shut down the wrong engine - but since this happened literally seconds after takeoff, it begs the question why they would be in a big hurry to shut down the engine. Short of an engine fire, there is nothing about an engine failure that requires quick action to shut it down - no evidence of an engine fire, and even with an engine fire, you normally have minutes to take action - not seconds. The one thing I keep thinking about is someone placing both fuel switches to cutoff immediately after TO. Yes, it's happened before (twice - 767s in the early 1980s), but the root causes of that mistake are understood and have been corrected. Hard to explain how it could happen ( unless, God forbid, it was intentional ). 3 users liked this post. |
martinebrangan
2025-06-20T09:07:00 permalink Post: 11906750 |
Engine failure due to water contamination is surely a different investigation to biocide contamination? I expect they're looking into both, but they're not that closely linked.
Surprising that you can do nearly a minute of takeoff+climbout then fail cleanly and silently within seconds of each other. |