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BrogulT
June 19, 2025, 17:48:00 GMT permalink Post: 11906226 |
This explanation comes with a money-back guarantee and if I'm wrong I'll send out refunds. First, vapor lock is simply where a pump or other device becomes inoperative because it is designed to pump liquids but is presented with a gas (vapor) at it's inlet and thus cannot develop pressure and pump the fuel. Think of a very old car with a mechanical fuel pump on the engine block that draws fuel through a long tube from the fuel tank. If you shut the car off on a hot day, the residual heat may boil off the fuel in the lines and carburetor so that when you try to restart, there's no fuel anywhere and your pump has lost it's prime. It is key to note that even with a very crude system like this and volatile gasoline as a fuel, vapor lock usually only affects starting and not running engines. There are exceptions, of course. The three key factors are the absolute pressure at a particular point in the fuel system, the vapor pressure of the fuel at whatever temperature it is at and system design. System design has all but eliminated vapor lock as a serious issue in the gasoline automotive world. At near sea level, the outside pressure is about 1 bar (15psi) and at 50C typical jet fuel will have a vapor pressure of perhaps 0.02 bar. So the only way to cause it to vaporize jet fuel, even at 50C+, would be to subject it to a very, very strong suction. AFAIK there are no vulnerable points where you'd have suction during normal operation because the fuel pumps are presumably (I don't actually know) immersed in fuel and the entire system has greater than 1 bar pressure all the way to the high pressure pumps. Even without the electric pumps, the inlet to the mechanical pump is below tank level. So absent some major fuel line restriction, there aren't any points where you'd have strong suction aka very low absolute pressure. The discussions about fuel temperature also seem a big irrelevant to me--even at 60 or 70C the vapor pressure is still very low and I doubt you'd see significant vapors at all under 100C with any reasonable fuel system design and properly blended fuel . I'm assuming the fuel temperature limits are for other reasons, perhaps flash point or ignitabilty (TWA 800) or viscosity and lubricity concerns with the high pressure pump. Again, IDK, but vapor lock with Jet A seems very far fetched to me. I would note that improperly blended fuel could have a much higher vapor pressure and still work OK in most cases as long as positive pressure was maintained. So if the electrics and the pumps went offline and the fuel vapor pressure was way too high, I suppose there could be vapors formed in the suction line going to the mechanical pumps. But I don't have nearly enough knowledge to proclaim that as a possibility. I presume they've taken fuel samples at the source and tested them. Here's a paper on Jet A vapor pressure: https://www.researchgate.net/publica...Kerosene_Jet_A Last edited by BrogulT; 19th June 2025 at 19:34 . |
jdaley
June 19, 2025, 20:35:00 GMT permalink Post: 11906349 |
slf/ppl here - with a respectable amount of experience in software delivery for real-time/embedded/safety critical systems. Software development in this area really is an engineering discipline and bears no resemblance to common practice in other areas. Couple that with the requirements for function duplication/triplication, harness separation et al then IMHO the chances of FADEC etc software errors are effectively zero.
I'm commenting to make that point but also to link the videos and the FR-24 dataset - (below with my deltas for height/time added) ![]() Extract from FR24 csv dataset As noted in both threads to date everything was normal until it wasn't - the two values for fpm above are subject to FR24 variance of +/- 25' so even these suggest a normal climb at this stage of flight ca 2,000fpm. FR24 Lat/Longs all follow the centre line. On this data the climb stops at around 70' AGL and electrical failure around 2s later. Again, as noted in the threads, this aligns with when gear up might have been expected. If the climb stopped because of fuel shutoff then 2s for spool down to electrical failure isn't out of the question. Looking at the two videos. The CCTV video indicates a total flight time, from rotation, of about 32s, subjectively levelling off ~14s after rotation. The rooftop video has a flight time ~14s suggesting the video starts ~18s after rotation. The rooftop video evidences the RAT as deployed from the beginning - meaning it must have been deployed by at least 16s after rotation - which aligns with the ADS-B indicated electrical failure. If the forward flight recorder really is being sent to the US for recovery then it's reasonable to assume that the rear recorder contains nothing after the electrical failure and they are hoping the forward recorder captured something from the cockpit in the final 16s. I don't have any experience of flight deck CRM but I don't see how those timings allow problem identification/misidentification and subsequent action - ie it wasn't down to the crew. However: The maximum aircraft height in the CCTV video, as judged by wingspan, appears higher than 71' - though it is certainly less than a wingspan height at the beginning of the rooftop video. I haven't seen, in the threads, any statement of what happens on the flight deck with a total electrical failure - is it a 4s blackout whilst the RAT deploys and systems restart? - or are there batteries that keep something alive? |
AirScotia
June 19, 2025, 21:06:00 GMT permalink Post: 11906372 |
In the ANA 787-8 incident, I think they couldn't restart the engines in order to taxi? Is that also a feature of TCMA?
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MatthiasC172
June 19, 2025, 22:06:00 GMT permalink Post: 11906425 |
TCMA restart
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AirScotia
June 19, 2025, 22:34:00 GMT permalink Post: 11906450 |
*On the ground* you get into a latched state, once TCMA deploys: after activation the relays stay latched to prevent a re-runaway. A full power reset of the affected EEC channel(s) and relay logic - normally done only at the gate - is required before fuel can flow again. So you can\x92t easily relight.
Technically, then, if TCMA deployed erroneously during takeoff, there would be no way for the pilots to restart the engines? |
EDML
June 19, 2025, 22:39:00 GMT permalink Post: 11906453 |
Even if it's possible - there is not enough time to do so in this phase of the flight. Doing a full restart of one engine will take 1-2min. That means it will need a couple thousand feet.
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MaybeItIs
June 20, 2025, 13:47:00 GMT permalink Post: 11906986 |
Indeed, thanks to you for your most informative reply! Great to know we're much on the same page.
I'll strive for brevity here. [Fail, sorry!]
However, the datagrams that FR24 actually received were correct. They contain the GPS position of AI171 and its unadjusted barometric altitude, as determined by its onboard instruments. This data is as reliable as the instruments themselves are.
It's uncertain because the 787 rounds all altitudes it sends to the nearest multiple of 25. The altitudes sent were from 575 ft to 625 ft.,
The RAT deploying is a consequence of a dual engine shutdown. It says nothing about whether the TMCA was involved.
If the TMCA did activate and shut off the fuel for whatever reason, what causes the TMCA/FADEC Hardware (and Software) to Reset, since it's independently powered off the engine-driven PMG after engine start? There is so much here that is just so unclear. I haven't seen anything about a Reset input anywhere, and since it's supposed to work only when on the ground, that's not really necessary, as the engine will eventually spool down. At some point before that, the PMG output voltage will go to low enough that the FADEC/TMCA should be forced into a Hardware Reset. That's all fine on the ground, but in the air, the engine will windmill, potentially until.... Is the PMG output fed through a switch/relay that cuts the FADEC/TMCA supply at low (i.e. windmill) RPM, so that a Pilot-activated Engine Off/On cycle can reconnect the Aircraft FADEC Supply link, thus Rebooting the FADEC so that it reopens the Fuel Shutoff valve(s)? It all seems so "awkward". And potentially fatal. Is this a scenario that the designers considered? (Who can answer that one? ![]() Just now, I realise that if this is roughly what happens, then maybe the engines did commence a restart just before impact, due to the plane being deliberately mushed/stalled to the ground as softly as possible, thereby reducing the windmill RPM. And maybe the engines restarting interfered with that planned landing. Or maybe I've got this all wrong. I'm hoping someone will tell us all.
[Now I just hope your post is still there as I post this.
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BrogulT
June 21, 2025, 19:48:00 GMT permalink Post: 11908009 |
30+ years of my experience as an aircraft engineer that forms a plausible (IMO) explanation of what may have happened.
That wing tank fuel could have picked up a fair amount of water. It is conceivable to me that the suction tube pickup could have been immersed in water, settled out from the fuel in the wing tanks. A supply likely heavily water contaminated. It would take a few seconds for that contaminated fuel to actually reach the engines, but when that contaminated fuel hit, Thrust would have been significantly reduced. The EEC's would have been doing their best to maintain the thrust, firewalling the throttles would probably have little effect at that exact moment. The engines would have likely worked through that bad fuel in a shortish period of time, but a period of time that our crew did not have. First, water in fuel is not a novel concept and I would presume that the designers of the 787 knew about it. You've simply stated that water might collect and settle out, but how much water might you expect under those conditions (57% humidity doesn't seem terribly high to me) and what features and procedures are already there to mitigage water contamination issues? Your theory would imply that there basically aren't any. IDK how the tank venting system works, but the idea that some huge amount of water could have condensed in the tank from the outside seems preposterous. Second, how much water do you think it would take to cause a sustained flameout in one of those engines? Remember that they have automatic continous relight, so you're going to have to sustain your flame suppression long enough for them to wind down completely. I think those engines were probably using something like 2 gallons per second of fuel along with 250lbs of air heated to over 1100F. Any fuel in the mix would burn and the water would be converted to steam so you'd need mostly water for a long time. So if you think a hundred gallons of water could have gotten into each tank then perhaps I'd buy your theory--which, btw, does fit the known facts pretty well. But I think that short of some woeful neglect, Boeing and AI already know about and have methods of dealing with water contamination. At least I hope so. |
GroundedSpanner
June 22, 2025, 00:15:00 GMT permalink Post: 11908173 |
I don't want to refute your theory, but given your 30 years of experience---presuming it is relevant--I'd ask you to clarify a few things.
First, water in fuel is not a novel concept and I would presume that the designers of the 787 knew about it. You've simply stated that water might collect and settle out, but how much water might you expect under those conditions (57% humidity doesn't seem terribly high to me) and what features and procedures are already there to mitigage water contamination issues? Your theory would imply that there basically aren't any. IDK how the tank venting system works, but the idea that some huge amount of water could have condensed in the tank from the outside seems preposterous. Second, how much water do you think it would take to cause a sustained flameout in one of those engines? Remember that they have automatic continous relight, so you're going to have to sustain your flame suppression long enough for them to wind down completely. I think those engines were probably using something like 2 gallons per second of fuel along with 250lbs of air heated to over 1100F. Any fuel in the mix would burn and the water would be converted to steam so you'd need mostly water for a long time. So if you think a hundred gallons of water could have gotten into each tank then perhaps I'd buy your theory--which, btw, does fit the known facts pretty well. But I think that short of some woeful neglect, Boeing and AI already know about and have methods of dealing with water contamination. At least I hope so. Experience. Without wishing to dox myself, I've worked in engineering at a major airline from apprentice through (in no particular order) Line Maintenance, Heavy and Light Maintenance, to technical support and maintenance control on both Boeing and Airbus products, with various qualifications and authorisations along the way. [Hmm - Scrap this sentence?]On the day 9/11 occurred, I should have been making modifications inside a fuel tank instead of staring at the TV with mouth on the floor. However, I would describe my experience as broad, yet shallow in respect to this incident. Some of my fleet I know every rivet. Some of my fleet I've only ever seen from a distance. I don't touch airplanes for a living any more. B787 though - is not my area of specialty. I'll dig in, but am not the expert. I am not a systems design engineer, so precise numbers and flow rates, are not what I do. But what the systems do, how they operate, what they look like, smell and taste like... yeah, I'm not a muggle. And I do have access to all the manuals and know how to use them. And - let me be clear, I am speculating. I was advancing a theory. It WILL be some flavour of wrong. The investigation will reveal all. I Agree, Water in fuel is not a novel concept. Aircraft fuel tanks attract water - fact. How much? It varies. I've sumped tanks and got no water, I've seen drops of water beading about in the bottom of a gallon jug, I've seen gallons of water. I've been so covered in fuel I cant smell it or think straight and taken gallon after gallon not being able to tell if its fuel or water. I also agree that 57% humidity doesn't seem particularly high - its not south east Asian jungle levels - but I'm not an expert at humidity, 32Deg c at 57% humidity at 02:30 am is not going to be comfortable for me though. I looked at recent weather in DEL, and those values were at the higher end of the range. Further, I believe the prevailing weather conditions on the ground are less important when it comes to the volume of water getting in. Fuel is cold, or gets damn cold during a 9 Hr flight. Fuel Temperature Management is an issue for our Drivers. So as the fuel is used at altitude, Air enters the tank through NACA Ducts in the outboard end of the wing. Its beneficial to maintain a slight positive pressure, amongst other things to reduce evaporation. (Added complication, there is also the Nitrogen Enrichment system due to TWA800 - but that's more about processing the air in the tank to change the properties and make it non-explosive). Then as the aircraft descends, more air enters as the air pressure increases. Its the humidity of that air in the descent that is going to determine the volume of water entering the tank and potentially the fuel. The water in the air condenses on the sides of the tank because of the cold post-flight fuel. It doesn't dissolve into the fuel, but sinks to the bottom. Ground temperature / humidity and time will likely affect how much water condenses out of that air while on the ground. There won't be a huge amount of air exchange on the ground. Likely if the AC landed at 2am, then from sunrise as the tank warmed up, there would actually be a flow out of the vents. What Features and procedures are there to mitigate Water? I apologise if my post gave the impression that there are no mitigation processes. There are. Water is well understood in the industry. Well for a start, Features / Design. The Aircraft has a water scavenge system. Water doesn't mix with fuel, it sinks to the bottom being about 20% denser than fuel, so at the very lowest point in the tank, the water scavenge system (Powered by the Aft Fuel Pump through a jet pump, a venturi like system) will suck up the 'fluid' at the very lowest point, where the water would collect and in Boeings words 'drip' that fluid into the path of the pump pickup inlet (but I'd describe it more as a 'squirt'). The idea being that a small amount of water injected into the fuel will be consumed by the engines harmlessly. There is also agitation. The wing tank pumps are pretty much running constantly, from before engine startup to after engine shutdown. The pumps are quite violent to the fuel and supply more pressure then the engine could ever need. Any excess pressure is dumped right back into the tank, quite close to the pump, in a direction that would further stir up the fuel and help break up any water into suspended droplets. This all works if there is a small amount of water in the fuel. The water scavenge pickup is right next to the pump inlet, but a bit lower. Little bits of water get managed. Looking at the pictures of the system, I'd say a couple of gallons of water would do no harm at all. But if there was significantly more water in that tank. Guessing 10-30 + gallons, then the pump would be circulating water, or highly water rich fuel. Then there's the suction pickup. Its in the same 'bay' as the aft fuel pump and located a little 'higher' than the pump inlet and water scavenge inlet. But also located between stringers that can separate out the settled water ( I wish I could share the pictures, but more than my job is worth ) I can imagine the suction pickup being in a pool of 'stagnant' water. I also saw a post from Metcha about the scavenge system blocking with Algae - I don't know about that (B787 not my fleet). But possible that could aggravate things. There's also the reports of the Indian AAIB looking at the Titan Biocide incident. Its possible that might be related and could modify the theory. Procedures - There's the (at my airline weekly I think) procedure to 'sump' the tanks. There are drain points in the tank. Valves that you can push in with a tool and fluid drains. As described earlier (and videos exist on YouTube), you drain about a gallon of fluid and examine it for water. Most often in temperate climates (my experience), there's a few 'beads' of water in the bottom of the jug, moving about like mercury. Except when there's more. Sometimes there's a clear line in the jug, half water, fuel above. And sometimes a gallon of water, that smells like fuel. You drain it until you are sure there's no water. Could 'that much' water have condensed in the tank? Well - There's the question. I guess the basis of the theory is that on descent into DEL, the wing tanks picked up some very humid air, which settled water into the tanks through the night. Then, as the theory I posited must work, the wing pumps must have circulated and suspended that water into the fuel. By design, the water from the CDG-DEL arrival should have been consumed in the DEL-AMD Sector. But desperately clinging to defending my theory (I appreciate this is a hole), lets assume that at DEL the pumps were running for a long time. Lets assume that the pumps allowed the water to be dispersed within the tank prior to being used through the engines. Then - in the DEL-AMD sector, the wing tanks could have picked up more water. How much water would cause a sustained flameout? I never posited a sustained flameout. I posited a significant reduction in thrust. Listening back to the rooftop video, which at first we were all listening for evidence of RAT, there's also a rhythmic pop-pop-pop of engines struggling. I think the engines were running, albeit badly. Heavily water contaminated fuel will do that. It doesn't have to be 100% water. Just enough water to make the engine lose thrust. Your 2 gallons per second figure assumes the engine running at full flow. I'm not a figures man, I'll not challenge that, I do recall flowmeters at max thrust spin like crazy. But an engine struggling due to a high perrcentage of contamination, is that using 2 gal/sec? or just trying to? What happens if there is e.g. 20% water in the fuel? There are also reported incidents of engine flameout / thrust reduction that have all happened at altitude. Incidents that have been recovered due to the altitude and time available. I Posited that the engines would have eventually regained full thrust once the contamination worked though. But 30 seconds of rough engine is very different at 40,000 feet than it is at 100 feet. The theory also relies on a second part - the electrical failure. That the electrical failure causes the fuel supply to switch, a few seconds after the failure. We go, at the point of electrical failure from a pumped centre tank supply to a sucked wing tank supply. It takes time for that different fuel to reach the engine. Ive written enough and am tired. Must stop now. |
SloppyJoe
July 09, 2025, 12:45:00 GMT permalink Post: 11918371 |
Firstly, it's not rapid cycling of the fuel control switches, you turn them off then back on and see if it starts, this can take more than a minute as you have to wait to see if the action was successful. Second problem as mentioned above, the speed was far too low for a successful relight, you would most likely end up with a hot start or no start, most likely with a lot of smoke out the back due to unburnt fuel.
edited to add, after reading about the 787 it seems it uses electrical power to start. Same sort of issue though if not enough power, which is likely given the RAT was out. Last edited by SloppyJoe; 9th July 2025 at 12:57 . |
Musician
July 09, 2025, 13:09:00 GMT permalink Post: 11918385 |
The idea is to set the switch to CUTOFF and then to ON as that resets the FADEC (the circuit that controls the engine) and hopefully clears any issues it might have. The hope is that the turbine is still rotating fast enough for the FADEC to restart it. I believe this works the same as the auto-relight feature.
The turbine rotation would also provide the electrical power for that. Do a thread search on "detent" to learn more about the construction of these switches than you ever wanted to know. ![]() There's also a section on them in paulross 's https://paulross.github.io/pprune-th...171/index.html , but it may not be up to date. (Still a great resource, though.) Unfortunately the wikipost linking to it is gone, presumably a victim to the recent forum changes. |
Magplug
July 09, 2025, 14:45:00 GMT permalink Post: 11918435 |
As a 787 operator I can observe a couple of things......
Deliberately cycling the Engine Cutoff switches just after rotate, in response to a dual power loss is inconceivable. You are way too low and slow for it to have any effect and your attention is better devoted to aiming for the flattest area ahead to crash into. Commencing the Dual Eng Fail/Stall checklist memory items is conditional upon both engines being at sub-idle and the aircraft being within the in-flight relight envelope. Neither of those conditions existed. The flight recorder will witness what came first - Power loss or Start Switches to Cutoff? It seems the 'Third Contingency' that I alluded to about a thousand posts ago, sadly now seems likely. Given the iron-grip that the government appears to have over the media, one wonders how the truth will ever surface? |
tdracer
July 09, 2025, 18:20:00 GMT permalink Post: 11918562 |
One thing that I remember from when I was a simulator TRI/TRE on a Boeing was that as an instructor you get very used to operating critical
switches rapidly without following any procedure, in order to set the sim up for a single engine landing etc. When I was then line flying next I had to guard against doing the same thing in the real aircraft. However, it can also bite us. The Delta dual engine shutdown during takeoff from LA (referenced way back when in the 1st accident thread) was caused by muscle memory - the pilot reached down to set the EEC switches (located near the fuel On-Off switches) but muscle memory caused him to do something else - set both fuel switches to OFF. Fortunately, he quickly recognized his error, placing the switches back to RUN and the engines recovered in time to prevent a water landing (barely). It is conceivable that a pilot - reaching down to the center console to adjust something unrelated - could have muscle memory cause him to turn the fuel off to both engines. While all new engines are tested for "Quick Windmill Relight" - i.e. the fuel switch is set to CUTOFF with the engine at high power - and the engine must recover and produce thrust withing a specified time (memory says 60 or 90 seconds) - it takes a finite amount of time for the engines to recover (spool down after a power cut at high power is incredibly fast - plus moving the switch to CUTOFF causes a FADEC reset, which means it won't do anything for ~ 1 second). Doing that at a couple hundred feet and the chance that an engine will recover and start producing thrust before ground impact is pretty much zero |
Subsy
July 09, 2025, 19:23:00 GMT permalink Post: 11918592 |
Muscle memory is a strange and (usually) wonderous thing. It allows us as humans to perform amazing things without actually thinking about what we are doing. Professional Athletes have perfected this to a high art, but the rest of us do things using muscle memory on a regular basis. Back when I was still racing, I happened to look down at my hands on the steering wheel in fast, bumpy corner, and I was simply amazed at the large, rapid steering inputs that I was making to compensate for the bumps - with absolutely zero conscious thought. Muscle memory at its best.
However, it can also bite us. The Delta dual engine shutdown during takeoff from LA (referenced way back when in the 1st accident thread) was caused by muscle memory - the pilot reached down to set the EEC switches (located near the fuel On-Off switches) but muscle memory caused him to do something else - set both fuel switches to OFF. Fortunately, he quickly recognized his error, placing the switches back to RUN and the engines recovered in time to prevent a water landing (barely). It is conceivable that a pilot - reaching down to the center console to adjust something unrelated - could have muscle memory cause him to turn the fuel off to both engines. While all new engines are tested for "Quick Windmill Relight" - i.e. the fuel switch is set to CUTOFF with the engine at high power - and the engine must recover and produce thrust withing a specified time (memory says 60 or 90 seconds) - it takes a finite amount of time for the engines to recover (spool down after a power cut at high power is incredibly fast - plus moving the switch to CUTOFF causes a FADEC reset, which means it won't do anything for ~ 1 second). Doing that at a couple hundred feet and the chance that an engine will recover and start producing thrust before ground impact is pretty much zero It's ironic that cognitive science arguably started with 'The Cambridge Cockpit'; an attempt to make sense of, and mitigate, pilots doing this sort of thing when tired, stressed and so on. This kick started an ergonomics revolution which appears to have come full circle. Now we have cognitive science offering Bayesian accounts of neural function that might explain how innocent but unfortunate priming of 'muscle memory' when practicing for emergencies could, almost predictably, lead to this sort of complex, protection overriding, error. As non consciously executing a complex, well practiced, but unintended, action is a fairly common experience in less critical situations, I'm surprised that there isn't already a more effective ergonomic fix than the safety switches fitted. Last edited by Subsy; 9th July 2025 at 21:58 . |
Chernobyl
July 09, 2025, 22:25:00 GMT permalink Post: 11918671 |
July 8 (Reuters) - A preliminary report into the deadly crash of an Air India jetliner in June is expected to be released by Friday, three sources with knowledge of the matter said, with one adding
the probe had narrowed its focus to the movement of the plane's fuel control switches.
But this is starting to devolve into a hamster wheel again. Last edited by Chernobyl; 10th July 2025 at 04:32 . |
AirScotia
July 09, 2025, 23:20:00 GMT permalink Post: 11918695 |
There has been discussion recently about a procedure that involves moving the fuel switches to CUTOFF and then back to RUN following a dual engine failure.
Attached is an image of a page from the Air India 787 Training Manual that discusses this procedure. I am submitting this without comment or opinion. ![]() |
skwdenyer
July 10, 2025, 00:08:00 GMT permalink Post: 11918713 |
As a 787 operator I can observe a couple of things......
Deliberately cycling the Engine Cutoff switches just after rotate, in response to a dual power loss is inconceivable. You are way too low and slow for it to have any effect and your attention is better devoted to aiming for the flattest area ahead to crash into. Commencing the Dual Eng Fail/Stall checklist memory items is conditional upon both engines being at sub-idle and the aircraft being within the in-flight relight envelope. Neither of those conditions existed. |
MaybeItIs
July 10, 2025, 00:21:00 GMT permalink Post: 11918716 |
![]() Obviously, because it's going to require quick action to catch high RPM. And maybe that's what they tried.
It also seems to be indicating that fuel switch resetting should be attempted if the restart has failed to start the engine?
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AerocatS2A
July 10, 2025, 01:30:00 GMT permalink Post: 11918727 |
I don't have any comment on it other than to note that the manual is not specific to Air India. My B787-9 FCTM is identical as far as I can tell. The actual memory item for dual failure is to reset the fuel switches and start the RAT. It is also conditional on the engines being sub idle as noted by the other poster.
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Magplug
July 10, 2025, 08:59:00 GMT permalink Post: 11918849 |
A couple of points if I may......
I don't see it written in the 787 FCOM but I have always been told that the action of resetting the Engine Cutoff switches in the event of a dual engine failure, is merely backing up what the FADECs have already done. If there is an 'engine event' the FADECs will manage ignition and fuel-flow to restore the thrust that was demanded before the event. If that management has failed then the manual resetting may be more successful. (The same holds true for the RAT, manual selection is merely backing up the auto-deployment). Any airline pilot will tell you that executing an in-flight relight on a big engine, no matter if it is by electric start, windmilling RPM or cross-bleed assisted, can take between 1 and 3 minutes to restore power. This aircraft was airborne for less that 30 seconds. No pilot in his right mind would prioritise an in-flight relight procedure, in a situation where they had neither the time, the height nor the speed for it to succeed. I have no doubt the crew focussed entirely on pointing the aircraft at the clearest area they could see, to mitigate what would inevitably follow. |