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Someone Somewhere
June 15, 2025, 06:56:00 GMT permalink Post: 11902163 |
Expect all the alarms, too. |
maddog2872
June 15, 2025, 07:01:00 GMT permalink Post: 11902166 |
The 320 starts even if you forget to turn on fuel pumps. Don't ask how I know.
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Someone Somewhere
June 15, 2025, 08:08:00 GMT permalink Post: 11902212 |
A thrust reduction is not an engine failure. Engine shutdown due to an action of crew (or inaction) is not a failure.
There is no evidence of an electrical failure. What evidence? A surviving passenger thought he saw flickering lights? Give me a break. The word evidence in English has a very specific meaning. Look for the simplest explanation here and then ask why the worldwide B787 fleet is still flying with no urgent inspection requirements from Boeing or GE. Think about that "evidence". If the aircraft had flaps deployed (the crash site photos look like it), flight controls working (no indications they weren't), and the thrust levers pushed full forwards, there is very very little that will cause it to sink other than lack of thrust. For the team pointing to the RAT out as a failure indicator, it could have been deployed by the crew after the initial reduction in climb performance. I am not convinced it is deployed but it really does not make a convincing argument for any type of failure. For the children on holiday, yes I fly transport category jets, current on two types. ​​​​​​​ In general, I think it's looking like dual engine failure/shutdown cutting electrics. I agree that why it occurred is very unclear. Outside chance of total electrical failure causing dual engine failure rather than the other way around, but that would perhaps be even more concerning a design failure. Similar to Jeju, we also have what is looking increasingly like a loss of ADS-B data at the moment things went wrong, not just a loss of coverage. That gives:
I think it has been suggested that the upload only happens every 30 minutes or so. Last edited by Someone Somewhere; 15th June 2025 at 08:21 . |
Epsomdog
June 15, 2025, 08:09:00 GMT permalink Post: 11902213 |
Best post until now in my view. We will find out very soon I think. Gear up command triggered the instant lack of fuel to both engines. I'm not sure on how the fuel flow is dependant on the power supplies on the 787 but I genuinely believe you are very very close to what might have happened here.
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Lead Balloon
June 15, 2025, 08:15:00 GMT permalink Post: 11902217 |
FIFY
Loss of electrical power
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Chuck Canuck
June 15, 2025, 08:22:00 GMT permalink Post: 11902223 |
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 switches to OFF 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’ imagination.😖🥴😬 This is a very plausible scenario. Above 400 ‘ AGL, memory items. |
Someone Somewhere
June 15, 2025, 08:24:00 GMT permalink Post: 11902225 |
If/when the centre tank is fully used or the pump fails, the two wing tank pumps supply the on-side engine. This happens on every flight that takes off with more than ~34t of fuel (two wing tanks) and lands with less. If neither on-side pump is operating, the pressure in the supply line drops below that of the tank and pulls open the suction check valve. The only 'reconfiguration' the pilots can do is open the crossfeed valve, or turn off pumps. |
amsm01
June 15, 2025, 08:54:00 GMT permalink Post: 11902253 |
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 switches to OFF 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.😖🥴😬 Am slightly puzzled as to why if flap reduction triggering climb thrust is part of the standard logic (and presumably clean-up technique) then partial dual thrust loss wouldn\x92t be immediately recognised as the classic symptom of gear / flap retraction handling error? I presume Boeing pilots / air India are just as aware of this it as everyone else, strikes me as odd that one would immediately go into full dual EF mode. My instinctive reaction without knowing the Boeing would be to firewall both TLs, would this have worked in the early flap retraction logic scenario? Many thanks all |
Someone Somewhere
June 15, 2025, 10:43:00 GMT permalink Post: 11902342 |
This is probably a very stupid question, but what would happen if a BPCU fault (or other cause) led to VFSGs on opposite sides of the aircraft being connected to the same 230 VAC bus?
My understanding is that the left engine VFSGs are not synchronized in frequency or phase with the right engine VFSGs. Cross-connecting them, electrically, could be quite violent from both an electrical and mechanical perspective. Is it realistically possible that the torque shock from cross-connected VFSGs could damage their associated accessory drive trains to the extent that the associated FADEC alternators would no longer make power? In this situation, there would be a loss of aircraft electrical power due to the BPCU fault, no FADEC alternator power due to damage to the accessory drive train, and, therefore, no engine thrust. I presume each VFSG has a frangible link to protect the accessory drive train in the event the VFSG seizes up, which ought to make this loss-of-engine-thrust scenario impossible, but presumption is not knowledge, and this is a possible failure chain that doesn't involve stacking up multiple 10e-9 events. In fact, I have inadvertently "done" such a thing - all I did was switch the generator room light from one genset to the other. But whoever installed that cheap and nasty two way light changeover switch didn't realise that it sometimes did a make-before-break transfer. There was a BANG and everything instantly went dark. Every single circuit breaker on the switchboard tripped. To this day, I still don't understand why all the Load Circuit Breakers tripped as well as the generator output breakers, and no one has really supplied a clear answer. Of course, any inductive loads connected at the time would cause that, but simple incandescent light circuits? Would a couple of hundred meters of underground power cable have enough inductance to cause a breaker trip? Anyway, Yes, the results were very dramatic, and these were only a pair of 10-15kVA Single Phase 230V gensets. If this happened on that plane with 225KVA(?) generators at a couple of hundred feet in the air, I'd imagine they had no chance of recovery. Could it happen? If something had been wired up incorrectly in the transfer circuits, I'd say Yes. When a fault-related transfer occurred. Still doesn't explain what could have stopped the engines, but sheared shafts would have done it, as you say. That would be pretty strong evidence. Now, if it's true that this plane had been scavenged for parts at some stage, all the couldn't happens probably evaporate. I'd guess... I expect the VFSG shafts would be designed to fuse/slip long before the main radial shaft feeding the gearbox, as noted. But if it occurred, it would knock out not just your FADEC alternator but also the high pressure fuel pumps. Engine would stop dead near instantly. It would partly be a question of how much interlocking is present. I guess bypassing/mis-adjusting mechanical interlocks is something poor maintenance could & would do. |
Sailvi767
June 15, 2025, 10:58:00 GMT permalink Post: 11902355 |
This is probably a very stupid question, but what would happen if a BPCU fault (or other cause) led to VFSGs on opposite sides of the aircraft being connected to the same 230 VAC bus?
My understanding is that the left engine VFSGs are not synchronized in frequency or phase with the right engine VFSGs. Cross-connecting them, electrically, could be quite violent from both an electrical and mechanical perspective. Is it realistically possible that the torque shock from cross-connected VFSGs could damage their associated accessory drive trains to the extent that the associated FADEC alternators would no longer make power? In this situation, there would be a loss of aircraft electrical power due to the BPCU fault, no FADEC alternator power due to damage to the accessory drive train, and, therefore, no engine thrust. I presume each VFSG has a frangible link to protect the accessory drive train in the event the VFSG seizes up, which ought to make this loss-of-engine-thrust scenario impossible, but presumption is not knowledge, and this is a possible failure chain that doesn't involve stacking up multiple 10e-9 events. |
old dawg
June 15, 2025, 11:03:00 GMT permalink Post: 11902361 |
Retired engineer here. Following my post a while ago on the avionics electrical system I have read all the posts and also noticed mention of the hydraulics system.
Returning to my original source, which is Book 1 Introduction to B787 Avionic/Electrical, I read on p. 96 that the RAT will deploy if any of three conditions are met. https://fliphtml5.com/quwam/qhdw/Boo...ics_Electrical These conditions for deployment of the RAT specifically are: Loss of both engines Loss of power to the instrument buses Loss of all three hydraulic systems The latter one may be worth a close look because it would appear that problems took place when the wheels left the runway and I assume there was a change of states in various sensors. I surmise these sensors are different from the engine systems where both commands and power are needed to force a change of state in, say, fuel pumps. Is it the same for thrust control? It says there are three hydraulic systems but is there a common reservoir? I'm not an expert in that field but google tells me that B787 has a bootstrap reservoir system which I understand to mean that a pressure of 5000 psi is maintained using a piston arrangement. At this point think timeline, and changes of states. There is an operational change when the wheels leave the ground. The associated sensors would send that data to the CCS. What was sent? Maybe the CCS read Hydraulic L + Hydraulic R + Hydraulic C = incorrect or fail, which would trigger deployment of the RAT. What would the electrical and control system do then? More importantly what exactly did all the systems do on this aircraft following such an event. Was there a problem with the fluid in the hydraulics? Does hydraulic fluid ever 'go off' in very hot conditions. Or maybe there wasn't as much fluid in there than there should have been? How would hydraulics systems be compromised if indeed that was the case. All speculation - but forensic system analysis is a bit like that. Finally - what was the noise the survivor heard? Was it before or after the lights flickered? It may have been a bit of the airframe hitting something and snapping. The survivors in the doctor's hostel heard a noise too which may be jet engines running. They would know the difference between that and other noises being close to an airport. Need a timeline for everything here. Apologies for the long post. Just my thoughts. RIP to all who didn't survive. |
Someone Somewhere
June 15, 2025, 11:16:00 GMT permalink Post: 11902370 |
Retired engineer here. Following my post a while ago on the avionics electrical system I have read all the posts and also noticed mention of the hydraulics system.
Returning to my original source, which is Book 1 Introduction to B787 Avionic/Electrical, I read on p. 96 that the RAT will deploy if any of three condions are met. Maybe the URL will work this time https://fliphtml5.com/quwam/qhdw/Boo...ics_Electrical These conditions for deployment of the RAT specifically are: Loss of both engines Loss of power to the instrument buses Loss of all three hydraulic systems The latter one may be worth a close look because it would appear that problems took place when the wheels left the runway and I assume there was a change of states in various sensors. I surmise these sensors are different from the engine systems where both commands and power are needed to force a change of state in, say, fuel pumps. Is it the same for thrust control? It says there are three hydraulic systems but is there a common reservoir? I'm not an expert in that field but google tells me that B787 has a bootstrap reservoir system which I understand to mean that a pressure of 5000 psi is maintained using a piston arrangement. At this point think timeline, and changes of states. There is an operational change when the wheels leave the ground. The associated sensors would send that data to the CCS. What was sent? Maybe the CCS read Hydraulic L + Hydraulic R + Hydraulic C = incorrect or fail, which would trigger deployment of the RAT. What would the electrical and control system do then? More importantly what exactly did all the systems do on this aircraft following such an event. Was there a problem with the fluid in the hydraulics? Does hydraulic fluid ever 'go off' in very hot conditions. Or maybe there wasn't as much fluid in there than there should have been? How would hydraulics systems be compromised if indeed that was the case. All speculation - but forensic system analysis is a bit like that Left and right hydraulics have an engine driven pump that will keep turning as long as the engine is turning unless explicitly disabled. Low reservoir levels are both a maintenance check and something that will raise an EICAS warning. |
medod
June 15, 2025, 11:34:00 GMT permalink Post: 11902390 |
There are a few comments along the lines of "it is incredibly unlikely that..." this is selection bias in reverse. Something incredibly unlikely
has
happened, and it's contained in this sample set.
To summarise some known facts about the TCMA system: 1) TCMA will shut down an engine if:
3) Since then the TCMA should have been updated/fixed (and indeed the software will have been updated by SB since the a/c was delivered, to detect a wider range of runaway conditions) And speculation: 4) It may be possible - given the close timings - that a TCMA activation occurred as the a/c was leaving the ground, with kinetic energy and spool down time getting the a/c from the ground to its peak height In the recent BA LGW incident the PF reduced thrust to idle at V1, then added thrust back, then committed to a RTO. I wonder if something similar could have occurred:
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SteinarN
June 15, 2025, 11:54:00 GMT permalink Post: 11902404 |
It could do it, assuming fuses/contactors didn't vapourise first.
I expect the VFSG shafts would be designed to fuse/slip long before the main radial shaft feeding the gearbox, as noted. But if it occurred, it would knock out not just your FADEC alternator but also the high pressure fuel pumps. Engine would stop dead near instantly. It would partly be a question of how much interlocking is present. I guess bypassing/mis-adjusting mechanical interlocks is something poor maintenance could & would do. Online/running generators connected together by accident/fault will cause a HUGE load on everything, electric connections, generator itself and the shafts and gears driving the generators. Heck, I wouldnt be surprised if the generator could disintegrate due to such an electromagnetic shock load. So, the question is if there is something between the generators that could limit the electric current. A VFD possibly would as the VFD maybe would not be able to pass the current required for shearing the drive shaft for example. But then again, electronic switches like IGBT/MOSFET and such are able to pass an incredibly large over current for some milliseconds before exploding. Possibly 50 to 100 times the nominal current. So I am not sure if a VFD really would save the rest of the system in a situation with two generators connected together in error. So, where is the VFD part installed, directly on each generator or somewhere else in the system? Are there physical interlocks on the contactors or only electric interlocks? |
Kraftstoffvondesibel
June 15, 2025, 11:56:00 GMT permalink Post: 11902405 |
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. 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? Last edited by Saab Dastard; 15th June 2025 at 21:36 . Reason: Unwarranted speculation removed |
PPRuNeUser548247
June 15, 2025, 12:18:00 GMT permalink Post: 11902422 |
There's some possible fuel contamination mechanisms which would only affect one aircraft
- The fuel truck’s water-absorbing “monitor” element breaks up, the first aircraft after the break gets the bead slug; later uplifts may be clear once the hose is flushed. The beads jam metering valves almost immediately. - After pipe maintenance, the first few hundred litres can carry residual cleaning surfactant that strips protective films and causes filter-monitor “soap lock”. - Biofilm growth happens inside one aircraft’s wing tanks when it sits in humid conditions or does short hops with warm fuel. On the next flight the biofilm shears off, blocks strainers, |
Ted633
June 15, 2025, 13:09:00 GMT permalink Post: 11902451 |
A flight test (at least one - it's often duplicated) is performed as a basic part of aircraft/engine certification. One engine with all boost pumps off and on 'suction' feed - the other engine with normal aircraft boost pump operation (for what should be obvious reasons). Start, taxi, takeoff, and climb in that configuration until the test engine quits due to fuel starvation as a result of the engine fuel pump cavitation (done using "unweathered" fuel - once fuel has been at altitude for a period of time (hours or more - i.e. 'weathered'), most of the dissolved gases in the fuel have vented off, and suction feed works far better - often up to cruise altitudes).
I don't think this test is ever done during normal operations or maintenance (at least not on purpose) as it is very abusive to the engine driven fuel pump - the sort of cavitation that this causes rapidly erodes the pumping surfaces (it's SOP to replace the engine driven fuel pump after such a test). Carried out as part of a 12k check. Fuel level in the wing tanks made to be between 3100 kg & 3400kg. Engines are started, APU shut down and boost pumps are selected off. As long as the engines keep running, it\x92s test passed. (Just have to remember to fire the APU back up before shutting the engines down!) |
scifi
June 15, 2025, 13:23:00 GMT permalink Post: 11902465 |
Seems to be funny that no-one has mentioned the Battery, which because of its age could have failed either Short-circuit or Open-circuit.
Maybe some Boeing Electro Techs, could explain what role the battery has in this circumstance. The simultaneous failure of both engines points towards an electrical problem, unless the high temperature had adversely affected the fuel flow. |
Someone Somewhere
June 15, 2025, 13:43:00 GMT permalink Post: 11902481 |
Sorry I am not a pilot but I did spend three years filming a TV series at Boeing for pBS/Channel 4 about the design and construction of the 777, and my response is not a technical one anyway. Do airfields have high definition video coverage of all takeoffs and landings? If so, they should be public domain and there would not be hundreds of posts about grainy over-magnified smartphone footage. If they don't, a 6-cam setup on each runway (3 either side of runway, one back, one across and one forward) could record continuously to hard disk or cloud. If airfields don't have this, shouldn't it be made mandatory?
I have been really wondering what single point of failure could take out both engines simultaneously as seems to be the case here. One single main bus contactor closing in error seems to possibly be such a single point fault.
Online/running generators connected together by accident/fault will cause a HUGE load on everything, electric connections, generator itself and the shafts and gears driving the generators. Heck, I wouldnt be surprised if the generator could disintegrate due to such an electromagnetic shock load. So, the question is if there is something between the generators that could limit the electric current. A VFD possibly would as the VFD maybe would not be able to pass the current required for shearing the drive shaft for example. But then again, electronic switches like IGBT/MOSFET and such are able to pass an incredibly large over current for some milliseconds before exploding. Possibly 50 to 100 times the nominal current. So I am not sure if a VFD really would save the rest of the system in a situation with two generators connected together in error. So, where is the VFD part installed, directly on each generator or somewhere else in the system? Are there physical interlocks on the contactors or only electric interlocks? VFDs are for frequency conversion to drive the motors (CAC/pumps/engine start). They won't be carrying the full generator load for galleys and anti-ice; that will be handled by cross-ties, which is a big black box on the 787. Fast fuses can be faster acting than circuit breakers, but are one-shot. I'm not sure how fast-acting and effective the generator contactors/controllers are; conventional ACBs/MCCBs will blow open magnetically under sufficient fault current regardless of what the trip unit or close coil commands. I wouldn't really expect electrical reconfiguration to happen on climbout, and I wouldn't expect it to be the first time this contactor gets used since maintenance - everything should get a good workout during sequential APU/engine starts.
No system would be designed to parallel two frequency wild generators. The output from each would be rectified to dc and conditioned before application to the load, but could be paralleled at dc level if required for redundancy. These are quarter megawatt generators, where an out of phase connection could shear drive shafts, destroy the drive train, or worse.
In a very simple main-tie-main arrangement you can close any two of three breakers and still keep the sources separate. It gets much more complicated when you have ten different sources. I suspect the 'large motor power centre' might parallel the rectified output of some generators.
I no longer believe in the no flaps / flaps raised early theory.
I think this was a major electrical failure most likely due to the engines quitting. The 787 is far more heavily dependent on electrical power to run it's systems than previous Boeing planes. It requires about 1.5 megawatts of power according to Wiki. 5X more than previous designs. Things that were done by engine driven pumps/compressors and engine bleed air are all done electrically on the 787. Flight controls that were moved hydraulically or pneumatically are moved by electric actuators. Etc. 1.5MW is the figure for all six generators; only four can be used at once. There's no indication they had any flight control issues.
Seems to be funny that no-one has mentioned the Battery, which because of its age could have failed either Short-circuit or Open-circuit.
Maybe some Boeing Electro Techs, could explain what role the battery has in this circumstance. The simultaneous failure of both engines points towards an electrical problem, unless the high temperature had adversely affected the fuel flow. |
Blake777
June 15, 2025, 13:54:00 GMT permalink Post: 11902489 |
There's some possible fuel contamination mechanisms which would only affect one aircraft
- The fuel truck\x92s water-absorbing \x93monitor\x94 element breaks up, the first aircraft after the break gets the bead slug; later uplifts may be clear once the hose is flushed. The beads jam metering valves almost immediately. - After pipe maintenance, the first few hundred litres can carry residual cleaning surfactant that strips protective films and causes filter-monitor \x93soap lock\x94. - Biofilm growth happens inside one aircraft\x92s wing tanks when it sits in humid conditions or does short hops with warm fuel. On the next flight the biofilm shears off, blocks strainers, |
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