2025-06-12T12:34:00
permalink Post: 11899162
For an aircraft that will likely have TOGA pressed and be at a high power setting (plus the RAT deployed) it sounds awfully quiet.
Perhaps the gear was down because they knew they were going to force land due to lack of thrust.
(Only a 738 driver), but the electric pumps to drive the hydraulics is much slower than the engine driven pumps and so flap selection / re-selection could be not as expected.
RIP to all involved.
Perhaps the gear was down because they knew they were going to force land due to lack of thrust.
(Only a 738 driver), but the electric pumps to drive the hydraulics is much slower than the engine driven pumps and so flap selection / re-selection could be not as expected.
RIP to all involved.
The 787 has 2x Enhanced Airborne Flight Recorders (EAFR), which each record both cockpit voice and flight data.
Hopefully flight data is not going to be an issue for this investigation.
It's also maybe visible in a few stills (e.g. post 64).
Last edited by Someone Somewhere; 14th Jun 2025 at 06:01 .
Subjects: APU CVR DFDR EAFR Engine Failure (All) Engine Shutdown FDR Gear Retraction Generators/Alternators NTSB RAT (All) RAT (Deployment) RAT (Sound) TOGA
2 users liked this post.
2025-06-13T08:06:00
permalink Post: 11900136
A220 has a RAT - so does the E-jets and the Sukhoi Superjet. You're right on the 737 and I'd forgotten the 717...
Spoiler
Last edited by Someone Somewhere; 13th Jun 2025 at 08:19 .
Subjects: Generators/Alternators RAT (All)
2025-06-13T08:24:00
permalink Post: 11900162
I believe the trim runaway on the 737 was originally only deemed 'major', hence the loose standards on the software. Dual engine flameout/forced-idle is definitely 'catastrophic' and there's no doubt about it.
Not saying it's impossible, but the software should get much more review.
Not saying it's impossible, but the software should get much more review.
Subjects: None
2025-06-13T11:34:00
permalink Post: 11900389
It's fine that the \x93Enhanced Airborne Flight Recorders\x94 have 10 minutes battery backup. If the bits of equipment/sensors sending data to be recorded don't have power, you will be recording 10 minutes of silence/blank data.
The concept of powering 'critical (sensor) equipment' has been floated - the problem being that it must be possible to power down malfunctioning equipment in case of fire - real or suspected. Having independent power supplies and battery back-ups all around the airframe, each with an ability to lose their magic smoke, is a poor idea.
Commercial passenger jet aircraft already have robust power supplies with multiple generators and emergency battery support. However, if one malfunctions, rather than fails completely, it can be difficult to decide which one to disable, as it can cause problems in all systems.
The concept of powering 'critical (sensor) equipment' has been floated - the problem being that it must be possible to power down malfunctioning equipment in case of fire - real or suspected. Having independent power supplies and battery back-ups all around the airframe, each with an ability to lose their magic smoke, is a poor idea.
Commercial passenger jet aircraft already have robust power supplies with multiple generators and emergency battery support. However, if one malfunctions, rather than fails completely, it can be difficult to decide which one to disable, as it can cause problems in all systems.
Once the RAT deployed at least some data should have come back.
Now, I am probably wrong about this, but if you forget to set the altitude window to the first altitude in departure and leave it at 0 (which with some airlines the previous crew will do on shutdown) the following might possibly occur. At 50 feet LNAV engages, at 100 feet the autopilot engages, at 400 feet VNAV engages but as the altitude window is set to 0 the aircraft (on autopilot) now descends to capture 0 feet. The speed at this point in VNAV is low (max V2 + 20 kts) so, to maintain that, both thrust levers close. This, of course, would be totally unexpected and could have a startle effect. If you do not realise what has caused this you might think that there is a problem with the engines and you have very little time to deal with it. I would suggest that putting out a Mayday call at this stage is not a good use of time.
As I stated at the beginning this is probably very unlikely and may not be possible, but could be tried in a simulator.
As I stated at the beginning this is probably very unlikely and may not be possible, but could be tried in a simulator.
It does not explain the RAT and generally you would expect crews to shove the thrust levers fully forward.
Subjects: APU CVR EAFR Generators/Alternators Mayday RAT (All) RAT (Deployment) V2 VNAV
1 user liked this post.
2025-06-14T03:05:00
permalink Post: 11901101
Miscellaneous comments:
I have seen in manuals for other airliners that because the bogie tilt is by a hydraulic actuator, gravity deploying the gear means the gear doesn't tilt to landing position.
With the loss of centre-system pressure*, would you expect the bogies to tilt naturally? I.e. spring pressure holds the gear in the stowed tilt, a hydraulic cylinder pushes the gear to the landing tilt. No pressure means the gear returns to the 'stowed' tilt.
The tilt actuator is designed to be overridden when the bogie hits the ground, so perhaps it has some kind of intentional bypass and doesn't stay in place without continually applied hydraulic pressure.
If so, that would also point towards total loss of electrics and no attempt to raise the gear.
* 787 centre system is powered by two electric pumps, plus the RAT. The RAT hydraulic pump only powers flight controls, not the landing gear.
Electric loss:
Surely even total AC power loss shouldn't result in engine loss, even if the RAT doesn't come online. The FADECs have their own alternators, bare minimum flight control computers and actuators are available on battery (though probably result in some equivalent of Direct Law), and boost pumps are unnecessary at low altitude. Left/right EDPs will remain active if the engines are running at any serious speed; providing flight controls.
Poor crew reaction to ending up in direct law is possible but it's hard to see the electrical issues as a cause, not a symptom.
Anti-terrorism squad looks to be doing an excellent job (/s) and recovered a convenience-store-grade CCTV recorder, probably from somewhere on the campus it crashed into:
https://economictimes.indiatimes.com.../121823103.cms
With the loss of centre-system pressure*, would you expect the bogies to tilt naturally? I.e. spring pressure holds the gear in the stowed tilt, a hydraulic cylinder pushes the gear to the landing tilt. No pressure means the gear returns to the 'stowed' tilt.
The tilt actuator is designed to be overridden when the bogie hits the ground, so perhaps it has some kind of intentional bypass and doesn't stay in place without continually applied hydraulic pressure.
If so, that would also point towards total loss of electrics and no attempt to raise the gear.
* 787 centre system is powered by two electric pumps, plus the RAT. The RAT hydraulic pump only powers flight controls, not the landing gear.
Electric loss:
Surely even total AC power loss shouldn't result in engine loss, even if the RAT doesn't come online. The FADECs have their own alternators, bare minimum flight control computers and actuators are available on battery (though probably result in some equivalent of Direct Law), and boost pumps are unnecessary at low altitude. Left/right EDPs will remain active if the engines are running at any serious speed; providing flight controls.
Poor crew reaction to ending up in direct law is possible but it's hard to see the electrical issues as a cause, not a symptom.
https://economictimes.indiatimes.com.../121823103.cms
Subjects: CCTV Fuel (All) Fuel Pumps Gear Retraction Generators/Alternators Hydraulic Failure (All) Hydraulic Pumps MLG Tilt RAT (All)
2025-06-14T07:22:00
permalink Post: 11901193
(I screwed up earlier and had a 767 image here...)
Taken together, it seems that there was an event (or events) shortly after rotation that compromised both engines and the electrical system.
Compromising both engines inherently compromises the electrical system: dropping below idle N2 (plus some safety margin) disconnects generators.
Last edited by Someone Somewhere; 14th Jun 2025 at 17:57 .
Subjects: Flaps (All) Flaps vs Gear Generators/Alternators Hydraulic Failure (All) Hydraulic Pumps
2 users liked this post.
2025-06-14T17:35:00
permalink Post: 11901681
What concerns me a little bit is if indeed AC power is lost, would the suction feed inlets in the wing tanks provide enough fuel flow to maintain TO thrust?
I know the system is designed to achieve this in a situation where all of the AC powered boost pumps are lost. But what about in a real situation...
Could this cause a degradation of thrust? Even the slightest decrease..
I know the system is designed to achieve this in a situation where all of the AC powered boost pumps are lost. But what about in a real situation...
Could this cause a degradation of thrust? Even the slightest decrease..
I did read and search this thread, but I found nothing about ADS-B loss just before the end of the runway and at 71 ft high, according to FR24. ADS-B coverage is poor on the ground on the north-east part of the airfield (hence the fake news about taking off from the intersection) but I don't think it would be lost once airborne, except if it has been shut off... electrical failure ?
more precisely, loss of the two Main AC buses (ADS-B not powered by Standby AC)
more precisely, loss of the two Main AC buses (ADS-B not powered by Standby AC)
There's a list of equipment operable on battery/RAT here, but I'm not sure which (if any) is the transponder (26:10):
If you had gear pins and an engine loss, I could maybe see climb rate being zero or slightly negative. Not the brick impression we see here.
There have been a couple comments regarding the tilt of the bogies not corresponding to the landing configuration which have taken this as an indicator for an attempted (but failed) retraction.
I don't think anybody has so far confirmed which of the two positions the bogie would have without hydraulic pressure, but I would strongly think it is the one used in the retraction/extension cycle and not the landing configuration, for the simple reason that otherwise the gravity drop would potentially not work (I assume it is tilted for the stowing because it would otherwise not fit).
Maybe someone with concrete knowledge can confirm this?
This would then only confirm that the bogies were unpressurized (likely because of loss of hydraulics, but of course could also still be a partial retraction that stopped for some reason)
I don't think anybody has so far confirmed which of the two positions the bogie would have without hydraulic pressure, but I would strongly think it is the one used in the retraction/extension cycle and not the landing configuration, for the simple reason that otherwise the gravity drop would potentially not work (I assume it is tilted for the stowing because it would otherwise not fit).
Maybe someone with concrete knowledge can confirm this?
This would then only confirm that the bogies were unpressurized (likely because of loss of hydraulics, but of course could also still be a partial retraction that stopped for some reason)
Subjects: ADSB APU Electrical Failure Engine Failure (All) Flap Retraction Flaps (All) FlightRadar24 Fuel (All) Fuel Pumps Hydraulic Failure (All) Hydraulic Pumps MLG Tilt RAT (All) RAT (Deployment)
2 users liked this post.
2025-06-14T17:48:00
permalink Post: 11901689
Much of the noise is from the core flow and combustion, not the fan and bypass air. Remove the fuel and the core exhaust is lower volume and cooler, even at high RPMs.
Subjects: FADEC
2025-06-14T18:08:00
permalink Post: 11901702
(the manual implies two in a pinch, but you shed all loads except the engine starters and a fuel pump)
Subjects: APU Fuel (All) Fuel Pumps
2025-06-15T02:36:00
permalink Post: 11902060
Difficult!? Maybe not. If very late the flaps were tagged stowed, and there was a simultaneous gear up command, with FlapDown command, the overload could have failed a GCS. Then it becomes a switching exercise. (Automatics).
Alarms Warnings Impacted EICAS, ETC. it happened long ago, but we know what happens when an engine driven generator quits ..first it bangs for awhile, then it burns itself up, then ...
Alarms Warnings Impacted EICAS, ETC. it happened long ago, but we know what happens when an engine driven generator quits ..first it bangs for awhile, then it burns itself up, then ...
Thanks for answering the question I hadn't yet asked but wanted to confirm!
I'm still sticking with "Major Electrical Fault" as my most likely cause, and this adds to my suspicions.
As I understand it, the landing gear is raised / retracted by electric motor-driven hydraulic pump (pumps?). This/these would create a significant electrical load.
If the plane's multi-redundant electrical system has a fault which is intermittent (the worst kind of electrical issue to diagnose), and which causes the redundancy controls to go haywire (as there are, of course, electronic controls to detect failures and drive the switching over of primary and backup electrical supplies), then this fault could to triggered by a large load coming on-line. It could even be as simple as a high current cable lug not having been tightened when a part was being replaced at some stage. The relevant bolt might be only finger-tight. Enough to work 99.99% of the time between then and now... But a little bit more oxidation, and particularly, a bit more heat (it was a hot day), and suddenly, a fault.
Having worked in electronics for years, I know that semi-conductors (and lots of other components, especially capacitors [and batteries]) can also degrade instead of failing completely. Electro-static discharges are great for causing computer chips to die, or go meta-stable - meaning they can get all knotted up and cease working correctly - until they are powered off for a while. They can also degrade in a way that means they work normally a low temperatures, but don't above a certain temperature.
Anyway, there MUST be ways that the redundant power supplies can be brought down, simply because, to have a critical bus powered from a number of independent sources, there must be "controls" of some sort. I don't know how it's done in the 787, but that's where I'd be looking.
As there is a lot of discussion already about how the bogies are hanging the wrong way suggesting a started but failed retraction operation, and it's now confirmed that the retraction would normally have taken place at about the point where the flight went "pear shaped", I'm going to suggest that the two things are connected. More than that: I'll suggest that the Gear Up command triggered the fault that caused both engines to shut down in very short succession. Nothing the pilots did wrong, and no way they could have known and prevented it.
It's going to be difficult to prove though.
I'm still sticking with "Major Electrical Fault" as my most likely cause, and this adds to my suspicions.
As I understand it, the landing gear is raised / retracted by electric motor-driven hydraulic pump (pumps?). This/these would create a significant electrical load.
If the plane's multi-redundant electrical system has a fault which is intermittent (the worst kind of electrical issue to diagnose), and which causes the redundancy controls to go haywire (as there are, of course, electronic controls to detect failures and drive the switching over of primary and backup electrical supplies), then this fault could to triggered by a large load coming on-line. It could even be as simple as a high current cable lug not having been tightened when a part was being replaced at some stage. The relevant bolt might be only finger-tight. Enough to work 99.99% of the time between then and now... But a little bit more oxidation, and particularly, a bit more heat (it was a hot day), and suddenly, a fault.
Having worked in electronics for years, I know that semi-conductors (and lots of other components, especially capacitors [and batteries]) can also degrade instead of failing completely. Electro-static discharges are great for causing computer chips to die, or go meta-stable - meaning they can get all knotted up and cease working correctly - until they are powered off for a while. They can also degrade in a way that means they work normally a low temperatures, but don't above a certain temperature.
Anyway, there MUST be ways that the redundant power supplies can be brought down, simply because, to have a critical bus powered from a number of independent sources, there must be "controls" of some sort. I don't know how it's done in the 787, but that's where I'd be looking.
As there is a lot of discussion already about how the bogies are hanging the wrong way suggesting a started but failed retraction operation, and it's now confirmed that the retraction would normally have taken place at about the point where the flight went "pear shaped", I'm going to suggest that the two things are connected. More than that: I'll suggest that the Gear Up command triggered the fault that caused both engines to shut down in very short succession. Nothing the pilots did wrong, and no way they could have known and prevented it.
It's going to be difficult to prove though.
In addition, the 787 has four main generators and I believe the switching is segregated into at least two controllers, on top of the four separate generator control units.
And again, electrical failure should not cause engine failure - consider QF32 where the wiring to the engine was mostly severed and they had to drown it with a fire truck.
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.
Yes, thanks, I've seen a few comments to this effect, and I have to accept most of what you say. I understand that they have their own dedicated generators and local independent FADECs (or EECs), but I'm trying to use what I do know to attempt to figure this out. I know that there are Fuel Cutoff switches in the cockpit. Somehow, if switched to Off, these will cut off the fuel to the engines, "no matter what". Of course, even that's not true, as the Qantas A380 engine burst apparently (comment in this thread) showed.
Anyway, the thing I'm looking at is how the fuel cutoff switch function could have been activated in some other way. To me, it seems obvious that there are wires that run between the engine fuel shutoff valves and the cockpit / flight control panel (no doubt with relays etc in between). I don't know where those shutoff valves are located, but logic says they should be located in the fuselage, not out at the engines. I also don't know how those valves operate - are they solenoid valves or electro-mechanically driven? Nor do I know where the power to activate those valves comes from, but using my logic, if those valves close when powered off, such as solenoid valves typically do, then the power cannot exclusively come from the engine-dedicated generators. If it did, you'd never be able to start the engines so they could supply their own power to hold those valves open. So, there must be some power (appropriately) fed from the main aircraft control bus to activate those valves - if the rest of what I'm assuming is correct. Anyway, like I say, I don't know enough about the details at this point, but there are many more ways to activate or deactivate a circuit than by flicking a switch. Killing the relevant power supply, for example. A screwdriver across some contacts (for example), another. Shorting a wire to Chassis, maybe. Just trying to contribute what I can.
You raise another interesting point: "TCMA notwithstanding". Could you elaborate, please? What will happen if the TCMA system, which apparently also has some degree of engine control, loses power? The problem with interlinked circuits and systems is that sometimes, unexpected things can happen when events that were not considered actually happen. If one module, reporting to another, loses power or fails, sometimes it can "tell" the surviving module something that isn't true... My concern is where does the power to the Fuel Cutoff switches come from? Are there relays or solid-state switches (or what?) between the Panel Switches and the valves? If so, is the valve power derived from a different source, and if so, where? Are the valves solenoids, open when power applied, or something else? What is the logic involved, between switch and valve?
Would you mind answering these questions so I can ponder it all further, please? If I'm wrong, I'll happily say so.
Anyway, the thing I'm looking at is how the fuel cutoff switch function could have been activated in some other way. To me, it seems obvious that there are wires that run between the engine fuel shutoff valves and the cockpit / flight control panel (no doubt with relays etc in between). I don't know where those shutoff valves are located, but logic says they should be located in the fuselage, not out at the engines. I also don't know how those valves operate - are they solenoid valves or electro-mechanically driven? Nor do I know where the power to activate those valves comes from, but using my logic, if those valves close when powered off, such as solenoid valves typically do, then the power cannot exclusively come from the engine-dedicated generators. If it did, you'd never be able to start the engines so they could supply their own power to hold those valves open. So, there must be some power (appropriately) fed from the main aircraft control bus to activate those valves - if the rest of what I'm assuming is correct. Anyway, like I say, I don't know enough about the details at this point, but there are many more ways to activate or deactivate a circuit than by flicking a switch. Killing the relevant power supply, for example. A screwdriver across some contacts (for example), another. Shorting a wire to Chassis, maybe. Just trying to contribute what I can.
You raise another interesting point: "TCMA notwithstanding". Could you elaborate, please? What will happen if the TCMA system, which apparently also has some degree of engine control, loses power? The problem with interlinked circuits and systems is that sometimes, unexpected things can happen when events that were not considered actually happen. If one module, reporting to another, loses power or fails, sometimes it can "tell" the surviving module something that isn't true... My concern is where does the power to the Fuel Cutoff switches come from? Are there relays or solid-state switches (or what?) between the Panel Switches and the valves? If so, is the valve power derived from a different source, and if so, where? Are the valves solenoids, open when power applied, or something else? What is the logic involved, between switch and valve?
Would you mind answering these questions so I can ponder it all further, please? If I'm wrong, I'll happily say so.
The valves are located in the spar (hence being called 'spar valves'. The fuel tank is immediately above the engine so it is a very short pipe for suction feeding. Tail mount engines are potentially a different story...
What\x92s the usual time frame for the release of preliminary data and report from the FDR and CVR? Is it around 6 months?
I guess if no directives come from Boeing or the FAA in the next 2 weeks, it can be presumed that a systems failure from which recovery was impossible was unlikely.
I guess if no directives come from Boeing or the FAA in the next 2 weeks, it can be presumed that a systems failure from which recovery was impossible was unlikely.
Subjects: CVR Electrical Failure Engine Failure (All) FAA FDR Flaps (All) Flaps vs Gear Fuel (All) Fuel Cut Off Switches Fuel Cutoff Fuel Pumps Gear Retraction Generators/Alternators Hydraulic Failure (All) Hydraulic Pumps TCMA (All)
1 user liked this post.
2025-06-15T04:53:00
permalink Post: 11902102
Ok, thanks for clarifying. Of course, an overload will simply cause the hydraulic pressure relief valves to activate. There will be a moderate increase in motor current when bypassing, but the electrical side should be fully able to cope with that. Should be! I'm suggesting here that there was a fault somewhere in the electrical supplies that effectively derated some part of it, and that maybe the GearUp load was too much for it on this occasion.
It uses a variable displacement pump to maintain 5000PSI constant pressure. The swashplate angle is varied to adjust pump output flow: more devices consuming fluid, more flow to keep the pressure up. If the pumps cannot deliver enough fluid, the swashplate reaches the full flow position and the output pressure decreases until flow consumed equals flow produced. Very much like a constant-current constant-voltage power supply.
Running in that area of maximum flow is 100% expected under some conditions, especially if an engine or EDP fails and the electric demand pump is supplying a whole hydraulic system sized for the larger EDP (although I think this would be less of an issue on the 787 as the L/R systems don't do much, but the same variable-displacement pump design has been around for a LONG time including on the 737).
And again, there's a VFD between the aircraft electrical bus and the pump motor, because the pump is 400Hz and the aircraft is wild-frequency. VFDs are very very good at isolating faults unless you are actually looking at a sustained overload on one of four generators .
Thanks for confirming the 4 gens. So there's probably quite a bit of switching required. Not sure how that's done, but I guess robust contactors are required. And even these can fail. Systems usually cannot tell that a contactor has failed on the open side until it's switched. So, a switchover may have been done, but a failed contact meant the backup generator wasn't connected. Who knows, so many possibilities.
No bus is essential on a modern aircraft.
Boeing treats everything electric as a black box but the A380 has this beautifully overkill drawing - given both have 4x generators, 2x APU generators, and a RAT, it should not be entirely dissimilar levels of redundancy:
Note that the reason for some links having two contactors in series (e.g. BTC5/6 or BTC7) is because this is spread across two separate units, so that a fire and total loss of one leaves ~half the aircraft powered and totally flyable.
Okay! Many thanks for that! Of course, it very much complicates the picture, and I'm very puzzled as to how the Fuel Cutoff Switches and Valves operate. Apparently, the TCAM system shuts off an errant engine on the ground at least, but my concern is not with the software but the hardware. It obviously has an Output going into the Fuel Shutoff system. If the TCAM unit loses power, can that output cause the Cutoff process (powered by the engine-dedicated generator) to be activated? I guess that's the $64 billion question, but if MCAS is any example, then: Probably!
Power-open power-close is very common in commercial/situations where you don't want to be wasting energy 24/7 and don't have a defined position for the valve/damper in case of power loss. Done a bunch of them in ductwork and electrically operated windows - your car likely has them, for example.
Last edited by Someone Somewhere; 15th Jun 2025 at 05:08 .
Subjects: APU FADEC Fuel (All) Fuel Cut Off Switches Fuel Cutoff Generators/Alternators Hydraulic Failure (All) Hydraulic Pumps RAT (All)
4 users liked this post.
2025-06-15T06:13:00
permalink Post: 11902137
The engine driven fuel pumps are regularly removed and overhauled - usually when the engines go through overhaul (somewhere in the 10-20,000 hour range). The results of these overhauls are monitored, and if there is evidence of unusual deterioration, etc., that will be reflected in the recommended maintenance/overhaul intervals (BTW, this is SOP for virtually every system on the aircraft, regardless of Boeing, Airbus, etc.).
The portion of the engine driven fuel pump that is subject to wear is the high-pressure gear pump - and excessive deterioration will become apparent in the inability to reach max TO thrust. The centrifugal pump (that part responsible for the suction feed) is relatively lightly loaded and seldom experiences excessive wear or deterioration - even when exposed to severe suction feed events.
As I've posted several times, in this business you 'never say never' - but the chances that both engines fuel pumps were deteriorated to the point where they could not adequately provide suction feed fuel to keep the engines running is very, very remote.
The portion of the engine driven fuel pump that is subject to wear is the high-pressure gear pump - and excessive deterioration will become apparent in the inability to reach max TO thrust. The centrifugal pump (that part responsible for the suction feed) is relatively lightly loaded and seldom experiences excessive wear or deterioration - even when exposed to severe suction feed events.
As I've posted several times, in this business you 'never say never' - but the chances that both engines fuel pumps were deteriorated to the point where they could not adequately provide suction feed fuel to keep the engines running is very, very remote.
Of course, those should be trivial to bench test.
Subjects: Fuel (All) Fuel Pump (Engine Driven) Fuel Pumps
1 user liked this post.
2025-06-15T06:42:00
permalink Post: 11902154
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".
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.
Subjects: Electrical Failure Engine Failure (All) Engine Shutdown
2 users liked this post.
2025-06-15T06:56:00
permalink Post: 11902163
Expect all the alarms, too.
Subjects: Electrical Failure Fuel (All) Fuel Pumps
1 user liked this post.
2025-06-15T08:08:00
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".
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:
- Sound of RAT
- Visible RAT
- (edit: APU door open implies APU autostart)
- Loss of ADS-B out
- Near-total loss of thrust.
- A/T rolled engines back
- Crew interpreted this as dual engine failure
- Crew didn't push throttles forward
- Crew did switch each engine off & on again and maybe deployed RAT manually as well.
I think it has been suggested that the upload only happens every 30 minutes or so.
Last edited by Someone Somewhere; 15th Jun 2025 at 08:21 .
Subjects: ADSB APU Dual Engine Failure Electrical Failure Engine Failure (All) Engine Shutdown Fuel (All) Fuel Pumps RAT (All) RAT (Deployment) VNAV
2025-06-15T08:24:00
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.
Subjects: Centre Tank Fuel (All) Fuel Pumps
2 users liked this post.
2025-06-15T10:43:00
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.
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.
Subjects: FADEC Fuel (All) Fuel Pumps Generators/Alternators
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2025-06-15T11:16:00
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
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.
Subjects: Fuel (All) Fuel Pumps Hydraulic Failure (All) Hydraulic Pumps RAT (All) RAT (Deployment) RAT (Electrical)
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2025-06-15T13:43:00
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?
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.
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.
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.
Subjects: APU CCTV Dual Engine Failure Electrical Failure Engine Failure (All) Fuel (All) Fuel Pumps Generators/Alternators
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2025-06-18T13:08:00
permalink Post: 11905228
I (and I think everyone else here) have been assuming that the FADEC does in fact have a dedicated permanent-magnet alternator, as is the case on the Airbuses (confirmed by FCOM) and surely the 737.
I have been told elsewhere that this is not the case. A read of the draft FCOM available online for the 777 & 787 makes no mention of a FADEC generator, but then neither does the 737 manuals. Is this simply a case of "Boeing thinks you don't need to know"?
It has been proposed that the primary source of power for the FADECs is actually the flight control PMGs, mounted on the engine gearbox, but that this power goes to the avionics bay, has failover switching gear, and comes back to the EEC.
Can anyone shed concrete light on this (e.g. a source that clearly states there is both an EEC alternator and a flight control PMG on the accessory gearbox)?
Alternator and generator seem to be used interchangeably in this context.
It's not quite that, but there is a
list of received channels for a GEnx 787 in the
FDR report into one of the original battery fires
.
Unfortunately, it is only a list of parameters that they used and verified in the investigation - the only ones listed for the engines are N1 and cutoff switch. Other accident/incident FDR reports might be more focused on engines and include a similar table.
I don't think you'll find an actual wire list for it (or it won't be useful) as apparently most/all of the data is via an ARINC bus.
I attempted to PM this but your inbox is full.
[SLF with an electrical background and some exposure to ground-side critical facilities power]
I have been told elsewhere that this is not the case. A read of the draft FCOM available online for the 777 & 787 makes no mention of a FADEC generator, but then neither does the 737 manuals. Is this simply a case of "Boeing thinks you don't need to know"?
It has been proposed that the primary source of power for the FADECs is actually the flight control PMGs, mounted on the engine gearbox, but that this power goes to the avionics bay, has failover switching gear, and comes back to the EEC.
Can anyone shed concrete light on this (e.g. a source that clearly states there is both an EEC alternator and a flight control PMG on the accessory gearbox)?
Alternator and generator seem to be used interchangeably in this context.
I don't think you'll find an actual wire list for it (or it won't be useful) as apparently most/all of the data is via an ARINC bus.
I attempted to PM this but your inbox is full.
[SLF with an electrical background and some exposure to ground-side critical facilities power]
Last edited by Someone Somewhere; 18th Jun 2025 at 13:32 .
Subjects: ARINC FADEC FCOM FDR GEnx (ALL) Generators/Alternators Parameters
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