2025-06-14T15:46:00
permalink Post: 11901586
The existence of the video taken from a building near the flight path adds a lot of weight, to me.
Think about living next to a flight path. I do. I never take videos of passing planes. I doubt this video-taker did either.
But something incited him to pick up his phone (I guess) and start videoing, even before he could see the plane, which is out of view at the start. I suggest that he heard the RAT coming, knew it was totally out of the ordinary and thought it worth filming.
Why else would you film just another passing plane?
Also, looking at that video, I can see a "shadow" where the RAT would be. The RAT is very small compared with the landing gear, but there's something there. Largely lost to video compression, but it adds up.
And I can hear it, but not on every copy of that video. Try slowing the video down, but I don't know if that's reliable.
Think about living next to a flight path. I do. I never take videos of passing planes. I doubt this video-taker did either.
But something incited him to pick up his phone (I guess) and start videoing, even before he could see the plane, which is out of view at the start. I suggest that he heard the RAT coming, knew it was totally out of the ordinary and thought it worth filming.
Why else would you film just another passing plane?
Also, looking at that video, I can see a "shadow" where the RAT would be. The RAT is very small compared with the landing gear, but there's something there. Largely lost to video compression, but it adds up.
And I can hear it, but not on every copy of that video. Try slowing the video down, but I don't know if that's reliable.
1 user liked this post.
2025-06-14T16:41:00
permalink Post: 11901643
I disagree. I think the lines of the underneath of the aircraft are quite obvious and its clear there's no RAT. Given it drops on the wing to body fairing just behind the main landing gear on the starboard side of the aircraft, it should be very obvious in this photo.
2025-06-14T16:56:00
permalink Post: 11901658
11 users liked this post.
2025-06-14T17:07:00
permalink Post: 11901665
So get the arguments in quick as we'll probably know definitively within a couple of days.
2025-06-14T18:01:00
permalink Post: 11901698
We can debate over a poor quality photo but the audio evidence presented earlier today is pretty conclusive.. The RAT was out.
17 users liked this post.
2025-06-14T19:12:00
permalink Post: 11901744
Studies show that for aircraft landing with engines at landing thrust, 30 - 50% of the noise generated is from the landing gear and flaps down, so if the aircraft here had engines at low thrust setting, as appears to be the case, then the sound heard approaching could have been in large part due to the landing gear and flaps, which were down.
3 users liked this post.
2025-06-14T19:26:00
permalink Post: 11901751
We're all shouting each other down with two main different theories on why the aircraft lost lift so shortly after takeoff.
1) Incorrect flap retraction causing the aircraft to lose lift and unable to recover the energy in time. (Not unheard of and plenty of reports where this has happened - albeit usually not to a crash).
2) Loss of engine thrust backed up two potential pieces of evidence that back up the RAT was deployed (apparent RAT sound, potential RAT seen on low res video).
It is impossible to know which of these is the case. Considering this summary of memory items is there the potential for a combination of both theories to have taken place?
Inadvertant flap retraction by PNF leading the PF to sense a sink and loss of lift. Pushes the thrust levers forward to the firewall and still the aircraft sinks. PF looking through the HUD and so very much 'outside focused' and doesn't realise that PNF has instead moved the flaps. PF defaults to memory items for loss of thrust on both engines before PNF can realise or communicate to PF what they've done, start switches are cut off which drops the RAT and from that point they're only heading one way. This would satisfy the strongly held belief that the RAT was extended, whilst also following the more likely initial cause of an action slip by PNF starting the sequence, rather than a dual engine failure.
1) Incorrect flap retraction causing the aircraft to lose lift and unable to recover the energy in time. (Not unheard of and plenty of reports where this has happened - albeit usually not to a crash).
2) Loss of engine thrust backed up two potential pieces of evidence that back up the RAT was deployed (apparent RAT sound, potential RAT seen on low res video).
It is impossible to know which of these is the case. Considering this summary of memory items is there the potential for a combination of both theories to have taken place?
Inadvertant flap retraction by PNF leading the PF to sense a sink and loss of lift. Pushes the thrust levers forward to the firewall and still the aircraft sinks. PF looking through the HUD and so very much 'outside focused' and doesn't realise that PNF has instead moved the flaps. PF defaults to memory items for loss of thrust on both engines before PNF can realise or communicate to PF what they've done, start switches are cut off which drops the RAT and from that point they're only heading one way. This would satisfy the strongly held belief that the RAT was extended, whilst also following the more likely initial cause of an action slip by PNF starting the sequence, rather than a dual engine failure.
On a flap 5 takeoff the FMS could be programmed to select climb power at flaps 1 which would seem like an apparent loss of thrust. Same as for F15 to F5 or further.
I`m not sure if they would have cycled the FCS switches or not. But the airplane certainly would have experienced a loss of lift would the flaps been inadvertently retracted. As well as perceived loss of thrust.
OTOH any castastophic failure which left the gear down would have essentially left the flaps where they were. They are hydraulically activated with electrical backup but it`s wayyyyy slow.
2025-06-14T19:34:00
permalink Post: 11901755
Now I'm curious of the mechanical switchover mechanism that prevents backtracking of the flaps in the event the hydraulics fail and pressure drops which would slowly retract the flaps as hydraulic fluid drains from the pressure reservoir.
2025-06-14T19:46:00
permalink Post: 11901769
This to me makes more sense; perhaps I`ve got it wrong but in the video the trailing edge flaps definitely look up. Maybe there`s more and they weren`t.
On a flap 5 takeoff the FMS could be programmed to select climb power at flaps 1 which would seem like an apparent loss of thrust. Same as for F15 to F5 or further.
OTOH any castastophic failure which left the gear down would have essentially left the flaps where they were. They are hydraulically activated with electrical backup but it`s wayyyyy slow.
On a flap 5 takeoff the FMS could be programmed to select climb power at flaps 1 which would seem like an apparent loss of thrust. Same as for F15 to F5 or further.
OTOH any castastophic failure which left the gear down would have essentially left the flaps where they were. They are hydraulically activated with electrical backup but it`s wayyyyy slow.
In some instances, the TO derate is so significant that the selection of climb power moves the thrust levers forward. AMD is sea level with a long runway, so can imagine it would be a fairly low power take off.
2025-06-14T21:40:00
permalink Post: 11901866
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.
4 users liked this post.
2025-06-14T22:05:00
permalink Post: 11901881
Indeed
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.
1 user liked this post.
2025-06-14T22:54:00
permalink Post: 11901926
This to me makes more sense; perhaps I`ve got it wrong but in the video the trailing edge flaps definitely look up. Maybe there`s more and they weren`t.
On a flap 5 takeoff the FMS could be programmed to select climb power at flaps 1 which would seem like an apparent loss of thrust. Same as for F15 to F5 or further.
I`m not sure if they would have cycled the FCS switches or not. But the airplane certainly would have experienced a loss of lift would the flaps been inadvertently retracted. As well as perceived loss of thrust.
OTOH any castastophic failure which left the gear down would have essentially left the flaps where they were. They are hydraulically activated with electrical backup but it`s wayyyyy slow.
On a flap 5 takeoff the FMS could be programmed to select climb power at flaps 1 which would seem like an apparent loss of thrust. Same as for F15 to F5 or further.
I`m not sure if they would have cycled the FCS switches or not. But the airplane certainly would have experienced a loss of lift would the flaps been inadvertently retracted. As well as perceived loss of thrust.
OTOH any castastophic failure which left the gear down would have essentially left the flaps where they were. They are hydraulically activated with electrical backup but it`s wayyyyy slow.
I believe this is the right wing, (the registration marking appears on the right wing in online photographs of the aircraft). These flaps look down (extended) to me. I believe the structure bottom left, aft of the markings is the right aileron. The flap structure is extended rearward past the aileron structure. You can just make out the rear edge of the LE slat, top right. It is deployed, not retracted.
I understand things “move” in an accident sequence. Verifying all this will be straightforward by examining the screw-jacks and of course, the flight data.
8 users liked this post.
2025-06-14T23:00:00
permalink Post: 11901935
2025-06-15T00:56:00
permalink Post: 11902014
I was going to wait until I'd read the full thread, but since I'm only a few pages off the end I might as well address this point while replying to the above.
in regard to the 'green and white light' - as mentioned, it is likely he is referring to the exit light above the door, which on the 787 is the universally understood 'running man'.
Now that in itself can be a clue - it's been a while since I was on a Boeing widebody, and my experience is more with Airbus widebody, but the operation 'modes' of exit lights might tell something, depending on the usual operation on a 787.
For example, on Airbus, they stay on until gear is retracted and stowed at which point they switch off and only illuminate again with loss of power, manual emerg lights selection (by FD or CC) or gear extension.
If the 787 follows the logic of older Boeing models, I believe (if memory hasn't failed me) that they are not on during takeoff but only if "required"- i.e. loss of power or emerg lights selected on by anyone (FD or CC)
If this is the case on 787, that they are not illuminated normally during takeoff, them coming 'on' means two things: gear extension - which we know the gear was already down, or some change in the power status. Is it possible if they were mid-retraction the lights would have gone off then on again? I don't know 787, only 777/A380, but in A380 the lights did not trigger 'off' until the gear doors closed (I could always hear this right before the 'ping' audio cue that the lights were now off.)
Any 787 people care to confirm what the exit lighting actually does? I would imagine the floor/aisle lighting and other lighting would also have come on in a total power loss scenario as well, but IME passengers often don't even notice it coming on during normal pre-departure when it's being check/power modes are switched over, let alone when they're experiencing what this guy did.
But it's an interesting comment from the witness and just one more piece to tell investigators what's gone on.
5 users liked this post.
2025-06-15T01:29:00
permalink Post: 11902033
2025-06-15T01:40:00
permalink Post: 11902038
Question: regardless of the intricacies of various aircraft-specific systems, is it possible to establish from sheer aerodynamics what can/cannot have happened here? Or to put it another way - leaving aside any and all rumours, theories, plausible sights/sounds, and other extraneous details, and focusing solely on the flight path, can loss of thrust be conclusively ruled in or out? Several times now I've seen someone put forth the argument that it's impossible for the flight path to have been as short as it is if the flaps were retracted but the engines were still producing (even derated) takeoff thrust. It might be helpful to reach a consensus on whether this is true or not - if it's inconclusive then we're back to where we already are, but if a conclusion
can
be reached it would probably save everyone a lot of breath going down various theoretical rabbit holes.
In the CCTV video, the aircraft stops climbing at 00:28. 3 seconds after, it starts visibly descending. At peak altitude, using the 197ft wingspan as a measure, the altitude is around 200ft or below. The fireball is at 00:48, 17s after descent starts visibly.
Per google maps and the impact location mapped at avherald, the impact point is ~3990ft from the airport boundary road and about 4200ft from the midpoint of the runway threshold and the airport boundary road.
16:1 to 25:1 is what I could find for the 787 glide ratio range (unpowered) with main landing gear down and flaps 5. So the aircraft could cover 16 to 25 ft horizontally for every 1 ft of descent.
With a starting altitude of 200ft, that would imply it could have covered 3200ft.to 5000ft during unpowered descent.
The actual distance covered, around 4000ft, certainly seems to suggest that the descent was unpowered.
5 users liked this post.
2025-06-15T02:05:00
permalink Post: 11902051
2025-06-15T02:13:00
permalink Post: 11902053
Pprune Mind Traps from overwhelming posts
Do not discount the mistaken early flap retraction scenario too easily. Mull on this:
PF commanded gear up on attaining positive rate of climb, fixating on the HUD.
PM mistakenly raise flap lever from 5 to Flap 1 gate. Thrust reduced to Climb Thrust. Landing gear remained deployed. Massive loss of lift misidentified as loss of thrust. If any one pilot just had a dual engine failure scenario on a recent sim ride, brain and muscle memory would jump to loss of thrust in dual engine, prompting them to accomplish the recall memory items which called for both engine fuel control switches to CUTOFF and then RUN, and physically deployed the RAT.
There would be immediate loss of thrust with the engine taking time to recover , if at all, at such low airspeed!
The rest is left for Ppruners’ imagination.😖🥴😬
PF commanded gear up on attaining positive rate of climb, fixating on the HUD.
PM mistakenly raise flap lever from 5 to Flap 1 gate. Thrust reduced to Climb Thrust. Landing gear remained deployed. Massive loss of lift misidentified as loss of thrust. If any one pilot just had a dual engine failure scenario on a recent sim ride, brain and muscle memory would jump to loss of thrust in dual engine, prompting them to accomplish the recall memory items which called for both engine fuel control switches to CUTOFF and then RUN, and physically deployed the RAT.
There would be immediate loss of thrust with the engine taking time to recover , if at all, at such low airspeed!
The rest is left for Ppruners’ imagination.😖🥴😬
Last edited by bakutteh; 15th Jun 2025 at 09:18 .
11 users liked this post.
2025-06-15T02:29:00
permalink Post: 11902059
This applies equally to a normal gear retraction: the centre hydraulic pumps must have stopped very early for the trucks to be in that position on an "interrupted" gear retraction, with the main gear doors still closed (and presumably locked). Seems unlikely.
I did raise this earlier... FCOMs say that the bogies remain in the stowed tilt after a gravity drop, but I don't know if that's because the gear has springs to hold it that way without hydraulics, or just they close the valves on the hydraulics so it stays in the last commanded position without pressure.
Alternate extension appears to rely on the truck positioner remaining in its previously "positioned" state - stowed - where it has been sitting cold, unloved and unpowered since the gear was previously retracted. Like other Boeing types, the wheel well has some bars to stop the truck moving while it's up and stowed.
It's remotely possible the main gear priority valves may have prevented more gear movement in the absence of good hydraulic pressure - however this wouldn't stop the nose gear from operating, so not likely.
Last edited by Lifer01; 15th Jun 2025 at 02:39 .
1 user liked this post.
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.
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