2025-06-14T00:22:00
permalink Post: 11901021
The B787 is a way way different and much more complex and sophisticated plane than your Gulfie. The B787's two outermost (left & right) hydraulic systems are primarily driven by the engines, mechanically driving the hydraulic pumps. The center hydraulics are primarily electrically driven, and power the main flight controls. The left and right ones power the main flight controls as well, some of the less important flight control surfaces like spoilers and thrust reversers -- pardon me for not having the exact list of things. They also have a backup/supplementary electric pump each. Each of the two main engines has redundancy for the power plant a.k.a. VFSG (and motor-driven pump?) in its own right as well. All three hydraulic systems work together in a redundant fashion when it comes to the primary flight controls. The RAT can provide both electrical and mechanical sources of hydraulic support, if I'm not mistaken. The flight instrument and information systems can also be powered from two backup batteries, the APU power plant itself, and/or the RAT.
1 user liked this post.
2025-06-14T02:16:00
permalink Post: 11901080
As many will know, on the Boeing 787-8,
each main gear door is hydraulically actuated and powered by its respective side’s hydraulic system
— the
left gear door by the left hydraulic system
, and the
right by the right
. This leads me to propose the following hypothesis:
The Centre Hydraulic system is powered by two Electric Motor Pumps.
Obviously, the two Centre pumps are ultimately powered by electrical power from the VFSGs on the engines and/or the APU.
Note: the RAT will not (and could not!) supply hydraulic power to the gear system.
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2025-06-14T08:01:00
permalink Post: 11901229
I would say an average passenger has problems differentiating between thrust and G.
Even after engines lost all power G could still vary quite a bit as the pilots tried to crash with as little energy as possible. Any passenger could feel this varying G as varying thrust instead.
Even after engines lost all power G could still vary quite a bit as the pilots tried to crash with as little energy as possible. Any passenger could feel this varying G as varying thrust instead.
It\x92s a known path that removing fuel from the jet engines will lead to (momentarily) loss of main electric power (if the APU is not runing). It\x92s a less speculated (and a less likely) area that what path might lead to loss of engine thust if main electric power is lost?
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2025-06-14T12:24:00
permalink Post: 11901432
The B787 is a way way different and much more complex and sophisticated plane than your Gulfie. The B787's two outermost (left & right) hydraulic systems are primarily driven by the engines, mechanically driving the hydraulic pumps. The center hydraulics are primarily electrically driven, and power the main flight controls, amongst other things like the gear. The left and right ones power the main flight controls as well, some of the less important flight control surfaces like spoilers and thrust reversers -- pardon me for not having the exact list of things. They also have a backup/supplementary electric pump each. Each of the two main engines has redundancy for the power plant a.k.a. VFSG (and motor-driven pump?) in its own right as well. All three hydraulic systems work together in a redundant fashion when it comes to the primary flight controls. The RAT can provide both electrical and mechanical sources of hydraulic support, if I'm not mistaken. The flight instrument and information systems can also be powered from two backup batteries, the APU power plant itself, and/or the RAT.
The Global Express has 4 engine driven generators, one APU generator, one RAT generator that provide AC and DC power to the aircraft's systems. On the hydraulic side, the aircraft has 3 fully independent and redundant hydraulic systems which power all flight control surfaces the exception being, the slats and flaps are AC power driven and are available even with only the RAT providing power. The 3 hydraulic systems are powered from each engine backed up by 2 EDPs (system 1 and 2) and system 3 is powered by 2 EDPs only. The RAT powers system 3 via one of its EDPs. In the event of a dual engine failure the RAT would deploy automatically and power the AC essential plus DC essential busses and one EDP on system 3. The APU is available to you up to FL450 and will supply full AC power but bleed air only up to FL300.
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2025-06-14T12:31:00
permalink Post: 11901444
Even though there is no point speculating about the cause of this accident, it is the nature of the beast to have questions. As pilots (most of us at least), we do have an inquiring mindset.
My initial thoughts were an inadvertent flap retraction. But with the ‘evidence’ that has been presented over the last 48 hours, I think we can safely discard that option.
What we think we know is:
- RAT was deployed (highly possible)
- Gear was selected up, but did not operate (bogey tilted, doors remained closed)
- APU was ‘on’ (APU door open on after crash pictures)
- Flight path
Any of these observations, alone, would mean very little. However, in combination, they all point to a dual engine flameout just at/after the rotation. The aircaft has enough kinetic energy to reach roughly 150ft altitude, and then starts a shallow descent at ‘alpha max’ into the buildings ahead. The RAT deployed, APU attempted auto-start, gear was unable to retract.
I only wonder why the engines spooled down. Bird strike seems to be out of the question, so that leaves us with only a very few options, which include a software bug or a suicidal pilot (not a popular option, I understand, but we have to take all options into account).
What I don’t believe is incorrect FCU selections, since that would not explain the high AOA on impact. It also would not explain the RAT, no gear retraction or the APU inlet flap open. Another thing that is highly unlikely is any switching done by the pilots, especially RAT etc.. The airborne time is just too little, pilots usually don’t take any action below approximately 400ft, and these switches are so ‘underused’ that a pilot would not find them instantaneously in a high stress situation.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
My initial thoughts were an inadvertent flap retraction. But with the ‘evidence’ that has been presented over the last 48 hours, I think we can safely discard that option.
What we think we know is:
- RAT was deployed (highly possible)
- Gear was selected up, but did not operate (bogey tilted, doors remained closed)
- APU was ‘on’ (APU door open on after crash pictures)
- Flight path
Any of these observations, alone, would mean very little. However, in combination, they all point to a dual engine flameout just at/after the rotation. The aircaft has enough kinetic energy to reach roughly 150ft altitude, and then starts a shallow descent at ‘alpha max’ into the buildings ahead. The RAT deployed, APU attempted auto-start, gear was unable to retract.
I only wonder why the engines spooled down. Bird strike seems to be out of the question, so that leaves us with only a very few options, which include a software bug or a suicidal pilot (not a popular option, I understand, but we have to take all options into account).
What I don’t believe is incorrect FCU selections, since that would not explain the high AOA on impact. It also would not explain the RAT, no gear retraction or the APU inlet flap open. Another thing that is highly unlikely is any switching done by the pilots, especially RAT etc.. The airborne time is just too little, pilots usually don’t take any action below approximately 400ft, and these switches are so ‘underused’ that a pilot would not find them instantaneously in a high stress situation.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
16 users liked this post.
2025-06-14T12:43:00
permalink Post: 11901451
Even though there is no point speculating about the cause of this accident, it is the nature of the beast to have questions. As pilots (most of us at least), we do have an inquiring mindset.
My initial thoughts were an inadvertent flap retraction. But with the ‘evidence’ that has been presented over the last 48 hours, I think we can safely discard that option.
What we think we know is:
- RAT was deployed (highly possible)
- Gear was selected up, but did not operate (bogey tilted, doors remained closed)
- APU was ‘on’ (APU door open on after crash pictures)
- Flight path
Any of these observations, alone, would mean very little. However, in combination, they all point to a dual engine flameout just at/after the rotation. The aircaft has enough kinetic energy to reach roughly 150ft altitude, end then starts a shallow descent at ‘alpha max’ into the buildings ahead. The RAT deployed, APU attempted auto-start, gear was unable to retract.
I only wonder why the engines spooled down. Bird strike seems to be out of the question, so that leaves us with only a very few options, which include a software bug or a suicidal pilot (not a popular option, I understand, but we have to take all options into account).
What I don’t believe is incorrect FCU selections, since that would not explain the high AOA on impact. It also would not explain the RAT, no gear retraction or the APU inlet flap open. Another thing that is highly unlikely is any switching done by the pilots, especially RAT etc.. These airborne time is just too little, pilots usually don’t take any action below approximately 400ft, and these switches are so ‘underused’ that a pilot would not find them instantaneously in a high stress situation.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
My initial thoughts were an inadvertent flap retraction. But with the ‘evidence’ that has been presented over the last 48 hours, I think we can safely discard that option.
What we think we know is:
- RAT was deployed (highly possible)
- Gear was selected up, but did not operate (bogey tilted, doors remained closed)
- APU was ‘on’ (APU door open on after crash pictures)
- Flight path
Any of these observations, alone, would mean very little. However, in combination, they all point to a dual engine flameout just at/after the rotation. The aircaft has enough kinetic energy to reach roughly 150ft altitude, end then starts a shallow descent at ‘alpha max’ into the buildings ahead. The RAT deployed, APU attempted auto-start, gear was unable to retract.
I only wonder why the engines spooled down. Bird strike seems to be out of the question, so that leaves us with only a very few options, which include a software bug or a suicidal pilot (not a popular option, I understand, but we have to take all options into account).
What I don’t believe is incorrect FCU selections, since that would not explain the high AOA on impact. It also would not explain the RAT, no gear retraction or the APU inlet flap open. Another thing that is highly unlikely is any switching done by the pilots, especially RAT etc.. These airborne time is just too little, pilots usually don’t take any action below approximately 400ft, and these switches are so ‘underused’ that a pilot would not find them instantaneously in a high stress situation.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
Last edited by Senior Pilot; 14th Jun 2025 at 19:08 . Reason: Double posting of image
2025-06-14T12:48:00
permalink Post: 11901455
Sorry but before you make a statement like this, you better read up on the "complexity and sophistication" of the latest business jets like the Gulfstreams and Global Express.
The Global Express has 4 engine driven generators, one APU generator, one RAT generator that provide AC and DC power to the aircraft's systems. On the hydraulic side, the aircraft has 3 fully independent and redundant hydraulic systems which power all flight control surfaces the exception being, the slats and flaps are AC power driven and are available even with only the RAT providing power. The 3 hydraulic systems are powered from each engine backed up by 2 EDPs (system 1 and 2) and system 3 is powered by 2 EDPs only. The RAT powers system 3 via one of its EDPs. In the event of a dual engine failure the RAT would deploy automatically and power the AC essential plus DC essential busses and one EDP on system 3. The APU is available to you up to FL450 and will supply full AC power but bleed air only up to FL300.
The Global Express has 4 engine driven generators, one APU generator, one RAT generator that provide AC and DC power to the aircraft's systems. On the hydraulic side, the aircraft has 3 fully independent and redundant hydraulic systems which power all flight control surfaces the exception being, the slats and flaps are AC power driven and are available even with only the RAT providing power. The 3 hydraulic systems are powered from each engine backed up by 2 EDPs (system 1 and 2) and system 3 is powered by 2 EDPs only. The RAT powers system 3 via one of its EDPs. In the event of a dual engine failure the RAT would deploy automatically and power the AC essential plus DC essential busses and one EDP on system 3. The APU is available to you up to FL450 and will supply full AC power but bleed air only up to FL300.
Elsewhere, there is a picture of the tail wreckage showing what looks likethe APU door partially open. The panel is otherwise undamaged indicating not caused by post-impact. I’ll try to poach it
its here, but wrong file extension on the photo
https://www.nytimes.com/interactive/...smid=url-share
Last edited by galaxy flyer; 14th Jun 2025 at 13:52 .
2025-06-14T14:09:00
permalink Post: 11901517
Max EGzt and autorelight
Combining all the bits and pieces of info from this thread so far, IMO we can theoretically sequence it thus using the video from the left:
00:18 Rotation. Normal takeoff config.
00:24 Gear up starts. per Raffael with FF.
......... FR24 ADSB last transmission (71ft, 172kt) just before runway threshold. Matches with video aircraft altitude at 1/2 wingspan.
......... ? Full power flameout leaves N2 ~ 60%; Airspeed < 200k so N2 will decay to 15% in 8-10s?
......... ? Takeoff EGT of 900C needs 25-35s to fall below 250C ?
00:27 Gear up stops. per Raffael with FF. Bogies tilted.
......... ? APU starts. 20-55s to 95%N?
......... Per 787 dual-engine fail/stall memory items, PM initiates Fuel Cutoff and Run.
00:28 Visible loss of thrust. Alt ~ 200ft using aircraft wingspan as measure.
......... Matches with eyewitness "within 5-10s ... it was stuck in the air".
......... Per 787 dual-engine fail/stall memory items, PM initiates RAT Switch for 1s. Whether auto or manual, the RAT initiates.
......... RAT "bang" heard by survivor
......... RAT coming online accounts for eyewitness "lights started flickering green and white".
......... Per 787 QRH below 1000ft, PF makes no change to Main Landing Gear and flaps, aircraft pointed straight for best glide.
00:31 Descending visibly, somewhere beyond the runway threshold. Alt ~ 200ft using aircraft wingspan as measure.
......... ? Because EGT > 250C FADEC blocks fuel (T-HOT hot restart inhibit?) so no relight though N2 > 15% ?
......... 787 glide ratio between 16:1 to 25:1 with MLG down, Flaps 5. About 15-20s and 3-5000ft of glide from 200ft?
......... Some flap accounts for the ground pictures.
00:34 ? N2 has presumably decayed to 15%, FADEC flips to X-START: airspeed outside envelope? No hope of relight now.
......... PM/PF transmits Mayday?
......... Video showing RAT deployed.
00:46 APU reaches some fraction of 95%N (APU sound accounting for survivor's perception of thrust?).
00:48 Impact. 4200ft from descent start, 3990ft from airport boundary road. 17s from visible descent start.
if this is a valid sequence, the only remaining question is why the dual-engine failure at ~200ft agl?
with condolences to the families and people affected.
00:18 Rotation. Normal takeoff config.
00:24 Gear up starts. per Raffael with FF.
......... FR24 ADSB last transmission (71ft, 172kt) just before runway threshold. Matches with video aircraft altitude at 1/2 wingspan.
......... ? Full power flameout leaves N2 ~ 60%; Airspeed < 200k so N2 will decay to 15% in 8-10s?
......... ? Takeoff EGT of 900C needs 25-35s to fall below 250C ?
00:27 Gear up stops. per Raffael with FF. Bogies tilted.
......... ? APU starts. 20-55s to 95%N?
......... Per 787 dual-engine fail/stall memory items, PM initiates Fuel Cutoff and Run.
00:28 Visible loss of thrust. Alt ~ 200ft using aircraft wingspan as measure.
......... Matches with eyewitness "within 5-10s ... it was stuck in the air".
......... Per 787 dual-engine fail/stall memory items, PM initiates RAT Switch for 1s. Whether auto or manual, the RAT initiates.
......... RAT "bang" heard by survivor
......... RAT coming online accounts for eyewitness "lights started flickering green and white".
......... Per 787 QRH below 1000ft, PF makes no change to Main Landing Gear and flaps, aircraft pointed straight for best glide.
00:31 Descending visibly, somewhere beyond the runway threshold. Alt ~ 200ft using aircraft wingspan as measure.
......... ? Because EGT > 250C FADEC blocks fuel (T-HOT hot restart inhibit?) so no relight though N2 > 15% ?
......... 787 glide ratio between 16:1 to 25:1 with MLG down, Flaps 5. About 15-20s and 3-5000ft of glide from 200ft?
......... Some flap accounts for the ground pictures.
00:34 ? N2 has presumably decayed to 15%, FADEC flips to X-START: airspeed outside envelope? No hope of relight now.
......... PM/PF transmits Mayday?
......... Video showing RAT deployed.
00:46 APU reaches some fraction of 95%N (APU sound accounting for survivor's perception of thrust?).
00:48 Impact. 4200ft from descent start, 3990ft from airport boundary road. 17s from visible descent start.
if this is a valid sequence, the only remaining question is why the dual-engine failure at ~200ft agl?
with condolences to the families and people affected.
In-flight, the Autorelight function should attempt to restart the engine as soon as a flameout is detected, and for an engine flaming out at high power it might catch it before it even goes sub-idle. Generally, Autorelight will continue attempting until some cutoff N2 at which time it will stop attempting, or if the pilot move the fuel switch to Cutoff. And while the EEC is still powered (via its own PMA) down to roughly 10% N2, the ignition exciters required for Autorelight do get their power from the airplane.
2025-06-14T14:35:00
permalink Post: 11901533
Even though there is no point speculating about the cause of this accident, it is the nature of the beast to have questions. As pilots (most of us at least), we do have an inquiring mindset.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
I'm asking this as a question, not claming to have "cracked the case". I'm not an aviation fuel system expert. Can anyone who is or has direct knowledge comment? The reason I thought of it is that I've seen very similar issues with diesel engine systems where the mechanical injection pump can typically suck fuel but is normally fed with pressure. An internal (or external) leak can cause it to not be able to suction fuel properly but as long as the other pumps keep it pressurized it can work forever.
2 users liked this post.
2025-06-14T15:32:00
permalink Post: 11901578
APU ON for take-off
Woulda shoulda coulda and might not have changed this particular outcome, but is there a case in taking off with APU ON? It would give some level of redundancy for electrics and hydraulics and perhaps avoid the added shock and workload of losing thrust, electrics and hydraulics pretty much simultaneously in a rare scenario like this one. During Hudson river accident, APU ON was the first thing Sully did (apart from saying \x91my aircraft\x92) but he had more altitude and speed and electrics and the gear up. I know there are other considerations for using or not using APU depending on flight phase, but if it is safe and within design parameters, perhaps SOPs should give pilots discretion on whether or not they use the APU for critical flight phases? Just a thought.
1 user liked this post.
2025-06-14T16:05:00
permalink Post: 11901610
Woulda shoulda coulda and might not have changed this particular outcome, but is there a case in taking off with APU ON? It would give some level of redundancy for electrics and hydraulics and perhaps avoid the added shock and workload of losing thrust, electrics and hydraulics pretty much simultaneously in a rare scenario like this one. During Hudson river accident, APU ON was the first thing Sully did (apart from saying \x91my aircraft\x92) but he had more altitude and speed and electrics and the gear up. I know there are other considerations for using or not using APU depending on flight phase, but if it is safe and within design parameters, perhaps SOPs should give pilots discretion on whether or not they use the APU for critical flight phases? Just a thought.
Furthernore mandating use of the APU would be quite hyppocratic, if reduced thrust take-offs, single engine taxi outs, landing with less than maximum available flap or other cost saving measures were still allowed.
1 user liked this post.
2025-06-14T16:09:00
permalink Post: 11901613
Yes, in one in a million (billion?) cases. If every take off and landing would be with the APU runing, there would be [some small number] of cases where the APU would shutdown at the critical moment causing electrics to reconfigure or the APU could shed a blade or catch a fire. Those events should not cause an accident, but then aircraft shouldn\x92t just fall out of the sky 30 seconds after lift off.
Furthernore mandating use of the APU would be quite hyppocratic, if reduced thrust take-offs, single engine taxi outs, landing with less than maximum available flap or other cost saving measures were still allowed.
Furthernore mandating use of the APU would be quite hyppocratic, if reduced thrust take-offs, single engine taxi outs, landing with less than maximum available flap or other cost saving measures were still allowed.
2 users liked this post.
2025-06-14T16:40:00
permalink Post: 11901639
1 user liked this post.
2025-06-14T17:01:00
permalink Post: 11901660
Fair point Pip.
I just saw a picture of the tail (taken from above) and the APU door is partially open?
I believe the 787 has a similar APU automatic start function with loss of AC power just like the 777. It looks like the APU door was starting to open to allow for an auto start.. Similar situation to that BA 777 that landed short in LHR due to fuel icing.
Its looking more and more like an AC power loss.
Interestingly, the DGAC order for AI maintenance to check those random 787 systems are all associated in some way to an automatic RAT deployment.
I just saw a picture of the tail (taken from above) and the APU door is partially open?
I believe the 787 has a similar APU automatic start function with loss of AC power just like the 777. It looks like the APU door was starting to open to allow for an auto start.. Similar situation to that BA 777 that landed short in LHR due to fuel icing.
Its looking more and more like an AC power loss.
Interestingly, the DGAC order for AI maintenance to check those random 787 systems are all associated in some way to an automatic RAT deployment.
5 users liked this post.
2025-06-14T17:07:00
permalink Post: 11901664
2025-06-14T17:21:00
permalink Post: 11901675
I flew on a BA A320 just a few days ago that departed with a non-functioning APU.
1 user 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)
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2025-06-14T17:40:00
permalink Post: 11901684
1 user liked this post.
2025-06-14T17:52:00
permalink Post: 11901690
On the B787/B788, you'd be expected to run it because you need the electrical power to spool up at least one of the engines, after which the one running engine can provide power to start the one yet to be started engine.
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)