June 14, 2025, 12:43:00 GMT
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 June 2025 at 19:08 . Reason: Double posting of image
June 14, 2025, 12:56:00 GMT
permalink Post: 11901460
I asked this yesterday, and was told no. You have to pull them out before you can move them up or down. So you can't operate them if, say, your hand slips violently off the throttle lever and drops down into the switches.
June 14, 2025, 13:07:00 GMT
permalink Post: 11901468
This crash reminds me of the crash of a 747 Military Transport plane at an airbase in Afghanistan.
Shortly after TO, the cargo shifted, the plane became very tail heavy and stalled a few hundred feet in the air. It was the weirdest sight. For what seems a few seconds, the plane just seemed to hang there, presumably on engine thrust.
In this crash, the problem also seems to occur soon after rotation, as if something inside moved in response to its change in attitude. Maybe a loose connection on a main bus cable that moved... Maybe only a millimetre. Or a tool left inside an electrical cabinet slid somewhere it shouldn't. The possibilities are numerous, and without a lot more information, there's no way to know what caused this. I suspect a major electrical fault, probably intermittent.
How long would it take to restart those engines after a Fuel Cutoff flame out? Is that what happened, just before impact?
Shortly after TO, the cargo shifted, the plane became very tail heavy and stalled a few hundred feet in the air. It was the weirdest sight. For what seems a few seconds, the plane just seemed to hang there, presumably on engine thrust.
In this crash, the problem also seems to occur soon after rotation, as if something inside moved in response to its change in attitude. Maybe a loose connection on a main bus cable that moved... Maybe only a millimetre. Or a tool left inside an electrical cabinet slid somewhere it shouldn't. The possibilities are numerous, and without a lot more information, there's no way to know what caused this. I suspect a major electrical fault, probably intermittent.
How long would it take to restart those engines after a Fuel Cutoff flame out? Is that what happened, just before impact?
June 14, 2025, 13:40:00 GMT
permalink Post: 11901495
Fuel cutoff switches
My next question, again I believe not discussed, is what do the 787 Fuel Cutoff switches actually do? Obviously, they cut off the fuel supplies to the engines - pretty important in engine fire and other scenarios, but goes without saying. The real question is, what do they activate (or deactivate)? I'm assuming a simple solenoid valve, which is open when powered and closed when unpowered, but of course, there will (certainly) be Electro-Mechanical or Solid-State (Electronic) relays between the switches and the (solenoid valves).
I guess the next obvious question is, is there anything else that can turn off those Fuel Cutoff Valves - a computer condition for example. I'm assuming not, but I think it needs to be considered.
Taking each switch individually, next, since this is part of an electrical circuit, and of necessity must include Electrical Relays, there is certainly at least one and in all probability two electric Power Sources involved in this circuit. One supply which passes through the switch to activate the relay, and, I'm assuming, a second, higher current and probably higher voltage supply which drives the (solenoid?) valve.
As I see it, interrupting either supply will have the same effect - if the system is wired in the Positive-Postive sense, meaning a current through the switch causes the relay to pass a current through the (solenoid). If either of these supplies is cut, the Fuel Shutoffs will shut off the fuel. So, the question is, where do these supplies come from, and under what circumstances could they be cut off?
Sure, it looks to some (myself included) like a near simultaneous cutoff of both engines, but that doesn't have to have been caused by either of the pilots. I know there is huge redundancy built into the 787 Electrical Systems, but some of the evidence is suggesting that there was something not right with the plane's electrical system. I'm also fairly sure that there will be parts and places where certain faults can take the system down, despite the redundancy. I can't say where, but it's very difficult to design a perfect system, especially where there has to be transfers between multiple potential supplies and single actuators, motors or valves.
Having spent years repairing electrical and electronic systems, I know that the most difficult of all electrical faults are the intermittent ones. And I suspect that this is at the root of this crash. An intermittent or faulty AOA sensor has "caused" (provoked) multiple famous crashes... Can't find the one I'm looking for (pre-1980, I think) as the Max AOA issues dominate.
I can cite a very personal example, which involved the electrical supply to my house. I had several computers running 24x365 so of course, ran them off a UPS, which turned out to be a very good thing. I started to notice that at certain times, the UPS would activate - it would cut in and take over the computer loads, its alarm would go off to indicate a power fault. But the power was still on! This carried on for weeks and I initially blamed the UPS. Then, I noticed that it only happened on very hot afternoons... Long story short, the fault was caused by an electrical linesman, probably 30 years earlier, failing to tighten up a joint clamp on the phase wire to our house, across the street. Heating caused expansion then movement, and the power would momentarily go off then back on, and the UPS detected this. I note that this crash was on a hot day, and maybe this plane (which I believe was repositioned for the flight), had not been operating in such high temperatures recently, meaning the problem went unnoticed.
I guess the next obvious question is, is there anything else that can turn off those Fuel Cutoff Valves - a computer condition for example. I'm assuming not, but I think it needs to be considered.
Taking each switch individually, next, since this is part of an electrical circuit, and of necessity must include Electrical Relays, there is certainly at least one and in all probability two electric Power Sources involved in this circuit. One supply which passes through the switch to activate the relay, and, I'm assuming, a second, higher current and probably higher voltage supply which drives the (solenoid?) valve.
As I see it, interrupting either supply will have the same effect - if the system is wired in the Positive-Postive sense, meaning a current through the switch causes the relay to pass a current through the (solenoid). If either of these supplies is cut, the Fuel Shutoffs will shut off the fuel. So, the question is, where do these supplies come from, and under what circumstances could they be cut off?
Sure, it looks to some (myself included) like a near simultaneous cutoff of both engines, but that doesn't have to have been caused by either of the pilots. I know there is huge redundancy built into the 787 Electrical Systems, but some of the evidence is suggesting that there was something not right with the plane's electrical system. I'm also fairly sure that there will be parts and places where certain faults can take the system down, despite the redundancy. I can't say where, but it's very difficult to design a perfect system, especially where there has to be transfers between multiple potential supplies and single actuators, motors or valves.
Having spent years repairing electrical and electronic systems, I know that the most difficult of all electrical faults are the intermittent ones. And I suspect that this is at the root of this crash. An intermittent or faulty AOA sensor has "caused" (provoked) multiple famous crashes... Can't find the one I'm looking for (pre-1980, I think) as the Max AOA issues dominate.
I can cite a very personal example, which involved the electrical supply to my house. I had several computers running 24x365 so of course, ran them off a UPS, which turned out to be a very good thing. I started to notice that at certain times, the UPS would activate - it would cut in and take over the computer loads, its alarm would go off to indicate a power fault. But the power was still on! This carried on for weeks and I initially blamed the UPS. Then, I noticed that it only happened on very hot afternoons... Long story short, the fault was caused by an electrical linesman, probably 30 years earlier, failing to tighten up a joint clamp on the phase wire to our house, across the street. Heating caused expansion then movement, and the power would momentarily go off then back on, and the UPS detected this. I note that this crash was on a hot day, and maybe this plane (which I believe was repositioned for the flight), had not been operating in such high temperatures recently, meaning the problem went unnoticed.
June 14, 2025, 13:43:00 GMT
permalink Post: 11901499
Reports coming in that Indian regulator has sent out a note for inspection of all GenX engines on the 787
June 14, 2025, 14:04:00 GMT
permalink Post: 11901512
A question for B787 pilots or mechanics.
Is it correct to assume that the EFSOV valves are actuated by the fuel flow and controlled by an electric signal coming directly from the relevant EEC. Meaning that the simultaneous closing of the 2 valves would require an improbable simultaneous failure of the 2 EEC, or that the 2 fuel switches are flipped from "run" to "cut-off" at almost the same time, feeding the same command to the 2 EEC.
And that the spar fuel valves are electrically actuated with the power coming from the hot battery bus and the signal coming from the aft electronic bay (possibly from the same control unit)?
(Note: not pretending to be a commercial pilot; just IR rated PPL).
Is it correct to assume that the EFSOV valves are actuated by the fuel flow and controlled by an electric signal coming directly from the relevant EEC. Meaning that the simultaneous closing of the 2 valves would require an improbable simultaneous failure of the 2 EEC, or that the 2 fuel switches are flipped from "run" to "cut-off" at almost the same time, feeding the same command to the 2 EEC.
And that the spar fuel valves are electrically actuated with the power coming from the hot battery bus and the signal coming from the aft electronic bay (possibly from the same control unit)?
(Note: not pretending to be a commercial pilot; just IR rated PPL).
June 14, 2025, 14:09:00 GMT
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.
June 14, 2025, 14:35:00 GMT
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.
June 14, 2025, 15:35:00 GMT
permalink Post: 11901582
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..
And if the Captain(?) mentioned power loss in his Mayday. Was he referring to electrical power loss?
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..
And if the Captain(?) mentioned power loss in his Mayday. Was he referring to electrical power loss?
June 14, 2025, 15:55:00 GMT
permalink Post: 11901596
June 14, 2025, 16:02:00 GMT
permalink Post: 11901606
Once the fuel LP and HP Shutoff valves are open, they stay there until commanded otherwise so an AC power failure will have no affect. They will remain in the last position at the time of the loss. They will then be on suction feed which, by design, should enable the engines to maintain their selected thrust level. They ‘should’ not suffer any loss of thrust.
Edit note: the engines have their own engine driven fuel pumps which can deliver anywhere up to and above 1,100 psi.
June 14, 2025, 16:04:00 GMT
permalink Post: 11901609
I believe the point being made by the person you quoted was that the noise of the engines might have become much quieter
before
the start of the video with the possible RAT noise (the one where the plane passes almost overhead).
June 14, 2025, 16:21:00 GMT
permalink Post: 11901619
During the nearly two years that elapsed between AF 447 disappearing and the recovery of the flight data recorders nobody suggested that the PF might have, unwittingly, flown the aircraft, stalled, into the ocean.
AI 171 may prove to also have a totally unpredicted cause.
AI 171 may prove to also have a totally unpredicted cause.
I\x92m absolutely not speculating this is the case here, but could you not achieve the effect this flight suffered by just switching off the fuel control switches at 100ft on takeoff?
There are now so many assumptions based on the assumed state of flap, RAT etc that it\x92s becoming pointless speculation.
June 14, 2025, 16:39:00 GMT
permalink Post: 11901637
The complex software.
Can anyone familiar with the 787 built in overspeed protections comment on what could possibly override a pilots TOGA button command or fire walling the throttles?
I am presuming that at some point just prior to the mayday call the pilots would have just commanded \x91full\x92 thrust and received no or a significantly mild response.
I don\x92t think fuel contamination, birds or anything else external to the aircraft affected this crash. There is no evidence of it.
could some combination of already MEL items and one or more faulty inputs to the computers cause the aircraft to \x91protect\x92 itself into the ground? Regardless of throttle position?
I am thinking - ground/air logic, faulty airspeed sense, faulty AoA sense or other.
I am presuming that at some point just prior to the mayday call the pilots would have just commanded \x91full\x92 thrust and received no or a significantly mild response.
I don\x92t think fuel contamination, birds or anything else external to the aircraft affected this crash. There is no evidence of it.
could some combination of already MEL items and one or more faulty inputs to the computers cause the aircraft to \x91protect\x92 itself into the ground? Regardless of throttle position?
I am thinking - ground/air logic, faulty airspeed sense, faulty AoA sense or other.
June 14, 2025, 17:35:00 GMT
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)
June 14, 2025, 17:42:00 GMT
permalink Post: 11901687
June 14, 2025, 17:53:00 GMT
permalink Post: 11901693
I have seen your previous posts about this, and I happen to agree. Visually, as a lay man non visuals expert, I am in your \xabcamp.\xbb
However, the rat is small, and the artifacts are plentiful. Small sensor, compressed video, compressed upload, zoom, it is in short an awful source.
However, the RAT is a much better noisemaker, and the audio signature is much more obvious than it\x92s visual appearance in this case, and though the recording isn\x92t fantastic quality, there was more than enough information there to objectively conclude the RAT is out. And that is my professional, on the weekend, opinion.
I want to ask a pretty frank question for all of you, and I hope it is ok, from an audio specialist non-pilot:
Provided the engines spooled down. Provided the RAT is out. (There are no explosions, no bird strikes.)
Isn\x92t software and previous electrical failures a red herring too?Would anything but a complete fuel shut off lead to this result? That still leaves everything from the Fate is the Hunter plot, to Airbus A350 center consoles and Alaska 2059 open as root causes.
However, the rat is small, and the artifacts are plentiful. Small sensor, compressed video, compressed upload, zoom, it is in short an awful source.
However, the RAT is a much better noisemaker, and the audio signature is much more obvious than it\x92s visual appearance in this case, and though the recording isn\x92t fantastic quality, there was more than enough information there to objectively conclude the RAT is out. And that is my professional, on the weekend, opinion.
I want to ask a pretty frank question for all of you, and I hope it is ok, from an audio specialist non-pilot:
Provided the engines spooled down. Provided the RAT is out. (There are no explosions, no bird strikes.)
Isn\x92t software and previous electrical failures a red herring too?Would anything but a complete fuel shut off lead to this result? That still leaves everything from the Fate is the Hunter plot, to Airbus A350 center consoles and Alaska 2059 open as root causes.
June 14, 2025, 18:08:00 GMT
permalink Post: 11901702
(the manual implies two in a pinch, but you shed all loads except the engine starters and a fuel pump)
June 14, 2025, 18:43:00 GMT
permalink Post: 11901720
There should not be a max pre-start EGT limit in-flight - that should only occur on the ground for a pilot-initiated Autostart where the starting EGT redlines are lower than for in-flight.
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.
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.
Could this mean that because there doesn't seem to have been any recovery once descent started, there was no fuel flow to support autorelight? Or that there was fuel flow and autorelight may have succeeded but there wasn't enough thrust generated before impact? From the video total descent time was only 17-20s. I guess what I'm asking is what would be the total cycle time if the first autorelight succeeded: flameout -> autorelight -> useful thrust? And if the PM executed dual-engine fail memory item fuel cutoff to run, how would that change the sequence?
June 14, 2025, 19:26:00 GMT
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.