June 13, 2025, 07:19:00 GMT
permalink Post: 11900098
On an auto throttle equipped aircraft, if for whatever reason the computer commands a thrust reduction, what will happen if you have you hand on the thrust levers applying take off thrust?
I wonder if startle effect would prevent a normally trained pilot from moving the thrust levers forward once the aircraft does not climb as expected?
I wonder if startle effect would prevent a normally trained pilot from moving the thrust levers forward once the aircraft does not climb as expected?
June 13, 2025, 11:18:00 GMT
permalink Post: 11900373
Plane crash near Ahmedabad
Here is a very unlikely scenario. It may be possible that there was nothing wrong with the aircraft.
We have been told the experience levels of the pilots but not how long they have been flying the 787.
The 787 is very automatic and, in my experience, the easiest aircraft to fly. It does a lot of things for you and reminds you of things that you may have forgotten to do. For that reason, in my opinion it is also the safest aircraft around. However, you have to understand what the automatics are doing in order to manage it correctly.
By putting the departure route into the FMC you set up the lateral navigation and also the vertical navigation including speeds and altitudes. After take-off the FMC will command you initially to fly at up to V2 + 20 until flap retraction ( normally no lower than 1000 feet agl), and then increase the speed with flap retraction until initial climb speed and then final climb speed above FL 100.
If your first altitude restriction on departure is 4000 feet (which will be in the FMC) and VNAV is engaged you will level at 4000 feet. But, if prior to departure, you put 3000 feet in the altitude window (maybe as instructed by ATC) the aircraft will level at 3000 feet.
If I remember correctly LNAV engages at 50 feet and VNAV engages at 400 feet agl. And, I may be mistaken, but I think that the auto-pilot could be engaged at 100 feet agl.
Now, I am probably wrong about this, but if you forget to set the altitude window to the first altitude in departure and leave it at 0 (which with some airlines the previous crew will do on shutdown) the following might possibly occur. At 50 feet LNAV engages, at 100 feet the autopilot engages, at 400 feet VNAV engages but as the altitude window is set to 0 the aircraft (on autopilot) now descends to capture 0 feet. The speed at this point in VNAV is low (max V2 + 20 kts) so, to maintain that, both thrust levers close. This, of course, would be totally unexpected and could have a startle effect. If you do not realise what has caused this you might think that there is a problem with the engines and you have very little time to deal with it. I would suggest that putting out a Mayday call at this stage is not a good use of time.
As I stated at the beginning this is probably very unlikely and may not be possible, but could be tried in a simulator.
We have been told the experience levels of the pilots but not how long they have been flying the 787.
The 787 is very automatic and, in my experience, the easiest aircraft to fly. It does a lot of things for you and reminds you of things that you may have forgotten to do. For that reason, in my opinion it is also the safest aircraft around. However, you have to understand what the automatics are doing in order to manage it correctly.
By putting the departure route into the FMC you set up the lateral navigation and also the vertical navigation including speeds and altitudes. After take-off the FMC will command you initially to fly at up to V2 + 20 until flap retraction ( normally no lower than 1000 feet agl), and then increase the speed with flap retraction until initial climb speed and then final climb speed above FL 100.
If your first altitude restriction on departure is 4000 feet (which will be in the FMC) and VNAV is engaged you will level at 4000 feet. But, if prior to departure, you put 3000 feet in the altitude window (maybe as instructed by ATC) the aircraft will level at 3000 feet.
If I remember correctly LNAV engages at 50 feet and VNAV engages at 400 feet agl. And, I may be mistaken, but I think that the auto-pilot could be engaged at 100 feet agl.
Now, I am probably wrong about this, but if you forget to set the altitude window to the first altitude in departure and leave it at 0 (which with some airlines the previous crew will do on shutdown) the following might possibly occur. At 50 feet LNAV engages, at 100 feet the autopilot engages, at 400 feet VNAV engages but as the altitude window is set to 0 the aircraft (on autopilot) now descends to capture 0 feet. The speed at this point in VNAV is low (max V2 + 20 kts) so, to maintain that, both thrust levers close. This, of course, would be totally unexpected and could have a startle effect. If you do not realise what has caused this you might think that there is a problem with the engines and you have very little time to deal with it. I would suggest that putting out a Mayday call at this stage is not a good use of time.
As I stated at the beginning this is probably very unlikely and may not be possible, but could be tried in a simulator.
June 13, 2025, 11:34:00 GMT
permalink Post: 11900389
It's fine that the \x93Enhanced Airborne Flight Recorders\x94 have 10 minutes battery backup. If the bits of equipment/sensors sending data to be recorded don't have power, you will be recording 10 minutes of silence/blank data.
The concept of powering 'critical (sensor) equipment' has been floated - the problem being that it must be possible to power down malfunctioning equipment in case of fire - real or suspected. Having independent power supplies and battery back-ups all around the airframe, each with an ability to lose their magic smoke, is a poor idea.
Commercial passenger jet aircraft already have robust power supplies with multiple generators and emergency battery support. However, if one malfunctions, rather than fails completely, it can be difficult to decide which one to disable, as it can cause problems in all systems.
The concept of powering 'critical (sensor) equipment' has been floated - the problem being that it must be possible to power down malfunctioning equipment in case of fire - real or suspected. Having independent power supplies and battery back-ups all around the airframe, each with an ability to lose their magic smoke, is a poor idea.
Commercial passenger jet aircraft already have robust power supplies with multiple generators and emergency battery support. However, if one malfunctions, rather than fails completely, it can be difficult to decide which one to disable, as it can cause problems in all systems.
Once the RAT deployed at least some data should have come back.
Now, I am probably wrong about this, but if you forget to set the altitude window to the first altitude in departure and leave it at 0 (which with some airlines the previous crew will do on shutdown) the following might possibly occur. At 50 feet LNAV engages, at 100 feet the autopilot engages, at 400 feet VNAV engages but as the altitude window is set to 0 the aircraft (on autopilot) now descends to capture 0 feet. The speed at this point in VNAV is low (max V2 + 20 kts) so, to maintain that, both thrust levers close. This, of course, would be totally unexpected and could have a startle effect. If you do not realise what has caused this you might think that there is a problem with the engines and you have very little time to deal with it. I would suggest that putting out a Mayday call at this stage is not a good use of time.
As I stated at the beginning this is probably very unlikely and may not be possible, but could be tried in a simulator.
As I stated at the beginning this is probably very unlikely and may not be possible, but could be tried in a simulator.
It does not explain the RAT and generally you would expect crews to shove the thrust levers fully forward.
June 13, 2025, 12:22:00 GMT
permalink Post: 11900444
Here is a very unlikely scenario. It may be possible that there was nothing wrong with the aircraft.
We have been told the experience levels of the pilots but not how long they have been flying the 787.
The 787 is very automatic and, in my experience, the easiest aircraft to fly. It does a lot of things for you and reminds you of things that you may have forgotten to do. For that reason, in my opinion it is also the safest aircraft around. However, you have to understand what the automatics are doing in order to manage it correctly.
By putting the departure route into the FMC you set up the lateral navigation and also the vertical navigation including speeds and altitudes. After take-off the FMC will command you initially to fly at up to V2 + 20 until flap retraction ( normally no lower than 1000 feet agl), and then increase the speed with flap retraction until initial climb speed and then final climb speed above FL 100.
If your first altitude restriction on departure is 4000 feet (which will be in the FMC) and VNAV is engaged you will level at 4000 feet. But, if prior to departure, you put 3000 feet in the altitude window (maybe as instructed by ATC) the aircraft will level at 3000 feet.
If I remember correctly LNAV engages at 50 feet and VNAV engages at 400 feet agl. And, I may be mistaken, but I think that the auto-pilot could be engaged at 100 feet agl.
Now, I am probably wrong about this, but if you forget to set the altitude window to the first altitude in departure and leave it at 0 (which with some airlines the previous crew will do on shutdown) the following might possibly occur. At 50 feet LNAV engages, at 100 feet the autopilot engages, at 400 feet VNAV engages but as the altitude window is set to 0 the aircraft (on autopilot) now descends to capture 0 feet. The speed at this point in VNAV is low (max V2 + 20 kts) so, to maintain that, both thrust levers close. This, of course, would be totally unexpected and could have a startle effect. If you do not realise what has caused this you might think that there is a problem with the engines and you have very little time to deal with it. I would suggest that putting out a Mayday call at this stage is not a good use of time.
As I stated at the beginning this is probably very unlikely and may not be possible, but could be tried in a simulator.
We have been told the experience levels of the pilots but not how long they have been flying the 787.
The 787 is very automatic and, in my experience, the easiest aircraft to fly. It does a lot of things for you and reminds you of things that you may have forgotten to do. For that reason, in my opinion it is also the safest aircraft around. However, you have to understand what the automatics are doing in order to manage it correctly.
By putting the departure route into the FMC you set up the lateral navigation and also the vertical navigation including speeds and altitudes. After take-off the FMC will command you initially to fly at up to V2 + 20 until flap retraction ( normally no lower than 1000 feet agl), and then increase the speed with flap retraction until initial climb speed and then final climb speed above FL 100.
If your first altitude restriction on departure is 4000 feet (which will be in the FMC) and VNAV is engaged you will level at 4000 feet. But, if prior to departure, you put 3000 feet in the altitude window (maybe as instructed by ATC) the aircraft will level at 3000 feet.
If I remember correctly LNAV engages at 50 feet and VNAV engages at 400 feet agl. And, I may be mistaken, but I think that the auto-pilot could be engaged at 100 feet agl.
Now, I am probably wrong about this, but if you forget to set the altitude window to the first altitude in departure and leave it at 0 (which with some airlines the previous crew will do on shutdown) the following might possibly occur. At 50 feet LNAV engages, at 100 feet the autopilot engages, at 400 feet VNAV engages but as the altitude window is set to 0 the aircraft (on autopilot) now descends to capture 0 feet. The speed at this point in VNAV is low (max V2 + 20 kts) so, to maintain that, both thrust levers close. This, of course, would be totally unexpected and could have a startle effect. If you do not realise what has caused this you might think that there is a problem with the engines and you have very little time to deal with it. I would suggest that putting out a Mayday call at this stage is not a good use of time.
As I stated at the beginning this is probably very unlikely and may not be possible, but could be tried in a simulator.
Last edited by JG1; 13th June 2025 at 13:15 .
June 13, 2025, 14:40:00 GMT
permalink Post: 11900581
Regarding the comments about who should be allowed to comment on such threads. I like the fact the mods have taken a pragmatic view of this. Theres a reason many in the accident investigation field come from an engineering background. Whilst highly experienced pilots are clearly crucial on an SME level, there can be a tendency for iwouldnthavedoneitthatway-itis. This can at times hinder investigations where an open mind free from confirmation bias is essential.
June 13, 2025, 23:20:00 GMT
permalink Post: 11900992
Gear possibly not selected up due to startle effect after a major event.
Bird strike unlikely to knock out both engines unless there is a flock of them, you might get a single bird into one engine but the odds of two birds each hitting separate engines are pretty long.
Aircraft often yaw slightly after takeoff, particularly with a crosswind which may be stronger in the air than on the ground.
Air India have had issues with pilot training and standards, reports not too long ago of Indian flight schools selling logbook hours which didn't involve any time in an aircraft.
Numerous reports of cabin maintenance issues with Air India, if they can't fix the seats and IFE possibly they can't fix other things.
These days, high resolution cameras aren't prohibitively expensive and installing a few at airports would be better than mobile phone footage.
Wouldn't an incorrect altitude setting pitch the nose downwards and keep power on for the aircraft to accelerate ?
Boeing philosophy is for the pilot to have ultimate control of the aircraft, Airbus try to protect the aircraft from pilot error. Inadvertent flap retraction on an Airbus will result in the slats remaining out and TOGA, which whilst not a guarantee, has saved a few necks.
Possible issue with the particular type of engines fitted to that aircraft, even worse would be an aircraft issue which would have had the same result regardless of the engine manufacturer.
The B787 has enough OEBs on it to fill up a small binder if printed out, some of which state that the issue is known about and the company is working on it.
Hopefully, given the time that the aircraft has been in service, it won't be a systemic problem suddenly coming to light in the way MCAS did on the B737 MAX relatively soon after EIS.
Bird strike unlikely to knock out both engines unless there is a flock of them, you might get a single bird into one engine but the odds of two birds each hitting separate engines are pretty long.
Aircraft often yaw slightly after takeoff, particularly with a crosswind which may be stronger in the air than on the ground.
Air India have had issues with pilot training and standards, reports not too long ago of Indian flight schools selling logbook hours which didn't involve any time in an aircraft.
Numerous reports of cabin maintenance issues with Air India, if they can't fix the seats and IFE possibly they can't fix other things.
These days, high resolution cameras aren't prohibitively expensive and installing a few at airports would be better than mobile phone footage.
Wouldn't an incorrect altitude setting pitch the nose downwards and keep power on for the aircraft to accelerate ?
Boeing philosophy is for the pilot to have ultimate control of the aircraft, Airbus try to protect the aircraft from pilot error. Inadvertent flap retraction on an Airbus will result in the slats remaining out and TOGA, which whilst not a guarantee, has saved a few necks.
Possible issue with the particular type of engines fitted to that aircraft, even worse would be an aircraft issue which would have had the same result regardless of the engine manufacturer.
The B787 has enough OEBs on it to fill up a small binder if printed out, some of which state that the issue is known about and the company is working on it.
Hopefully, given the time that the aircraft has been in service, it won't be a systemic problem suddenly coming to light in the way MCAS did on the B737 MAX relatively soon after EIS.
June 21, 2025, 00:59:00 GMT
permalink Post: 11907419
It's starting to look more like a massive electrical or computer issue which resulted in both engines failing, the landing gear may have been left down longer than normal due to startle effect.
It could be maintenance related or a latent condition in the B787 which only occurred due to the required factors all being present on this occasion i.e. the holes in the Swiss cheese all lined up.
Boeing and Air India will be wanting to blame each other, hopefully having the UK AAIB involved will provide a balance as they don't have a dog in the fight.
If this turns out to be another MCAS, it will be difficult for Boeing to continue in it's present form. The B787 has been beset with problems since its introduction, the B777X has had numerous issues during development and the B737 is overdue for replacement. Airlines are starting to drop Boeing due to quality, safety and delivery issues. China is on the rise and if the C919 proves itself, it might be the main alternative to the A320.
It could be maintenance related or a latent condition in the B787 which only occurred due to the required factors all being present on this occasion i.e. the holes in the Swiss cheese all lined up.
Boeing and Air India will be wanting to blame each other, hopefully having the UK AAIB involved will provide a balance as they don't have a dog in the fight.
If this turns out to be another MCAS, it will be difficult for Boeing to continue in it's present form. The B787 has been beset with problems since its introduction, the B777X has had numerous issues during development and the B737 is overdue for replacement. Airlines are starting to drop Boeing due to quality, safety and delivery issues. China is on the rise and if the C919 proves itself, it might be the main alternative to the A320.
Last edited by krismiler; 21st June 2025 at 01:19 .
July 11, 2025, 22:15:00 GMT
permalink Post: 11919893
For those sky gods who confidently state they would reset the cutoff switches immediately I would say that 10 seconds is not a particularly unusual time for startle effect to impair cognition, especially for something as monumental and unexpected as a dual engine failure at rotation. One reference amongst many:
https://www.icao.int/Meetings/LOCI/P...Strategies.pdf
And for those who scoff at the possibility of the PM inadvertently operating the cutoff switches (which is done as frequently as operating the gear lever), I\x92d remind you that more than one Airbus has landed with its parking brake on after the PM inadvertently set it rather than arming the spoilers.
And for those who scoff at the possibility of the PM inadvertently operating the cutoff switches (which is done as frequently as operating the gear lever), I\x92d remind you that more than one Airbus has landed with its parking brake on after the PM inadvertently set it rather than arming the spoilers.
July 12, 2025, 03:55:00 GMT
permalink Post: 11920156
This is pure speculation but I can envision the following sequence of events that would match the timeline and the little we know from the CVR and sequence of events.
- While PF is concentrated on flying the airplane, PNF moves the switches from RUN to CUTOFF in quick succession (for whatever reason).
- While PF is concentrated on flying the airplane, PNF moves the switches from RUN to CUTOFF in quick succession (for whatever reason).
What reason would any 787 Training Captain have for doing that at rotation, or slightly after rotation?
Really. Think about that. It makes Zero Sense.
@tdracers's point about the startle effect is at least plausible.
July 12, 2025, 12:25:00 GMT
permalink Post: 11920578
AI171 Threads by Subject
I have rebuilt the site that organises these three threads by subject here:
https://paulross.github.io/pprune-th...171/index.html
Changes:
Raise issues here https://github.com/paulross/pprune-threads/issues or PM me.
Changes:
- Build threads up to July 12, 2025, 11:59:00 (built at July 12, 2025, 13:03:09).
- Add thread about the published report: Preliminary Air India crash report published
- Add subjects: "Guards", "Timeline (Preliminary Report)", "EICAS", "RUN/CUTOFF", "Special Airworthiness Information Bulletin", "SAIB NM-18-33", "Gear Lever", "Startle Effect" and "Cockpit Area Audio".
- Minor improvements to the index.html page.
Raise issues here https://github.com/paulross/pprune-threads/issues or PM me.
July 13, 2025, 18:03:00 GMT
permalink Post: 11921493
Electrical effects of engine rollback
As I understand it from previous discussions, without the APU, all electrical power except for that DC power provided by battery to essential systems would have been lost.
With the copilot as PF, would he have lost his instrument displays? If so, possibly additional startle effect and workload for him.
Why did the ADS-B information keep going on for so long? My understanding from previous threads was that loss of ADS-B was considered an indication of loss of electrical power.
What else would be expected with loss of power?
Some general speculation: I find it hard to understand the long delay from what must have been the onset of obvious issues to the time the first engine is set to "RUN". I wonder if much more cockpit dialog intervened, e.g. PF requesting PM to turn the fuel switches back on (since he had his hands full), and eventually operating the switches himself, with the delay and time gap between the two switches being turned to "RUN" being attributable to being preoccupied with flying the aircraft under trying conditions.
July 13, 2025, 18:39:00 GMT
permalink Post: 11921522
I would like to raise a subject that I don't believe has been discussed here since the Preliminary Report was published, namely what happened to the aircraft's electrical systems as a consequence of the dual engine rollback and thereafter (RAT deployment, partial engine recovery, etc.). Apologies if I've missed posts on this topic here, but I have tried to review all of this thread quickly after previously reading most of it in detail.
As I understand it from previous discussions, without the APU, all electrical power except for that DC power provided by battery to essential systems would have been lost.
With the copilot as PF, would he have lost his instrument displays? If so, possibly additional startle effect and workload for him.
Why did the ADS-B information keep going on for so long? My understanding from previous threads was that loss of ADS-B was considered an indication of loss of electrical power.
What else would be expected with loss of power?
Some general speculation: I find it hard to understand the long delay from what must have been the onset of obvious issues to the time the first engine is set to "RUN". I wonder if much more cockpit dialog intervened, e.g. PF requesting PM to turn the fuel switches back on (since he had his hands full), and eventually operating the switches himself, with the delay and time gap between the two switches being turned to "RUN" being attributable to being preoccupied with flying the aircraft under trying conditions.
As I understand it from previous discussions, without the APU, all electrical power except for that DC power provided by battery to essential systems would have been lost.
With the copilot as PF, would he have lost his instrument displays? If so, possibly additional startle effect and workload for him.
Why did the ADS-B information keep going on for so long? My understanding from previous threads was that loss of ADS-B was considered an indication of loss of electrical power.
What else would be expected with loss of power?
Some general speculation: I find it hard to understand the long delay from what must have been the onset of obvious issues to the time the first engine is set to "RUN". I wonder if much more cockpit dialog intervened, e.g. PF requesting PM to turn the fuel switches back on (since he had his hands full), and eventually operating the switches himself, with the delay and time gap between the two switches being turned to "RUN" being attributable to being preoccupied with flying the aircraft under trying conditions.
There seems to be a period around second 12/13 post V1 where engines are (or should) be likely below idle, but prior to RAT power generation.
Note that the report explicitly states the RAT started providing hydraulic power 5 seconds after engine shutdown commenced. It doesn't reference electrical power. So we don't know whether this was at the same time - others may clarify re: RAT operation.
But either way, it would appear there would be a gap in power (which, incidentally, would tie in with the survivor commentary). But yet ADS data continued.
If in fact there was a momentary loss of power then that would contribute heavily to the startle and "delay" in refiring (although comments here make me think there wasn't really such a delay anyway).
(And incidentally would make what appears to be a really rather valiant attempt to save the aircraft even more impressive)
July 17, 2025, 16:12:00 GMT
permalink Post: 11924495
If it was a plan, the plan worked. Same with MH: if it was a plan, the plan worked. The aircraft disappeared without trace, taking all the evidence with it. These are plain facts.
If it was a plan, why do we assume this was the first attempt to execute it? The plan required accurate recognition of the effective window of action, and this would have taken research and practice. It required the FO flying, a takeoff over a built-up area to assure destruction, and a heavy fuel load for the same purpose. All of those conditions were met. If it were a plan, it appears that it included steps to create sufficient ambiguity that the proximate cause, whether premeditated suicide/mass murder or some kind of medical or cognitive event, could never be conclusively established. If this were part of the plan, it's working so far.
Others have pointed out open spaces either side of the flight path that might have facilitated a more survivable landing. The video clearly shows no attempt to turn. Why? Were these spaces actually reachable given the aircraft's vertical trajectory, or would a turn attempt in that condition merely precipitate a stall? Or was it startle effect? Or flying straight, hoping for power to come back?
If it was a plan, why do we assume this was the first attempt to execute it? The plan required accurate recognition of the effective window of action, and this would have taken research and practice. It required the FO flying, a takeoff over a built-up area to assure destruction, and a heavy fuel load for the same purpose. All of those conditions were met. If it were a plan, it appears that it included steps to create sufficient ambiguity that the proximate cause, whether premeditated suicide/mass murder or some kind of medical or cognitive event, could never be conclusively established. If this were part of the plan, it's working so far.
Others have pointed out open spaces either side of the flight path that might have facilitated a more survivable landing. The video clearly shows no attempt to turn. Why? Were these spaces actually reachable given the aircraft's vertical trajectory, or would a turn attempt in that condition merely precipitate a stall? Or was it startle effect? Or flying straight, hoping for power to come back?