Posts about: "paulross" [Posts: 22 Page: 1 of 2]¶

Originally Posted by Roo

Thanks for doing this.
Someone else created an external page a few days ago that indexed and sorted all the topical posts in this thread and the original one under major headings.
I can no longer find it. Did that get deleted by mods for non compliance or is it still around somewhere?

Originally Posted by Machinbird

This might be a useful starting point for understanding what could have gone wrong.

Originally Posted by MaybeItIs

https://paulross.github.io/pprune-th.../Suicide0.html

Originally Posted by Musician

What is an action slip?

There's a possible scenario we're discussing here that fits all of the available evidence. It proposes that one of the pilots operated the switches in an unconscious action called an "action slip". This is a rote action that we do without conscious thought when we're distracted: we mean to do something, and then we get our signals crossed and do something else. To learn more, search for "action slip" or "cerebellum" on this thread; I hope paulross adds the keyword to the next build of his excellent index at https://paulross.github.io/pprune-th...171/index.html .

How would this scenario play out?

We don't have enough evidence to pin down the exact sequence, so there are some assumptions here that I hope you find plausible. (And obviously it's not the only scenario that fits the evidence.) We especially do not know who did what and why, so that is all guesswork on my part. The times are taken from the preliminary report. The report places the verbal exchange among the pilots where I put it.

\x97\x97\x97

8:08:39 The 787 becomes airborne. The F/O is pilot flying (PF), with both hands on the yoke. The Captain is PNF (not flying).

8:08:42 The PNF unconsciously flicks both fuel switches to CUT OFF, one after the other. This is a rote action performed after each flight, or as training captain in the simulator.
The action cuts power to the engines; they stop delivering thrust almost immediately, and the turbines start slowing down.
The 787 systems disconnect the electrical generators in advance of them failing. The right side (Captain's side) of the cockpit loses power to most instruments. With all 4 generators offline, the RAT deploys to provide emergency power.

The PF feels the cessation of thrust. He looks at the display to see an ENGINES SHUT OFF message. He assumes the PNF shut them off, and asks him why he shut them off. This is the lowest "probe" level on the PACE assertiveness scale; see e.g. https://psychsafety.com/pace-graded-assertiveness/ or search for "probe alert" on pprune if you wish to know more. The highest level of assertiveness, E for "emergency", would have the F/O put the switches back himself immediately, but that would have required a high degree of confidence in the face of the older Captain that may have been difficult to achieve.

Since the action was unconscious, the PNF replies that he did not do that.

8:08:47 The RAT starts delivering hydraulic power, the engines decelerate past idle.

The PNF realizes that engine power is in fact cut. Eventually he checks the switches he thinks he did not touch, sees the engine 1 switch first and flips it back to RUN at 8:08:52. He then thinks to check the second switch and flips it up at 8:08:56.

The accident sequence ensues.

There's really not much the PNF can do at this point. At 8:09:05, he transmits a MAYDAY.

\x97\x97\x97

Obviously there are variations to this, for example it could have been the PF who put the fuel switches back. (In the above scenario, the PF is focused on flying\x97aviate!\x97and never turns his head to see the switches.) My goal was simply to set out a possible sequence, to see whether it feels plausible. Remember, as you see other scenarios put forth, that any issues a person could wrestle with would also be distracting. While both pilots would be very focused during the takeoff run, the moment the aircraft lifted off, the PNF could well have mentally relaxed a little, opening an opportunity for the action slip.

Thoughts?

Originally Posted by Musician

What is an action slip?

There's a possible scenario we're discussing here that fits all of the available evidence. It proposes that one of the pilots operated the switches in an unconscious action called an "action slip". This is a rote action that we do without conscious thought when we're distracted: we mean to do something, and then we get our signals crossed and do something else. To learn more, search for "action slip" or "cerebellum" on this thread; I hope paulross adds the keyword to the next build of his excellent index at https://paulross.github.io/pprune-th...171/index.html .

How would this scenario play out?

We don't have enough evidence to pin down the exact sequence, so there are some assumptions here that I hope you find plausible. (And obviously it's not the only scenario that fits the evidence.) We especially do not know who did what and why, so that is all guesswork on my part. The times are taken from the preliminary report. The report places the verbal exchange among the pilots where I put it.

———

8:08:39 The 787 becomes airborne. The F/O is pilot flying (PF), with both hands on the yoke. The Captain is PNF (not flying).

8:08:42 The PNF unconsciously flicks both fuel switches to CUT OFF, one after the other. This is a rote action performed after each flight, or as training captain in the simulator.
The action cuts power to the engines; they stop delivering thrust almost immediately, and the turbines start slowing down.
The 787 systems disconnect the electrical generators in advance of them failing. The right side (Captain's side) of the cockpit loses power to most instruments. With all 4 generators offline, the RAT deploys to provide emergency power.

The PF feels the cessation of thrust. He looks at the display to see an ENGINES SHUT OFF message. He assumes the PNF shut them off, and asks him why he shut them off. This is the lowest "probe" level on the PACE assertiveness scale; see e.g. https://psychsafety.com/pace-graded-assertiveness/ or search for "probe alert" on pprune if you wish to know more. The highest level of assertiveness, E for "emergency", would have the F/O put the switches back himself immediately, but that would have required a high degree of confidence in the face of the older Captain that may have been difficult to achieve.

Since the action was unconscious, the PNF replies that he did not do that.

8:08:47 The RAT starts delivering hydraulic power, the engines decelerate past idle.

The PNF realizes that engine power is in fact cut. Eventually he checks the switches he thinks he did not touch, sees the engine 1 switch first and flips it back to RUN at 8:08:52. He then thinks to check the second switch and flips it up at 8:08:56.

The accident sequence ensues.

There's really not much the PNF can do at this point. At 8:09:05, he transmits a MAYDAY.

———

Obviously there are variations to this, for example it could have been the PF who put the fuel switches back. (In the above scenario, the PF is focused on flying—aviate!—and never turns his head to see the switches.) My goal was simply to set out a possible sequence, to see whether it feels plausible. Remember, as you see other scenarios put forth, that any issues a person could wrestle with would also be distracting. While both pilots would be very focused during the takeoff run, the moment the aircraft lifted off, the PNF could well have mentally relaxed a little, opening an opportunity for the action slip.

Thoughts?

Originally Posted by paulross

I have rebuilt the site that organises this thread by subject here: https://paulross.github.io/pprune-th...171/index.html

It studies 3703 posts (and discards 1043 of them).

Originally Posted by The Brigadier

At this point, we may just be going in circles until more data or the final report is released.

Originally Posted by paulross

On the site that I maintain that covers this thread here: https://paulross.github.io/pprune-th...171/index.html I removed the subject that described deliberate action on the part of the pilot(s) for reasons I explained here: Air India Ahmedabad accident 12th June 2025 Part 2

I would restore that subject if any hard evidence appears that suports that theory, not on the basis of speculation (and out of respect to the families and memories of the flight crew).

For those thinking along those lines could I offer this challenge: All the civil aviation pilot suicide cases that I have heard about have been achieved by a rapid descent from cruising altitude. It is a pretty sure outcome. But to switch off the fuel just after takeoff, would you really expect that to succeed? Supposing the other pilot noticed and corrected this in one or two seconds rather than ten, then you would have failed.

I'm not saying people intent on this behaviour are being rational but even by the laws of un-rationality it seems an unlikely way of trying to achieve your goal.

Originally Posted by paulross

On the site that I maintain that covers this thread here: https://paulross.github.io/pprune-th...171/index.html I removed the subject that described deliberate action on the part of the pilot(s) for reasons I explained here: Air India Ahmedabad accident 12th June 2025 Part 2

I would restore that subject if any hard evidence appears that suports that theory, not on the basis of speculation (and out of respect to the families and memories of the flight crew).

For those thinking along those lines could I offer this challenge: All the civil aviation pilot suicide cases that I have heard about have been achieved by a rapid descent from cruising altitude. It is a pretty sure outcome. But to switch off the fuel just after takeoff, would you really expect that to succeed? Supposing the other pilot noticed and corrected this in one or two seconds rather than ten, then you would have failed.

I'm not saying people intent on this behaviour are being rational but even by the laws of un-rationality it seems an unlikely way of trying to achieve your goal.

Originally Posted by paulross

On the site that I maintain that covers this thread here: https://paulross.github.io/pprune-th...171/index.html I removed the subject that described deliberate action on the part of the pilot(s) for reasons I explained here: Air India Ahmedabad accident 12th June 2025 Part 2

I would restore that subject if any hard evidence appears that suports that theory, not on the basis of speculation (and out of respect to the families and memories of the flight crew).

For those thinking along those lines could I offer this challenge: All the civil aviation pilot suicide cases that I have heard about have been achieved by a rapid descent from cruising altitude. It is a pretty sure outcome. But to switch off the fuel just after takeoff, would you really expect that to succeed? Supposing the other pilot noticed and corrected this in one or two seconds rather than ten, then you would have failed.

I'm not saying people intent on this behaviour are being rational but even by the laws of un-rationality it seems an unlikely way of trying to achieve your goal.