Posts about: "Fuel Cutoff Switches" [Posts: 802 Pages: 41]

I don't think this answers my question? Evidently there is an interruption in power, the (quite stable, at that point) ADS-B stream cuts out and doesn't return for the final twenty seconds of flight. And there are other indications that non-essential loads were shed, like the survivor remembering what must have been emergency exit lighting in the cabin. Though I would have liked explicit confirmation of AC power loss happening or not in the report.

The timing of data loss seemingly lining up with the first cutoff switch being flipped back to RUN seems a little too coincidental to me, but again hopefully someone with relevant knowledge has a mundane explanation for this.

Regardless of what actually happened in that cockpit, reasoning like this seems completely backwards to me. Since when do humans reliably, instantly recognise that they've just made a mistake? If they were that attuned to their actions they're almost certainly attuned enough to not make the mistake in the first place, especially if we're talking about an action slip. I've e.g. absentmindedly added salt to my tea instead of sugar and I certainly didn't immediately realise that I'd done that - in fact it took a good few seconds even after sipping and spitting it out for my brain to catch up to what must have happened. Even if an observer had pointed out to me before drinking it that my tea had salt in it, I would just have been confused because obviously I wouldn't do something that silly (spoiler alert: I did).

On top of that I feel like people are overestimating how long ten seconds actually is, especially considering some of those seconds are reported to have been taken up by confused dialogue (that isn't even reported in its entirety). I thought it was common wisdom that accidents are never down to one thing; it would be light-years from being the first time that suboptimal crew response turned a maybe-recoverable error into a definite disaster without an ounce of malice in the mix.

The FO had 1128 hours on type. Unless he was a slow learner he was not in training.

People please, read the report before posting.

https://aaib.gov.in/What's%20New%20A...t%20VT-ANB.pdf

​​​​​​​A huge generalisation which I find to be untrue.

The fuel control switches were moved to the off position approximately 3 seconds after weight off wheels.

Loss of hydraulics or electrics will auto deploy the rat. The timing to me however seems to match up with when the engines were selected off.

If the thrust levers were found in idle but, according to the EAFR, were set to TO thrust until the end, doesn\x92t that also raise further questions? I mean: Of course, the impact causes compression at the nose, but the centrifugal forces act in the opposite direction. So, if there is an objective inconsistency here, and we have a pilot who says he did not operate the fuel cut-off switches, while the EAFR indicates otherwise, then we have yet another inconsistency.

Relevant section in the preliminary report

If the shutdown was intentional there likely would be a struggle to restore the switches.

Since when do humans reliably, instantly recognise that they've just made a mistake?
When they rip their hand away from the hot stove they’ve just touched.

Had this been a silly mistake, it was one with immediate, severe consequences, not something like discovering a mistake you made some time ago. As for response to the mistake, see below

After making a mistake like accidentally turning off the engines, most pilot's brains would immediately realize what they’d done, and their hand being right there, they’d immediately reset both fuel switches to run. If you were slow, it would take 2 seconds, not 10.
Again, the situation isn’t a surprise to you, you know what just happened.

Deliberate pilot action should be ruled out until any evidence and motivation for why that's the case emerges.

All we know is the fuel cut off switches were flipped to Cutoff for 10 seconds and then to run again. Not how or by what. The focus should be on how this could occur. Accidentally, technical malfunction, a foreign object somehow hitting and moving them or other reason?

Theories needs to be tested in a cockpit with the exact configuration of this aircraft and with the angles and forces involved as much as we can. It should be possible to simulate it pretty closely and whatever happened should be repeatable. It's going to be something extremely unlikely, or we'd have seen it before in 10 years of 787 service.

The one pilot asked the other one, \x93why did you cutoff?\x94
He didn\x92t say, \x93did you just see that pink elephant fall off the dashboard?\x94

How are you going to \x93simulate something pretty closely\x94 when it\x92s also \x93extremely unlikely\x94?

The chance that it was a mechanical or electrical failure of both fuel switches , 2 seconds apart , is for all intents and purposes, zero.

Therefore they were moved by hand.

From a PPRuNe perspective, good discussion here is desirable, as it is from a pilot perspective too. Nonsense or needlessly accusatory discussion, though it is discussion here, is not so good for pilots, and other well informed readers.

Some members want this thread locked, which is a choice we moderators can make, other members want discussion, which, if good, is desirable for everyone. We moderators prefer to not lock threads, we like to moderate, not terminate!

So, could we all agree that knowing that both condition switches were selected to cutoff by a pilot, we do not have information as to which pilot? What interest are we serving anyone by speculating which pilot here and now? Perhaps later, a full report adds to this knowledge, but possibly never.

I see four groups of readers here: Pilots of two crew airplanes, who are now instinctively more alert to what they are doing, and what their co crew is doing; Single crew pilots, who know that they are their own guardian against mistakes anyway; Designers, who are now thinking about improving designs to minimize the effects of pilot error; And, politely, everyone else.

Pilots of two crew airplanes, you know what you have to do. Is slighting two members of our community helpful right now? In my opinion, I don't see how...

Single pilots, you're on your own. Designers, yeah, we're thinking....

Everyone else, the professional pilots forum is accepting your participation, please be respectful with what you post - you're posting it about pilots who recently passed away with high trauma. Is what you're about to post something helpful? Do you really want to say it? Will the pilot group be better because you did?

We moderators don't want to lock the thread. And, we don't want to allow our core group of professional pilots to become profoundly aggravated by pages of low value posts. Please make our moderator jobs easier for us!

Thanks, Pilot DAR

Nothing should be ruled out!

Maybe it took the pilot 9 seconds to determine the switches were in cutoff.

I have not seen this question asked anywhere and I'm a software engineer (non-aviation), so felt I had to ask it:

Do these solid-looking mechanical fuel switches really act directly upon the fuel system or are they routed via the control system as logic (0/1) signals?

It would certainly save a lot of copper and looming time to convert their output into a logic signal before it leaves the cockpit...

If the former, ignore all that follows, as it is wrong.

If the latter, a control software glitch or electrical noise/short could cause the fuel switches to appear to the control system as being briefly off,
while the pilots see the physical switches are still in the on position.

Even if such a noisy electrical signal rapidly reverted to correctly indicating fuel-switch on-state after even a few milliseconds,
any control system might well have embarked upon a relatively slow relight/startup/engine-protection procedure.

In such a scenario, the pilot who first noticed the engines spinning down would query it, while the other pilot would look at the physical switches and see that they were (still) on, and initially be non-plussed by the question.

Need to ask the question now satisfied.

Andy

Question: (which I hope goes to the issue of lessons possibly to be learned.)
Irrespective of whether the switching to cutoff was inadvertent or deliberate or (somehow) without human involvement is there any other time in the course of operations from start-up to shutdown except rotation when those switches should be disabled for 20-30 seconds?

(First, I've read the whole thread, and most of the content in the previous threads, though they are obviously of less relevance in some areas now.)
This notion has caused me some concern, since seeing at least one very similar remark when I read the other threads (possibly by the same poster, though?).
It seems extremely undesirable for TCs to end up habituated to taking actions like this without thought. I wonder if it creates a case for the sim setups being performed by non-flying personnel?

Meanwhile, I read the prelim report. The English is generally fairly good but I note multiple mistakes/typos, and some oddities. One such oddity is that the timestamp of the second cutoff switch change isn't listed explicitly anywhere I can find, but instead just a relative time: "gap of 01 second". To write "1" as "01" like this invites speculation that it's a typo for 0.1; this is unlikely, given the polling frequency mentioned by some posts above, but nonetheless seems odd. (I am aware that Indian conventions differ from those in US/UK English, including placement of commas in large numbers, but I don't think this is such a case.)
Another indication to suggest it hasn't been proof-read very effectively: the FADEC is also described as a "... Dual ..." instead of "... Digital ...".

One suggestion about why the report was sanitised and a fuller transcript was not provided could be to delay public reaction on this and avoid copycat events.
Jump seaters should be mandatory on all flights. On AS2059 the jumpseater maniac was overpowered by the other pilots. Two against one is better than pilot against pilot.
The 10 second delay could be explained by a cabin altercation when one pilot saw the other one deliberately perform the cutoff.

Too many people not wanting to acknowledge what is staring them in the face.

The switches were physically moved to cut off. The report says so, they will have heard them on the CVR.

The switches don\x92t move unless you intend to move them. You can give me all the worn mechanism, SAIB, phone/ipad theories you like. You\x92re clutching at straws.

If you had a massive brain fart and moved one to cutoff by mistake, you would realise instantly. These switches are distinctive in sound and feel. You would know what you had done before you had even released it in the cut off position.

Almost instantly you would get aural warnings and pages of EICAS Warnings and advisory\x92s. You\x92d get a massive clunk and momentary blanking of screens as power transferred.

if it was a mistake, you would instantly move it back to run\x85..you sure as hell wouldn\x92t double down and do the second engine.

it\x92s very sad, but I fear it is staring us in the face.

I've been on record in the past advocating for this, but not as the means for intervention. - in the kind of instance we may have seen here, that likely wouldn't have helped anyway - but as a moderating influence on a crew member who may have been contemplating wayward actions. Being observed is often a powerful influence in behavioural extremes.

On edit: and No, I doubt the preliminary report was written to avoid the risk of copycat actions or delay public reaction. The investigatory team are not at all likely to be considering that kind of audience in what is essentially a finding of fact. An altercation would have been caught on the CVR... and reported upon.

Question:
What messages, if any, are displayed on-screen when the fuel cutoff switches are re-positioned (especially to OFF)? I'm wondering if the pilot who asked about the shutoff SAW the other pilot manipulate the switches or if he was alerted by a message... or perhaps he looked down at rollback and realized they were in the OFF position.

Typically, no. Switching one to cut off mid-flight is an unusual event. Switching both to cut off mid-flight would typically be done after a catastrophic event.

Further, it is non-standard for one to be switched to cut off immediately after take off (even if that is the eventual required action, it is rarely done as immediately as described in the report).

Cutting fuel to your engines a few hundred feet of the ground doesn\x92t end well.