Posts about: "Fuel (All)" [Posts: 1005 Pages: 51]

NM-18-33 SAIB left me wondering the same thing. It give a procedure for detecting the defect but omits to explain the cause. I was thinking that the wrong switches had been supplied/fitted. Assuming the image from the Chinese web site is correct, it is disappointing that the actuator can get into that state. I did not see anything that said whether that was how the switch arrived from Honeywell or if there was a defect that allowed the actuator to turn.

One other useful thing from that web site is a partial schematic which shows the connection of the 4 poles in the switch. I believe this is from a 737NG but it should be the same idea.

SLF. But I've read in full both original threads and this thread.

The Preliminary Report is written in excellent English, so I think one should pay close attention to what it says.

One thing I noticed is that at the bottom of P4 NTSB are stated as "..participated in the investigation". However UK AAIB are only stated as "visited the site". My reading is that UK AAIB are not participating?

Another is that some items on the timescale are v precise, others much more vague.

A question :

If the fuel switches were moved to cutoff, for whatever reason, what exactly would each pilot see as an EICAS warning. I'm still unclear why one pilot asked the other why he cut off - actual observation of the action, or message.

SLF: I have a small observation but I'm not sure what it means or if it has any relevance to the accident.

Previously I had assumed that the ADS-B data cut out at the same time as power was lost, so I imagined that whatever caused the fairly clear loss of thrust would have happened not too long before. But this report throws a bit of a wrench in my understanding of that.

According to the report, the fuel cutoff switches transition from RUN to CUTOFF at or very shortly after 08:08:42 UTC. Both engines' N2 values pass below minimum idle speed and the RAT begins supplying hydraulic power at about 08:08:47. Does this not imply that the generators have already been lost? With the APU also being off (the APU inlet door is noted to start opening at 08:08:54), I would have expected ADS-B data to cut out at or before 08:08:47. But curiously FlightRadar24 at least claims to have received data frames from the aircraft until 08:08:51.640970, almost five seconds later and almost ten seconds after the transition to CUTOFF (though the last frame containing coordinates comes at 08:08:50.871005).

Could anyone with relevant experience confirm how long it would take for AC power to be lost in this situation? Also, is it usual/unusual for a preliminary report like this to mention if/when the flight recorder switched to its independent power supply? I imagine it would definitely be in the final report, but I'd hoped it would be easily observable enough to be in this one.

Beyond idle curiosity I'm asking because the report also says the no. 1 engine's cutoff switch transitioned from CUTOFF to RUN at "about 08:08:52", which oddly coincides with the last ADS-B data frame at 08:08:51.640970, and that seems important somehow. Or more likely I'm just ignorant of some quirk of the 787's electrical system.

For reference FR24's CSV containing all ADS-B frames supposedly received from the aircraft can be found in their post here: https://www.flightradar24.com/blog/f...rom-ahmedabad/

Quote:

"The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec."

This might have been discussed but as has been suggested upthread; a possible scenario is that at some point, PIC took their hands off the thrust levers and/or placed them in a guarding position behind the thrust levers at their base - but by doing so unfortunately nudged the Fuel cut-off switches to 'Off' - perhaps 'helped' by there either being incorrectly fitted locking mechanisms or worn locking mechanisms ?

3 possibilities come to mind:

1. Pilot who moved fuel switches to off did not do so intentionally to cause the outcome, but for some reason unknown (extreme fatigue, medical condition, medication/drug) somehow confused the action of retracting gear with shutdown procedure at end of flight.

2. Unthinkably, but very possibly, pilot who moved fuel switches did so intentionally, likely planned ahead of time to catch out other pilot at a moment where focus was intently on flying & recovery most unlikely. Mental illness, drug use, personal circumstances behind it.

3. Something extraordinary which was never encountered before which caused or allowed fuel switches to move on their own.

When both pilots flying & personal history is investigated, more is likely to emerge, maybe something to support possibility 1 above, where a pilot had on some previous occasions got sequences confused, or suffered brief episodes of seizures whee he took strange actions.

10 seconds to respond is a long long time if you’ve just made a silly mistake, you’d have those switches back on in a second. The startle factor isn’t really a factor here, because you know what just happened.
What is also unusual to me is the 4 second gap between moving Eng 1 fuel switch from cutoff to run, and moving Eng 2 fuel switch from cutoff to run.

One would imagine that in this situation, speed of response would have been critical. Why the slow, deliberate ‘reaction’?

I believe the fuel cutoff switches are one of the exceptions to this. They are direct wired. Stab trim may well be too.

I think they're called remote data concentrators - in many cases it is a conversion from a direct digital input to a bus signal; electronics would not call it an 'analog' input unless it was actually measuring a quantitative value.

I think I have seen a previous reference that the generators are disconnected when you select the switches to cutoff (or very shortly afterwards), not when the engine actually drops below idle. That could account for a few seconds of spool down time.

That is a very good question IMHO.

tdracer hit the nail on the head in one of the earlier threads. Two possibilities: Software shut down the engines, or someone put the fuel switches to cutoff.

It wasn\x92t software. The question now is who shut down the engines and why?

Argue fuel switches mechanics, liquid, falling items, electronics, etc, as much as you want, but who and why is where we will end up.

On a British twin fast jet in the early 80\x92s a pilot incorrectly assessed his accel on take off in formation was too slow. In aborting he moved his hand towards the hook deployment lever under the LH console which required a cupped hand, straight pull back to drop the hook. Instead he flipped out a horizontal lever on the side of the same console that he then grasped and pulled back, jettisoning the canopy\x85The aviation psychologist explained that once the wrong handle was selected, even though it required a different method of operation , the brain ( muscle memory) would trigger the correct action to operate it. That would explain the action of operating the incorrect switch.
It doesn\x92t explain the reason behind going for the stab cut out switches when the report makes no mention of any stab warning - which surely would be a highly Important event given the closeness of the switches.

This crossed my mind too. This is called an "action-slip" by designers: a valid and frequently practised action being applied to entirely the wrong situation, resulting in an (extremely) invalid action.

On this flight, the relative drop in noise and calm that follows the landing gear doors closing after the gear retracts during the initial climb, might have caused an action slip by PIC to perform the engine shut-down procedure used when parking on stand.

Unlikely though, I would hope.

Has anyone answered whether there is any message when the engine CutOff switches are transitioned in this situation?

If there isn't then the asker must have seen it being done. If there is, then it's still not absolutely pinned to a pilot, is it?

Just read all 16 pages - been flying! I think comment \x93why did you cutoff\x94 is not the reaction I would expect from a Training Captain who has just witnessed the co-pilot turn both fuel control switches off. They would possibly utter an exclamation, but would surely correct the error immediately - this didn\x92t happen for 10secs. The words are more likely to have come from an FO who has both hands on the control column and is concentrating on the rotation.

Every flight we do as PM we move both fuel control switches to cutoff, 1 after the other, with a gap of about 1 sec between each one. It\x92s a learnt action in response to the phrase \x93shutdown\x94.
Every sim the TC has conducted he will have moved critical switches without much thought in order to setup the sim for the exercise. I remember being slightly shocked one day on the aircraft, having been training in the sim the previous day, that I nearly operated a critical control without thought. It\x92s something I had to consciously guard against after that.

There is no rational explanation for doing it though - moving both fuel control switches down instead of moving the gear lever up is not a likely action slip. It seems either a totally subconscious act or a totally deliberate act.

Engine shutdown/restart.
As Captains of Boeing twins, which fuel switch do you typically move first, Eng 1 or Eng 2?
As First Officers, same question.

Higher probability that the PM (Captain) manipulated the switches given the sequence of events.

Seriously??
Come on! The gear never moved! You're an Airbus pilot; do you really think that could happen? If so, would the captain then sit there fat, dumb and happy wondering what was now going on... for 10 seconds? Even I would say "Sh1t" and whip those fuel switches back on quicker than the FO could say "WTF!".

Mods, if you don't lock the thread, I'm going back to Facebook!

in that fraught moment of engines not functioning very close to the ground, the last thing to do at this critical moment when you don\x92t really known what has happened is communicate a MayDay. With the buildings looming up fast, the action required is to attempt to restart, as seems to have been done by a pilot putting the fuel switch to \x93run\x94, but too late to rescue aircraft. I think the timing of the MayDay call is strange given that the scenario called for Aviate, Navigate\x85 then Communicate.

Firstly, 10 seconds is a more than reasonable time for startle factor to impair cognition (as discussed repeatedly). Secondly, why do so many people assume it was the FO that moved the cutoff switches? He was PF, I find it more likely that the PM moved the switches (for whatever reason).

This is a Professional Pilot's Forum. Nonsense and bizzaredness doesn't live here.

And the CVR? "why did you cutoff?" ... "I didn't, the ipad did!".

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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.