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

You're quoting me out of the context in which you contended a media report with no evidential background could prove a point you were making.

Having added your newer arguments too, you appear to have ignored what I've said since. But to respond to your direct question, my time in an airline cockpit is that which related to participating (as a human factors SME) in an aircraft accident investigation. Not much, but not actually relevant to the point I made relating to your post, or this subsequently - unless you contend that investigators have no place in investigating an accident.

Well. Was there a “positive rate-gear up” exchange? This is SOP as we all know, but it does become relevant.
AFAIK you state the nature of any (perceived) failure when you select the gear to up.
They didn’t even get to that point. Action was already unilaterally done by someone, before that.
It is so incomprehensible that the fuel control switches were already in cutoff, before they even came to the pos-rate gear-up part.

Reading SAIB NM-18-33
My Interpretation/reading:
Some 737 Operators reported incorrect/broken locking features on cutoff switches - PN 766AT613-3D
If you have PN 766AT61 3 -3D installed - Replace it with 766AT61 4 -3D, which includes an improved locking feature.
The other Aircraft listed - have switches with similar design. In the case of the B787, switch PN 4TL837-3D. Check those AC to ensure locking is OK, and if you do happen to find something odd, let us (the FAA) know.
No-one, has ever found anything wrong with any of those other switches, or there would be AD's.
Thus there is not a problem with 787 Fuel Switch locking features.

Based on the news coming out of India, it appears that your suspicions regarding malicious intent may well be correct, but it is not the younger FO under suspicion as your post seems to suggest but the older more experienced captain. Other comments in this thread had already made me think that the younger pilot was the PF and that it was he who had challenged the PM because he would have been focused on flying the aircraft and would have had neither the time nor the inclination to adjust the critical fuel cut off switches which you yourself categorically claim would never be mistaken for other switches.

While this is thread is still deeply into hamster wheel status, there are some valuable inputs being made. I'll try to continue with that...

Thrust lever position post-accident - it takes very little force to move the thrust levers, a little more than one pound-force at the knob. I'd be very surprised if the post impact position was the same as pre-impact (and lever angle is recorded on the FDR, so the investigators know where they were). In short - the post-accident lever position is not meaningful.

Fuel condition switch position detents - if the Indian investigators had any reason to believe that a failed or inoperative detent was a contributing fact, the authorities would have ordered a fleet-wide inspection (especially since it literally takes only seconds to do the inspection - the paperwork would take many times longer than the actual inspection).

Engine restart (i.e. "Quick Windmill Relight"): Even if the igniters were firing, at high power they won't actually spark (the electrical resistance or the air at several hundred psi prevents a spark) - so they won't spark until you get down somewhere near idle if you're close to sea level. Once the engine has dropped below the min idle, it takes a long time for it accelerate back to even an idle condition. At takeoff power, the compressor components get very hot - do a power cut the air coming in the compressor gets heated by the residual heat in the compressor. This in turn limits how fast you can add fuel in the burner without excessively back pressuring the compressor and causing a compressor stall. So it actually takes longer for the engine to accel to idle that it would during a normal (cold engine) start. The 5 seconds to 95% accel requirement referenced earlier is from a stable 'high' idle (we typically call it 'approach idle' since it's automatically selected when landing flaps are selected). Approach idle is ~10% N2 higher than the in-flight minimum idle, so that takes several more seconds. Bottom line, after initiating the Quick Windmill Relight, you're not going to have usable thrust for at least 30 seconds - probably closer to 60 seconds.

For all the complaining about this preliminary report, it actually goes into more detail than is typical.

BTW, my money is still on the 'muscle memory/action slip' or whatever you want to call it. I can easily imagine a scenario along the line of 'why did you turn off the fuel' - 'I didn't - oh wait - oh ...

Regarding the thrust lever position.

The EAFR data revealed that the thrust levers remained
forward (takeoff thrust) until the impact.

Would that position be consistent with a restart attempt?

Long time lurker, first time poster here.

I cannot post links, but I came across a short video on Reddit (search for r/aviation and a post called "Fuel cut off switch". It shows someone operating the switches up and down, and the movement / considerable effort required to do so. The video is quite illustrative.

Hoping this contributes to the thread.

BF

Thank you for your kind reply. I confess to you that my post was not my best effort. I was in a deeply cynical mode when typing it.

I've reviewed the report a couple of more times since then, with some of the insights offered by PPRuNers to aid me. It had seemed to me, on first read, that they (whomever approved the final language of the report that we have all read) were hanging the FO out to dry...but...that may have been me reading too much between the lines . As others have noted, there's a lot not said.
Yes, that makes sense.

I've got some thoughts on compartmentalization still cooking in my head, to include "where was the captain's attention during take off, something he'd done hundreds of times?" I do not yet have those thoughts in coherent enough form to concisely present them to the very critical (as well it should be!) audience here.

The CRM piece has me grabbing at straws. I had mentioned in a previous post the bit about No Fast Hands and Confirmation of important switches/handles/levers before activating as general CRM principals, which it seems someone did not adhere to.

Nothing (yet) can tell me "what did the captain see with his eyes during the three seconds between leaving the ground and the switches being moved?"
I am not sure how much of the EICAS info ends up being recorded on the EAFR/FDR, or if there was a light that illuminated before the switches were moved, perhaps triggering a 'fast hands' moment / error...
Perhaps a subsequent report can shed some light on that.

And yes, it might have been an attempt at suicide for {X reasons} which are known only to someone who is now dead.

This just popped up on my news feed - seems relevant...

Amid Air India probe, US FAA, Boeing notify fuel switch locks are safe, document, sources say

Unless I've missed it, za9ra22 has not been denying that a deliberate pilot action is not plausible. What za9ra22 and others \x97 I among them \x97 are arguing is that there is no credible evidence that either of the pilots deliberately moved the fuel control switches to CUTOFF intending to crash the airplane and kill all aboard . That is certainly one of the plausible possibilities, but only one of them. We don't know, cannot know, what actually happened, because we have available only fragments of evidence, fragments that don't come close to being sufficient to reach a conclusion. And accusing a pilot of deliberately killing hundreds of people, without conclusive evidence that he actually did so, is, IMHO, a grave injustice.

tdracer, thank you.

I have watched the nonsense posted about 'that is a bad design' as regards the fuel switches and have bitten my tongue.

It's a sane and rational design choice unless one is a default Boeing basher.

There are two sets of two switches near to each other (see the photos and figures further up) that are important (one due to fuel, one due to a primary flight control, the horizontal stab). They are protected from inadvertent movement in two different ways based on their physical proximity.
1) Stab (influencing) switches use the covered guard. (The Horizontal Stab is a primary flight control).
2) The fuel switches are stopped from casual movement by the design of that switch (which has been discussed to death) unless you pull out then them move them to the other position.

See how this works, folks who don't fly?

Stab switches: uncover, then move. Two steps.
Fuel switches: pull out, then move. Two steps.
They look different and they feel different.

Given their proximity, the designers (who have to deal with ergonomics) provided both a visual and a tactile clue that they are different, and what switch your fingers are touching or trying to move.

Will that choice guarantee that some idiot won't activate a wrong switch?
No, it won't, because you can't idiot proof everything ... the universe will always provide a bigger idiot.

But it does offer two, not one, cues to "wait, what switch am I about to activate?" for the trained user and is thus a sound design choice. Yes, pilots do undergo training for how to use all of the switches in the cockpit/flight deck.
Really.
Not kidding about this.
(Have I ever moved a wrong lever or switch? Yes).

Oh, by the way, those who have posted here who fly the 737, 757, 767, 777, and 787, have affirmed the operation and usefulness of the fuel switches. IIRC one of our 777 flyers pointed out that his captain had written up one such switch since it wasn't working right.

Yes, friends on PPRuNe, you can know how they work and if they are worn, or feel as though they are not working correctly. You can do the write up and the maintenance team can replace the switch (or fix it, or replace the quadrant, yadda yadda).
As noted by others, those switches are used on every flight.
You'll know how it should feel/work, and if it doesn't feel or work correctly you make mention of that to the engineers/maintenance crew (depending on which side of the pond you are on).

The Bulletin from several years ago does not prevent normal maintenance, and write ups, from happening on a routine basis (as with various other things on aircraft that get written up).

I had three switch design and placement factors explained to me - visual, tactile, and positional - over 40 years ago when I was going through blind cockpit checks prior to getting initially qualified in the SH-2F.
As I flew other aircraft I would notice various choices made as regards all three factors. (A fascinating sub topic of its own, but I'll stop there).

I thus say to DiffTailShim, and whatever test pilot from the UK posted his noise: no, you are wrong.
The design decision is sound.
That Embraer did/does it differently (which is cool, there is more than one way to peel an onion ) has little or nothing to do with this accident.

One could argue that their proximity might have an impact, but that would require evidence that something to do with the Stab Switches was involved in this event.
So far, that vague mention of a write up from a previous flight about a stab light gives us a tenuous thread, but not a lot to work with.

Well said TDR, the report expressly states that the T/R levers are bent but in the stowed position, so it is quite probable that the thrust lever angle is not as they were in flight pre impact.

The last line, is not a zero possibility, but at present the whole wiring system for the fuel control switches would need to be evaluated for any potential common fault that may be intermittent before I would lean towards the cognitive slip type error. The poor old FO would have both hands on the yoke from V1, irrespective of the company's SOP and so would have been rather unpleasantly surprised by the loss of performance. I think the 10 seconds in this case is remarkably fast observation-orientation-decision-action sequence, and that one engine had already started to recover towards operation is a credit to the design of the engine.

The prelim report very specifically states that the co-pilot ( the FO, younger pilot) was the PF.

Am seeing reports pop up suggesting there is a "chip" that needs replacing, which could have caused the issue.

Not sure what chip, or the validity of the claim generally, and why its only coming from him.

I believe the FAA has - together with GE, General Electric, the engine manufacturer - has issued a service bulletin, i.e. I believe it was about 11,000 cycles, they will have to replace the chip. And if it is not replaced or maintenance isn't done correctly, it could lead to intermittent loss of signal. Once you have a loss of signal, the fuel isn’t commanded i.e. in the cut off position, then there's no fuel going to the engine

I can't post URL's but search for Marko Chan and it pops up pretty easily from a few sources.

More media trying to event a story. Consider this:
Each FADEC has two independent channels - if one channel has a fault that makes in incapable of controlling the engine, the other channel takes over. This happens in milliseconds - quite likely the pilots never know it happens. There are two engines.
The chances that this failure could affect both channels of both engines within a second or so is literally trillions to one.

LH engine had around 4300 cycles, RH engine had around 6200 cycles. The airframe had around 7200 cycles (current airframe cycles not listed in the report). The quoted SB wouldn't have been due yet. Not to mention, having both engine controls fail at the exact same time is ridiculously unlikely.

Originally Posted by Mrshed
The question is what impact was had on attempts to recover the aircraft by the (presumed) lack of most or all electrical power.

Response from BrogulT: From the point that the fuel cutoffs were switched back to run, the primary (perhaps only) relevant issues were time and altitude. The left engine was relit and recovering on it's own but the right would probably have needed cranking as it appears to have had a hung start because it was spooled down too far and the airspeed was too low. However, I'm pretty sure that even if the APU had already been running at takeoff, they still would have needed at least another 30 seconds if not longer for full thrust. Also, there was nowhere near enough time for the APU to start and come online here.

Your claim that at least 30 seconds were needed to achieve full thrust prompted me to look up reports on the Airbus A320 crash at Habsheim in France in 1988 where the aircraft had been flown at low altitude at the minimum allowable speed and was unable to achieve sufficient thrust to ascend above a copse of trees. The extract below shows that from Idle to 83% N1 took 5 seconds after the initiation of a TOGA, so I think your estimate of 30 seconds is probably too high. However, after reading that report, I am of the opinion that AI 171 had no chance of recovering. If the FCS switches had been set to Run within 5 seconds of being set to Cut Off, there might just have been a chance, but it is not at all certain.

(From Aviation Safety Network Sunday 26 June 1988)
The aircraft took off from nearby Basle-Mulhouse Airport at 14:41 and climbed to 1000 feet agl. The crew started the descent three minutes later and Habsheim was in sight at 450 feet agl. The Pilot Monitoring informed the Pilot Flying that the aircraft was reaching 100 feet at 14:45:14. The descent continued to 50 feet 8 seconds later and further to 30-35 feet. Go-around power was added at 14:45:35. The A320 continued and touched trees approximately 60 meters from the end of runway 34R at 14:45:40 with a 14 degree pitch attitude and engines at 83% N1. The plane sank slowly into the forest and a fire broke out.

PROBABLE CAUSES: "The Commission believes that the accident resulted from the combination of the following conditions: 1) very low flyover height, lower than surrounding obstacles; 2) speed very slow and reducing to reach maximum possible angle of attack; 3) engine speed at flight idle; 4) late application of go-around power. This combination led to impact of the aircraft with the trees. The Commission believes that if the descent below 100 feet was not deliberate, it may have resulted from failure to take proper account of the visual and aural information intended to give the height of the aircraft."

The Australian Transport Safety Bureau recently investigated the loss of an R66 and praised the ability of the factory-fitted video recorder to assist in identifying the cause of the accident. DFDR & CVR legislation was written, literally, half a century ago, long before on-board video was even possible, yet alone considered, and technology hasn't kept up with the times. It's about time it did.

Truck & bus driver's, cabbies, train driver's, even the kid at Macca's who hands you your burgers are all filmed at work and don't feel it's a hostile workplace, so sorry to say that airline pilots are most certainly not special enough to argue against the introduction of such technology - no matter how big your ego. The same argument of Big Brother was used when CVR's were introduced and no one bats an eye anymore, it's widely accepted, even though you'll still get the odd bloke here or there who erases the CVR before handing over to the next crew. If regulators want to introduce onboard CCTV with the same protections as CVR data, you won't win an argument against it. E specially when the increasing number of fatalities whose ultimate cause is pilot suicide will sway public opinion against you by people who themselves already subject to such surveillance at work. "Why are they so special?" will be the sentiment...

Granted, accident investigates are good at what they do, and I'm in awe of their ability to reconstruct the majority of accidents to determine the ultimate cause (without video). but when technology is available that would have already solved this accident ie. "On-board CCTV shows the Effo selecting the engine run switches to OFF for reasons that remain under investigation" (and to be clear, I AM NOT suggesting that's actually what happened...), it would solve a lot of issues and put to bed speculation about what actually happened to the fuel control switches, who did what and when and I'm at a genuine loss as to why people would argue against it, when it's already so widespread and entrenched in other industries.

Even now - with the preliminary report, I haven't seen mention of which pilot asked the other "Why did you [go to] CUTOFF?" whereas a video would have already told the whole story of this accident - with the exception of the why?

My final thoughts for this event.
Misinformation, most of us including myself was of the view that Gear Up had been selected because we saw an image believed to be the accident aircraft with the bogeys stowed for retraction.The report image shows that they were not and the Gear Selector was down. A crucial element in the sequence of events.

The preliminary report around the cause is deliberately vague for obvious reasons.The investigators would know exactly what was done/said and by who. The clack clack of the fuel switches would be on the CVR and align with the FDR. The First Officer was the Pilot Flying and his control inputs would be on the FDR (trim operation) when the engines were commanded to shutdown.
The full version will leak otherwise we have to wait for the Final Report. I'm of the view that the only thing misunderstood was the Captains meaning of Retirement..

As I understood the question, the issue was what impact the lack of electrical power had on the restart. In this case, without the APU (or the other engine) for power the right engine was apparently never going to start despite heroic efforts on the part of the FADEC. With the APU running it could have been cranked. However, going from flight idle to full thrust is one thing, going from so far below idle that the engine needs to be cranked to flight idle will take a lot more time. How much more IDK since exactly how far the N2 speed had dropped, actual airspeed, temperature, etc are all factors. My guess is that it would feel like the engine was taking a million years to start. But the APU was not running and the point is moot.