Posts about: "Fuel Cutoff Switches" [Posts: 827 Pages: 42]

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.

Or did the F/O call for the gear up, the Captain still looking outside, did an action with his right hand, both pilots felt and heard the engines wind down, The F/O looking down realised what had happened, the Captain looked down and couldn't reconcile his intended action (bringing the gear up) hence the "I didn't do it " comment, then selected the FCO switches back to run but it was to late for the situation to be recovered. The only action they could take that they felt they had some control of was to broadcast a MAYDAY.

For me the prelim report just reveals an unintended consequence of relying on muscle memory to carry out an action that has been performed multiple times without confirmation. It happens a lot but rarely with such a tragic consequence. I have turned the ignition switch to Normal during an engine start when asked to set the park brake during a pushback. There have been multiple occasions where an A320 park brake was set when a flap setting was commanded. On more than one occasion the flaps have been raised when "gear up" was commanded. This may not have been the first time the FCO switches have been selected but definitely the first time it wasn't picked up early enough to reverse the action.

As to the CVR recordings, I will repeat what I have often stated previously. There is no inherent right of the public to receive a full transcript of the CVR in order for them to form their own opinion of what happened. It is up to the Indian AAIB to conduct an investigation under the requirements of Annex 13 and possibly a fuller transcript of the CVR will be published in the Final Report to help the reader gain an understanding of what happened.

My belief is that CVideoRs, with robust protections and legislation around their use, will help accident investigations immensely by answering some of the what questions that the FDR and CVR don't seem able to. It doesn't have to be set up like the many Go-Pro images that are on social media. All that is needed is an image of the center console and the engine display and EICAS/ECAM screens .There would be no need to have images of the pilots faces.

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.

There has been discussion about sim instructor muscle memory translating to the live cockpit. We of course do not know if that has any relevant to this yet, but I believe that is a hazard of training in an environment (eg FFS) that has psychological impacts on the candidate by design.

When running a sim, on repo', setup or end of session I never let any candidate push any buttons or do any actions that would not be considered not part of a normal flow that would normally be conducted at that point. On a reposition to a threshold, I might get the candidate to cycle the FDs or LSK in the MCDU once we are lined up and visuals back but that's about it. Everything else, start lever reengagement, flap resets etc are all off limits to the candidate and I brief as such.

Furthermore when I do the odd simulator in seat instruction exercise and do OEM prescribed "non normal" training (like a "gear up" -> Flap react incorrect selection) I will clench my non operating hand or squeeze my toes until they hurt and consciously tell myself I am about to do something incorrect... then do the (incorrect) action. That is my way of - hopefully - preventing muscle memory habits.

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.

I was thinking about this scenario when PF with the HUD down. The fuel switches are not in my field of view, so if you weren\x92t expecting it (and you wouldn\x92t be), a complete loss of thrust at v2 would come as a surprise to you as there are no engine indications on the HUD. I am not sure the PF would look down at the fuel switches in this situation, maybe at the EICAS but likely you will be busy flying the aircraft and leave the troubleshooting to the PM.

So if it were deliberate by the PM, the PF would be very slow to identify the problem. Unless you saw it happen (very unlikely), it would be virtually unrecoverable.

Just to clarify, I'm not aware of any confirmation at this point that the Fuel Cutoff switches were physically moved from RUN to CUTOFF and back again.
We do have evidence that the FDR, thus the databus, received signals that the Fuel Cutoff switches were in the RUN position, then the signals changed to CUTOFF one second apart, and then back to RUN at four second intervals.
In the absence of video, we could only use CVR data to determine that the switches were physically moved - either through flight crew conversation or sound of switches being moved.
When the PF asks why the PNF "Why did you cut off" we don't know whether he concluded the fuel was cutoff by checking the physical position of the switches or through instrument annunciations.
I accept that with sampling rates the physical movement of switches to CUTOFF at one second intervals could be logically explained. I can understand why there would be such an interval between physically moving the two switches back to RUN, unless there was some sort of struggle which presumably would be easily detectable on CVR.
Unless I've missed something, I'm not ready to conclude that the switches ever physically moved.

Looking at some past FDR data, it appears that the fuel cutoff switches are sampled at 1 Hz, but the actual valve position is sampled at 4 Hz. The position of the fire switch (fire handle) is also recorded. N1 and N2 are sampled at 1 Hz.

That's interesting and potentially tightens the time window a little (if one presumes that the valve position is a proxy of switch position, which in this case there's no reason to believe otherwise, and if the prelim uses this info to feed it's timestamps which I'd loosely assume it probably does...).

He's talking about a 10 sec delay between fuel cutoff and back to run (after 4min15sec into the video)

Look at 5.06 in the video, he simulates the CVR comments immediately after the cutoff and times the gap until they are switched back on. He may be right, but that timeline has no more validity than the CVR comments being 1 second before the switches are turned back on again, which could paint a very different picture (inadvertent or mechanical).

I don't think a ten second gap between event and recovery action is particularly noteworthy in terms of demonstrating malfeasance.

Bear in mind that it would take 1 to 2 seconds for this to have become fully apparent, plus then initial surprise to figure out it was engine related - being optimistic, 3 seconds total.

7 seconds does not seem remotely unreasonable to then deduce cause, especially given what various other posters have said that FC switches wouldn't be high on their list to check. In fact, it seems like pretty good going.

If it was 10 seconds between the CVR and recovery action (as per your quoted poster) then that changes things quite a bit. But it wasn't.

PS the conclusion may be right (or it may not be), I'm open on the topic. But that 10 seconds gap doesn't tell us the answer.