Posts by user "Abbas Ibn Firnas" [Posts: 13 Total up-votes: 11 Page: 1 of 1]¶

Originally Posted by Lonewolf_50

Thank you for that answer, edge cases do abound in complex systems, but would not moving the throttles forward by hand (as the thrust was beginning to reduce {for that strange reason}) overcome that and restore thrust?
(As I don't fly the 787, I may be missing something basic on how the systems work).

Originally Posted by SRMman

I still think that one of the most puzzling things from the Preliminary Report is the 4 second gap between Engine 1 fuel cutoff switch being returned to RUN, and that of Engine 2. It seems generally agreed one second is a reasonable time to operate both switches, so why did it take so long to move the 2nd switch?

Originally Posted by Mrshed

I'd assume that the prelim wouldnt (surely?) call out the gear down item explicitly and not reference a command for gear up if it existed - but could be wrong. For me your former suggestion is more likely I think.

Incidentally, on the topic of lever positions in the wreckage, anyone find the thrust position at idle in the wreckage (at odds with the data) of interest? My assumption is this must have happened post impact, but it's a (small) oddity.

Originally Posted by tdracer

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 ...

Originally Posted by tdracer

It doesn't really matter - the FADEC will do it's best to get the engine running again regardless of the lever position - in that regard the only real difference is once the engine reaches min idle, it'll simply keep accelerating to the target N1 (or EPR). There is no need to move the thrust lever to idle to get a successful start.

There have been a few cases that I know about where the flight crew did a normal ground start with the thrust lever at mid-power, and the engine simply continues to accelerate to the 'commanded' N1 or EPR. In one case (a 777), this happened during pushback. As the engine continued to accelerate above idle, the thrust caused the aircraft to jackknife around the tug, causing the tug driver to have to dive for cover to prevent serious injury. That even happened while we were doing the development of the 747-8 - it prompted me to ask the 747 Chief Pilot if we wanted to consider a 'start inhibit' in the FADEC logic that would prevent a ground start attempt if the thrust lever wasn't at idle (ground starts only - for what should be obvious reasons). He didn't like the idea, and it went no further...

Originally Posted by 1stspotter

So how many fuel control switches on the Boeing 787 were since the release of this SAIB found with a faulty switch locking?

Originally Posted by tdracer

I watched it last night - nothing new or that hasn't been discussed endlessly here. Reasonably even handed, although I didn't like all the attention to the 737 MAX fiasco (IMHO, a Red Herring with regard to this crash).
Go into some detail regarding the possibility of pilot suicide (although not much attention to the "brain fart" possibility) - with the obligatory rebuttal from another pilot.
Lots of interviews with grieving relatives.

Originally Posted by Fursty Ferret

1. Which is why no one looks at anything until the flight path is under control (essentially above 400' RA).
2. This is taken into consideration at the design stage and isn't an issue.

Originally Posted by Magplug

Iam not aware of a spate of pilots purposely (or even accidentally) moving both fuel switches to cut-off at rotatethat would require the investment of an interlock to prevent it. In fact, the very presence of such an interlock might introduce it's owns risks.
That's is though, the scenario that many on here seem to think is the most likely cause of the 'accident'

The chances of a pilot wishing to commit suicide may also be one in ten million. If he is denied the fuel cut-off switches then there are plenty of other options. If a pilot decides to execute a half-roll and pull-through on final approach, or some other non-recoverablemanouvre then there is not a lot to prevent him.... not even the bloke sat next to him. (Please don't lecture me on Airbus AOB protections - You get my point)

Yes, not a lot to prevent that, although it would be easily identified for what it was. With the incident in question, it's the insidious nature of the event, that so far, is preventing it being positively identified as an act of malice.

For all you heating engineers with pet theories on how to design bad stuff out of aeroplanes, and all you wannabe airline pilots and CRM instructors let me tell you..... When I turn up for a trip, very often the other guy/gal is a complete stranger to me. I might have heard good things about them or they might have a bit of a reputation. As a Captain I have a limited amount of time to gauge this guy/gal before I get locked in the inner sanctum and I have to vest my TOTAL trust in them. TBH I have only ever flown with one guy who I would not trust alone in the flight deck, he was hyper-religious and just plain odd. I took my concerns to the adults and learnt I was not the first Captain making the same observation. I don't know what happened to him but our paths never crossed again.

Captain Magplug,
use lowercase when referring to the position generally .

With reference to your tone in the first sentence of the above paragraph. Hopefully this is not a personality trait, certainly not something desirable for someone in your profession.

The message here is simple.... Occasionally there are those amongst us who have their demons. It is the responsibility of us all to make sure they get the help they need before they hit rock-bottom and do something stupid.... oblivious to the 350 innocent souls sat behind the door.

Yes, there have been occasional demonic acts in recent years, and those responsible for identifying such cases might have hoped to be more effective. Sadly, it is entirely possible it could happen again, unless something changes.

Originally Posted by Chernobyl

The problem with your stated concern is how do you prevent it? Simple, you say: interlock it with the thrust levers and/or radio alt and/or baro alt in some combination to ensure you can ONLY switch to cutoff if not below 400' ft or at takeoff thrust. But what happens if this new logic fails in a novel way in the future preventing an engine shutdown when it really IS needed? Any new complexity adds potential unintended consequences and hence risks. Is the cure worse than the disease? Right now, the switch design is entirely consistent with Boeing standard practice: flight crew actions are the final say.