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Boeing 787 Suffers Rare Dual Engine Failure on Landing

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Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#51

Post by Someone1234 »

danielvf wrote: post #30
aaronbrethorst wrote: post #5

Earlier quoted context omitted.

and causing trouble for everyone You mean killed 189 people, right? https://en.wikipedia.org/wiki/Lion_Air_Flight_610

That aircraft was being knowingly flown with [edit: a broken sensor]. It was unsafe on takeoff. The final problem that brought the aircraft down - the trim run-away - happens all the time in airliners you've flown in. When the run-away starts, the pilot is supposed to flip two switches to disable the trim system motors. In the Lion Air crash, it is indeed believed that a software bug from the misbehaving sensors star…

> That aircraft was knowingly flown with multiple broken sensors. It was unsafe on takeoff.

You'll need to cite that, since it contrary to any information I can find on the Lion Air accident e.g.:

> The chief executive officer of Lion Air, Edward Sirait, said the aircraft had a "technical issue" on Sunday night, but this had been addressed in accordance with maintenance manuals issued by the manufacturer. Engineers had declared that the aircraft was ready for takeoff on the morning of the accident

Your claim that it was "unsafe to takeoff" and had "multiple broken sensors" is pretty remarkable. So I'll definitely need to see a source backing up such remarkable claims.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#52

Post by teraflop »

dajohnson89 wrote: post #33
chrisper wrote: post #24

Earlier quoted context omitted.

It doesn't at all. It's an explanation why it might happen.They never said that this behavior won't be fixed or changed. It's not blaming the pilots.

There is a notion of blame wrapped up with "too quickly".

"Too quickly" appears to be the article's wording, not Boeing's, although I couldn't find a copy of the actual bulletin to confirm that.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#53

Post by jessaustin »

laretluval wrote: post #2

I hope people are beginning to understand that the presence of software in any system is a liability.

It's a liability when you're getting equipment serviced, whether there's software or not. We have a Cat 287B skid-steer. After a month of inactivity, it wouldn't come out of "park" mode. A mechanic lifted the cab, tested a couple of solenoids, and stated "must be a bad computer". This is an old machine, so I called Cat and confirmed that it doesn't actually have a computer. I took up the floorboard and found some wires that had been chewed by rodents. We're lucky we don't have a computer, because replacing it wouldn't have helped...

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#54

Post by seiferteric »

exabrial wrote: post #12

Sort of off topic, but reverse thrust sort of boggles my mind. If you're sucking air in from the front of the aircraft and ejecting it out the front, don't those forces counterbalance each other?

Your forgetting that the cool dense intake air is expanded (greatly) in the engine via combustion with fuel, so the volume of air being exhausted is much greater than went in and at much higher pressure, this is where the thrust comes from in the first place. It's not just a big fan :)

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#55

Post by RobLach »

samfisher83 wrote: post #15
onewhonknocks wrote: post #4

I'm not sure this is a bug. It sounds like pilot-error to me (I am not a pilot): "In the bulletin, Boeing said that selecting full reverse too quickly upon landing before the aircraft has fully transitioned to ground mode could cause the system to activate."

There should be manual override. What if this happened in-AIR?

A pilot engaging reverse thrust mid-flight can break apart a plane:

https://lessonslearned.faa.gov/ll_main.cfm?TabID=3&LLID=34&L...

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#56

Post by teraflop »

Someone1234 wrote: post #51
danielvf wrote: post #30

Earlier quoted context omitted.

That aircraft was being knowingly flown with [edit: a broken sensor]. It was unsafe on takeoff. The final problem that brought the aircraft down - the trim run-away - happens all the time in airliners you've flown in. When the run-away starts, the pilot is supposed to flip two switches to disable the trim system motors. In the Lion Air crash, it is indeed believed that a software bug from the misbehaving sensors star…

> That aircraft was knowingly flown with multiple broken sensors. It was unsafe on takeoff. You'll need to cite that, since it contrary to any information I can find on the Lion Air accident e.g.: > The chief executive officer of Lion Air, Edward Sirait, said the aircraft had a "technical issue" on Sunday night, but this had been addressed in accordance with maintenance manuals issued by the manufacturer. Engineers h…

From the same Wikipedia article that was just linked:

> "The aircraft suffered an airspeed indicator problem for its last four flights, including the flight to Denpasar. Thinking that it would fix the problem, the engineers in Bali then replaced one of the aircraft's AoA sensors, but the problem persisted on the penultimate flight [...] [the crew] recorded a twenty-degree difference between the readings of the left AoA sensor and the right sensor."

> "On 28 November, Indonesia investigators said the Lion Air jet was not airworthy on flight before crash."

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#57

Post by Xixi »

deugtniet wrote: post #10

Is there something special about the software in new Boeings? Dual engine failure is nothing to sneeze at, and should never happen. Airbus also had its fair share of software errors in history, but if we count the recent Lion air crash as software related, Boeing has had 2 serious software related incidents in a year and I haven't heard anything serious from airbus. Is it because Airbus started its fly-by-wire develo…

The first Airbus FBW airliner was the A320, introduced in 1988 (31 years ago), while on Boeing side it was the 777, introduced in 1995 (24 years ago). By now I don't think it would make much of a difference, if any at all.

If anything quarterly reports to shareholders who only care about the very short-term would be the culprit (or management teams whose bonuses only depend on the next quarter revenues). But numbers are stubborn and don't tell that story: the more recent the plane the safer it is. As such 787 and A350 are probably the safest airliners currently flying, followed by 777 and A380.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#58

Post by Mithorium »

aaronbrethorst wrote: post #5
nitinreddy88 wrote: post #3

How many easter eggs will emerge from Boeing. In last 2 months, we had similar incidents from Boeing where an undocumented software safety kicked in and causing trouble for everyone

and causing trouble for everyone You mean killed 189 people, right? https://en.wikipedia.org/wiki/Lion_Air_Flight_610

To save people the reading, the safety feature triggered was an automatic dive maneuver initiated by the flight computer as a result of an incorrect angle-of-attack sensor reading causing the plane to believe it was in a stall, when it actually wasn't

I didn't look into it any further, but based on that alone I would agree that this seems like a shitty feature, perhaps a loud alarm or other warning would be more appropriate than putting the plane in a dive without human intervention

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#59

Post by sbradford26 »

samfisher83 wrote: post #43
opwieurposiu wrote: post #31

Earlier quoted context omitted.

You really, really do not want the reverse thrust to turn on in-AIR. That would be way worse then then engine shutting down.

I don't mean specifically reverse thrust. I am saying features such as this. The Pilot expects something and computer does something else.

There are usually failsafe modes that disable most of the additional software features. It is pretty rare though for pilots to switch into those modes though since those features are what fly the plan a majority of the time.

It is like the issue that are running into with self driving cars, there is a point where the flight controls become so good that pilots are less likely to intervene when something is going wrong.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#60

Post by Someone1234 »

laretluval wrote: post #2

I hope people are beginning to understand that the presence of software in any system is a liability.

My take-away is a little different: As software grows it is hard to quantify.

If you have several small distinct systems, you can often quantify them down to inputs, outputs, and expected logic. Once systems get too complex, you have too many possible states, and bugs are harder to find (and the system cannot be fully defined).

I often go back to the famous Therac-25 accident. The bug in Therac-25 existed LONG before the accident, but there were two systems interacting, one system checked the other system's output and threw away invalid state. Once those two systems were merged, it was only then that the bug turned into an accident.

If aircraft stopped building monolithic software and instead built parts that ran on software, parts that could each be individually verified, it would likely result in safer software.

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