Boeing 787 Suffers Rare Dual Engine Failure on Landing • Hacker News Board

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#181

Post by avian » Wed, Jan 30, 2019, 6:59 PM UTC

sp0ck wrote: post #166

asdfadsfgfdda wrote: post #148

Earlier quoted context omitted.

Thrust reversers can never be deployed while airborne. This engine shutdown system is only enable on the ground. It's designed to shutdown an engine if the engine thrust doesn't match the commanded thrust, so an engine malfunction on the ground cannot cause the plane to taxi out of control. But it is still possible for the pilots to deploy reverse thrust too soon, after touchdown but before there there is enough weig…

Definitely you can use thrust reversers before touchdown at least on B737. I wonder how big is a difference between software on B737 and B787. Aviation industry doesn't have tendency to build software from scratch. Here is example video: https://youtu.be/-RO66a_nvus

Hey, thanks for this video. I was on a flight that did that some years ago when I was doing a lot of traveling. I don't remember anymore where exactly in Europe it was, but no one I later talked to believed me that the pilot would engage thrust reverser before touchdown.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#182

Post by jiveturkey » Wed, Jan 30, 2019, 7:00 PM UTC

> Engineers inspected the engines and could find no reason for the dual failure. With the post-inspection finding nothing to cause the engines to fail, engineers are saying the likely cause for the shutdown is a software issue onboard the aircraft.

Very interesting that

a) one of the first checks by engineers is not an evaluation of the software "log" or similar. either they have a specific checklist they MUST go by and that checklist doesn't include software log, and/or such log is simply not available to them.

b)"likely cause"? again, why don't engineers have easy access to a software event log?

I can very well imagine such instrumentation of software caused events not even existing for the shit apps we build, but for safety critical systems in an airplane? The log MUST exist. Why don't engineers on the ground have easy access to it. The software is integral these days.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#183

Post by threeseed » Wed, Jan 30, 2019, 7:08 PM UTC

maxxxxx wrote: post #112

nck4222 wrote: post #110

Earlier quoted context omitted.

Do you have experience with aircraft engine design, or landing protocols, or insight in to the meetings when the engines were designed? If so, I'll take back my words but considering the manufacturer doesn't know exactly why this happened, and the engineers on the ground said it seems like a "software bug", it seems a bit presumptuous and frankly a bit comical to start saying things like: "Surely a better solution wo…

I always love it when you have worked on something for months and someone new comes by and says "Why don't you just X?".

HN is the worst for it. Especially when it comes to tech stacks.

If you use anything other than non-SPA, Go, PostgreSQL then it's over engineered and doomed to fail.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#184

Post by salawat » Wed, Jan 30, 2019, 7:08 PM UTC

ChuckMcM wrote: post #132

nck4222 wrote: post #110

Earlier quoted context omitted.

Do you have experience with aircraft engine design, or landing protocols, or insight in to the meetings when the engines were designed? If so, I'll take back my words but considering the manufacturer doesn't know exactly why this happened, and the engineers on the ground said it seems like a "software bug", it seems a bit presumptuous and frankly a bit comical to start saying things like: "Surely a better solution wo…

Reminds me of the quote, "For every complex problem there is an answer that is clear, simple, and wrong." -- H.L. Mencken One of the things I have experienced in my career is the mind boggling complexity of the software in systems that are capable of killing people. The more people it can kill the more complex the software. As a result when I read articles like the one posted I find it tantalizing to speculate about…

If the reverser could rip the engine off the wing, it wouldn't be safe to engage on the ground. Just thought that was worth pointing out.

A reverser only redirects thrust, and only generates about 60% of max thrust pushing backwards.

It's only on for a limited time on the ground because under a certain speed, you run the risk of blowing FOD into the intake path, putting the engine at risk.

I'm not aware of any reason to outright lockout a reverser in flight other than to hedge your bets against a very, very poor set of configuration choices by the pilot (reversing near stall speed too low to recover). I could foresee scenarios where being able to use reversers in the air could save the aircraft with the right combination of subsystem casualties.

Not a pilot or engineer, but absolutely LOVE aviation.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#185

Post by booi » Wed, Jan 30, 2019, 7:10 PM UTC

0xFFFE wrote: post #104

Seems like reasonable choice on the Boeing's part, the objective of the reverse thrust is to provide additional braking to the aircraft, if shutting down the engine has similar effect (albeit to a lesser extent), why not? Better than getting stuck in a dangerous situation if the reverse thrust was deployed prematurely.

You're joking right? The engine is required for nearly everything else including but not limited to applying thrust to abort the landing.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#186

Post by jacquesm » Wed, Jan 30, 2019, 7:11 PM UTC

anonu wrote: post #48

laretluval wrote: post #2

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

I think software has existed in computer systems for 7 or 8 decades now - and the pitfalls are well understood. I think the problem is one of simplicity vs complexity. New systems today rely on dozens - hundreds even - of packages and libraries - many of which are not written by the implementer. How can you ensure reliability in all these components? This is why engineering from first principles - even in today's sof…

> I think software has existed in computer systems for 7 or 8 decades now - and the pitfalls are well understood.

This would be funny if it weren't tragically wrong. Time and again we learn that software is very much not yet well understood, especially in large and complex systems. And aviation does this a lot better than most other lines of business.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#187

Post by threeseed » Wed, Jan 30, 2019, 7:11 PM UTC

jagger27 wrote: post #73

ravingraven wrote: post #62

Earlier quoted context omitted.

No, it would not. If the engine is shut down moments before touching down it would mean that there would be no reverse thrust after touching down since it takes a considerable amount of time to re-start a turbo-fan (not 60 seconds as OP wrote as the engine is still spooling but still a significant amount of time and I don't think that any pilot would go through the workload and checklists of re-starting an engine dur…

> or to only engage reverse thrust once the landing gear has weight on it. Having reverse thrust depend on a sensor that could fail seems like a poor choice. What if the landing gear don't drop? Is there a situation where you would still want reverse thrust without landing gear?

Just have multiple sensors like they do already.

It's also a sensor that you can simply put on each wheel to determine if there is weight applied.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#188

Post by jlg23 » Wed, Jan 30, 2019, 7:11 PM UTC

Retric wrote: post #158

ergothus wrote: post #116

Earlier quoted context omitted.

It's worse when they are right though. I wish I could say that had not happened to me.

Is that from other experts with a very close understanding of the specifics, or random people online? What I find is you start with several viable approaches, pick one and go down the path enough to figure out the downsides. At which point you need to decide to backtrack or keep going. That’s the hard part not simply coming up with a seemingly simple solution.

> Is that from other experts with a very close understanding of the specifics, or random people online?

These groups are not mutually exclusive, membership can only be assigned by a domain expert and is finally irrelevant if the other is right.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#189

Post by esemor » Wed, Jan 30, 2019, 7:11 PM UTC

I think the auto shutdown of engines in flight, in case it senses reverse thrust, is a great design.

The 787 is a replacement for my 767 (currently a pilot on the aircraft) and in 1991 a Lauda Air 767 suffered a failure in one of its thrust reverser and it became activated during cruise. The aircraft was destroyed in flight.

The thrust reversers should not activate during flight (a air/ground sensors prevents that) but as it is a catastrophic failure, having the engine shut down automatically seems like a great fail safe device.

In this case it seems that the 787 engines were reversed before the air/ground sensor had sensed ground and it is a potential problem.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#190

Post by SomeHacker44 » Wed, Jan 30, 2019, 7:14 PM UTC

markdown wrote: post #98

Xixi wrote: post #57

Earlier quoted context omitted.

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…

> 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. I'd argue that a new model of an old plane like the 737MAX would be safer, Lion Air incident notwithstanding.

Many actual pilots would likely disagree. Shoehorning vastly different planes into the same type certificate can be dangerous. Convenient for pilots due to certification and recurrency issues, but not necessarily a good idea.

Do you really want a pilot to jump into a 737MAX who only ever flew the -100? I bet the memory items are very different if not also all the speeds and weights.

(NB: jet pilot, not Boeing airliner pilot though)