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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

#191

Post by gugagore »

salawat wrote: post #184
ChuckMcM wrote: post #132

Earlier quoted context omitted.

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…

The cruising airspeed of an airplane is faster than its landing speed. I don't know if that alone is enough to rip the engine off the wing, but it's something that it sounds like you did not consider in making your point.

[EDIT remove "roughly speaking an order of magnitude"]

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#192

Post by aaronmdjones »

ricardobeat wrote: post #129
cm2187 wrote: post #114

Earlier quoted context omitted.

By self destruct, I meant switching off the engines in flight seems to me to be a terribly dangerous behavior.

I think almost every plane can glide safely for a lot longer than it takes to restart the engines. Could be dangerous at low altitudes still.

That and restarting an engine in-flight is faster than starting it on the ground because it's already spinning (by virtue of sailing through the air, like a windmill). This is, aptly, called windmill starting.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#193

Post by imsofuture »

threeseed wrote: post #183
maxxxxx wrote: post #112

Earlier quoted context omitted.

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.

Tech is the worst. Fetishizing disruption leads to neophytes thinking they're breaking new ground when they're just re-discovering long dismissed ideas.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#194

Post by burfog »

asdfadsfgfdda wrote: post #148
code4tee wrote: post #19

Boeing’s answer seems to say if you accidentally pull the thrust reverser lever before the aircraft is on the ground it just force shuts down the engines. That sounds like an odd safety override. Surely a better solution would be to just not activate reverse thrust. Unlike car engines a jet engine can’t just be quickly restarted if it accidentally shuts down. It typically takes 30-60 seconds to get going. This and ea…

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…

Maybe the 787 won't allow airborne use, but other aircraft allow it. It's useful for steep descent. If the feature were more common, obstructions near airports (like mountains) would be less of an issue. We could build new runways at some airports.

https://en.wikipedia.org/wiki/Thrust_reversal#In-flight_oper...

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#195

Post by Glawen »

jiveturkey wrote: post #182

> 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 where would you store these logs ? I'm sure the engine stores its faults somewhere, but i'm not expecting more.

You have to realise that you can run safety critical software on certified microcontrollers, which have usually like 10 mb of flash. Moreover it is an aicraft, and worse it is an engine, so I guess that the mechanical requirements are insane (able to withstand a lot of vibrations, operate in -60 to 160 deg celsius, withstand cosmic rays). A samsung ssd does not fit the bill.

It's probable however that the aircraft communications lines are recorded in a black box, but you can only see the data exchanged by the ECUs, not the relevant internal variables telling you about the bug.

Mind you i'm not working in the aicraft industry, my assumptions may be false, but my guess is that the engine controller is on the engine itself.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#197

Post by AshleyGrant »

gugagore wrote: post #191
salawat wrote: post #184

Earlier quoted context omitted.

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…

The cruising airspeed of an airplane is faster than its landing speed. I don't know if that alone is enough to rip the engine off the wing, but it's something that it sounds like you did not consider in making your point. [EDIT remove "roughly speaking an order of magnitude"]

>The cruising airspeed of an airplane is roughly speaking an order of magnitude faster than its landing speed.

No. No it is not. 787 approach speed is 145-153 knots. It does not cruise at 1400+ knots.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#198

Post by DuskStar »

danielvf wrote: post #113
IshKebab wrote: post #106

Earlier quoted context omitted.

A big issue with that flash was that there was a way to disable the feature, but Boeing didn't tell anyone about it and it wasn't documented anywhere.

You can still disable the stabilizer trim from switches in the cockpit, though. This was in the checklists that the pilots had, and done by other pilots in that aircraft in the days before the accident.

Yeah, it's hard to make the argument that a recovery procedure is so incredibly difficult and obscure when several previous flights of that plane experienced the same issue and successfully followed that procedure... And apparently without considering it extremely outside of the norm.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#199

Post by goodcanadian »

dba7dba wrote: post #35
exabrial wrote: post #18

Earlier quoted context omitted.

It's not just Boeing unfortunately. Every software driven aircraft seems to suffer from these bugs. The F35 lost radio communication after crossing the international date line the wrong direction IIRC, and the pilots had to use hand signals to land.

> The F35 lost radio communication after crossing the international date line the wrong direction IIRC, and the pilots had to use hand signals to land. From what I remember, the first time 4 USAF F22 were flying across international date line to deploy to Hawaii(?), they had software related issues. As they flew across the international date line (first time in a real flight), all computers on the jets crashed, inclu…

Deploying to Guam. Hawaii is on the same side of the dateline as the continental United States. Also, as I recall, they simply rebooted the computers.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#200

Post by focom »

esemor wrote: post #189

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) b…

There is Airplane pilot on HN? I am surprised, did you make a career switch from IT?
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