Boeing 787 dual engine failure

[bitchstewie]

Interesting read https://thepointsguy.com/news/boeing-787-suffers-r...

[Gary C]

Suspect software issues !

We can hardly move for software reliant systems these days, which is a nightmare in safety critical industries, very difficult to prove bug free.

[dhutch]

Computer says no!

[Mabbs9]

It's a software glitch. A certain sequence of reverser handling is the trigger.

[twister]

Hmm, so computer might say no to ongoing engine operation if thrust reversers are deployed too early, yet computer doesn't say no to prevent thrust reversers being deployed too early...

If you can't guarantee that deploying the reversers at a given point in the flight will have the expected result, is there any scenario where you might still want to do it anyway, and where being prevented from doing so might then cause more trouble than it solves?

[Krikkit]

Gary C said:

Suspect software issues !

We can hardly move for software reliant systems these days, which is a nightmare in safety critical industries, very difficult to prove bug free.

But, in this case, it's a system added by Boeing rather than RR itself by the sounds of it. More appropriate title would be "engine command failure" I suppose as the engines are probably fine, but the flight computer is blocking them from being restarted. What's surprising is there isn't a way to reset the system mentioned in the checklist.

Yes software is very difficult to certify bug-free in safety-critical environments, but you couldn't run a modern jet engine without FADEC, not to mention all the fancy systems on aircraft that pilots woudn't want to do without now.

[dhutch]

I don't know the details, but I can see a point in preventing and or making it very hard to give reverse thrust while mid-flight !

However equally suddenly having your brakes, and all other motive power, taken away unexpectedly during landing could also have considerable consequences !

Mehhh, planes stuff.


Daniel

[Mabbs9]

The problem is going from full reverse to forward idle in one selection. The thrust control computer thinks it's lost control of the engines. It'll only happen on the ground and when the decision has been made that reverse thrust is not required.

Many airliners have a list of computer glitches. Particularly the Airbus family. We brief the specifics before every departure.

[Krikkit]

dhutch said:

I don't know the details, but I can see a point in preventing and or making it very hard to give reverse thrust while mid-flight !

Apparently it's a safety feature brought in after a 767 managed to deploy a thrust reverser in flight and the aircraft was destroyed.

In this case the flight computer needs to have recognised it's in "ground" mode and allow the reverser deployment, presumably they tried engaging the reverser a fraction before touchdown?

[J4CKO]

Krikkit said:

dhutch said:

I don't know the details, but I can see a point in preventing and or making it very hard to give reverse thrust while mid-flight !

Apparently it's a safety feature brought in after a 767 managed to deploy a thrust reverser in flight and the aircraft was destroyed.

In this case the flight computer needs to have recognised it's in "ground" mode and allow the reverser deployment, presumably they tried engaging the reverser a fraction before touchdown?

Is that the Lauda Air one ? I got the impression that was an electronic system as well, I watched the Air Crash programme a while back.

People fret about software but airliners typically have four independent systems with voting rights and to be honest, since computer control has got more prevalent, flying has got safer, not just the control systems but stuff like TCAS.

[Gary C]

Krikkit said:

Gary C said:

Suspect software issues !

We can hardly move for software reliant systems these days, which is a nightmare in safety critical industries, very difficult to prove bug free.

But, in this case, it's a system added by Boeing rather than RR itself by the sounds of it. More appropriate title would be "engine command failure" I suppose as the engines are probably fine, but the flight computer is blocking them from being restarted. What's surprising is there isn't a way to reset the system mentioned in the checklist.

Yes software is very difficult to certify bug-free in safety-critical environments, but you couldn't run a modern jet engine without FADEC, not to mention all the fancy systems on aircraft that pilots woudn't want to do without now.

Its a nightmare getting new software systems through certification at work for anything that might possibly affect Nuclear Safety. Replacing the coolant circulation post trip variable speed drives was a prime example. The original discrete component & relay drives are obsolete and were becoming unreliable, but replacing them with a drive without programmable logic was impossible. So we have spent millions over the last 15 years since the issue arose refurbishing the original drives and finally getting approval to replace 2 out of the 8 drives on each reactor as reliability test which will probably run to the end of the stations life.

But there again, analogue systems can have the same hidden faults, the hydraulic lockout in United Airlines flight 535 and subsequent events is one such.