Earlier quoted context omitted.
There should be manual override. What if this happened in-AIR?
You really, really do not want the reverse thrust to turn on in-AIR. That would be way worse then then engine shutting down.
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Boeing 787 Suffers Rare Dual Engine Failure on Landing
61–70 of 365 posts
Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing
#62Boeing’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…
A tough call. Your solution would disappoint a pilot who actually wanted to slow down ASAP more than Boeing's solution, and might contribute to a runway overrun.
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 during the landing roll anyway). This leads to a longer braking distance.
The sane choice would be to not engage reverse thrust at all (until the pilot has reset the reverse thrust throttle) or to only engage reverse thrust once the landing gear has weight on it.
Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing
#63"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." That sounds like apple's "you are holding it wrong" when "antenagate" happened. Not something I want to hear from an aircraft company where people's lives depend on it working.
Reading between the lines, and having read other comments here, I can interpret Boeing’s remark as “if the pilots or the on-board software try to reverse engines when it still is really, really dangerous, the Thrust Control Malfunction Accommodation system (TCMA) will try to make matters less bad, in some cases by shutting down the engines instead”.
They may have to fine-tune that system, but from a safety perspective, this event had a good ending, and making its decision system more complex also carries risks, so, maybe, nothing has to change.
Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing
#64Earlier quoted context omitted.
There should be manual override. What if this happened in-AIR?
You really, really do not want the reverse thrust to turn on in-AIR. That would be way worse then then engine shutting down.
It has occurred. Lauda Air Flight 004 was a Boeing 767-300ER that crashed due to an uncommanded reverse on the number one engine.
Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing
#65I'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?
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Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing
#66Sort 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 :)
But is it the hot air out of the engine being reversed or the air from the big fan? I thought it was the latter.
Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing
#67Earlier quoted context omitted.
> 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 A…
Those are prior flights. The aircraft was fully repaired:
> 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
So you still haven't supported your extraordinary claim that the aircraft was:
> unsafe on takeoff.
In fact we know it was safe on takeoff.
Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing
#68I would bet this is going to get a lot more common as a whole generation of heads-down nerdy programmers who got into the industry because of sheer geek joy get replaced by Stack Overflow copy/paste Uber brogrammers who are just looking for a paycheck to fund their weekends in Tahoe. I mean, that's OK and all, but they need to stick to making Fyre apps that crush it by changing the world through social influencers or whatever and stay away from heavy machinery like automated cars and fucking airplanes.
Sadly, supply and demand isn't going to let this happen. This, combined with rampant ageism that forces out the older workers who know better means we're all going to be seeing this a lot more over the next decade. "Remember when that Facetime bug made national news?? LOL! Those were the good old days!"
Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing
#69Is 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…
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Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing
#70Boeing’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…
I thought that most modern aircrafts were not allowing the reverse to be deployed if the wheels didn't touch the runway. Talking about an odd safety override. It's kind of a self-destruct button.
It's not an odd safety override. An overthrust situation is always dangerous for various reasons. One of the more spectacular is the possibility of liberating airfoils from the engine and shooting them into the cabin.
It's not a self-destruct button, it's anti-destruct limit.
As for the thrust reverser, there are many integrated systems on the aircraft. It's possible that the cockpit detected weight-on-wheels, but the flight mode hadn't yet transitioned for the engine controls.