I wonder if the cowling contained the initial disintegration but was removed in the process. I'm not an engineer, but from the way that looks and the fact that nothing flew off and did further damage makes me at least wonder if that's what happened.
What amazes me more is that the newest twinjets are now considered reliable enough to fly six hours away from the nearest landing strip -- that's how far they can coast on the single remaining engine if necessary!
Out of curiosity, I just checked for the A380 and the best guess is 15:1, so it does glide better than I expected, but still not that far.
Google tells me that it'd glide ~130 miles if it had a starting altitude of 45,000'. That's better than I expected.
The 747-200 also has a glide ratio of 15:1. I can't tell if that's amazing, good, or average.
A sailplane can have up to 60:1! That's pretty impressive!
According to this: A "clean A320" has 17:1. Neat.
Something I never knew was this:
>As someone said above, you have to remember, pretty well all descents are done with the thrust at idle.
So I imagine the glide ratio is pretty important for all-purposes of flight and not just when engines go out.
>Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress.
A Cessna 172 is worse, for comparison. I believe they are just 9:1. I guess it improves if you stop the prop entirely. I assume it is less drag.
Quite directly, from ground altitude, a range within which to look for a place to land. As you mentioned the impressive finesse of gliders gives you more room, but gliders won’t generally be flying as high as cruising powered planes.
Combined with speed, a timeframe within which you have to observe, orient, decide and act. Here, both top speed and stall speed give you some hints, and within which there’s a best speed where finesse is optimal. You can imagine how it’s very different between an A320 and a glider, the former for which time runs quickly, you have to decide where to go in as few minutes as possible, the latter for which decision time brought back at a human thinking time scale makes it less stressful but you have to keep cautious of your goal for a longer stretch of time.
Obviously that’s without counting on soaring, which A320s can hardly benefit from (I suppose they can but would largely not move up and certainly not turn since it would would incur too huge drag).
That's statute miles (or 111 nautical miles or 205 km). It's quite impressive, really.
Can a plane takeoff with just one engine ?
Thus a twin has 50% more power than a similar 4 engine. At least conceptually-ish.
The fans spin very fast, and will fly out radially, not just fall back. They'll slice right through anything they contact. The Airbus flight was very, very lucky.
The documentary didn't say why they wanted it to be at such a specific place, only that they did. I've long since forgotten the margin of error, but it was very small.
You probably noticed that the individual blade is painted a different color and is different colors. My recollection is that they use the multiple colors because they do very high definition recording and the colors are all in different areas of the spectrum, so they can observe it better as the thing tends to be quickly obscured by fire and smoke.
I probably do watch too many documentaries.
You are not alone. I actually watch more and more documentaries than movies or TV series. Reality is even stranger than fiction often.
I watch documentaries pretty much to the exclusion of all other genres, except American football. Even if I'm not actively paying attention, I'll frequently have a documentary playing in the background.
It's not a scholastic pursuit. It is purely entertainment. I watch them because I enjoy them. Learning is incidental and not the objective.
I like to queue up playlists of documentaries and let them play through. The 'net has been excellent at facilitating this.
Yes, but uncontained failures can and do happen. Qantas Flight 32 is an example of an uncontained engine failure on an A380, though with a Rolls Royce engine instead of Engine Alliance (GE + P&W). 
I do think they're very lucky that this uncontained engine failure didn't cause more damage. QF32 was heavily damaged by debris coming out of the engine, so the fact that this seems to be relatively contained to the engine itself is fortunate.
The Quantas flight is remarkable in that engine parts were not contained successfully and managed to damage critical systems inside the wing not related to the engine itself. Some reports say that the flight crew was overwhelmed by over 50 individual failure reports resulting from this damage. I was actually quite surprised when I learned that it was so easy to damage that many major systems with a seemingly small puncture in a wing.
When people talk of pilot-less airliners I have to think of incidents like this. Pilots do make mistakes and people die as a result, but when equipment fails and nobody dies because a pilot does what is needed to land safely despite the issue, it rarely makes news. Sometimes people on board don't even know.
That's the ideal general case. You really don't want hundreds of panicked people trapped in a broken tin can thousands of feet above ground while you're trying to handle the situation.
However, that brings up another question I've been wondering about: Could the pax/cabin crew of an airplane collaborate in bringing a jet down, by e.g. all together going to the very front of the plane (near the cockpit door), moving the trim up, then all running to the very end of the plane, bringing it into an uncontrollable stall?
I haven't really seen a satisfactory answer to that question. See Quora and Stackexchange (where I attempted an answer):
One engine failed completely, two others were seriously degraded, aircraft control was minimal, fuel could not be dumped (leading to an overweight laading). The impression from one documentary was that the first officer spent much of his time overwhelmed with system reports which had to be cleared from his displays. Systems and information design and flows seem a net negative for this incident -- there is such a thing as too much information.
Overall, many reserve margins were exceedingly tight.
Your comment seems to me to grossly understate the severity, and overly credit Airbus and Rolls Royce, in this case
However, I'm wondering - would the blade go straight lateral? Or, relieved from having to pull the whole damn plane forward, would it fly forward and hit the fuselage in front of the engine? Or, slowed down by the air resistance, would it hit the fuselage behind the engine?
Best, I suppose, to sit up front in first class...
If you're concerned about which seats are safer, the ones in steerage in the back are the safest. They tend to arrive last at the scene of the accident :-)
Good shoes can save your life, because you can walk out over hot, burning wreckage.
Wear cotton, not synthetic, clothes, and you'll have less severe burn injuries.
And, of course, pay attention to where the exits are and the flight crew's safety instructions. They really do know what they're talking about, and they're well trained.
> They really do know what they're talking about, and they're well trained.
I wonder, btw, whether people on Saudia 163 would have survived if they had stormed the emergency exits after landing against (presumably) the orders of the crew...
I have never heard of an incident where prop debris penetrated the cabin, but avoided the seats on that row if at all possible, just in case.
Update: in 1981, the fan of the rear engine on an L-1011 separated, and chewed its way through the inlet duct ("The 'S' duct was damaged internally from next to the fan blades forward about 16 feet") before exiting the fuselage sideways, sending shrapnel into a lavatory and doing serious damage to the flight controls: "The displacement of the fan module in the course of the engine failure sequence caused loss of hydraulic systems A, B, and D and jammed the captain's and first officer's rudder pedals in the neutral position."
The aircraft landed safely, but with a little more damage, the airplane would have been uncontrollable.
Yes, there's also a short video about that:
It's very interesting since ETOPS affected the financial bets that Boeing made on 787 (point-to-point) vs Airbus with the A380 (hub-and-spoke).
The extra complexity of extra engines actually reduces reliability, since there are more components that can fail.
> There's no other part of the airplane behind the engines either, so nothing to be hit by debris.
No, but there's a wing and the fuselage nearby. Again, I'm not an engineer, but I'm assuming that in this type of failure, the part of the engine that's spinning might want to come laterally (is that the right word?), and that seems like it could be trouble. I'm amazed that it didn't.
> What amazes me more is that the newest twinjets are now considered reliable enough to fly six hours away from the nearest landing strip -- that's how far they can coast on the single remaining engine if necessary!
Totally amazing. I'm not sure, but is that only the A350XWB for now, or have others been certified past ETOPS-360? It's basically certified to the design limit of the aircraft, so I'm not sure what else has been designed for that. Even 5+ hours is nuts though.
Somewhat related, but check out the Chilean regs on flying from the mainland to IPC/PPT. As far as I know, they still have the one aircraft rule.
Not unless the cowling was armored, which it wasn't at least back in the 80's. That thin sheet of aluminum won't even be noticed by the high strength fan spinning at tremendous speeds.
AFAIK part of engine qualification is proving that the nacelle will retain a fan blade breaking off at full throttle. There are remarkable youtube videos of these qualification tests.
The entire fan is another matter though. I assume the nacelle will offer some resistance, but not contain it entirely.
And the turbines as well, they don't even attempt to retain those.
When did that become a requirement?
> And the turbines as well, they don't even attempt to retain those.
I knew about the turbine blades, I just assumed the fan blades were as uncontainable. I think my information is out of date. Thanks for the correction.
Looks like it became a requirement in 1984, after I left Boeing. So that's why I didn't know about it.
As it turns out, I learned something as well. Contrary to what I said, that same passage requires failing turbine blades to be retained as well. However, they seem to be drawing the line at complete fan or compressor assemblies or turbine disks.
And after >100 years of that, we have pretty safe planes.
What most amazes me is that despite the scientific knowledge we "have", we can't design a new engine from first principles directly. We do it through trial and error. Lots of hilarious/horrible error.
Rolls Royce prides themselves on hiring interns. The little cone piece in front of the jet engine had issues with icing up. This had plagued jet engines for years.
They tried all sorts of ways to fix it, including complex methods of supplying heat.
One of their interns just happened to hear about this problem and suggested they simply make it out of rubber. Sure enough, it worked and the problem with that pointy bit freezing was solved.
I'm sure it has a formal name and that it is probably not pointy bit or little cone piece. I don't actually know anything about jet engines, I just watched a documentary about Rolls Royce's jet manufacturing.
Anyhow, that wasn't something that could probably have been designed with first principles. Someone, pretty much in passing, pretty much had to have that creative spark at just the right time and with just the right information.
It's things like that story that make me think humans are going to be in the loop for a long time still and that AI taking over the world is still a long ways away.
I've found that the world continues to turn contingent on tremendous amount of what I call "dark wisdom" - crucial pieces of knowledge not found in any server, spec sheet, or manual. Usually inside the noggin of one or a few people. It just seems like a consequence of maintaining complex systems. In order for AI to fully take over, it would have to control and account for every corner case of every system, from mining the ore, to fabbing chips, to replacing wires chewed by rodents.
where they just shut one engine down above canada and continued on 3 accross the atlantic to kuwait (they couldn't safely - with enough fuel reserve for multiple approaches and a diversion - reach dubai)
In this case the whole fan disk is gone. Uncontained failure like this can down the plane depending on the where the parts fly.
One possibility is that the fan shaft failed, and since the fan was no longer attached to the plane that it had been pulling through the sky, it went happily ahead by itself (perhaps still in one piece), taking the cowling with it.
It doesn't say anything about jokes.
Let's compare: Qantas 32 lost throttle on one engine, lost one engine completely (obviously), flaps, and ABS. United 232 lost its tail engine, elevator, rudder, aileron, flaps, and had no ABS to begin with.
Qantas 32 was able to maintain a holding pattern for an hour while diagnosing the aircraft, and was given enough time to calmly calculate a glide path and put the airplane down safely. United 232 landed at twice the safe speed, with 6x the safe sink rate, on its wing.
Qantas 32 had 0 fatalities or injuries, United 232 had 111 fatalities and 172 injuries.
I'd like to hope that this wasn't caused by ground crew error, i.e. an improperly secured cowling or access hatch, which snowballed into major component failure...
Which is of course what happened in that linked incident below:
The three hydraulic systems were separate, so that failure of any one of them would leave the crew with full control, but lines for all three systems shared the same narrow passage through the tail where the engine debris had penetrated, and thus control surfaces were inoperative.
A quick search for "A 380 hydraulic fuses" finds sources like http://www.airliners.net/forum/viewtopic.php?t=765509 :
> If one or both hydraulic systems fail, the following hydro-electrical backups remain available: For flight controls: The Electrical-Hydrostatic Actuators (EHAs) and the Electrical Backup Hydraulic Actuators (EBHAs)
For braking and steering: The Local Electro-Hydraulic Generation System (LEHGS)"
That's depicted in the image bad_alloc showed.
And, "hopelessly intertwined"? Is that your viewpoint as a software developer, or are you an aircraft designer? Because I'm sure that an outsider would see my code as "hopelessly intertwined" even when it isn't.
Even with modern aircraft, even with the A380, when a fan lets go or the engine grenades bad things happen.
Qantas Flight 32, an A380, suffered a UCE and everyone was very lucky that there were additional, experienced pilots on board. Take a look at the ATSB report. Pretty much everything that could fail, did. Engine control for the #1 (IIRC) engine had been destroyed and it took the firefighters three hours to pump enough water to shut down the engine. Without the extra crew things could have gone very differently.
British Airways 2276, a 777 -- a plane that has an excellent safety record, suffered a UCE and the plane caught fire. Luckily the pilots were able to abort the takeoff, but fire on a plane is about the worst possible failure mode.
AA #383, a 767, also suffered a UCE on takeoff that resulted in a massive fire.
Cameroon Airlines Flight 786, same deal. UCE, punctured fuel tank, fire.
So, yes, things have almost certainly gotten better but given how much energy is released when a high bypass turbofan lets go, it's pretty damn hard to design something that's completely failsafe.
I'd hope so, given that all the redundancy didn't prevent an engine control failure on the A380.
As for Qantas Flight 32, which I believe is the engine control failure you are referring to, my reading of http://www.atsb.gov.au/media/4173625/ao-2010-089_final.pdf says that only one hydraulic system, Green, was damaged. The redundancy worked.
> Damage to the wiring also resulted in the loss of monitoring capability of the
Yellow hydraulic system engine-driven pumps on the No. 4 engine and the crew disconnected both pumps as per the ECAM procedure. The Yellow hydraulic system was powered by the No. 3 engine for the remainder of the flight. The Yellow hydraulic system maintained 5,000 psi for the remainder of the flight and subsequent examination found no fluid loss.
The inability to shut down engine #1 was due to "[d]amage to wiring looms located in the left wing and the fuselage belly fairing."
Again I ask why "hopelessly intertwined" is a meaningful description for the A380 hydraulic control systems.
It isn't luck. It is the result of millions of engineering hours spent on the development of highly reliable and resilient passenger aircraft, an emphasis on public identification and dissemination of design weaknesses, errors, and failures, and an unwavering focus by industry regulators on safety.
This is a particularly egregious failure mode and very hard to contain, but also one which a lot of design hours have been spent mitigating. They were very lucky to have suffered (apparently, as far as has been reported) no significant damage of any kind, but even an extremely egregious uncontained engine failure is frequently flyable because of the emphasis on redundancy in modern plane designs.
Is the a way to connect two A380s together? (wild guess)
> As a result of the accident, the airplane was determined to be damaged beyond repair and was dismantled on-site
Amazing that one one person lost her life.
Does anybody know how this works? Why not just use any old ladder?
Interestingly enough, an A330/340 can be even higher, but only slightly (~30cm).
They could also use the self-inflatable chutes, but those are likely to create injuries, so they are an option of last resort.
Also, they need to be replaced if used, which costs extra time and money.
Basically, they are more like an airbag on a car.
Now on the other hand, you could be taken out by an entire airplane crashing, e.g. https://en.wikipedia.org/wiki/American_Airlines_Flight_587
But that's not debris, that was a whole damn 747.
Watch out for blue meteorites :-)
B787: first flight 2009, about 600 built
A350: first flight 2013, about 100 built
Off the three, I'd mostly avoid the 787. I still find the A380 the most comfortable, due to all the space. Lower cabin altitude in 787 and 350 is nice, but doesn't compensate for cramped conditions.
I'm a bit concerned about bleed air. (The high pressure air to maintain cabin pressure comes from the compressor stage of the engines, and could be contaminated with oil/fuel/?, and so far only the 787 has done away with that ("bleedless aircraft").) But, damn, that spacious A380 cabin.
It could be a manufacturing defect, it could be all kinds of other things including a design flaw, to conclude that it 'screams of bad servicing' without having any evidence on an incident that is not even a day old is jumping to conclusions.
You are trying to counter my observation about terminology, guess vs conclusion, by saying that evidence is better. Not really relevant.