Author Topic: And now the Boeing 777...  (Read 8585 times)

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Offline ve7xen

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Re: And now the Boeing 777...
« Reply #50 on: March 03, 2021, 10:55:33 pm »
Anyway, apologies for dragging this off topic, just get tired of people bringing up AF447 as if it's clearly the fault of Airbus; even with the most generous interpretation, the airplane plays a minor part in this accident.

It's not clearly the fault of Airbus, I just don't hold that "Airbus = awesome". The whole concept of preventing the pilot from making improper control inputs and applying flying skill right up until the moment those skills are necessary is, in my opinion, a mistake, and one I believe contributed to that incident, among others. AF296, perhaps - yes, pilot error, compounded by "the computer will protect us" (the whole point of the demonstration) and "oh crap, the computer won't let me pull up".

Fair enough. Planes still crash occasionally, so none of them are awesome yet  :-+.

Pilots definitely need experience hand flying regardless of airframe, but outside of the sim they're not going to and shouldn't have much experience flying on the edge of the envelope or in multiple failure scenarios. A 737 pilot is going to have no more experience riding the stick shaker than an A320 pilot will in alternate or direct law, but both pilots need to know what to do if they end up in those situations. Aside from the 737 and 767, Boeing has at least caught up on their control systems, so I don't think there is much between them on their modern designs (which does not include 737MAX). I think the next major Airbus design will probably have force feedback on the sticks that will at least be used to more clearly communicate DUAL INPUT, but they will probably still rely on the priority switch to deal with that, rather than having pilots fight each other.

AF296 was so irresponsible that I'd call it criminally negligent (and the courts agreed); the Captain's overconfidence is on him, not the plane. Alpha prot and alpha floor are protections, they shouldn't be something you intentionally include in your flight plan, and double especially not when already very low and slow with the engines at idle and with one of those protections disabled. If you wouldn't hand-fly it without any protections at all, you shouldn't fly it. The protections in that incident worked exactly as designed, and protected against the stall he was trying to initiate; the reason they crashed wasn't because he couldn't pull up, it was because he made the call too late for the idle engines to provide enough thrust to climb out with the dangerous low energy state he'd put the aircraft in. The only alternative would have been it letting him stall it, and who knows how that would have turned out. It doesn't matter what type of aircraft you're flying, or whether it prevents you from stalling it or not, low and slow is a dangerous regime.

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I do very much prefer the Boeing cockpit layout. Although I am not a pilot myself, mechanically coupling the controls on both seats is one of those things that just seems like an obviously good idea. I also think a yoke is a much more logical input device for something like an airliner than a stick, but again I'm not a pilot so I have not experienced either one outside of PC simulators.

Counterpoint: yokes get in the way of other controls, displays, charts, etc, are more cumbersome to operate one-handed, so they are noticeably less ergonomic, and both sides could be jammed simultaneously by an incapacitated pilot, in which case your only recourse is to un-jam them.

There's a more fundamental difference though, which I think is usually more what people are referring to when they compare the two. The Boeing design (ex. 787) has the controls coupled approximately to the deflection of the control surfaces as in a classical airplane. Want to execute a turn? Hold the yoke over to maintain the desired bank angle, pull back slightly to counter the loss of lift, and return it to centre when you want to roll out. In the Airbus design, the sidestick is instead (roughly speaking) coupled to roll/pitch rate, and the flight computer determines the deflection to achieve it, so you just roll the plane over to the desired bank angle, then release the side stick and the plane will maintain that bank angle and your previous pitch until you roll it back the other way. Likewise to climb you pull back to the desired attitude and then release until you want to level out when you push the nose forward. But even Boeing is getting on board with this as 787 has a similar rate-based model as Airbus, despite still having yokes.

The Boeing protections also work differently in a way that maybe depends a bit on the yoke itself, as the flight control system doesn't simply stop you if you try to command something unreasonable, it will fight you with strong force feedback, but you can override it all the way into stall, overbank, or I think overspeed if you push hard enough. Their philosophy is to inform about the envelope, but not to limit the inputs of the pilots even if they're about to violate it.

Which is better? Both have proponents, it seems to mostly come down to preference. I'm not an airline pilot either, but I can see how the rate-based design could reduce workload slightly during manual flight as you only need to provide input to change attitude, not to maintain it (even when faced with changing speed or wind), and it definitely makes it easier to take notes, deal with paper charts, and eat without a yoke in your lap. Those that prefer the more direct model see the fact that in certain multiple failure scenarios the Airbus controls may degrade to be more direct, and pilots are likely inexperienced with flying that way as a significant risk. Or that in some extremely unlikely scenarios it's possible the computers may be wrong and prevent you from doing something you need to do, and there is no way to override them on Airbus. And as we've discussed here, the lack of coupling between sticks, though force feedback to communicate this is available now in some sidestick aircraft (none from Airbus, AFAIK). I don't think the choice of yoke vs. sidestick itself has much in it, it's just a familiarity thing.
« Last Edit: March 03, 2021, 10:59:03 pm by ve7xen »
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Offline WattsThat

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Re: And now the Boeing 777...
« Reply #51 on: March 04, 2021, 01:44:50 am »
Blancolirio’s interview with the captain of UAL 1175. Spoiler alert: this earlier fan blade failure was uncontained, unlike the failure over Denver. After watching this video, all I can say is wow, I did not know how close they were to ditching. So many things went the right way. Well worth the time to watch.

« Last Edit: March 04, 2021, 01:48:31 am by WattsThat »
 

Offline SiliconWizardTopic starter

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Re: And now the Boeing 777...
« Reply #52 on: March 04, 2021, 02:45:53 am »
Fresh news today, a Rossiya Airlines 777 departed from Hong Kong to Madrid made an emergency engine warning landing in Moscow.

Indeed. Different engines though, those 777 are equipped with GE90 engines. Apparently this would be due to an engine sensor's fault.
Curious epidemic though.
 

Offline SilverSolder

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Re: And now the Boeing 777...
« Reply #53 on: March 04, 2021, 02:50:59 am »

Can planes catch Covid??
 

Offline james_s

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Re: And now the Boeing 777...
« Reply #54 on: March 04, 2021, 05:09:20 am »

Can planes catch Covid??

I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
 
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Offline langwadt

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Re: And now the Boeing 777...
« Reply #55 on: March 04, 2021, 09:30:39 am »
Blancolirio’s interview with the captain of UAL 1175. Spoiler alert: this earlier fan blade failure was uncontained, unlike the failure over Denver. After watching this video, all I can say is wow, I did not know how close they were to ditching. So many things went the right way. Well worth the time to watch.

afaiu none of them were technically uncontained, the blade didn't go through the shield around the fan
 

Offline SilverSolder

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Re: And now the Boeing 777...
« Reply #56 on: March 04, 2021, 01:07:11 pm »

Can planes catch Covid??

I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.

Yes, it is amazing how cars dislike being ignored - they are almost like ladies in that way!  :D
 
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Online coppice

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Re: And now the Boeing 777...
« Reply #57 on: March 04, 2021, 02:42:40 pm »

Can planes catch Covid??

I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
As Neil Young so wisely observed, Rust Never Sleeps.
 

Offline Retep

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Re: And now the Boeing 777...
« Reply #58 on: March 04, 2021, 03:08:53 pm »
I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
My understanding is (based on what was said on one of the YouTube channels - I think it was Mentour Pilot) that engines are started every 3 weeks or so and also that commercial planes have to be flown every once in a while, otherwise they would loose their airworthiness certificate and have to be re-certified when they are put back into use.
 

Offline SiliconWizardTopic starter

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Re: And now the Boeing 777...
« Reply #59 on: March 04, 2021, 06:30:56 pm »
I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
My understanding is (based on what was said on one of the YouTube channels - I think it was Mentour Pilot) that engines are started every 3 weeks or so and also that commercial planes have to be flown every once in a while, otherwise they would loose their airworthiness certificate and have to be re-certified when they are put back into use.

Yes. I've heard from a couple specialists that planes sitting "idle" for weeks or even months was not that rare these days, even before the pandemic, due to large differences in trafic depending on the season for some companies. So they are normally used to take care of planes just parked for extended periods of time.

Now it'll still be interesting to know whether the Covid crisis did actually have an influence even on this routine maintenance. It's not at all unlikely. In particular, I'd really be curious to know if maintenance in general didn't significantly drop as air trafic droped... even though idle planes definitely need very regular maintenance. Whereas, as said above, this kind of maintenance was a common thing before Covid, the sheer number of parked planes has obviously increased a lot, so that increased this parked plane maintenance a lot, which companies were probably not ready for - while their revenue plumetted. So yeah. I'm curious if those incidents will at all tell us something about that.
 

Offline james_s

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Re: And now the Boeing 777...
« Reply #60 on: March 04, 2021, 08:12:59 pm »
Yeah there are a lot of unknowns. Previously planes sat idle occasionally for weeks or months, but we have never had such a large number of planes sitting idle for so long. Makes me wonder how well they have all actually been taken care of. Hopefully it will turn out to not be a problem.
 

Offline hans

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Re: And now the Boeing 777...
« Reply #61 on: May 18, 2022, 10:35:47 pm »
Well, finally these 777s are allowed to fly passengers again: https://www.cnbc.com/2022/05/17/united-airlines-says-faa-cleared-grounded-boeing-777s-to-fly-again.html


I do wonder if failed engine blades of turbofan engines is going to be a more common theme. I also remember reading about another recent incident (Southwest_Airlines_Flight_1380) with a 737. Totally different engine mfgr though, but nonetheless, the trend for turbofan is to go big.. get the largest bypass ratio you can make fit and produce reliably. Intuitively those longer fan blades will put more strain at the connection points to the axle. For the Southwest flight, it were mini cracks that caused failure, which has seen increased inspection measures to prevent them..
« Last Edit: May 18, 2022, 10:37:39 pm by hans »
 

Offline SilverSolder

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Re: And now the Boeing 777...
« Reply #62 on: May 19, 2022, 03:42:11 pm »
I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
My understanding is (based on what was said on one of the YouTube channels - I think it was Mentour Pilot) that engines are started every 3 weeks or so and also that commercial planes have to be flown every once in a while, otherwise they would loose their airworthiness certificate and have to be re-certified when they are put back into use.

Yes. I've heard from a couple specialists that planes sitting "idle" for weeks or even months was not that rare these days, even before the pandemic, due to large differences in trafic depending on the season for some companies. So they are normally used to take care of planes just parked for extended periods of time.

Now it'll still be interesting to know whether the Covid crisis did actually have an influence even on this routine maintenance. It's not at all unlikely. In particular, I'd really be curious to know if maintenance in general didn't significantly drop as air trafic droped... even though idle planes definitely need very regular maintenance. Whereas, as said above, this kind of maintenance was a common thing before Covid, the sheer number of parked planes has obviously increased a lot, so that increased this parked plane maintenance a lot, which companies were probably not ready for - while their revenue plumetted. So yeah. I'm curious if those incidents will at all tell us something about that.

There has to be a business opportunity here...   have a courier company fly the parked planes on rotation for light cargo, or something like that...
 

Offline SiliconWizardTopic starter

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Re: And now the Boeing 777...
« Reply #63 on: May 19, 2022, 04:50:06 pm »
Oh, I can smell the business opportunity here... new companies selling plane pooling services.
 
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Online tom66

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Re: And now the Boeing 777...
« Reply #64 on: May 19, 2022, 04:51:15 pm »
Oh, I can smell the business opportunity here... new companies selling plane pooling services.

You've basically described wet leasing.
 

Offline james_s

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Re: And now the Boeing 777...
« Reply #65 on: May 19, 2022, 05:14:01 pm »
I do wonder if failed engine blades of turbofan engines is going to be a more common theme. I also remember reading about another recent incident (Southwest_Airlines_Flight_1380) with a 737. Totally different engine mfgr though, but nonetheless, the trend for turbofan is to go big.. get the largest bypass ratio you can make fit and produce reliably. Intuitively those longer fan blades will put more strain at the connection points to the axle. For the Southwest flight, it were mini cracks that caused failure, which has seen increased inspection measures to prevent them..

I'd like to see turboprop make a comeback for large airliners. While not as fast, they're considerably more efficient than turbofans, the controllable blade pitch offers significant advantages. I remember reading that the fuel burn on a Q400-8 is around 25% lower than a comparable turbofan jet. I think they look cooler too.
 

Online tom66

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Re: And now the Boeing 777...
« Reply #66 on: May 19, 2022, 06:16:37 pm »
I doubt it would ever make economical sense.  The "life" of the aircraft is one of the significant costs you pay for when you fly.  Would you pay 2x more per flight to get to your destination more slowly?  Not to mention ETOPS certification for a twin turboprop is uncommon so it would be restricted to internal flights only - might work for USA but unlikely to work well for European carriers.
 

Offline ve7xen

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Re: And now the Boeing 777...
« Reply #67 on: May 19, 2022, 09:50:07 pm »
I also don't think they are actually more efficient during the cruise phase. They get used for short-haul flights because their efficiency in the dense air near the ground, and therefore for takeoff and climb, is somewhat better. There is not enough time in cruise on these short haul flights for the high altitude efficiency of turbofans to make up for their poorer efficiency in the climb, and most of the flight time is not affected by the higher speed too (taxi, takeoff, climbout are a significant part of such flights, and more or less fixed-time). So for such flights, they will not take much longer but will use less fuel than with a jet. The longer the flight, the more the cruise advantage matters, and there will be a turning point somewhere where the jet wins. And it's faster too.

There are also a lot of time-based costs that would need to be factored into it too, if you're taking about the nearly 50% slower cruise speed. Fewer destinations accessible with a single crew, crew hours, time on the airframe and engines for maintenance, the need for a larger fleet to service the same routes, and so on.

I also wonder if it's even technically feasible to build a long-range widebody turboprop. You'd probably have to start getting into weird things like contra-rotating props and stuff to put enough thrust on the wing to carry the extra fuel and passengers, which seems like it's inviting mechanical issues. Turboprops are already more mechanically complex than turbofans, and this wouldn't be helping.
« Last Edit: May 19, 2022, 09:54:27 pm by ve7xen »
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Offline Bassman59

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Re: And now the Boeing 777...
« Reply #68 on: May 23, 2022, 06:05:12 pm »
Sad days for Boeing really.
https://www.nbcnews.com/news/us-news/faa-orders-stepped-inspections-boeing-777s-after-engine-failure-united-n1258477

Somebody give the pilots a huge bonus and a medal of honor (or whatever they call the local equivalent).
 

Offline hans

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Re: And now the Boeing 777...
« Reply #69 on: May 23, 2022, 07:47:32 pm »
I think the ETOPS rating is a pretty big deal for airliners, especially the larger ones. Even though the ETOPS rating is minutes, it's about being able to fly safely with 1 engine into an alternate airport with 1 engine (=range, nm). The turboprop engines may be more fuel efficient but they also tend to fly at a lower Mach number while doing so. I'm sure they can get a ETOPS rating on the airplane given the resources, you got to wonder why would you? If a turboprop flies at half the speed, then an ETOPS-370 rating of the A350XWB halves to that of a pretty mainstream jet with ETOPS-180 rating (A320, 737, etc.).

Or in other words, the plane has to divert it's routing to fly over anything but a small puddle of water.   The 777 is often used to fly routes over or close to the north pole, and newer planes will only go on more direct routes. The A350XWB has a ETOPS-370 rating and claims to be able to fly 99.7% of earth's surface in 1 trip, e.g. do flights like Sydney-London without any intermediate stops, etc. Taking those shortcuts also saves fuel.

And any of those long haul flight you might do, may now take 36hrs instead of 18hrs, probably requiring close to a dozen pilots onboard (and also some serious safety/health concerns of locking a few hundred people in a big tube for 36hrs)

So I doubt we'll ever see them on large airliners again. Economically it doesn't make sense, unfortunately.
 

Offline james_s

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Re: And now the Boeing 777...
« Reply #70 on: May 24, 2022, 05:58:20 am »
I don't think it would make sense on something as big as a 777, but something like the 737 or A320 size is certainly feasible and there are loads of those. The speed is also a lot more than half, the Q400-8 which is the only turboprop I've been on cruises at 360 knots, the 737-800 has a cruising speed of 444 knots, it's faster but not THAT much faster. The Russian TU-95 is the fastest and most powerful turboprop I'm aware of and cruises at 510 knots but being a military aircraft and 1950s technology I'm betting it is not  particularly efficient and it certainly is not quiet. There are lots of short flights that operate 737s, and there are lots of smaller regional jets in similar sizes to currently operating turboprops but props seem largely to have gone out of fashion. Aesthetically I find them much more pleasing than jets and I like the sound they make better too. 
 


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