Had to build a runway for one take-off to get this private jet back in the air in 1983: https://www.irishexaminer.com/lifestyle/features/humanintere...
Getting a 787 back in the air after a diversion
61–70 of 139 posts
Re: Getting a 787 back in the air after a diversion
#62It just seems like a very bad idea that twin-engine planes can fly so far from an air strip. If the #1 engine had failed as well it would have been game over. There's no possibility of gliding a 787 for 2+ hours and hundreds of miles. If the FAA wanted to prioritize safety, it would still require the use of four-engined planes, as it used to for most long ocean routes. The desire to fly twin-engine planes over the oc…
The only thing that a 3rd+ engine helps with in this context is uncorrelated engine failures. (Correlated ones - like "oops we used the wrong fuel units" or "that volcanic ash cloud sure is pretty" - are the same for two engines as they are for 4) These failures are really, really rare. A very conservative approximation would be one in 100,000 flights. (That would be once every other day in the US, for reference. Lik…
If you must allow for the failure of one engine, adding more engines reduces weight.
2 engines: You need to install and carry 200% of the engine power needed to fly the plane.
3 engines: You need to install and carry 150% of the engine power needed to fly the plane.
4 engines: You need to install and carry 133% of the engine power needed to fly the plane.
It is really quite interesting that twin-engine planes are cheaper to operate than planes with more engines. The engines in twin-engine planes should be larger and thus more expensive in every way. It seems that larger engines must be discounted somehow, either by the manufacturer or by the maintenance crews, or that there is a scaling factor that hugely effects efficiency of large passenger jet engines.
For example, are maintenance costs dominated by paperwork? That could be enough to overcome the extra expense of needing powerful equipment to lift and otherwise manipulate the parts of a huge engine.
Re: Getting a 787 back in the air after a diversion
#63It just seems like a very bad idea that twin-engine planes can fly so far from an air strip. If the #1 engine had failed as well it would have been game over. There's no possibility of gliding a 787 for 2+ hours and hundreds of miles. If the FAA wanted to prioritize safety, it would still require the use of four-engined planes, as it used to for most long ocean routes. The desire to fly twin-engine planes over the oc…
ETOPS seems to have done pretty well. As far as I know, no ETOPS-certified twinjets have been lost due to both engines failing. There are a couple cases of the jet running out of fuel (the famous Gimli glider and Air Transat Flight 236), but that is going to be bad no matter how many engines you have. There are cases of airplanes flying into volcanic ash clouds and losing all engines; but more engines doesn't help yo…
Volcanic ash is a completely different beast from normal ops: you could have four engines and it still wouldn't be enough, prompting what was perhaps the most British announcement in the history of aviation, as narrated here: https://everything2.com/title/The+most+engine+failures+in+on...
Re: Getting a 787 back in the air after a diversion
#64Earlier quoted context omitted.
Except this ignores that the motivation was not increased safety but money. It does seem true that twin-engine planes can be quite safe but if Boeing/Airbus were motivated to create the safest possible plane, it would probably have four engines. I doubt the US President will be flying on a twin-engine plane any time soon. They'll choose the safest (American made) option. Probably an updated 747 model, no?
And my point was that motivation is irrelevant, and I would find it quite plausible that a two engined airliner would be safer than a four engined jet. Two fewer things to explode, after all. The president flies a 747 for size and prestige more than safety. Safest option would be to recommission an Iowa and use it as an armed ocean liner or something and skip planes entirely. Or just to stay home.
If we're talking about a command center, "stay at home" is not safe at all. Even Google Maps knows the coordinates and elevation for 2600 Pennsylvania Avenue (or Cheyenne Mountain, or Area 51, or whatever). Hence, Air Force One.
Re: Getting a 787 back in the air after a diversion
#65Earlier quoted context omitted.
The only thing that a 3rd+ engine helps with in this context is uncorrelated engine failures. (Correlated ones - like "oops we used the wrong fuel units" or "that volcanic ash cloud sure is pretty" - are the same for two engines as they are for 4) These failures are really, really rare. A very conservative approximation would be one in 100,000 flights. (That would be once every other day in the US, for reference. Lik…
If you must allow for the failure of one engine, adding more engines reduces weight. 2 engines: You need to install and carry 200% of the engine power needed to fly the plane. 3 engines: You need to install and carry 150% of the engine power needed to fly the plane. 4 engines: You need to install and carry 133% of the engine power needed to fly the plane. It is really quite interesting that twin-engine planes are che…
Flight with inoperative engine(s) is altitude constrained. The aircraft is going to be able to fly with one engine operative, but not at its usual altitude, so the 200/150/133 idea doesn’t really hold.
Further, larger engines are more efficient than smaller ones. You pretty much want to install the largest engines you can fit. It’s the underlying reason for the 737 Max debacle.
Re: Getting a 787 back in the air after a diversion
#66Earlier quoted context omitted.
I might get some of the backstory halfway off, but my grandfather was in Alaska during WWII for the construction of the Alaska Highway. They tried to never turn off truck and equipment engines because if you did, you had to build a fire under them to get them warm enough to start again.
Cars in northern Canada sometime have block heaters installed for cold starting. How cold should it be before you use it? Ask the internet: https://www.theglobeandmail.com/amp/globe-drive/culture/comm...
Standard in every car I've owned in Canada. Never needed it.
Re: Getting a 787 back in the air after a diversion
#67Earlier quoted context omitted.
"Prodigious Rate" -- To put this in context, the latest numbers I saw is about $125 per min of unscheduled delay. It also doesn't take that many delays to wipe profitability to zero.
Southwest had a really memorable slogan: “wheels up” and the business really rallied around that priority ruthlessly for many years. It was pretty cool and gets used in business analysis as an example a lot about how to achieve big goals.
One such (very lightweight) analysis: https://www.cnbc.com/id/43768488
It really is a great systems thinking story. Set the overall context and goal and then figure out how to optimize for the thing that drives results.
Re: Getting a 787 back in the air after a diversion
#68Back when I worked at Boeing they had the AOG (Airplane On Ground) crew to do this sort of thing. Their job was to be on call 24/7 and do whatever it took to get that airplane back in the air, and they pretty much had a blank check to do it. Naturally, they were the best mechanics Boeing had. An airplane makes money only when it is flying. When it is sitting on the ground, it loses money at a prodigious rate. A large…
There's an episode of "World's Toughest Fixes" that follows an AOG team during the replacement of a 767 pressure dome.
https://www.google.com/search?q=Worlds+Toughest+Fixes+S01+E0...
Re: Getting a 787 back in the air after a diversion
#69Earlier quoted context omitted.
I might get some of the backstory halfway off, but my grandfather was in Alaska during WWII for the construction of the Alaska Highway. They tried to never turn off truck and equipment engines because if you did, you had to build a fire under them to get them warm enough to start again.
Old farm tractors used what was called "farm oil" in the old days. Basically the cheapest form of fuel you could buy since it was effectively a byproduct of the refining process. It was closer to paraffin wax than diesel, solid at room temperature. In order to start the tractor there was a second tank with diesel that was used until the engine warmed up enough to melt the primary fuel. If your tractor stalled out and…
The more modern takes on this likely include "greasecar" diesel conversions that still have a small diesel tank, plus the different summer and winter blends of diesel fuel itself (since "A" diesel that gels at 5C is going to be a problem in a lot of places).
Re: Getting a 787 back in the air after a diversion
#70I was wondering why didn't the crew elect to divert directly to Anchorage, reading the event description http://avherald.com/h?article=49f44548 it seems they were 2h from CDB and ANC would be another hour from there. Not sure what's the ETOPS rating of that aircraft but it might not have been 180min (though even longer times are common now)