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Old Dec 16, 2018, 6:40 am
  #16  
 
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The same issue applied to the early explorers going to the North and South Poles.

Dozens of men (and horses) would carry food for the few men that would eventually make the final push for the Pole. The food would be dropped off along the way and the the extra men would turn back way short of the Pole.

Of course, the horses were also "dropped off" along the way and supplied some of the food for the return trip.
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Old Dec 17, 2018, 8:24 am
  #17  
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Originally Posted by s0ssos
I guess I mean a route that doesn't make sense on a flat versus curved world view. Like if you look at SIN to LAX vs SFO, one goes further north than the other. And if you look at SIN to JNB it is basically a straight line, not really curving. So same as if you just put a map on a table and traced the shortest distance point by point, disregarding the curvature of the earth.
The problem is that there is no such thing as "a map." There are dozens of ways to project a sphere onto a flat surface, none of them good for all purposes. Conclusions such as these may be correct for one projection but not for another. If you are assuming a Mercator projection, say so, though its distortion at high northern and southern latitudes makes it useless for flight paths that go into those regions or that one is comparing with other paths that go into those regions.

Aside from that, though, your earlier point about the lack of refueling stops anywhere near the middle of several long-distance great-circle routes is valid. Breaking up a long trip to refuel, thus carrying less fuel, makes sense only if such stops exist. On most polar routes they don't, though IIRC some flights from the US east coast to Asia refueled in Anchorage in the days before non-stop flights of that distance were practical. ANC may not have been in the ideal location for that purpose, but it was close enough.
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Old Dec 17, 2018, 3:01 pm
  #18  
 
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Pan Am went to great lengths to build up the infrastructure for its TPAC Clipper services...including setting up the then-desolate Wake Island among other Pacific stations for refueling and resupply. It's unlikely we'll ever see an airline take, or need to take, such an initiative to build a few fuel stops from the ground up like that. But such will be necessary for various space travel needs in the future. A brief article on the early Pan Am setup days:

https://www.clipperflyingboats.com/t...irline-service

Of course the world's top air forces do have the flexibility to place an aircraft refueling point at lots of locations as needed for a given mission, thanks to air-to-air refueling! And no need to land and taxi in for the fill-up!
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Old Dec 18, 2018, 3:25 pm
  #19  
 
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Originally Posted by pinniped
It begs the question: does it make financial sense to do a technical stop? Assume it is a route where only one carrier flies the nonstop, so there's no competitive disadvantage to 17 hours gate-to-gate vs. 16 hours. Would flying two 8-hour segments (plus reserves) burn less total fuel than a single 16-hour segment? Or do the costs associated with the 2nd take-off and climb to cruise altitude more than burn up the savings?

Airlines used to have technical stops all over the place because they were limited by aircraft range. With longer range aircraft, I assume they got rid of them for competitive reasons. But maybe they make sense on these ultra-long flights?

Some portion of passengers might actually *like* them on a 16+ hour trip.
Cargo carriers do this, like FedEx/UPS. They'll make a technical stop in Alaska before continuing on to Asia. The slight loss in time is made up with fuel savings.
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Old Dec 18, 2018, 5:40 pm
  #20  
 
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Originally Posted by caburrito
Cargo carriers do this, like FedEx/UPS. They'll make a technical stop in Alaska before continuing on to Asia. The slight loss in time is made up with fuel savings.
They don't do it for fuel savings. They do it because the cargo load is too heavy to make it non-stop.
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Old Dec 18, 2018, 6:16 pm
  #21  
 
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Originally Posted by LarryJ
They don't do it for fuel savings. They do it because the cargo load is too heavy to make it non-stop.
For the method in which the cargo is carried, it represents a fuel savings, ie 1 heavy trip with a fuel stop, lighter trip with no stop.
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Old Dec 18, 2018, 7:26 pm
  #22  
 
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Originally Posted by caburrito
For the method in which the cargo is carried, it represents a fuel savings, ie 1 heavy trip with a fuel stop, lighter trip with no stop.
How is it a fuel savings when you left cargo behind that will have to be flown on an additional flight? The will certainly burn more fuel.
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Old Dec 18, 2018, 7:50 pm
  #23  
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Originally Posted by LarryJ
How is it a fuel savings when you left cargo behind that will have to be flown on an additional flight? The will certainly burn more fuel.
In terms of fuel per weight*mile, isn't a heavier plane with a fuel stop cheaper?
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Old Dec 18, 2018, 10:20 pm
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Originally Posted by LarryJ
How is it a fuel savings when you left cargo behind that will have to be flown on an additional flight? The will certainly burn more fuel.
whoops, should have said
ie 1 heavy trip with a fuel stop vs lighter cargo trip with no stop.
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Old Dec 19, 2018, 2:17 am
  #25  
 
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not sure when the energy equation will ever make sense, for there to be electric-assisted commercial passenger aircraft... just like cars. fixed weight. on-demand power delivery. limited capacity, but enough to assist on take-off phase, and then "sip" on jet fuel for the cruise....
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Old Dec 19, 2018, 8:36 am
  #26  
 
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Originally Posted by nerd
In terms of fuel per weight*mile, isn't a heavier plane with a fuel stop cheaper?
No. Flying non-stop will use less fuel. You also save time on the aircraft which reduces maintenance and crew costs.
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Old Dec 20, 2018, 11:48 am
  #27  
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your course assumptions are further complicated by wind velocities. the last couple times on the western route, we flew from middle of southern europe to iAd, we used the great southern trade wind route. south of great Britain and Gurrnsey,

Last edited by slawecki; Dec 20, 2018 at 11:54 am
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Old Dec 20, 2018, 1:30 pm
  #28  
 
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Originally Posted by tmiw
I saw this video on YouTube recently that goes into the issue:

https://www.youtube.com/watch?v=TNUomfuWuA8

At ~3:45 into the video, there's a graph showing that the lowest pounds/mile fuel burn is around 3,000nm, which would take around 5-5.5 hours to fly at Mach 0.85. Of course, as also mentioned in the video, passengers (especially business travelers) really don't want to stop all that often if they can avoid it.
This is a really really good video that explains it well. It's mind blowing how much fuel it takes to move fuel.
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