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Faro
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ULR's Unefficient With Distance?

Tue Feb 12, 2008 9:35 pm

Given that an ULR flight has to burn proportionately more fuel simply to carry the fuel to fly it further, I wonder whether, with increasing distance, a point is reached where it becomes more economic to schedule a fuel stop? With a fuel stop, proportinately less of the average airborne weight is fuel, in turn requiring less fuel to maintain it aloft.

I think that ULR's in general are an overblown phenomenon commercially; I have a creeping suspicion that this may apply to their fuel efficiency too.

Faro
The chalice not my son
 
tdscanuck
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Joined: Wed Jan 11, 2006 7:25 am

RE: ULR's Unefficient With Distance?

Wed Feb 13, 2008 12:57 am



Quoting Faro (Thread starter):
Given that an ULR flight has to burn proportionately more fuel simply to carry the fuel to fly it further, I wonder whether, with increasing distance, a point is reached where it becomes more economic to schedule a fuel stop? With a fuel stop, proportinately less of the average airborne weight is fuel, in turn requiring less fuel to maintain it aloft.

The short answer is, "yes." The long answer is, "It depends on how you measure your economics."

In pure fuel burn terms, you're absolutely right. This is why a whole bunch of air cargo stops in Anchorage or Honolulu going across the Pacific. Even when you throw in the extra fuel to descend, land, and climb back to altitude, you come out ahead on fuel burn.

However, that's not the only cost that figures into your economics. People are willing to pay a premium to fly nonstop, so you can go somewhat onto the "backside" of the fuel burn curve if you're carrying passengers instead of cargo and still come out ahead on profit. At some point, peoples' preference for non-stop gives out and they just won't pay what it costs...that's why ULR flights are pretty rare, heavy on premium classes, and only connect large cities.

Tom.
 
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Faro
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RE: ULR's Unefficient With Distance?

Wed Feb 13, 2008 5:51 pm

Thanx Tom, you said it all.

Faro
The chalice not my son
 
Rj111
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Joined: Wed Sep 08, 2004 9:02 am

RE: ULR's Unefficient With Distance?

Wed Feb 13, 2008 9:07 pm

Every plane has an optimal stage length for a set payload.

Take off is very taxing so for a short flight which is primarly made up of the takeoff and little crusing, the overall fuel consuption for distance flown will be very hight.

The other factor that you mention, fuel to carry fuel, is also influencial at the extreme ranges.

The optimal stage length is somewhere in between.

So yes, it can often be cheaper to make a fuel stop, and it normally means you can take more payload with you too.
 
astuteman
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RE: ULR's Unefficient With Distance?

Thu Feb 14, 2008 8:20 am



Quoting Tdscanuck (Reply 1):
The short answer is, "yes." The long answer is, "It depends on how you measure your economics."

If I recall correctly, Tom, we used SYD-SIN-LHR as an example and concluded that the fuel burn could be as much as 15% higher.
According to Airbus GMF, fuel burn typically accounts for about 40% of trip costs.
If so, the fuel burn increase would increase the trip costs by 6%.
I'm guessing that if you remove the landing at SIN, you'll lose some landing/navigation fees.

So the overall cost might go up 5% or so. Perhaps.


Quoting Tdscanuck (Reply 1):
People are willing to pay a premium to fly nonstop, so you can go somewhat onto the "backside" of the fuel burn curve if you're carrying passengers instead of cargo and still come out ahead on profit.

Taking those figures as an example, if you can up your revenue by 6% or more, the flight becomes economically viable.

Regards

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