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hawker111

A Film Featuring the F-86 Dog Sabre - Fuel Consumption Question

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Here is a link to a film that features the F-86 Dog Sabre:


The Sabre pilot takes off and climbs to 30,000 feet (7:43). He runs out of oxygen (8:23) and has to dive down to a lower altitude.

At 9:24-9:30 the pilot says: "Better watch that fuel though*. This can is really gulpin' it down at this altitude."

Later on the pilot is running low on fuel. At 13:35-13:41 the pilot says: "If I just had some oxygen I could have stayed at altitude and cut down my fuel consumption."

My question is, if the Sabre is cruising at 30,000 feet, its engine will consume less fuel at that altitude than at a lower altitude with the same throttle setting?

Thanks,

hawker111

* or does he say: "Better watch that fuel load."
 

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I think, and if I'm wrong, someone in the know correct me, that the lower drag at 30,000 ft leads to lower fuel consumption. Down in the dense lower altitudes, increased drag causes you to burn more fuel.

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Fuel is proportional to mass air flow. At high altitude the air is less dense (up to 36,000 feet). So the amount of fuel required at max throttle is much less (about 30% of the value used at sea level).

The lower air density does reduce drag, but it also reduces thrust and lift.

Aircraft that want to be fuel efficient AND fast fly at high altitudes where the indicated airspeed that determines optimum cruise speed remains the same, while the actual ground speed increases thanks to the net changes in air temperature and pressure (density) at altitude.

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Thanks, Streak I knew someone with the technical knowledge would answer. CombatAce is the place to ask questions like this. 

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