Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Do heavy planes really consume more fuel?

skyking · 05-01-2016, 02:45 AM

Ok, look at it this way.
two planes, A and B
Each plane is the same but plane A weighs more.
At any given speed and altitude, in unaccelerated level flight, plane A must have a higher angle of attack.
Going faster makes no difference. Plane A must have a higher angle of attack to produce the needed lift, to overcome that added weight.
Speed up both planes and look again. Plane A still has the same problem, still has to fly at a higher angle of attack than plane B does.
Unfortunately speeding up has a big fuel penalty. Drag increases as approximately the square of speed.
Thrust increases as approximately the cube of speed.
To go 10% faster could require as much as 33% more thrust. Not a good tradeoff.

05-01-2016, 02:45 AM	#8 (permalink)
skyking Master EcoModder Join Date: Apr 2011 Location: Tacoma WA Posts: 1,399 Woody - '96 Dodge Ram 2500 SLT Team Cummins 90 day: 23.82 mpg (US) Avion and Woody - '96 Dodge/Avion Ram 2500/5th wheel combo 90 day: 15.1 mpg (US) TD eye eye eye - '03 Volkswagen Beetle GLS 90 day: 49.05 mpg (US) Mule - '07 Dodge Ram 3500 ST Thanks: 743 Thanked 528 Times in 344 Posts	Ok, look at it this way. two planes, A and B Each plane is the same but plane A weighs more. At any given speed and altitude, in unaccelerated level flight, plane A must have a higher angle of attack. Going faster makes no difference. Plane A must have a higher angle of attack to produce the needed lift, to overcome that added weight. Speed up both planes and look again. Plane A still has the same problem, still has to fly at a higher angle of attack than plane B does. Unfortunately speeding up has a big fuel penalty. Drag increases as approximately the square of speed. Thrust increases as approximately the cube of speed. To go 10% faster could require as much as 33% more thrust. Not a good tradeoff. __________________ 2007 Dodge Ram 3500 SRW 4x4 with 6MT 2003 TDI Beetle 2002 TDI Beetle currently parked - 1996 Dodge 2500 Cummins Turbodiesel Custom cab, auto, 3.55 gears Last edited by skyking; 05-01-2016 at 02:50 AM..