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>Flying slower is actually a environmental win since aircraft are more efficient at slower speeds Do you have any more information on this? Obviously slower-sp
by Klathmon 8y ago
>Flying slower is actually a environmental win since aircraft are more efficient at slower speeds
Do you have any more information on this? Obviously slower-speed turboprop planes are much more efficient than jet powered planes, but I've read in the past that flying a jet engine slower can actually increase fuel consumption and increase emissions.
- sokoloff 8y agoThere is an efficiency curve for jet transports. There is a defined MRC (max range cruise, which varies by weight) and a calculated LRC (long range cruise, typically defined as 1% less fuel efficient [in kg/nm], which gives 99% of efficiency and about 104% of cruise speed vs MRC). Modern flight management systems have economy calculators that can predict not only fuel-at-destination figures, but can incorporate winds and other airline cost indices (crew, maint reserves, etc) to emit an "ECON" speed target. It is only speeds below the MRC that cause a decrease in (still-air) fuel efficiency. Airlines do not typically operate in that speed range in cruise absent an ATC directive to slow down to avoid holding ahead. (Obviously, flying a hold is done below MRC as well.)
- aeroevan 8y agoThere are two optimal values for speed depending on the objective. There is a max endurance speed (for holding, etc.) and a max range speed, both are a function of altitude. So slowing down under those speeds will decrease efficiency, but typically the airline's cost index (~additional hourly cost to operate, like crew cost) will typically push the speeds higher to minimize the overall cost. http://www.eaa1000.av.org/technicl/perfspds/perfspds.htm http://www.eaa1000.av.org/technicl/perfspds/perfspds.htm is about the best thing I can google right now as a reference.