To get the best MPG you need to fly as high as possible! ;)
Tailwind does really help with MPG as well …
arj1 wrote:
To get the best MPG you need to fly as high as possible! ;)
Yes but still needs a fast climb speeds otherwise you wasting fuel not covering much terrain in those climbs…
Carson wrote excellent papers on best MPG & best LD for piston airplanes, I think it’s close to the truth, you just fly at 2*VS0 all the time climb/cruise/descent, with no engine VBG = 1.33*VS with engine VBMPG = 1.33*VBG as rough approximations
In general, the question is ill posed, the goal is to max MPG but you may have to penalise low speeds using some negative exponent, engines are not designed to fly those…
Actually, Pipistrel Virus with long wings.
A guy from the next hangar over can spend all day flying around and burn 5 liters of car gas. He’ll take off, find a wave, shut down, soar, soar, soar, then fire the Rotax back up, find another wave, rinse, lather, repeat, and when he gets hungry or needs a bio break, glide or fly back home.
In the summer he’d do 50h+ of this stuff per month.
Yes, I know this isn’t exactly what OP had in mind, but for those who are looking to build time on the cheap… Not sure if one can pick up any glider prizes while at it, doubt it.
tmo wrote:
Yes, I know this isn’t exactly what OP had in mind
The question was how to get the best MPG in an airplane. What else could he have in mind? and how would you know?
tmo wrote:
Yes, I know this isn’t exactly what OP had in mind, but for those who are looking to build time on the cheap… Not sure if one can pick up any glider prizes while at it, doubt it.
Maybe the OP means in “closed thermodynamic systems” and straight flights A-to-B rather than A-to-(A or X) missions…
PS: don’t try taking the Mooney in waves/ridges to save fuel, it hurts in the head even when you are well strapped
Pipistrel Virus with long wings is a heck of a design when you look at it’s “scaled speed range” for stall, best glide, cruise and never exceed given it’s light wing-load and low power, indeed it almost defies lot of physics…
Fly slower. Drag increases with the square of speed.
I always understood best MPG to be slightly faster than best glide.
Leaving aside questions of whether it’s good for the engine to operate at such low power settings….
Ignoring atmospheric factors, including air density and wind for the moment, as Ibra says fly more slowly, close to L/D speed if practical. If you’re instrumented, and the engine model permits, LOP operation will help. Running a C/S prop an inch or two oversquare may help a little if the engine permits (Some Lycomings do). And, if altitude is not a factor, and the surface is level with good features, flying within ground effect will help..
Pilot_DAR wrote:
And, if altitude is not a factor, and the surface is level with good features, flying within ground effect will help..
That is an interesting one!
I’d argue it is very theoretic as the only surface that is “level” enough to actually do this is water w/o any significant waves – and perhaps some salt lakes.
Actual terrain, however, is always so much uneven, that you loose more energy by correcting to keep the right altitude than you save due to ground effect.