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Old 01-07-2023, 10:53 AM   #11 (permalink)
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Dynamic soaring is the defination of pulse and glide, at least at at model scale. Cant comment at full scale, havent seen them succeed.

Aircraft engines are mirrors of 1940's car engines, same characteristics, just newer parts.

Friends compression was 6:1, his prop windmilled during glide after stopping. Mine was "high compression" or 8:1, rated for 125 hp on 290 cubic inches but only ror 5 minutes.

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Old 01-07-2023, 02:23 PM   #12 (permalink)
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Helicopters can auto-rotate. When there's a loss of power, push the cyclic down so the blades are spun up to speed as the chopper descends, then cyclic up as the ground approaches to trade blade momentum for lift. Ultimate pulse and glide.
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Old 01-08-2023, 11:13 PM   #13 (permalink)
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Pulse and glide seems like it would do very little in an airplane. A friend the other day was rebuilding a motor that some newbie pilots burned a cylinder out on the other day and he was explaining it to me. The airplane was a beechcraft bonanza. Basically they prop it for a speed range they want with an adjustable prop you can tune it to bite just enough at x speed to be most efficient and then drop it down a bit, and then they will lean the motor out for the altitude and speed they chose until it will barely maintain the cruise and call it good. But if you go to far you burn pistons and overheat motors. Kinda odd how most airplanes for people outside of the 1% still just use 1960s technology. Makes them more affordable and reliable though.
So with that said if you have it able to make just barely enough power to maintain speed it seems like that would do pretty good already. The only thing i would be worried about is piston speed and pumping losses like the throttle body not being completely open.
I agree its an interesting idea though as airplanes get horrible gas mileage. At least the straight shot trips make up for it.
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Old 01-09-2023, 12:50 AM   #14 (permalink)
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Quote:
airplanes get horrible gas mileage
You're paying money for lift. Airships lose on frontal area. But they can pulse and glide:

www.sciencedirect.com: Full model of a buoyancy-driven airship and its control in the vertical plane
Quote:
Abstract
A new concept of airship without thrust, elevator or rudder is considered in this paper. It is actuated by a moving mass and an internal air bladder with adjustable mass. This results into the motion of the center of gravity and the change of the net lift. The development of this concept of airship is motivated by energy saving. The moving mass and the airshipʼs rigid body are viewed independently, which renders the modeling easy and displays clearly the interconnection of the two subsystems.
[snip]
Section snippets
The buoyancy-driven airship
The concept of this airship is derived from a combination of conventional airships [5] and underwater gliders [10], which replace traditional propulsion by a cyclic change of the net lift and the position of the center of gravity. This new concept of airship is first introduced and proven to be efficient in [16].

The basic structure is shown in Fig. 1.
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Old 01-09-2023, 01:09 AM   #15 (permalink)
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Airplanes don't get horrible gas mileage. A Cessna gets 15 nMPG, which is better than some trucks. They are made to be aerodynamic, unlike trucks.

A full 737 gets something like 100 passenger MPGs.

You know what gets horrible fuel economy? A single occupant truck driver hauling nothing but his own butt.

Also, public transit busses get horrible passenger MPGs because most of the time they are hardly utilized. The average is something like 20 passenger MPGs. You could do better with a fleet of Priuses shuffling people from where the DO live to where they ACTUALLY want to go, unlike stupid public busses.
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Old 01-09-2023, 11:22 AM   #16 (permalink)
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Econo cruise in a plane shouldn't burn a piston, not paying attention during full power climb will. Older Bonanzas were time limited on full power climb, not current an brand new ones.

At altitude in cruise you throttle back some amount then lean the engine until it misses or shuts down then add fuel until it runs smooth again. If you run full throttle you dont lean much but use the same process. If youre really into fuel economy, you have an exhaust temp gauge and you set the mixture to 50 degrees rich of peak temperature.
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Old 01-09-2023, 10:22 PM   #17 (permalink)
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AFAIK there were plans to use DC-3 airframes turned into gliders for some operation in WWII. But anyway, the only aircraft actually meant for something analogue to pulse-and-glide are those motor-gliders. On a sidenote, once a Brazilian Air Force flight instructor told me gliding should be a part of pilots training because it could be useful during some emergency, even though it might not work for every aircraft type.
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Old 01-10-2023, 01:42 AM   #18 (permalink)
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Gather 'round chilluns, and listen to the tale of the Gimli Glider...

timeline.com/in-1983-two-pilots-miraculously-landed-a-jumbo-jet-with-no-fuel-from-40-000-feet


images.thestar.com/content/dam/thestar/news/canada/2013/02/22/boeing_767_known_as_gimli_glider_up_for_auction/gimli1.jpg
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Old 01-10-2023, 10:24 AM   #19 (permalink)
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As it's a boeing 767, it has mechanical attached boosted control surfaces and electric trims so you need armstrong pilots. Can't do that in newer airbus fly by wire. Notice it landed in clean configuration?
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Old 01-10-2023, 11:35 AM   #20 (permalink)
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Quote:
Originally Posted by Piotrsko View Post
Econo cruise in a plane shouldn't burn a piston, not paying attention during full power climb will. Older Bonanzas were time limited on full power climb, not current an brand new ones.

At altitude in cruise you throttle back some amount then lean the engine until it misses or shuts down then add fuel until it runs smooth again. If you run full throttle you dont lean much but use the same process. If youre really into fuel economy, you have an exhaust temp gauge and you set the mixture to 50 degrees rich of peak temperature.
Crazy enough they just had a notecard on the dash that said "Don't go past x and x" which comes out to some afr they had determined. But its just a manual stick and he said it will let you go too far. So thats interesting.

I say bad gas mileage because it can be unless the road is windey. 15-20mpg for a straight shot trip with avgas (33% extra usually) a friend would fly from the hometown to college was 185 miles, but in a car it was 210 miles with 87. So half the time we would take the prius instead.

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