6 ms·

The engines are actually fairly efficient. Unlike an automobile engine, they really only operate in a very narrow range and are usually run at a substantial fra

by avalys 4y ago

The engines are actually fairly efficient. Unlike an automobile engine, they really only operate in a very narrow range and are usually run at a substantial fraction of full power (60% or more). Automobile engines are very challenging because the power demands are highly variable and they can’t be optimized for any specific load.

bombcar 4y ago
Amusingly enough the Piper Cherokee I flew got better ground gas mileage than the '66 Fury I had at the time.
- ketzo 4y ago
  Wow, that’s a hilarious stat. How is that even… possible?
  - sokoloff 4y ago
    1960s cars were terribly inefficient is a big part of the story.
  - NonNefarious 4y ago
    It's quite possible for a plane to net higher mileage than many cars today, especially light-sport planes that only burn 5 gallons per hour or so.
    - Filligree 4y ago
      Yes, but this was while taxiing.
      - bombcar 4y ago
        “Ground gas mileage” meant converting the KIAS to mph on the ground (while flying). I never checked mpg while taxiing but the motor would be almost idle.
      - NonNefarious 4y ago
        No, not while taxiing. Who the fuck are you to misrepresent what I said? I said GALLONS PER HOUR. If you're taxiing for hours, you're doing it wrong.
  - bombcar 4y ago
    The '66 Fury weighs in at 3500 pounds and got about 10-12 miles per gallon based on my pump-to-pump odometer tests. The Piper Cherokee PA-28-140 weighs a petite 2150 pounds (max loaded weight) and burns 10 gallons an hour and would do about 115 KIAS, which translated to roughly 130 miles per hour ground speed, which is 13 miles per gallon. It would do even better if you flew for efficiency, but since rental was by hours of engine time wet (I didn't pay for fuel and would be reimbursed for fuel purchased), there was really no reason to not throttle that baby up to full rental power.
    - Symbiote 4y ago
      > there was really no reason to not throttle that baby up to full rental power. The reason is to reduce pollution, but that's obviously no concern at all for most GA pilots and passengers.
  - outworlder 4y ago
    > Wow, that’s a hilarious stat. How is that even… possible? There's nothing magical about flight. Take-off takes a bunch of energy. Maintaining that energy, not so much. Planes are pretty aerodynamic, imagine that :) Some are much lighter than cars since every pound counts. To the point that people often opt to not have AC (if it's even an option) to save a few pounds. They will cover a lot of ground in the same amount of time. That helps even more. Not all planes are that economical, of course. But some are indeed hilarious. Check ultralights (or microlights as they are known in Europe).
    - bombcar 4y ago
      A/C is amusing because it’s only needed on the ground - once you’re at cruise you can just open the window if it’s too hot - the outside air temp will almost always be pretty Low.
    - midoridensha 4y ago
      >There's nothing magical about flight. Take-off takes a bunch of energy. Maintaining that energy, not so much. Yep, take-off and ascent burns a lot of fuel, much more for the time duration than cruising. It's too bad there isn't a way of recovering some of that energy when descending, similar to how electric cars recover energy when braking.
      - ryandrake 4y ago
        > It's too bad there isn't a way of recovering some of that energy when descending, similar to how electric cars recover energy when braking. A descent is a pretty efficient conversion between potential energy (altitude) and kinetic energy (speed/horizontal distance) so you get it back. Your RPM difference between cruise and descent is a proxy for your recovered energy. An engine out glide/landing is the extreme demonstration of this.
      - weberer 4y ago
        >It's too bad there isn't a way of recovering some of that energy when descending But that's exactly what happens already. Point the aircraft down and it will pick up speed.
  - mschuster91 4y ago
    All kinds of planes have by necessity far better drag coefficients than cars. A truck, SUV, even a minicar is like a brick wall moving at high speeds while a plane essentially slices through the air like a knife. Additionally, planes tend to fly at constant and pretty high speed for most of their operation, while a car has a lot of acceleration and deceleration going on. Planes can also use wind thermals to change altitude (sail planes can only use that!) or can stay at the same altitude while a car driving below it is stuck with the geography (i.e. it has to follow and climb hills).
NikolaNovak 4y ago
I guess it depends. I understand some ultralights and new airplanes may be efficient. But it is my understanding that a Cessna 172 lycoming is basically 50-70 years old, depending on how you count, and horribly inefficient, and completely prevalent. Faa certification for new engines is such that innovation is stifled. I mean it took the industry what, 3-4 decades and counting, to phase out leaded fuel which we all agree is God awful :-0
- sokoloff 4y ago
  The C172 (most common small airplane) has a Lycoming 4-cylinder engine of various sizes throughout the years. A representative engine, the O-320, is around 89% as efficient as traditional (non-hybrid, non-Atkinson) ICE automobile at turning gasoline into productive work. I don’t view an 11% spread as “horribly inefficient” given the need for many redundant systems, air-cooling, high diameter pistons, and relatively low RPM. 0-https://michaelsoroka.com/2014/03/26/are-airplane-engines-inefficient/ https://michaelsoroka.com/2014/03/26/are-airplane-engines-in...
  - nimish 4y ago
    They lack a bunch of emissions control equipment like fuel injection, catalytic converters, and the like. They are 60's or maybe 80's car engines that are still made since nobody in GA wants to pay for better ones.
    - laverya 4y ago
      > since nobody in GA wants to pay for better ones. Since nobody wants to pay to certify better ones. The engine in a Cessna 172 is going to run you $20-40k (20k rebuilt, 40k new afaict - check out [0]) - far more expensive than an automobile engine with 'equivalent' performance. The difference is that the Lycoming is certified by the FAA for use with your airframe. (And it'll work in whatever conditions you care to name, and with a car engine that's only a 'probably') 0: https://www.coronaengines.com/In-Stock https://www.coronaengines.com/In-Stock
    - jcoby 4y ago
riffic 4y ago
that's what transmissions are for though. variable valve timing also helps. EDIT: This comment is about automobile engines.
- outworlder 4y ago
  Transmissions == variable pitch in aircraft.
- worewood 4y ago
  But until very recently transmissions worked on steps and could never keep the engine at peak efficiency. CVTs are fairly recent and people managed to stifle it by adding simulated gears.
- imoverclocked 4y ago
  Transmissions also lose a lot of energy.

by avalys 4y ago

bombcar 4y ago

Amusingly enough the Piper Cherokee I flew got better ground gas mileage than the '66 Fury I had at the time.

ketzo 4y ago
Wow, that’s a hilarious stat. How is that even… possible?
- sokoloff 4y ago
  1960s cars were terribly inefficient is a big part of the story.
- NonNefarious 4y ago
  It's quite possible for a plane to net higher mileage than many cars today, especially light-sport planes that only burn 5 gallons per hour or so.
  - Filligree 4y ago
    Yes, but this was while taxiing.
    - bombcar 4y ago
      “Ground gas mileage” meant converting the KIAS to mph on the ground (while flying). I never checked mpg while taxiing but the motor would be almost idle.
    - NonNefarious 4y ago
      No, not while taxiing. Who the fuck are you to misrepresent what I said? I said GALLONS PER HOUR. If you're taxiing for hours, you're doing it wrong.
- bombcar 4y ago
  The '66 Fury weighs in at 3500 pounds and got about 10-12 miles per gallon based on my pump-to-pump odometer tests. The Piper Cherokee PA-28-140 weighs a petite 2150 pounds (max loaded weight) and burns 10 gallons an hour and would do about 115 KIAS, which translated to roughly 130 miles per hour ground speed, which is 13 miles per gallon. It would do even better if you flew for efficiency, but since rental was by hours of engine time wet (I didn't pay for fuel and would be reimbursed for fuel purchased), there was really no reason to not throttle that baby up to full rental power.
  - Symbiote 4y ago
    > there was really no reason to not throttle that baby up to full rental power. The reason is to reduce pollution, but that's obviously no concern at all for most GA pilots and passengers.
- outworlder 4y ago
  > Wow, that’s a hilarious stat. How is that even… possible? There's nothing magical about flight. Take-off takes a bunch of energy. Maintaining that energy, not so much. Planes are pretty aerodynamic, imagine that :) Some are much lighter than cars since every pound counts. To the point that people often opt to not have AC (if it's even an option) to save a few pounds. They will cover a lot of ground in the same amount of time. That helps even more. Not all planes are that economical, of course. But some are indeed hilarious. Check ultralights (or microlights as they are known in Europe).
  - bombcar 4y ago
    A/C is amusing because it’s only needed on the ground - once you’re at cruise you can just open the window if it’s too hot - the outside air temp will almost always be pretty Low.
  - midoridensha 4y ago
    >There's nothing magical about flight. Take-off takes a bunch of energy. Maintaining that energy, not so much. Yep, take-off and ascent burns a lot of fuel, much more for the time duration than cruising. It's too bad there isn't a way of recovering some of that energy when descending, similar to how electric cars recover energy when braking.
    - ryandrake 4y ago
      > It's too bad there isn't a way of recovering some of that energy when descending, similar to how electric cars recover energy when braking. A descent is a pretty efficient conversion between potential energy (altitude) and kinetic energy (speed/horizontal distance) so you get it back. Your RPM difference between cruise and descent is a proxy for your recovered energy. An engine out glide/landing is the extreme demonstration of this.
    - weberer 4y ago
      >It's too bad there isn't a way of recovering some of that energy when descending But that's exactly what happens already. Point the aircraft down and it will pick up speed.
- mschuster91 4y ago
  All kinds of planes have by necessity far better drag coefficients than cars. A truck, SUV, even a minicar is like a brick wall moving at high speeds while a plane essentially slices through the air like a knife. Additionally, planes tend to fly at constant and pretty high speed for most of their operation, while a car has a lot of acceleration and deceleration going on. Planes can also use wind thermals to change altitude (sail planes can only use that!) or can stay at the same altitude while a car driving below it is stuck with the geography (i.e. it has to follow and climb hills).

NikolaNovak 4y ago

I guess it depends. I understand some ultralights and new airplanes may be efficient. But it is my understanding that a Cessna 172 lycoming is basically 50-70 years old, depending on how you count, and horribly inefficient, and completely prevalent. Faa certification for new engines is such that innovation is stifled. I mean it took the industry what, 3-4 decades and counting, to phase out leaded fuel which we all agree is God awful :-0

sokoloff 4y ago
The C172 (most common small airplane) has a Lycoming 4-cylinder engine of various sizes throughout the years. A representative engine, the O-320, is around 89% as efficient as traditional (non-hybrid, non-Atkinson) ICE automobile at turning gasoline into productive work. I don’t view an 11% spread as “horribly inefficient” given the need for many redundant systems, air-cooling, high diameter pistons, and relatively low RPM. 0-https://michaelsoroka.com/2014/03/26/are-airplane-engines-inefficient/ https://michaelsoroka.com/2014/03/26/are-airplane-engines-in...
- nimish 4y ago
  They lack a bunch of emissions control equipment like fuel injection, catalytic converters, and the like. They are 60's or maybe 80's car engines that are still made since nobody in GA wants to pay for better ones.
  - laverya 4y ago
    > since nobody in GA wants to pay for better ones. Since nobody wants to pay to certify better ones. The engine in a Cessna 172 is going to run you $20-40k (20k rebuilt, 40k new afaict - check out [0]) - far more expensive than an automobile engine with 'equivalent' performance. The difference is that the Lycoming is certified by the FAA for use with your airframe. (And it'll work in whatever conditions you care to name, and with a car engine that's only a 'probably') 0: https://www.coronaengines.com/In-Stock https://www.coronaengines.com/In-Stock
  - jcoby 4y ago

riffic 4y ago

that's what transmissions are for though. variable valve timing also helps. EDIT: This comment is about automobile engines.

outworlder 4y ago
Transmissions == variable pitch in aircraft.
worewood 4y ago
But until very recently transmissions worked on steps and could never keep the engine at peak efficiency. CVTs are fairly recent and people managed to stifle it by adding simulated gears.
imoverclocked 4y ago
Transmissions also lose a lot of energy.