# Is this principal possible and could it save lots of fuel?l? **URL:** \ **Category:** Factual Questions\ **Created:** [December 20, 2000, 8:39am UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497 "2000-12-20T08:39:03Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![warmgun](https://avatars.discourse-cdn.com/v4/letter/w/ecccb3/32.png) [@warmgun](https://boards.straightdope.com/u/warmgun)\ **Post date:** [December 20, 2000, 8:39am UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/1 "2000-12-20T08:39:03Z")
A helecopter pilot friend of mine was explaining the advantages of the autogyro to me. He says that while flying some windy valleys in Hawaii he could kill the engine and stay aloft through the autogyro principal. Regardless, it got me thinking. Wouldn’t a autogyro-type ‘hang glider’ be a better solution than the normal confiuration? It seems like it would produce more lift. And to digress, what if we put BIG brass plates in the ground (painted black) every 20 miles or so apart between popular destinations to create thermals for gliding craft. Solution to fuel effecient travel? ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [December 20, 2000, 9:14am UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/2 "2000-12-20T09:14:32Z")
An autogyro is a compromise between a helicopter and an airplane. As such, it has some of the benefits and drawbacks of both. It can land in a shorter space than a regular airplane, but it can’t hover, and can’t land on a spot without a headwind. They’re slower than airplanes, but about as fast as a helicopter on less horsepower. They’re also less complex than helicopters. But they aren’t as efficient as airplanes, and they can’t be used for the primary roles of helicopters - air rescue, medevac, etc. Just having a dark spot on the ground won’t guarantee thermals. And columns of rising air are usually surrounded by columns of descending air. The only way to gain overall lift is to circle in the thermal. Somehow I can’t imagine a jumbo jet circling in a thermal. It’s also not particularly safe to be wheeling a large aircraft around inside a thermal. It’d also make for a very slow, uncomfortable trip. But the biggest problem of all is that you can’t get a large airplane to both glide a long way and glide slowly. Large jets have decent glide ratios (and a 767 glided over 80 miles to land on an airstrip after losing its engines), but the best glide speed is very fast, so you really can’t be leisurely circling around in a thermal. ---
**Author:** ![The\_Ryan](https://avatars.discourse-cdn.com/v4/letter/t/7feea3/32.png) [@The\_Ryan](https://boards.straightdope.com/u/The_Ryan)\ **Post date:** [December 20, 2000, 9:24am UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/3 "2000-12-20T09:24:51Z")
Commercial jets also have a very small surface area to mass ratio. Also, I doubt that a glider could cross the country in a few hours. ---
**Author:** ![warmgun](https://avatars.discourse-cdn.com/v4/letter/w/ecccb3/32.png) [@warmgun](https://boards.straightdope.com/u/warmgun)\ **Post date:** [December 20, 2000, 10:05am UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/4 "2000-12-20T10:05:43Z")
I was thinking more along the lines of personal gliding craft, like hang gliders, used instead of cars. In regards to the autogyros, I’m talking about a non-powered version, not autogyros proper. Desent (or up-drafts) would cause the rotor blades to turn causing lift in return resulting in what should be a long gide ratio. I realise there would probably be a ‘cabin’ turning problem but this might be able to be mittigated by a peddle-powered tail rotor. As an experement, since I posted, I made the best gliding paper airplane I could and a paper ‘helicopter’ and tossed them off my 2nd story balcony. The ‘airplane’ did indeed glide gently to the ground, but the ‘helicopter’ actually rose! (slight up draft involved) ---
**Author:** ![justwannano](https://avatars.discourse-cdn.com/v4/letter/j/7ab992/32.png) [@justwannano](https://boards.straightdope.com/u/justwannano)\ **Post date:** [December 20, 2000, 3:04pm UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/5 "2000-12-20T15:04:12Z")
warmgun Hey neat How did you made the paper helicopter? ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [December 20, 2000, 4:25pm UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/6 "2000-12-20T16:25:43Z")
What you propose is already a growing sport called “Gyrogliding”. Try [this link](http://www.avnet.co.uk/melmorrisjones/gyro12.htm) for more info. It appears the unpowered autogyro is towed to altitude behind a truck or plane, then cut loose, much like a sailplane. It remains aloft by taking advantage of rising thermals, though I doubt the glide ratio can approach a high performance hang glider, which can be as high as 14:1. ---
**Author:** ![Finagle](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@Finagle](https://boards.straightdope.com/u/Finagle)\ **Post date:** [December 20, 2000, 5:55pm UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/7 "2000-12-20T17:55:04Z")
> [@](#): > > \*Originally posted by warmgun \* > \*\*I was thinking more along the lines of personal gliding craft, like hang gliders, used instead of cars. > \*\* The mind does sort of boggle at the idea of carting a week’s worth of groceries, a few bags of cat litter and a laptop computer in a hang glider. And even if baggage were not a consideration, my mind continues to boggle at the idea of putting some of the idiots I encounter in my morning commute in control of flying machines. ---
**Author:** ![douglips](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@douglips](https://boards.straightdope.com/u/douglips)\ **Post date:** [December 20, 2000, 6:42pm UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/8 "2000-12-20T18:42:31Z")
> [@](#): > > \*Originally posted by justwannano \* > \*\*warmgun > Hey neat > > How did you made the paper helicopter? \*\* [Roto-Copter: Exploratorium](http://www.exploratorium.edu/science_explorer/roto-copter.html) ---
**Author:** ![warmgun](https://avatars.discourse-cdn.com/v4/letter/w/ecccb3/32.png) [@warmgun](https://boards.straightdope.com/u/warmgun)\ **Post date:** [December 21, 2000, 1:49am UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/9 "2000-12-21T01:49:06Z")
Thanks, douglips. That’s it. That saved me some intricate verbal gymnastics! ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [December 21, 2000, 7:59am UTC](https://boards.straightdope.com/t/is-this-principal-possible-and-could-it-save-lots-of-fuel-l/46497/10 "2000-12-21T07:59:28Z")
Autogyros have lousy glide ratios. But they can have a low sink rate, which means you can stay aloft longer in thermals. But you won’t travel very far. A Cessna probably glides better than an autogyro. The reason an autogyro doesn’t have a good glide ratio is because the speed at which it is most effective in glide isn’t very high. And the rotors have a lot of drag compared to, say, the laminar flow over a high performance glider’s wing. A high performance glider can have a glide ratio of better than 30:1 - I’d be surprised if an autogyro is much better than 10:1.