# Small Plane Pilots: Flying in a Corkscrew

**URL:** <https://boards.straightdope.com/t/small-plane-pilots-flying-in-a-corkscrew/803241>\
**Category:** In My Humble Opinion\
**Created:** [December 1, 2017, 12:42pm UTC](https://boards.straightdope.com/t/small-plane-pilots-flying-in-a-corkscrew/803241 "2017-12-01T12:42:57Z")\
**Posts on this page:** 2\
**Page:** 3

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**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\
**Post date:** [December 2, 2017, 12:31pm UTC](https://boards.straightdope.com/t/small-plane-pilots-flying-in-a-corkscrew/803241/41 "2017-12-02T12:31:59Z")

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> [@Richard\_Pearse](#):
>
> It’s not relevant from an aerodynamics point of view. If you are talking about gliders using thermals to gain altitude, then that’s really a navigation issue not an aerodynamic one (i.e., vertical navigation).
> 
> My comments all assume a stable airmass. If the air is turbulent then you get various effects on the airspeed as you move through bits of air that have different velocities. These still don’t manifest as a loss of airspeed or lift from turning from a headwind to a tailwind though.

Agree, you’re right when I think about it more. Ground speed is irrelevant, what a glider depends on is air masses that have a vector component pushing the opposite direction from gravity. (aka, upwards). A glider that gains altitude now has potential energy and can use convert it back to forward motion, which it uses for lift and to maneuver to find the next upwards thermal.

I assume that’s what screwed the cessna - downwards thermals.

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**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\
**Post date:** [December 2, 2017, 12:47pm UTC](https://boards.straightdope.com/t/small-plane-pilots-flying-in-a-corkscrew/803241/42 "2017-12-02T12:47:40Z")

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> [@SamuelA](#):
>
> I assume that’s what screwed the cessna - downwards thermals.

Yep the effect of hills on wind can be pretty dramatic. It is not at all unusual for the air on the lee side of a ridge to be descending faster than a small GA plane can climb. It’s a big consideration when mountain flying. For example, if you have to cross a ridge line at low level you do it at an angle so if you get caught in sink you can make a safe descending turn away from the ridge. This assumes you have relatively open terrain behind you.

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