On Sat, 20 Jun 2009 13:13:43 +0000 (UTC), Hul Tytus
wrote:

rec.aviation.homebuilt
Help needed understanding turbojets

Horsepower is defined/measured as 550 foot pounds per second. ie,
lifting 1 pound 550 feet every second is 1 hp. If you lift 550 pounds one foot
every second and keep that going for 12 hours or so every day, you are a
horse.
Similarly, an airplane with a one horsepower engine that travels at
550 feet per second at full power is pushing with the force of one pound.
Conversally, as above, if the plane's max speed is 1 foot per second the
thrust is 550 pounds.
Handy for gauging such questions.

Hul

I thought it was originally defined as lifting a Ton a Foot a Minute.
ie what a shire horse could achieve lifting stuff out of a mine on a
windlass.