Aeronautical Terms beginning with H

Hand Propping

Starting an engine by rotating the propeller by hand.

High Performance Aircraft

An aircraft with an engine of more than 200 horsepower.

Horsepower

The term, originated by inventor James Watt, means the amount of work a horse could do in one second. One horsepower equals 550 foot-pounds per second, or 33,000 foot-pounds per minute.

Hydraulics

The branch of science that deals with the transmission of power by incompressible fluids under pressure.

Hydroplaning

A condition that exists when landing on a surface with standing water deeper than the tread depth of the tires. When the brakes are applied, there is a possibility that the brake will lock up and the tire will ride on the surface of the water, much like a water ski. When the tires are hydroplaning, directional control and braking action are virtually impossible. An effective anti-skid system can minimize the effects of hydroplaning.