static electricity. Electrical pressure produced by an excess of electrons (a negative charge) or a deficiency of electrons (a positive charge). Static charges accumulate on an insulated surface because of friction, and remain in a still, or static, condition until a conductive path is provided to an oppositely charged surface, or to ground. When a path is provided, electrons flow and neutralize the charge.
static port (aircraft instruments). A small hole, or port, in the skin of an aircraft at a location where the airflow is not disturbed. The airspeed indicator, altimeter, and vertical speed indicator get their reference static air pressure from this port. Some aircraft pick up their static pressure from a combined pitot-static tube.
static pressure, Ps (fluid pressure). The pressure of a fluid that is still, or not moving, measured perpendicular to the surface exposed to the fluid. Static pressure and dynamic pressure, which is caused by the movement of the air, make up the total pressure of a mass of air. Static air pressure relates to the density of the air, and density is affected by both the altitude (pressure) and the air temperature.
static pressure pickup (aircraft instrument system). The location on the surface of an aircraft where the static air pressure used in the altimeter, airspeed indicator, and the vertical speed indicator is picked up. Static pressure is often taken from flush static ports on the sides of the fuselage or on the sides of the vertical tail surface. In other installations, static pressure is picked up from ports in the side of a combination pitot-static tube.
Static pressure pickups must be located in an area where there is no movement of air in a direction that could blow into the static holes.
static radial engine. A type of reciprocating engine in which the cylinders are arranged radially around a small crankcase. Static radial engines are different from rotary radial engines in that their cylinders do not rotate with the propeller. Static radial engines were at one time the most popular configuration of engine used in airplanes, because of their low weight-to-power ratio. But they have so much frontal area that they produce too much drag for modern high-speed aircraft.
Radial engines can have three, five, seven, or nine cylinders in one row. Two or four rows of cylinders can be stacked together to make an engine with 14, 18, 28, or 36 cylinders.
static RPM (aircraft reciprocating engine operation). The number of revolutions per minute an aircraft engine can produce when the aircraft is not moving. The static RPM is lower than the RPM the engine develops in flight because of the increased power made possible by forward movement ramming air into the carburetor inlet.
static stability (aerodynamics). The characteristic of an aircraft that causes it to try to return to straight and level flight after it has been disturbed from this condition.