What is a Static Pressure Port?

Aero Instruments Static Pressure Ports are flush mounted, electrically heated orifices installed on aircraft and helicopters to supply ambient static pressure measurements to altimeters, airspeed indicators, vertical speed indicators and overspeed warning switches. Static Pressure Ports are installed in pairs, on the right and left sides of the aircraft. They are connected by a manifold to minimize the effects of yaw (see MIL-P-26292 (USAF)). Optimum fore-aft locations are selected using the considerations detailed in the illustration. Although Static Pressure Port locations are carefully considered, positive or negative positioning errors may occur. Optimum locations for Static Pressure Port installations will vary with projected aircraft speed and altitude. Some Aero-Instruments Static Pressure Port models are pressure compensated by the addition of small projecting surfaces in the vicinity of the orifices. These projections alter the local air flow to more closely match the static pressure of the free air stream.

Useful References:
Military Specification MIL-P-26292 (USAF)
"Pilot and Static Pressure Systems, Installation and Inspection Of"
NASA Reference Publication 1046
"Measurement of Aircraft Speed and Altitude," Wm. Gracey, May 1980 #N80-24296