Trailing cone

Trailing cones (or trailing wires as they are often incorrectly called or trailing static cones), were first developed and tested in the 1950s and 1960s as a simple means of calibrating the static pressure (altitude reporting) error of an aircraft's pitot-static system. It does this by giving an accurate measurement of the ambient atmospheric pressure (static pressure) well clear of the aircraft's fuselage. The trailing cone system trails generally 1 to 1.5 times the wing span length behind the aircraft via a high-strength pressure tube. Static pressure is measured forward of the cone by several static ports. The cone stabilizes and aligns the ports relative to the freestream airflow.