Definition
An inaccuracy in the readings of pitot-static instruments (altimeter, airspeed indicator, and vertical speed indicator) caused by the static port sensing a pressure that differs slightly from the true ambient atmospheric pressure surrounding the aircraft. The error varies with airspeed, altitude, and aircraft configuration, and is corrected for through calibration data and, in RVSM operations, through tightly controlled aircraft design and certification standards.
Plain English
The static port is supposed to measure the outside air pressure, but airflow around the aircraft can disturb that pressure slightly. That small disturbance throws off the altimeter, airspeed, and vertical speed readings by a known amount.
Context Anchor
Seen in pitot/static instrument discussions, especially in high-altitude operations where very small altitude errors can affect required separation from other aircraft.
Derivation
Static here comes from Latin staticus, meaning 'at rest' or 'standing still' — the port measures the pressure of air not moving relative to the aircraft. Source refers to the static port itself as the source of pressure data. Error simply means the difference between what is measured and what is true.
Why Pilots Care
Even small errors can cause altitude deviations that violate RVSM separation standards and trigger airspace violations.
Grounding Statement
As air flows around the airplane, the pressure at the static opening can be slightly different from the undisturbed outside air pressure at the same altitude.
Intuition Check
“Static” does not mean electrical static here. “Error” does not mean the pilot made a mistake; it means the pressure system is sensing a value that is not exactly the true outside air pressure.
Example Sentence 1
The aircraft's static source error was within RVSM limits, so it was approved to operate between FL290 and FL410.
Example Sentence 2
In RVSM airspace the crew monitored for static source error because any undetected offset could produce a 200-foot altitude deviation.