Definition
The small altitude-indication error that remains after the aircraft's static pressure system has been calibrated and corrected. It represents the unavoidable inaccuracy in the static port's ability to sense true ambient atmospheric pressure, even after manufacturer corrections are applied. In RVSM operations, this residual error must be kept within tight tolerances so that the altimeter accurately reflects the aircraft's true pressure altitude.
Plain English
Even after an aircraft's pressure-sensing system is carefully calibrated, a tiny amount of altitude-reading error always remains. That leftover error is what this term refers to.
Context Anchor
Seen in RVSM altimetry system discussions, aircraft approval data, and maintenance checks that verify the airplane can hold very accurate altitude.
Derivation
Residual means 'what is left over' (from Latin residuus, 'remaining'). Static source refers to the static port that senses outside air pressure. Together: the leftover error from the static pressure source after corrections have been made.
Why Pilots Care
It directly affects how accurately the altimeter shows altitude in RVSM airspace where tight vertical separation is required.
Grounding Statement
Airflow around the aircraft can make the static port sense pressure that is slightly different from the undisturbed air pressure outside the airplane.
Intuition Check
Do not read “residual” as “too small to matter.” Here it means “left over after correction,” and in RVSM even a small leftover altitude error matters. Do not read “static” as electricity. Here it means outside air pressure sensed by the aircraft’s static system.
Example Sentence 1
The aircraft's RVSM certification confirmed that residual static source error was within the allowable tolerance across the certified flight envelope.
Example Sentence 2
The maintenance log noted a residual static source error of 30 feet after the static system calibration.