Definition
A malfunction of the aircraft's pitot tube, static ports, or the plumbing connecting them to the flight instruments, causing the airspeed indicator, altimeter, and vertical speed indicator to display inaccurate or unreliable readings. The failure may be partial or complete and is most commonly caused by blockage from ice, water, insects, debris, or by a leak in the system.
Plain English
The little pressure-sensing tubes and ports on the outside of the aircraft that feed three of your flight instruments have stopped working properly. As a result, your airspeed, altitude, or rate of climb readings can no longer be trusted.
Context Anchor
Encountered during instrument flying, instrument checks, and abnormal instrument indications when the airspeed indicator, altimeter, or vertical speed indicator does not make sense.
Derivation
Pitot comes from Henri Pitot, the 18th-century French engineer who invented the pressure tube used to measure fluid flow. Static comes from the Latin staticus, meaning standing still — referring to the still, undisturbed air pressure measured at the static ports on the side of the fuselage. Together they describe the two pressure inputs the system relies on.
Why Pilots Care
Unrecognized failure can produce loss of control or spatial disorientation in instrument conditions.
Analogy
It is like a gauge connected to a blocked or leaking hose. The gauge itself may still work, but the information reaching it is bad, so the reading cannot be trusted.
Grounding Statement
If the pitot tube, static port, or pressure line is blocked or leaking, the instrument may move normally but still show the wrong information.
Intuition Check
Do not assume “failure” means the instrument display has gone blank or broken completely. In a pitot or static system failure, the instrument may still show a number, but that number may be incorrect because the pressure source is wrong.
Example Sentence 1
After climbing through icing conditions without pitot heat on, the pilot suspected a pitot or static system failure when the airspeed indicator began dropping toward zero in level cruise.
Example Sentence 2
Following the checklist for pitot or static system failure, the crew activated the alternate static source to restore usable altitude information.