Definition
A condition in which the pitot tube — the forward-facing tube that captures ram air pressure for the airspeed indicator — becomes obstructed by ice, insects, debris, or a left-on pitot cover, preventing accurate airspeed indication. Depending on whether only the pitot intake is blocked or both the intake and the drain hole are blocked, the airspeed indicator will respond incorrectly to changes in altitude and may read high, low, or remain stuck.
Plain English
Something is plugging the small forward-facing tube that the airspeed indicator uses to sense the air rushing past the airplane. When that tube is blocked, the airspeed reading becomes unreliable and can fool the pilot.
Context Anchor
Seen in instrument flying, preflight inspection, icing conditions, heavy rain, insects, or any situation where the airspeed indicator does not behave normally.
Derivation
‘Pitot’ comes from Henri Pitot, the 18th-century French engineer who invented the tube used to measure fluid flow. Knowing it’s named after the inventor reinforces that the pitot tube is a specific, single-purpose device — and that ‘blocked pitot’ means that one device is obstructed.
Why Pilots Care
Incorrect airspeed readings can lead to stalls, overspeeds, or loss of control in instrument conditions.
Grounding Statement
Picture a small tube on the airplane that needs clean airflow; if ice, water, a bug, or a cover blocks it, the speed instrument may no longer show the airplane’s true speed.
Intuition Check
Do not think of “blocked” as only meaning the outside opening is plugged. In this context, the blockage can be in the pitot opening, the drain hole, or the line carrying pressure to the airspeed indicator.
Example Sentence 1
During the climb, the airspeed indicator kept rising even as the pilot reduced power, suggesting a blocked pitot system rather than a real airspeed change.
Example Sentence 2
After climbing through icing conditions the blocked pitot system caused the airspeed indicator to read zero on final approach.