Pitot Tube
Definition
The little probe on aircraft wings that measures airspeed by comparing ram pressure to static pressure.
Unit: m/s
Technical definition
A tube facing the flow measures stagnation (total) pressure; combined with static pressure ports, airspeed follows from Bernoulli: v = √[2(P_total − P_static)/ρ]. Standard on every aircraft.
Example
Your flight's displayed airspeed comes from pitot tubes — block one with ice (as happened to Air France 447) and the speed readings fail dangerously.
Common confusion
A pitot tube measures pressure, not speed directly — airspeed is computed from the pressure difference using air density. Wrong density assumption (altitude, temperature) means wrong speed.