Question

What is the difference between the static pressure and the stagnation pressure when the aircraft is stationary?

(a) Infinite

(b) Any random value

(c) No difference

(d) Static pressure

The question was posed to me by my school principal while I was bunking the class.

This intriguing question originated from Pressure Measurements topic in division Air Data Systems, Altitude and Heading Reference of Avionics

Answer 1

Correct option is (d) Static pressure

To elaborate: when the aircraft is stationary, the pressure sensed by the static port is the free stream air pressure and the stagnation pressure ports are zero. Since the aircraft is not moving stagnation pressure is zero and hence the difference between the two values is the static pressure.