Question

Why is it dangerous to fly over hilly areas with pressure altitude?

(a) Affected by temperature

(b) Not reliable

(c) Costly

(d) Not the true altitude

I got this question in my homework.

I'm obligated to ask this question of Air Data Equations topic in section Air Data Systems, Altitude and Heading Reference of Avionics

Answer 1

Right answer is (d) Not the true altitude

For explanation I would say: Pressure altitude is always referenced from the sea level. When flying over hilly areas, the actual altitude of the aircraft from the ground is definitely lesser than the pressure altitude, thus showing erroneous altitude readings.