Question

What instrument is used to measure the aircraft’s altitude during the approach phase?

(a) Pressure altimeter

(b) Radio altimeter

(c) Sound altimeter

(d) Infrared altimeter

I had been asked this question during an online interview.

This is a very interesting question from Phases of Flight topic in section Introduction & Navigation Equations of Avionics

Answer 1

Correct option is (b) Radio altimeter

The best I can explain: A radio altimeter can accurately measure the altitude of an aircraft and works on the radar principle. Typically, radio altimeters provide accurate altitude measurements till 5000ft and are used only during takeoff and landing.