Question

What is the pressure ratio of an aircraft moving in air at a mach number 1?

(a) 1.893

(b) 1.558

(c) 1.444

(d) 1.555

This question was addressed to me by my college director while I was bunking the class.

This is a very interesting question from Measurement of Airspeed in portion Atmosphere and Air Data Measurement of Aircraft Performance

Answer 1

Right option is (a) 1.893

The explanation is: The answer is 0.458. Given M=1. We know γ of air is 1.4. From \(\frac{p_1}{p_2}=\Big\{1+\frac{\gamma-1}{2}(M)^2\Big\}^\frac{\gamma}{\gamma-1}\)

On substituting the values \(\frac{p_1}{p_2}=\Big\{1+\frac{1.4-1}{2} 1^2\Big\}^\frac{1.4}{1.4-1}\)

 \(\frac{p_1}{p_2}\)=1.893.