Question

What is the pressure ratio of an aircraft moving in air at a velocity 500m/s and speed of sound is 244 m/s?

(a) 4.556

(b) 3.327

(c) 6.256

(d) 2.565

The question was asked during an interview for a job.

Query is from Measurement of Airspeed topic in chapter Atmosphere and Air Data Measurement of Aircraft Performance

Answer 1

Correct option is (b) 3.327

Best explanation: The answer is 0.458. Given V=500m/s, a=244m/s. We know γ of air is 1.4. From  \(\frac{p_1}{p_2}\)=\(\Big\{1+\frac{\gamma-1}{2}(\frac{V1}{a1})^2\Big\}^\frac{\gamma}{\gamma-1}\)

On substituting the values \(\frac{p_1}{p_2}=\Big\{1+\frac{500}{244}\Big\}^\frac{1.4}{1.4-1}\)

\(\frac{p_1}{p_2}\)=3.327.