Question

What is the mach number of an aircraft flying with a speed of 450m/s at a temperature of 290 K?

(a) 1.318

(b) 2.045

(c) 3.214

(d) 0.235

The question was posed to me in homework.

This question is from Measurement of Mach Number in chapter Atmosphere and Air Data Measurement of Aircraft Performance

Answer 1

Correct option is (a) 1.318

Easy explanation: The answer is 1.318. Given T=290K , V= 450m/s. We know γ of air=1.4 and R=287 J/kg-K.

From the formula-M=\(\frac{V}{a}\) where a=\(\sqrt{\gamma RT}\)

On substituting the values to find “a”,

we have a=\(\sqrt{1.2*287*290}\)

a=341.35m/s.

Now substituting the value of “a” in the formula=\(\frac{V}{a}\),

we get M=\(\frac{450}{341.35}\)

M=1.318.