The GATE Grind

GATE 2024 AE – Question 61

Flight Mechanics & Space Dynamics · Aircraft classification and configuration, pressure altitude, equivalent, calibrated and indicated air speeds · 2 marks · Numerical answer

For an aircraft moving at 4 km altitude above mean sea level at a Mach number of 0.2, the ratio of equivalent air speed to true air speed is _______ (rounded off to 2 decimal places).

The density of air at mean sea level is 1.225 kg/m$^3$ and at 4 km altitude is 0.819 kg/m$^3$.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: 0.81 to 0.83

Explanation

The equivalent airspeed is defined by $V_{EAS} = V_{TAS}\sqrt{\frac{\rho}{\rho_0}}$. So $\frac{V_{EAS}}{V_{TAS}} = \sqrt{\frac{0.819}{1.225}} = 0.818$, which is 0.82.