1. TAS stands for _________
a) true air speed
b) temperature air speed
c) troposphere air speed
d) thermal air speed
Explanation: TAS stands for true air speed. True airspeed is the relative speed of aircraft with respect to the surrounding air flow. As the altitude increases the pressure decreases and the true airspeed is greater than indicated airspeed.
2. IAS stands for ___________
a) inductor air speed
b) indicated air speed
c) induced air speed
d) isentropic air speed
Explanation: IAS stands for indicated air speed. Indicated air speed is the speed indicated on the airspeed indicator in the cockpit. Airspeeds are of four types. They are ground speed, true airspeed, calibrated airspeed and indicated airspeed.
3. GS stands for __________
a) gravitational speed
b) greater speed
c) ground speed
d) gradual speed
Explanation: GS stands for ground speed. Ground speed is the relative movement between the aircraft and the ground. It is corrected for true air speed. For example, 98 knots true air speed + 10 knots tailwind=108 knots ground speed.
4. CAS stands for __________
a) calculated air speed
b) casual air speed
c) crucial air speed
d) calibrated air speed
Explanation: CAS stands for calibrated air speed. Calibrated air speed is the indicated air speed corrected for the instrument and positional errors. Airspeeds are of four types. They are ground speed, true airspeed, calibrated airspeed and indicated airspeed.
5. Which of the following is the correct relationship between R and Cp?
a) R=Cp\(\frac{\gamma-1}{\gamma}\)
b) Cp=R\(\frac{\gamma-1}{\gamma}\)
c) R=Cp\(\frac{\gamma+1}{\gamma}\)
d) Cp=R\(\frac{\gamma}{\gamma-1}\)
Explanation: R=Cp\(\frac{\gamma-1}{\gamma}\) is the correct relationship between R and Cp where R= characteristic gas constant, γ is the ratio of specific heat at constant pressure to that of specific heat at constant volume and Cp is the specific heat at constant pressure.
6. Which of the following is the correct relationship between γ and Cv?
a) Cv=R\(\frac{\gamma}{\gamma-1}\)
b) Cv=\(\frac{R}{\gamma-1}\)
c) Cv=\(\frac{R}{\gamma+1}\)
d) Cv=R\(\frac{\gamma}{\gamma\mp1}\)
Explanation: Cv=\(\frac{R}{\gamma-1}\) is the correct relationship between γ and Cv where R= characteristic gas constant, γ is the ratio of specific heat at constant pressure to that of specific heat at constant volume and Cv is the specific heat at constant volume.
7. Which of the following is the correct formula for speed of sound?
a) \(\sqrt{\gamma RT}\)
b) \(\sqrt{pRT}\)
c) \(\sqrt{\rho Rt}\)
d) \(\sqrt{\gamma R0T}\)
Explanation: The correct formula for speed of sound is \(\sqrt{\gamma RT}\) where R=characteristic gas constant, T=temperature and γ is the ratio of specific heat at constant pressure to that of specific heat at constant volume.
8. What is the speed of sound in air at an altitude where temperature is 299K?
a) 346.61K
b) 343.61K
c) 71.61 °C
d) 70.61 °C
Explanation: The answer is 346.61K. Given T=299K. We know that R=287J/kg-K, γ for air is 1.4.
From a=\(\sqrt{\gamma RT}\)
a=\(\sqrt{1.4*287*299}\)
a=346.61K.
9. What is the relation between pressure and air speed in isentropic relations?
a) \(\frac{p_1}{p_2}\)=\(\Big\{1+\frac{\gamma-1}{2}(\frac{V1}{a1})^2\Big\}^\frac{\gamma}{\gamma-1}\)
b) \(\frac{p_1}{p_2}\)=\(\Big\{1+\frac{\gamma+1}{2}(\frac{V1}{a1})^2\Big\}^\frac{\gamma}{\gamma+1}\)
c) \(\frac{p_1}{p_2}\)=\(\Big\{1+\frac{\gamma+1}{2}(\frac{V1}{a1})^2\Big\}^\frac{\gamma}{\gamma-1}\)
d) \(\frac{p_1}{p_2}\)=\(\Big\{1+\frac{\gamma-1}{2}(\frac{V1}{a1})^2\Big\}^\frac{\gamma}{\gamma+1}\)
Explanation: The relation between pressure and air speed in isentropic relations is
\(\frac{p_1}{p_2}\)=\(\Big\{1+\frac{\gamma-1}{2}(\frac{V1}{a1})^2\Big\}^\frac{\gamma}{\gamma-1}\) where p1, p2 are pressures at two points, V1=velocity at one point, a1=speed of sound at point one and γ is the ratio of specific heat at constant pressure to that of specific heat at constant volume.
10. 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
Explanation: 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.