# Aircraft Performance Questions and Answers – Measurement of Airflow Characteristics

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This set of Aircraft Performance online test focuses on “Measurement of Airflow Characteristics”.

1. What is the relation between pressure and density in an adiabatic air flow?
a) $$\frac{p_1}{p_2}$$=($$\frac{\rho_1}{\rho_2}$$)$$\frac{1}{\gamma}$$
b) $$\frac{p_1}{p_2}$$=($$\frac{\rho_1}{\rho_2}$$)γ
c) $$\frac{p_1}{p_2}$$=($$\frac{\rho_1}{\rho_2}$$)γ+1
d) $$\frac{p_1}{p_2}$$=($$\frac{\rho_1}{\rho_2}$$)γ-1

Explanation: The relation between pressure and density in an adiabatic air flow is given by $$\frac{p_1}{p_2}$$=($$\frac{\rho_1}{\rho_2}$$)γ where p1, p2 are pressure values and ρ1, ρ2 are density values and γ is the ratio of specific heat at constant pressure to that of specific heat at constant volume.

2. What is meant by airspeed?
a) The relative velocity between the aircraft and the air mass in which the aircraft is flying
b) The ratio of velocity between the aircraft and the air mass in which the aircraft is flying
c) The relative acceleration between the aircraft and the air mass in which the aircraft is flying
d) The ratio of velocity between the aircraft and the ground in which the aircraft is flying

Explanation: Airspeed is the relative velocity between the aircraft and the air mass in which the aircraft is flying. The unit of airspeed is knot. There are different types of airspeeds. They are ground speed, true airspeed, calibrated airspeed and indicated airspeed.

3. Airspeeds are of three types.
a) True
b) False

Explanation: Airspeeds are of four types. They are ground speed, true airspeed, calibrated airspeed and indicated airspeed. Airspeed is the relative velocity between the aircraft and the air mass in which the aircraft is flying. The unit of airspeed is knot.

4. Which of the following is the general equation that relates flow temperature to true airspeed?
a) CpT+$$\frac{V^2}{2}$$=constant
b) CpT-$$\frac{V^2}{2}$$=constant
c) CvT+$$\frac{V^2}{2}$$=constant
d) CvT-$$\frac{V^2}{2}$$=constant

Explanation: CpT+$$\frac{V^2}{2}$$=constant is the general equation that relates flow temperature to true airspeed, where Cp=specific heat at constant pressure, T=temperature, V=true airspeed.

5. What is true airspeed?
a) relative speed of aircraft with respect to the surrounding air flow
b) relative speed of aircraft sound with respect to the surrounding air flow sound
c) moment of aircraft with respect to air
d) moment of aircraft with respect to ground

Explanation: 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. It is also represented as TAS.

6. 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.

7. 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.

8. GS stands for __________
a) gravitational speed
b) greater speed
c) ground 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.

9. 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.

10. 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.

11. 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. 