# Aircraft Performance Questions and Answers – Cruise Method 2

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This set of Aircraft Performance Multiple Choice Questions & Answers (MCQs) focuses on “Cruise Method 2”.

1. Which factor must be reduced in constant angle of attack and constant altitude method?
a) Mach number
b) Angle of attack
c) Altitude
d) Temperature

Explanation: The factor that must be reduced in cruise method 2 (also known as constant angle of attack and constant altitude method) is mach number. Also the ratio of lift to drag and relative airspeed are kept constant i.e. L/D ratio and uare constant throughout the method.

2. Which of the following indicates the range formula in cruise method 2?
a) R=$$\frac{1}{C}\big(\frac{2}{\rho SC_L}\big)^{\frac{1}{2}}\int_{W_{i}}^{W_{f}}\frac{dW}{W^{\frac{1}{2}}}$$
b) R=$$\Big(\frac{2}{\rho SC_L}\Big)^{\frac{1}{2}}\frac{L}{D}\int_{W_{i}}^{W_{f}}\frac{dW}{W^{\frac{1}{2}}}$$
c) R=$$\Big(\frac{2}{\rho SC_L}\Big)^{\frac{1}{2}}\frac{LC}{D}\int_{W_{i}}^{W_{f}}\frac{dW}{W^{\frac{1}{2}}}$$
d) R=$$\frac{1}{C}\Big(\frac{2}{\rho SC_L}\Big)^{\frac{1}{2}}\frac{L}{D}\int_{W_{i}}^{W_{f}}\frac{dW}{W^{\frac{1}{2}}}$$

Explanation: The correct range equation of cruise method 2 is given by R=$$\frac{1}{C}\Big(\frac{2}{\rho SC_L}\Big)^{\frac{1}{2}}\frac{L}{D}\int_{W_{i}}^{W_{f}}\frac{dW}{W^{\frac{1}{2}}}$$ where R is range of the cruise, C is specific fuel consumption, S is span, ρ is density, CL is coefficient of lift, L/D is lift to drag ratio, Wf and Wi are final and initial weights.

3. Which of the following is the correct integrated range equation of cruise method 2?
a) R=$$\frac{1}{C}\Big(\frac{2W_i}{S_{\rho}}\Big)^{\frac{1}{2}}\frac{C_L}{C_D}2\Big(1-\omega^{\frac{-1}{2}}\Big)$$
b) R=$$\Big(\frac{2W_i}{S_{\rho}}\Big)^{\frac{1}{2}}\frac{C_{L}^{0.5}}{C_D}2\Big(1-\omega^{\frac{-1}{2}}\Big)$$
c) R=$$\frac{1}{C}\Big(\frac{2W_i}{S_{\rho}}\Big)^{\frac{1}{2}}\frac{C_{L}^{0.5}}{C_D}2\Big(1-\omega^{\frac{-1}{2}}\Big)$$
d) R=$$\frac{1}{C}\Big(\frac{2W_i}{S_{\rho}}\Big)^{\frac{1}{2}}\frac{C_{L}^{0.5}}{C_D}2\Big(1-\omega\Big)$$

Explanation: The correct equation of cruise method 2 is R=$$\frac{1}{C}\Big(\frac{2W_i}{S_{\rho}}\Big)^{\frac{1}{2}}\frac{C_{L}^{0.5}}{C_D}2\Big(1-\omega^{\frac{-1}{2}}\Big)$$ where R is range of the cruise, C is specific fuel consumption, S is span, ρ is density, CL is coefficient of lift, Cl/Cd is ratio of coefficient of lift to drag, Wi is initial weight and ω is fuel ratio.

4. Cruise method 2 is also known as ____________
a) constant angle of attack and variable mach number
b) constant angle of attack and constant mach number
c) constant angle of attack and constant altitude number
d) constant mach number and constant altitude number

Explanation: Cruise method 2 also known as constant angle of attack and constant altitude method. In cruise method 2 altitude, the ratio of lift to drag and relative airspeed are kept constant i.e. L/D ratio and u and h are constant throughout the method.

5. Which of the following factors are not constant in cruise method 2?
a) altitude
b) relative airspeed
c) mach number
d) angle of attack

Explanation: Cruise method 2 also known as constant angle of attack and constant altitude method. In cruise method 2 altitude, the ratio of lift to drag and relative airspeed are kept constant i.e. L/D ratio and u and h are constant throughout the method.

6. The range factor of cruise method 2 is identical to that of cruise method 1.
a) True
b) False

Explanation: In cruise method 2 the range factor is given by R=$$\Big[\frac{V_{mdi}}{C}E_{max}\Big]\Big\{\frac{2u^3}{u^4+1}\Big\}2\Big(1-\omega^{\frac{-1}{2}}\Big)$$ where $$\Big[\frac{V_{mdi}}{C}E_{max}\Big]$$ is range factor and is same of that in cruise method 1 but overall range of cruise method 2 is less than that of cruise method 1.

7. The endurance of cruise method 2 is identical to that of cruise method 1.
a) True
b) False

Explanation: The endurance of cruise method 2 is identical to that of cruise method 1. E=$$\Big[\frac{E_{max}}{C}\Big]\Big\{\frac{2u^2}{u^4+1}\Big\}l_n\omega$$ where V is true airspeed, C is specific fuel consumption, L is lift, D is drag, Emax is endurance, u is relative airspeed and ω is fuel ratio.

8. Which of the following is a reason of disadvantage of cruise method 2?
a) Increased mach number
b) Fuel saving
c) Increased time of flight
d) Increased weight of aircraft

Explanation: The disadvantage of cruise method 2 is that to compensate the weight of aircraft the mach number and relative airspeed are decreased and there is an increase in the time of flight thus does not making any fuel saving.

9. In which of the following cases cruise method 2 is used?
a) Commercial aircraft
b) Fighter aircraft
c) Military
d) Patrol and surveillance

Explanation: Cruise method 2 is used mainly for patrol and surveillance purposes as there is more endurance and time of flight and short range which is best suitable for the surveillance purpose.

10. In Cruise method 2 endurance is more concentrated than distance travelled.
a) True
b) False 