1. How will you determine climb mission weight fraction?
a) Climb Endurance
b) Loiter
c) Always constant
d) Cruise Speed
Explanation: Climb phase usually measured by rate of climb. Climb endurance formula is used to determine the endurance of aircraft at climb phase. Typically we can find climb weight fraction from historic time line however in some cases we can also use climb endurance formula to determine fuel fraction.
2. If all the other factors remain unchanged and only aerodynamic efficiency of the aircraft is doubled then, what will be the cruise segment fuel weight fraction?
a) Will increase
b) Will decrease
c) Will remain same
d) Will be independent of aerodynamic efficiency
Explanation: Cruise phase fuel fraction is determined by using range formula as follows:
Wn/Wn-1 = \(e^{\left(-\frac{R*C}{V*\frac{L}{D}}\right)}\)
Now if we double the value of aerodynamic efficiency the denominator will increase which in turn increases fuel fraction during cruise.
3. Fuel consumption during cruise is affected by wetted area.
a) True
b) False
Explanation: Fuel conception or fuel fraction during cruise segment will be affected by the overall aerodynamic efficiency. The aerodynamic efficiency is ratio of lift and drag. Lift is directly affected by the wetted area, which affects L/D. As a result, it will affect fuel fraction during cruise mission phase.
4. A prop-driven aircraft is cruising with 90% propeller efficiency. If, range of aircraft is 7*106 ft, C=1.38*10-7 s-1 and L/D = 14 then what will be the fuel weight fraction for the cruise?
a) 0.9216
b) 0.9261
c) 0.9289
d) 0.9365
Explanation: Given, a prop-driven aircraft,
Range R = 7*106 ft, C = 1.38*10-7 s-1, L/D =14
Here, propeller efficiency is 90% hence, η = 0.9
Now cruise weight fraction is given by range formula. For, prop-driven aircraft it is given by,
Wcruise / W0 = \(e^{\left(-\frac{R*C}{\eta*\frac{L}{D}}\right)}\) = \(e^{-(\frac{7 * 10^ 6* 1.38 * 10^ {-7}}{0.9*14})}\) = 0.9261.
5. The cross-sectional shape of wing is called _____
a) airfoil
b) circle
c) camber
d) chord
Explanation: Wings are designed with airfoil cross-section. Engine inlets are typically circular in cross-sections. Camber and chord are parameters of an airfoil.
6. Aerofoil affects the performance parameters of aircraft.
a) True
b) False
Explanation: Airfoil is cross-section of the wing. Airfoil will affect lift, drag, take-off characteristics etc. In general, crucial performance parameters are affected by airfoil selection.
7. Which of the following is correct?
a) Lift produced by an airfoil is always equal to weight
b) Drag by sphere is more than the drag produced by an airfoil for similar conditions
c) Drag by sphere is less than that of produced by an airfoil for similar conditions
d) Drag by sphere is equal to the drag produced by an airfoil for similar conditions
Explanation: Lift produced is not always same as weight. Sphere is a 3D object. Drag produced by sphere will be more due to increased friction and 3D effects. An airfoil is 2D shape which will have less drag as compare to sphere for all similar conditions.
8. An aerofoil is operating with flow velocity of 100m/s. Aerofoil is symmetric and is at 0° AOA. Determine lift produced by this aerofoil.
a) 10.5 N
b) 0 N
c) 50 N
d) 100N
Explanation: Lift is an upward force produced by pressure difference.
Given, velocity V=100m/s, AOA = 0°.
For symmetric airfoil at 0° AOA pressure will be same as upper and lower surface.
Hence, lift = 0N.
9. Which of the following is not type of an airfoil?
a) Symmetric
b) Camber
c) Whitcomb
d) Vortex
Explanation: Symmetric airfoils have symmetric curvature at both side. Camber are non-symmetric airfoils. Whitcomb is also type of airfoil. Vortex is a phenomena, not the type of an airfoil.
10. Airfoil is a streamline shape.
a) True
b) False
Explanation: Streamline shape is that shape which gives streamlined flow. An airfoil has that characteristic. An airfoil is able to provide much smoother flow than non-streamlined body.