Aircraft Design Multiple Choice Questions & Answers (MCQs) on “Flight Mechanics – Gliding Flight-1”.
1. For a typical gliding flight, thrust will be ________
a) zero
b) equal to the lift
c) always same as drag
d) always same as weight
Answer: a
Clarification: For a typical gliding flight, Thrust Will be zero. Gliding flight is often termed as unpowered flight. Lift and drag during gliding flight will be determined by using glide angle.
2. The tangent of glide angle is ________
a) equal to drag to lift ratio
b) lift to drag ratio
c) inverse of thrust
d) equal to thrust
Answer: a
Clarification: The tangent of glide angle is equal to the drag to lift ratio. Lift to drag ratio is called aerodynamic efficiency of the aircraft. Tangent of Glide angle is inverse of the Aerodynamic efficiency or inverse of the lift to drag ratio.
3. If aerodynamic efficiency of the glider is 20 then, found the value of corresponding glide angle.
a) 2.86 unit
b) 3.8
c) 5.6
d) 12.12
Answer: a
Clarification: Glide angle = arctan (1/Aerodynamic efficiency) = arctan (1/20) = 2.86 unit.
4. A typical glider has weight of 150N and has glide angle of 2.5°. Find Lift produced by the glider.
a) 149.85N
b) 150kN
c) 322N
d) 120Kn
Answer: a
Clarification: Lift = weight* cos (glide angle) = 150*cos (2.5°) = 149.85 N.
5. Glider with glide angle of 4.2° is gliding with gliding ratio of _____
a) 13.6
b) 12.9
c) 15
d) 25.4
Answer: a
Clarification: Glide ratio = 1/tan (glide angle) = 1 / tan (4.2°) = 13.6.
6. Typically, a high performance unpowered aircraft is called ________
a) sailplane
b) glider
c) jet
d) twin engine
Answer: a
Clarification: Typically, a high performance unpowered aircraft is termed as sailplane. A glider is crude, low performance unpowered aircraft. This is based on typical sailplane terminology.
7. Find the velocity required for maximum range. Consider a sailplane has wing loading of 110N/m2 and K/CD0 of 0.35.
a) 10.3m/s
b) 10.3mph
c) 12.5mph
d) 9.2mph
Answer: a
Clarification: Velocity = (sqrt{frac{2*wing ,loading*sqrt{K/CD0}}{density}})
= (sqrt{frac{2*110*sqrt{0.35}}{1.225}})
= (sqrt{106.24}) = 10.3 m/s.
8. If a glider needs to be flown at maximum range then, at which value of CL we should fly this glider? Consider CD0/K is 2.8.
a) 1.67
b) 3.2
c) 5.6
d) 2.5
Answer: a
Clarification: CL = [CD0/K] 0.5 = 2.80.5 = 1.67.
9. Which of the following is correct for a typical glider?
a) Drag D = W*cos (gamma)
b) Drag D = W*arcsine (gamma)
c) Drag D = W
d) Drag D = Thrust T
Answer: a
Clarification: Above equation is used to provide information about drag of atypical glider. Drag can be given by, Drag D = W*cos (gamma) where, D is drag, W is weight of the glider and gamma is the glide angle.
10. If my glider has lift coefficient at maximum lift to drag as 1.5 and induced drag factor K is 0.007 then, find parasite drag coefficient.
a) 0.01575
b) 0.01 N
c) 0.02N
d) 0.0157N
Answer: a
Clarification: Parasite drag coefficient = K*lift coefficient2 = 0.007*1.5*1.5 = 0.01575.
11. All the gliders are unpowered.
a) True
b) False