This set of Aircraft Design Multiple Choice Questions & Answers (MCQs) focuses on “Wing Geometry-1”.
1. Wing and airfoil both are 3D phenomena.
Explanation: An airfoil is a 2D concept. Airfoil is cross sectional shape of the wing. When airfoil has finite span it is called a wing.
2. A 3D airfoil is called _____________
Explanation: Wing is generated by elongating an airfoil. Airfoil is 2D shape. Engine is main source of power. Lofting is skin modelling.
3. If taper ratio is T and span is b with surface area as S then the root chord is _____
a) Croot = 2*S / (b*(1+T))
b) Croot = 2*S / (b*(3+T))
c) Croot = 2*S / (2b*(1+T))
d) Croot = 2*S / (1+T)
Explanation: Taper ratio represents how much wing is tapered. For any given area S, span b and taper ratio T, root chord is given by,
Croot = 2*S / (b*(1+T)). The value of root chord will be different for different aircrafts.
4. A wing has root chord of 2m and taper ratio of 0.5. Determine what will be the value of tip chord?
Explanation: Given, wing has root chord of 2m
Taper ratio T = 0.5
Now, taper ratio T = tip chord / root chord
Tip chord = T*root chord = 0.5*2 = 1m.
5. Wing planform is affected by _____
a) sweep only
b) aspect ratio, sweep angle, taper ratio
c) aspect ratio only
d) taper ratio only
Explanation: Wing planform is shape of the wing when viewed from top. Aspect ratio will affect span and area. Overall planform will be affected by aspect ratio, taper ratio, sweep etc.
6. Wing aspect ratio is defined as _____
a) span square divided by reference area
b) span square multiplied by reference area
c) span square plus reference area
d) span square
Explanation: Aspect ratio of wing gives relation between span of wing and wing reference area. It is defined as the ratio of span square to the reference or planform area. Higher aspect ratio wings will be long with less area.
7. A typical wing has aspect ratio of 7 and span of 2m. If taper ratio T = 0.2 then, find the value of root chord.
Explanation: Given, span = 2m, aspect ratio = 7 and taper ratio T = 0.2
The root chord is given by,
Croot = 2*S / (b*(1+T))
Here, S is not given but aspect ratio is given.
Aspect ratio AR = Span square / S = 2*2 / S
7 = 4/ S
S = 0.5714 m2
Hence, Croot = 2*S / (b*(1+T))
= 2*0.5714 / (2*(1+0.2)) = 0.4761m.
8. If a sailplane is to be designed then, the aspect ratio of the sailplane will be ______
a) higher than military aircraft
b) same as military aircraft
c) lower than military aircraft
d) exactly half of the military aircraft
Explanation: Sailplanes are different from military aircrafts. Sailplanes are designed to glide through air. For such requirements, it will require higher lift capability which can be provided by using higher aspect ratio wings than military aircrafts.
9. A jet fighter is operating at Mach number of 1.4. Wing chord is 1m then, find the location of aerodynamic centre.
Explanation: Given, jet fighter aircraft which is cruising at Mach 1.4.
For such high speed aircraft, location of the aerodynamic center is given by,
Location of aerodynamic center = 40% of chord = 40% of 1 = 0.4*1 = 0.4m.
10. Which of the following is correct?
a) Weight will be more for higher aspect ratio wing
b) Military aircraft have much higher aspect ratio
c) Civil aircraft are flying at hypersonic speed
d) Lofting is a conceptual design of wing
Explanation: Aspect ratio affects span and reference area. For same area if aspect ratio is more then, the corresponding value of span will be more as well. This will increase material requirements and which increases weight of the wing.
Explanation: Tapered wings have finite value of taper ratio. In taper wing root and tip chord will have different values of chord. Elliptic wings are of elliptic shape. Rectangular wing has taper ratio of unity which shows a rectangular profile.
12. Determine the corrections or otherwise of the following assertion [A] and reason [R]:
Assertion [A]: Taper ratio will affect the weight of wing.
Reason[R]: For finite taper ratio, wing thickness will be different at root and tip.
a) Both [A] and [R] are true and [R] is the correct reason for [A]
b) Both [A] and [R] are true but [R] is not the correct reason for [A]
c) [A] is true but [R] is false
d) [A] is false but [R] is true
Explanation: Taper ratio is defined by ratio of tip chord to the root chord. Hence, for tapered wing the thickness of the wing will be different at each location. For, finite value of taper ratio root and tip chord will have different values. These different values of the chord will affect the weight of wing as well.
13. A twin turboprop engine is flying with 120m/s. Wing of the aircraft has span of 2m and lift co-efficient as 0.15 with aspect ratio as 9.2. Find the lift produced by the wing.
a) 574.18 N
c) 120 N
d) 620 N
Explanation: Given, a twin turboprop
Velocity V = 120m/s, CL = 0.15, Aspect ratio = 9.2, span b=2m
Aspect ratio = b*b/S
9.2 = 2*2/s
S = 0.434m2
Now, lift is given by,
L = (1/2)*ρ*V2*S*CL = 0.5* 1.225*120*120*0.434*0.15 = 574.18N.
Sanfoundry Global Education & Learning Series – Aircraft Design.
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