Question 1
A constant percent chord line is drawn from root airfoil to tip airfoil in linear interpolation method.
A. True
B. False
View Answer
Answer: Option A
Explanation:
Linear interpolation technique is used to create intermediate airfoil section as weighted average. To do so first both airfoils are connected with line. Next step is to draw a constant percent chord line from root to tip airfoil. After following respective steps we will get airfoil section as per our requirements.
Question 2
A fighter jet is flying with wing span of 90ft. If mean aerodynamic chord MAC is at 30ft from tip chord then, to design such wing which type of planform should I use?
A. Delta
B. Rectangular
C. Square
D. Triangle
View Answer
Answer: Option A
Explanation:
Given, wing span b=90ft, location of MAC from tip = 30ftLocation of MAC from root y = b/2 – 30ft = 90/2 – 30 = 45-30 = 15ft.To find planform let’s find taper ratio first from y.Location of MAC is given as, y = (b/6)*(1+t+t2) / (1+t). …. (1)From given options, let’s consider delta wing first.Delta wing has taper ratio near to none. Let’s consider taper ratio to be zero for idle case.Hence, by substituting value of taper ratio in eq (1),Y = (90/6)*1+0+0/1+0 = 90/6 = 15ft.This value is same as we found earlier from given data. Hence, wing planform is delta.
Question 3
A wing is to be loft with span as 2m and reference area of wing is 4m2. If we want to design the wing with taper ratio of 0.6 then what will be the value of root chord?
A. 2.5m
B. 2.50m
C. 2.65m
D. 25.6m
View Answer
Answer: Option A
Explanation:
Given, span b=2m, area S = 4m2, taper ratio t = 0.6Now, root chord Cr is given by,Cr = 2*s / b (1+t) = 2*4 / 2(0.6+1) = 8/2*1.6 = 2.5m.
Question 4
An unstable A/C configuration is a typical wing-aft tail body. IF MAC is 4m then, what would be the approximated location of the CG?
A. 2m
B. 5m
C. 6m
D. 7m
View Answer
Answer: Option A
Explanation:
Typical location Cg for an unstable wing = 50% of MAC = 50% of 4 = 0.5*4 = 2m.
Question 5
As a designer, our job is to design a wing which has root chord Cr as 1m. What should be the approximate radius of fillet?
A. 0.1m
B. 1m
C. 2m
D. 2.1m
View Answer
Answer: Option A
Explanation:
typically fillet radius can be approximated as 10% of the root chord.Hence, radius = 10% of Cr = 10% of 1 = 0.1*1 = 0.1m.
Question 6
As a designer, our task is to design wing layout such that the location of MAC from root chord or centre line is at 8ft. Find the appropriate value of the wingspan if wing is rectangular.
A. 32ft
B. 50ft
C. 28m
D. 32m
View Answer
Answer: Option A
Explanation:
Given, rectangular wing.MAC location y = 8ft. As wing is rectangular taper ratio t =1.Wingspan b = (6*y*(1+ t)) / (1+t+t2) = 6*8*(1+1) / (1+1+12) = 6*8*2/3 = 32ft.
Question 7
At maximum thickness point, fillet is in ____________
A. purely vertical plane
B. purely in hp
C. plane at an angle of less than 20° always
D. plane at 45° always
View Answer
Answer: Option A
Explanation:
Fillet arcs will be normal to wing surface only at the maximum thickness point. At any other section it is not perpendicular to surface. Hence, at maximum thickness point, fillet is in pure vertical plane.
Question 8
Fillet radius is typically more at rear of the aircraft.
A. True
B. False
View Answer
Answer: Option A
Explanation:
Fillet arcs can be of constant radius or can be of varying radius. Typically, at rear of an a/c fillet arc radius is more. This will result in reduction of the flow separation.
Question 9
If wing has MAC of 8m then, what will be the location of aerodynamic centre?
A. 2m from l.e.
B. 2m from t.e.
C. At l.e.
D. At t.e.
View Answer
Answer: Option A
Explanation:
Given, MAC = 8MLocation of aerodynamic center = 25% of MAC = 25% of 8 = 0.25*8 = 2m from l.e.
Question 10
In linear interpolation method, new airfoil is created as ____________
A. weighted average of root and tip airfoil
B. heavier than the root airfoil always
C. higher chord than root always
D. lower chord than tip always
View Answer
Answer: Option A
Explanation:
Linear interpolation method is used to create new airfoil station between root and tip airfoil. In general, root airfoil is based on performance and tip is selected for stall properties. Linear interpolation will give new airfoil as weighted average of the root and tip airfoil.
Question 11
Which of the following is correct in terms of the wing layout with twist?
A. Incidence at each span station must be considered and chord should be rotated accordingly
B. Only untwist airfoils can be used for layout
C. Only rotation of chord line is required at c/6 points
D. Only chord line should be rotated by reducing length of chord
View Answer
Answer: Option A
Explanation:
In general, airfoils are drawn to find the complete wing layout. When wing has some twist then, we need to find incidence at each span station in order to include effects of twist. Also chord needs to be rotated accordingly before drawing an actual airfoil for lofting.
Question 12
Which of the following is correct?
A. Generally, tip airfoils are selected for stall characteristics
B. Always root airfoils are elected for stall characteristics
C. Wing twist will increase thrust by engine
D. Wing twist is not considered for layout
View Answer
Answer: Option A
Explanation:
Generally, tip airfoils are selected for gentle stall properties. Root airfoils are selected for best performance. By doing so we will have better wing which has overall good performance and stall properties.
Question 13
Which of the following is correct?
A. We can generate flat wrap surface by using linear interpolation method
B. Flat surfaces can only be generated by using linear interpolation
C. Linear interpolation will never give flat surface
D. Linear interpolation is only used for flat wrap surfaces
View Answer
Answer: Option A
Explanation:
A flat wrap surface has same tangent angles for different conic curves. When linear interpolation method is used, it does not always provide constant cross-sections or c/s with same tangent angles. Hence, it may or may not produce flat wrap. We can generate flat wrap by providing some constraints as well.
Question 14
Wing planform is always elliptic.
A. True
B. False
View Answer
Answer: Option B
Explanation:
Wing planform is shape generate when viewed from top. Elliptic wings are more efficient in terms of lifting properties. However to manufacture it is also difficult. Hence, wing planform is not always elliptic rather it will be selected according to mission requirements.