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Right answer is (b) False

The best explanation: Lofting is the method for DEFINING EXTERNAL geometry of the aircraft. Production lofting is most detailed TYPE of the lofting. It is USED to provide EXACT and accurate mathematical model of the body.

Correct answer is (a) SMOOTH lines which controls overall shape of the CONIC cross-section

Easy explanation: Longitudinal control lines are smooth lines through which conic CURVES are connected. SINCE, it CONNECTS all different conics, it will control the overall shape of the body itself during lofting.

The correct choice is (a) Circle to square ADAPTER

Best explanation: Above diagram is showing a typical problem during lofting NAMELY, ‘circle to square adapter’. In such cases, DESIGNER is required to loft body with different cross-section. For e.g. A nozzle of typical jet is square at inlet but at front face it is circular. HENCE, such problems are required to be solved through various techniques of circle to square adapter.

The CORRECT option is (a) overall aerodynamic concepts, LOCATION of components ETC

Explanation: A GOOD sketch is the one that highlights as much as detail as it can. It should include overall aerodynamic concepts, internal placements of components, landing gear location etc.

The CORRECT option is (a) Availability of DIVERSE curves

For explanation: Conic lofting is DONE by using conic curves. A conic has number of different curves in family such as circle, ELLIPSE etc. We can generate all such shapes via conic lofting. Hence, it is one of the ADVANTAGES of it that it has availability of diverse curves.

Right ANSWER is (a) 2M

Explanation: TYPICAL LOCATION Cg for an UNSTABLE wing = 50% of MAC = 50% of 4 = 0.5*4 = 2m.

Correct option is (a) evaluate the smoothness of A/C FUSELAGE

Easy explanation: BUTTOCK planes or butt planes are vertically oriented cuts which can be used to FIND smoothness of the A/C fuselage. Lift curve SLOPE is found by using lift and AOA. Lift can be estimated by measuring pressure difference between UPPER and lower surface.

The correct CHOICE is (a) cross-section DEVELOPMENT VIA longitudinal control lines

Explanation: Above diagram is representing the development of a typical cross-section via longitudinal control lines. Lines which are connecting various cross-section is nothing but the longitudinal control line. This diagram is showing EITHER typical plan or SIDE view.

The correct ANSWER is (a) 0.4142-0.5

Best explanation: Given, intermediate cross section = elliptic.

Conic shape parameter CSP = DS / DC, where D = midpoint of line drawn from end point A to end point B, C = tangent point, S = SHOULDER point.

When CSP = 0.4142 and AC = BC then it will generate circular shape.

Now, when CSP = 0.5 it will produce parabola. Hence, to generate elliptic cross section value of CSP should be between 0.4142 and 0.5 BASED on our REQUIREMENT.

The CORRECT choice is (a) True

For explanation I would say: 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.

Right choice is (a) Delta

The best explanation: Given, wing SPAN b=90ft, location of MAC from tip = 30FT

Location 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+t^2) / (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.

Correct answer is (a) LOFTING

Explanation: Lofting is defined as the process in which external geometry of an A/C is defined. It is nothing but the mathematical modelling the OUTER layer of the AIRCRAFT. FLUTTER is RELATED to control surface. Drawing and drafting are related to each other.

The correct choice is (a) Flat WRAP technique is cost effective

The BEST I can explain: Flat wrap method is USED for flat surfaces. Complex curvature are required more money to fabricate. If a surface is flat-wrapped then we can directly wrap a flat sheet around its cross section. By doing so we can REDUCE the cost and HENCE, it is cost effective.

Correct CHOICE is (a) 5.8m

For EXPLANATION: Given, Cr = 10m, Ct = 2M and TAPER ratio t = Ct/Cr = 2/10 = 0.2

MAC is given by,

MAC = (2/3)*Cr*((1+t+t2) / (1+t))

= (2/3)*10*((1+0.2+0.2^2) / (1+0.2)) = 5.79 = 5.8m.

Correct choice is (a) 77m^3

Easy explanation: Volume = area under the curve

= area of triangle + rectangle area + 8 + 4 + 6 = 0.5*6*3 + 5*10 + 8 + 4 + 6 = 9+50+8+4+6 = 77m^3.

Right choice is (a) 20.55m^2

The explanation: GIVEN thickness t = 15% of chord = 0.15*c, A = 10m^2.

For given thickness, wetted area AW is given by,

Aw = A*(1.977+0.52*(t/c)) = 10*(1.977+0.52*0.15) = 20.55m^2

The CORRECT option is (a) Wing fillet

For EXPLANATION I would say: Wing fillets are arcs as shown in figure. Wing fillets are USED to improve smoothness of the root of the AIRFOIL as shown. This will result in improvement of aerodynamic efficiency. A typical fillet is a circular ARC.

Correct answer is (a) 3.42 per m

The EXPLANATION: GIVEN, Stop=10m^2, Aside=14m^2, L = 10m.

Now ratio of wetted area AW and volume V is given by,

Aw/V = 2*L*(Stop + Aside) / (Stop*Aside)

Aw/V = 2*10*(10+14) / (10*14) = 20*24/140 = 3.42 per m.

Correct choice is (a) We can generate flat WRAP surface by using linear interpolation method

To explain: 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.

Correct option is (a) True

To explain I would say: Wetted area will affect the AMOUNT of the fluid FRICTION when it touches the skin of the BODY. Hence, it affects skin friction of the body. As skin friction is affected, the drag ESTIMATION is also been affected.

Right choice is (a) 5.06m

Best EXPLANATION: GIVEN, LENGTH of old fuselage L1 = 10.12m, volume of old fuselage V1 = 8m^3.

Now, we are asked to design same fuselage which has volume of 16m^3.

Hence, new volume V2 = 16m^3.

Internal volume V is inversely proportional to length L of the fuselage.

Here, we have been asked held all other PARAMETERS constant.

Hence, L2 = (V1/V2)*L1 = (8/16)*10.12 =5.06m^3.

Correct answer is (a) 88.6m^2

Easiest explanation: Given, average projected AREA A = 9 m^2.

Now, WETTED area AW = π*A = π*28.2 = 88.59 = 88.6m^2.

Right choice is (a) AX^2 + BY^2 + CXY + DX + EY + F = 0

The explanation: A conic is a 2^nd degree curve. Conic in simple mathematical language is defined by USING AX^2 + BY^2 + CXY + DX + EY + F = 0. Constants are based on our requirements. WE can PRODUCE different cross-section shape such as circle, PARABOLA etc. by using conic.

The correct option is (a) Any arbitrary value

Easy EXPLANATION: After the selection of end points (A and B) and their tangent point C next step is to find point-S. When it is done the next step is to DRAW a line from a tangent point that can be at any arbitrary angle. This line COULD be at 20°, 50°, 60° or any arbitrary value as we DESIRED. Once, this step is completed then, we can go further to find the next point of conic curve.

Correct CHOICE is (a) 2.5m

Easiest explanation: GIVEN, SPAN b=2m, area S = 4m^2, TAPER ratio t = 0.6

Now, root CHORD Cr is given by,

Cr = 2*s / b (1+t) = 2*4 / 2(0.6+1) = 8/2*1.6 = 2.5m.

The CORRECT CHOICE is (a) 2m from l.e.

For explanation: Given, MAC = 8M

Location of aerodynamic center = 25% of MAC = 25% of 8 = 0.25*8 = 2m from l.e.

The correct option is (a) True

To EXPLAIN: 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.

The correct option is (a) DEVELOPMENT of CONIC lofting

For EXPLANATION I would SAY: A typical intermediate step of conic lofting is shown in the figure. Here, ‘A’ and ‘B’ points are selected as per requirements and called END points. C is the tangent point and S is known as the shoulder point for given conic lofting development.

Correct choice is (a) square C/S shape

The best I can EXPLAIN: Above diagram is showing typical conic development. As shown shoulder point s is much NEAR to the tangent point C. Now as a result of this it will generate square or rectangle cross SECTION depending UPON DISTANCE AC and BC. Hence, correct option will be square.

Correct OPTION is (a) weighted average of root and tip airfoil

The best I can explain: 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.

The correct choice is (a) wetted area

The explanation: Wetted area is the total EXPOSED area which would get wet if we immersed body in fluid. Volume is product of area and length or DEPTH. Length is measurement of how long an object is. Wing PLANFORM is SHAPE of wing when viewed from top.

The correct option is (a) Most detailed drawing drawn to SHOW greater details of internal components

For explanation: before a DESIGN can be finalized it needs to go through number of iterations. After this iterative process we make a design which has most detailed information. This detailed LAYOUT is called INBOARD profile. TYPICALLY, it is far more detailed than the initial layout.

Correct option is (a) LOFTING done by using various conic curves

Explanation: When lofting is done by using conic curves then, it is termed as conic lofting. Conic lofting MAY include only CIRCLES but it is not mandatory that if conic lofting is MENTIONED then, it will have circles only.

Correct OPTION is (a) 3.3m

For EXPLANATION: Given, Cr = 4M, Ct = 2m, S = 20m^2

Taper ratio t = Ct/Cr = 2/4 = 0.5.

Hence, wing span of given wing b/2 = S/Cr*(1+t) = 20/4*(1+0.5) = 20/4*1.5 = 3.3m.

Right answer is (a) Generally, TIP airfoils are SELECTED for stall characteristics

To explain: 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.

The CORRECT OPTION is (a) 0.1m

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.

Right answer is (a) 65m^2

Easiest explanation: For GIVEN diagram,

Wetted AREA Aw = area under the curve = area of triangle + area of rectangle

Aw = (0.5*6*5) + (10*5) = 15+50 = 65m^2.

Right answer is (a) T.e. kick

The best I can EXPLAIN: Above figure is often termed as trailing EDGE kick. A straightened out trailing edge will increase the FLAP chord. It also reduces induced drag. Rounded tip will permit air to flow AROUND tip easily.

Correct option is (a) Rounded wingtip

For explanation I WOULD say: WINGS can have different wingtip shapes. Above figure is showing a typical rounded wingtip. A smoothly rounded tip allows air to flow EASILY around tip. LEX STAND for leading edge extension.

The correct answer is (a) Circle

The explanation is: CONIC shape is DEPENDENT on the way we cut the cone. As SHOWN in the figure, if conic is cut through a plane which is perpendicular to the AXIS of the cone then, the resultant shape will be a circle. Similarly, if plane is slanted then it will produce an ellipse.

The correct option is (a) circle with nozzle exhaust diameter

To EXPLAIN: Control station are the original cross-section which are required to COMPLETE the lofting process. Here, our MAIN body is nozzle which has circular cross-section. Hence, original shape required to LOFT this nozzle will be circular also. Hence, control station should be circle with similar diameter as the nozzle.

Right option is (a) Buttock plane is at a distance of 40 UNIT from fuselage centerline

To explain: Butt-PLANES or buttock planes are defined as vertically oriented cuts which are used for fuselage lofting VERIFICATION. It cuts from the horizontal INTERSECTION of the A/C with vertical planes. These planes are defined by their distance from centerline. Hence, butt-plane 40 can be interpreted as butt plane is at distance of 40 unit from AIRCRAFT centerline.

The correct choice is (a) 32ft

To elaborate: Given, rectangular wing.

MAC location y = 8FT. As wing is rectangular TAPER RATIO t =1.

Wingspan b = (6*y*(1+ t)) / (1+t+t^2) = 6*8*(1+1) / (1+1+1^2) = 6*8*2/3 = 32ft.

The correct answer is (a) Swet = 2.003*Sexposed

Explanation: Thin BODY has thickness TENDS to NEGLIGIBLE. For a paper thin body WETTED area is twice of the EXPOSED or true planform area. However, for finite thickness of t <= 0.05*c wetted area is approximated as Swet = 2.003*Sexposed.

Right OPTION is (a) V = 3.4*(Stop*Aside/4L)

The explanation is: Internal volume of FUSELAGE will be total available volume for crew, cargo, passenger etc. Typically, from side and TOP VIEW we can estimate internal volume. If area of side is Aside and area of top is Stop then, internal volume is given as, V = 3.4*(Stop*Aside/4L), where L = LENGTH of the fuselage.