Q1. Duration 3 Hrs

a) Explain how you would go about the comparative configuration study of

different types of airplanes, if your task is to undertake a conceptual design of a

300 seater medium range passenger aircraft? (30 marks)

b) What would be the main Design Drivers that would govern the design of the

aircraft from the beginning till end, through various stages of design? (30 marks)

c) Why is it that when you add a small weight correction to compensate for the

mismatch between available empty structural weight and theoretical empty

structural weight, the final weight, after iterations, varies disproportionately?

(40 marks)

Q2. Duration 3 Hrs

a) What are the various performance aspects that can be specified by mission

requirements? Explain each of them briefly (40 marks)

b) What are the steps involved in a Conceptual design of an aircraft? (40 marks)

c) What are the different Design Drivers? Name a few of them (20 marks)

Q3. Duration 3 Hrs

a) First step in the design of a new aircraft is to obtain an estimate of the Takeoff

weight WT0. Explain how you would arrive at a tentative starting point for the

takeoff weight by referring to Janes book? (30 marks)

b) What are the constituents which make up for the total weight of an aircraft and

in what proportion? (30 marks)

c) Explain briefly the various flight phases considered in the flight plan, to assess

the fuel weight at the end of each phase. Draw a neat schematic to show the phases

(40 marks)

Q4. Duration 3 Hrs

a) What are Fuel fraction estimates (or Fuel weight fractions)? (20 marks)

b) Explain how you would estimate the fuel weight fraction during (i) Start up &

Takeoff and (ii) Climb & acceleration to cruise phases ( 20 marks)

c) Fuel weight fraction during cruise out to destination is given by Breguets range

equation: R = (V/C). (L/D). Ln [Wi/Wf], for jet engine What does each symbol

stand for in the above equation? Explain briefly the procedural steps for Jet

Engine to work iteratively for one iteration from start up till landing. (60 marks)

Q5. Duration 3 Hrs

a) What do you understand by Loiter? Why is it necessary to provide loiter time

for every aircraft? (20 marks)

b) Loiter E is given by the endurance equation E= (1/C) .(L/D). Ln [Wi /Wf], for

reciprocating engined aircraft. Explain each of the terms. What are the conditions

for maximising endurance for a reciprocating engine? (60 marks)

c) How do you find the fuel weight fraction for the landing phase? (20 marks)

Q6. Duration 3 Hrs

a) What is structure factor? What is its significance? (15 marks)

b) How do you find the available empty structural weight for an aircraft? What

would you do if the available empty structural weight is less than the theoretical

required empty structural weight at the end of iteration? (45 marks)

c) How will you find the total weight of fuel required to be carried on the aircraft

to meet the conditions imposed by the design driver.s (40 marks)

Q7. Duration 3 Hrs

a) How will you find the cruise velocity of the aircraft, given the cruise Mach

number and cruise altitude at which the aircraft is expected to cruise? How will

you estimate the values of Design CL bandwidth? What criterion would you look

into while selecting an airfoil with matching drag polar graph connecting CD Vs

CL? (40 marks)

b) What is the effect of Aspect Ratio on (L/D)max? Draw a representative graph

connecting (L/D)max and Mach number for different aspect ratios. (40 marks)

c) What all constitute total takeoff weight WTO? What are the two categories of

payload? (20 marks)

Q8. Duration 3 Hrs

a) What do you understand by Wing Loading? What are its units? What are the

representative values of wing loading for a long range transport aircraft and for a

combat fighter? (30 marks)

b) Which parts of a flight plan are affected by the wing loading? (30 marks)

c) What is the effect of wing loading on takeoff , given that the takeoff parameter

TOP is given by TOP = (W/S)TO. (1/ CLmax). (W/T)TO. (1/). What are the

various terms involved in the equation? Why is take off distance more critical than

landing distance? (40 marks)

Q9. Duration 3 Hrs

a) Design of a wing consists of selecting the airfoil cross section shape, average

chord length, maximum thickness-to-chord ratio, Aspect ratio, taper ratio and the

sweep angle. Draw a schematic of a wing cross section and planform views that

illustrate these parameters. (40 marks)

b) Briefly analyze the effect of each of these parameters on the aerodynamic

performance ( 30 marks)

c) The choice of airfoil section type that is most suitable for a design depends on

the general type of aircraft. Discuss the characteristics that make the choice of

NACA airfoil types given below as the best fit for the following types of mission

requirement:

I. NACA five-digit series: for smaller, low subsonic (MCruise= 0.4) aircraft

II. NACA Supercritical airfoils for high subsonic speed aircraft

(MCruise=0.8)

III. NACA series 6 airfoils for supersonic military aircraft

(30 marks)

Q10. Duration 3 Hrs

a) How would you find the drag due to wing for an aircraft in cruise? (30 marks)

b) Explain the method to find the thrust required at cruise altitude. How would you

find the maximum thrust at full throttle of the engine? (30 marks)

c) Explain how you would find the equivalent thrust required at max rpm at sea

level, given that TH = (TSL). (PH/ PSL). (SL/ H). Explain the terms involved and

also indicate what would be the source for obtaining the data on parameters

mentioned and for selection of a matching engine. ( 40 marks)