GOJAN SCHOOL OF BUSINESS AND TECHNOLOGY, REDHILLS, CHENNAI.
DEPARTMENT OF AERONAUTICAL ENGINEERING
MODEL EXAM ANSWER KEY EVEN (2023-2024)
AE3601/AIRCRAFT DESIGN
PART-A (5x3=15 Marks)
1. Compare all the key parameters involved in aircraft design.
Aircraft design involves multiple parameters, including:
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Aerodynamics: Lift-to-drag ratio, stall characteristics, wing loading.
Structures: Material selection, weight distribution, strength, and fatigue life.
Propulsion: Engine type, thrust-to-weight ratio, fuel efficiency.
Performance: Range, endurance, rate of climb, service ceiling.
Stability & Control: Static and dynamic stability, center of gravity, control surface
effectiveness.
Operational Factors: Maintainability, cost, safety, environmental impact.
2. Classify airplanes based on configuration.
Airplanes are classified based on:
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Wing Configuration: High-wing, mid-wing, low-wing, canard.
Fuselage Type: Conventional, blended-wing-body, flying wing.
Landing Gear Configuration: Tricycle, taildragger, retractable gear.
Powerplant Co nfiguration: Single-engine, twin-engine, turboprop, turbojet,
turbofan.
Special Purpose Configurations: UAVs, VTOL, STOL, amphibious aircraft.
3. Illustrate what is meant by Wing Load? What is its significance?
Wing Loading (WL) = Aircraft Gross Weight / Wing Area (N/m² or lb/ft²)
Significance:
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Higher Wing Loading: Faster cruise speed, lower maneuverability, longer takeoff
and landing distances.
Lower Wing Loading: Better lift performance, slower stall speed, shorter runway
requirement.
4. Sketch the front view of a cantilever low-wing monoplane.
(Provide a labeled sketch of a cantilever low-wing monoplane, showing fuselage, wings,
landing gear, and tail section.)
5. Illustrate the Sources for Aircraft Design Data.
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Experimental Data: Wind tunnel tests, flight tests.
Empirical Data: Historical aircraft trends, previous designs.
Analytical Methods: Computational Fluid Dynamics (CFD), Finite Element Analysis
(FEA).
Industry Regulations: FAA, EASA, ICAO standards.
Manufacturer Specifications: Engine data, material properties.
PART-B (2x13=26 Marks)
6.a Explain different phases involved in airplane design.
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Conceptual Design: Mission definition, initial sizing, preliminary weight estimation.
Preliminary Design: Detailed aerodynamics, structural layout, propulsion analysis.
Detailed Design: CAD modeling, stress analysis, system integration.
Prototype and Testing: Wind tunnel, ground tests, flight tests.
5. Certification & Production: Regulatory approval, manufacturing optimization.
(OR)
6.b Explain classification of airplanes based on function and list down the factors
affecting aircraft configuration.
Classification Based on Function:
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Civil Aircraft: Commercial airliners, general aviation.
Military Aircraft: Fighters, bombers, transport, UAVs.
Special Purpose: Surveillance, research, firefighting.
Factors Affecting Configuration:
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Mission Profile (speed, altitude, endurance).
Aerodynamics (drag, lift, stability).
Weight Constraints (fuel, payload, materials).
Operational Considerations (runway length, environment).
7.a Explain the aim of project feasibility study in the aircraft design process. Discuss the
work carried out in this phase.
The Project Feasibility Study evaluates:
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Technical Feasibility: Viability of design, aerodynamics, propulsion.
Economic Feasibility: Manufacturing costs, operational expenses.
Regulatory Feasibility: Compliance with FAA, EASA, ICAO.
Work Done in this Phase:
o Market Research
o Technology Assessment
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Preliminary Weight & Performance Estimates
Risk Assessment
(OR)
7.b Explain how the specifications or design requirements of an airplane are decided by
its function. Discuss the requirements for the following aircraft.
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Passenger Aircraft: Large cabin volume, high fuel efficiency, low noise.
Cargo Aircraft: High payload capacity, wide cargo doors, reinforced fuselage.
Fighter Aircraft: High speed, agility, stealth, advanced avionics.
Trainer Aircraft: Stability, low operating cost, dual control systems.
8.a Compare all study the data collection and prepare 3D drawings before the design of
an aircraft.
Data collection involves:
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Aerodynamic Data (CFD, wind tunnel tests).
Material Data (strength, fatigue life).
Structural Load Data (stress-strain behavior).
Performance Data (thrust, drag, endurance).
3D Drawings Preparation:
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Use of CAD Software (CATIA, SolidWorks).
Component-wise Modeling (fuselage, wings, landing gear).
Assembly and Simulation (structural analysis, CFD testing).
(OR)
8.b Classify the design of the main wing of a typical aircraft based on type of wing,
aspect ratio, taper ratio, and sweep angle.
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Type of Wing: Rectangular, tapered, delta, swept, elliptical.
Aspect Ratio (AR): High AR for efficiency (gliders), Low AR for speed (fighters).
Taper Ratio (λ): λ = Tip Chord / Root Chord. Affects lift distribution.
Sweep Angle: Higher sweep for transonic/supersonic flight, lower sweep for better
lift at low speeds.
PART-C (1x14=14 Marks)
9.a How is the first estimate of aircraft gross weight obtained? How is the estimate of
the gross weight refined? Write down the typical weight fraction values for a 60-seater
passenger aircraft designed to cruise at 500 kmph at 4.5 km altitude with a range of
1300 km.
1. Initial Gross Weight Estimate:
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Empirical Relations: Based on similar aircraft.
Mission Breakdown: Fuel, payload, empty weight fractions.
2. Refining the Estimate:
o Iteration using Weight Fractions:
 W_empty / W_0 ≈ 0.55
 W_fuel / W_0 ≈ 0.30
 W_payload / W_0 ≈ 0.15
o Performance Checks (Range, Climb, Takeoff).
o Structural Adjustments (Materials, Configuration).
(OR)
9.b Explain wing loading effect on take-off and landing.
1. Take-off:
o Lower Wing Loading → Shorter takeoff roll, better climb rate.
o Higher Wing Loading → Longer takeoff roll, more thrust required.
2. Landing:
o Lower Wing Loading → Lower stall speed, safer landings.
o Higher Wing Loading → Higher approach speed, increased runway length
needed.
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