JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III CONCEPTUAL DESIGN OF FLIGHT VEHICLES Previous Question Paper (February/March - 2022 - R15)

Aircraft are primarily classified based on their mission profile, aerodynamic configuration, and propulsion systems. The classification is essential for defining the design requirements, performance envelopes, and structural constraints.

1. Civil Aircraft: Designed for commercial transport or general aviation. Examples include the Boeing 737 (transport) and Cessna 172 (general aviation). These are classified by payload capacity, range, and passenger comfort requirements.

2. Military Aircraft: Designed for combat, reconnaissance, or logistics. Examples include the F-22 Raptor (fighter) and C-130 Hercules (transport). Classification is based on maneuverability, stealth, and weapon carriage capabilities.

3. Rotary-Wing Aircraft: Designed for vertical takeoff and landing (VTOL). Examples include the AH-64 Apache. These are classified by their ability to hover and operate in confined spaces, necessitating distinct aerodynamic analysis compared to fixed-wing aircraft.

4. Unmanned Aerial Vehicles (UAVs): Designed for autonomous or remote operations. Examples include the MQ-9 Reaper. These are classified by their endurance and mission-specific sensor payloads rather than human-centric design factors.

Preliminary design is the phase where the aircraft configuration is frozen and its feasibility is established. Key aspects include:

1. Mission Specification and Requirements: Defining the payload, range, cruise speed, and field performance (takeoff/landing distance) which dictate the size and power requirements.
2. Weight Estimation: Using statistical methods and historical data to estimate the takeoff gross weight, empty weight, and fuel weight required to meet mission goals.
3. Aerodynamic Configuration: Selecting the wing planform (aspect ratio, sweep, taper), airfoil sections, and tail geometry to optimize lift-to-drag ratios and stability.
4. Propulsion Selection: Choosing engine type (turbofan, turboprop, etc.) and sizing the powerplant based on thrust-to-weight ratio requirements for takeoff and cruise.
5. Performance Analysis: Calculating the flight envelope, including climb rates, turn rates, and endurance, to ensure the design meets the specified mission profile.
6. Stability and Control: Preliminary sizing of control surfaces and determining the center of gravity (CG) range to ensure static and dynamic stability.