Jawaharlal Nehru Technological University Hyderabad B.Tech III INTRODUCTION TO AEROSPACE ENGINEERING Previous Question Paper (November/December - 2020 - R16)

Sir George Cayley, often referred to as the Father of Aviation, established the modern configuration of the airplane by separating the functions of lift, propulsion, and control. His systematic approach involved identifying the four forces of flight: weight, lift, thrust, and drag.

His most significant attempt at a full-sized airplane was the 1853 glider. This aircraft featured a fixed main wing set at a dihedral angle for lateral stability, a cruciform tail assembly providing both vertical and horizontal control surfaces, and a boat-shaped fuselage (nacelle) to house the pilot. The design was tested at Brompton Hall, where it successfully carried his reluctant coachman across a valley, marking the first recorded instance of a manned, fixed-wing flight.

The 'Boy-carrier' refers to an earlier, smaller-scale experiment conducted by Cayley in 1849. This was a triplane glider configuration designed to test the feasibility of carrying a human passenger. The features of the 'Boy-carrier' included:

• A triplane wing arrangement to increase the total wing area and lift capacity within a compact structure.
• A long, sturdy tail boom attached to the wing structure to provide longitudinal stability.
• A simple landing gear system consisting of a wheel, designed to absorb the shock of landing.
• A passenger compartment sized specifically for a young boy to minimize weight while proving that a human could be transported through the air.

These designs were revolutionary because they moved away from the ornithopter (flapping-wing) concept, focusing instead on the concept of a fixed wing generating lift through forward motion, which remains the fundamental principle of aeronautical engineering today.

The Earth's atmosphere is divided into layers based on temperature gradients, which directly influence the variation of pressure, temperature, and density with altitude. The standard atmosphere model describes these changes as follows:

Pressure and Density: Both atmospheric pressure and air density decrease exponentially with an increase in altitude. This occurs because the weight of the air column above a given point decreases as one moves higher, leading to a reduction in both the force exerted by the air (pressure) and the number of molecules per unit volume (density). The relationship is governed by the hydrostatic equation:

where P is pressure, h is altitude, ρ is density, and g is the acceleration due to gravity.

Temperature: The variation of temperature with altitude is non-linear and defines the atmospheric layers:

• Troposphere: Temperature decreases linearly with altitude at a standard lapse rate of approximately 6.5°C per kilometer until the tropopause.
• Stratosphere: Temperature remains constant initially and then increases with altitude due to the absorption of ultraviolet radiation by the ozone layer.
• Mesosphere: Temperature decreases again with altitude, reaching the coldest point in the atmosphere at the mesopause.
• Thermosphere: Temperature increases significantly with altitude due to the absorption of high-energy solar radiation by sparse gas molecules.

Summary of Trends:

A graphical representation would show the pressure and density curves as smooth, downward-sloping exponential decay lines starting from sea-level values. The temperature profile would appear as a zig-zag line, moving left (decreasing) in the troposphere, shifting right (increasing) in the stratosphere, moving left again in the mesosphere, and finally shifting right in the thermosphere.