Download ITU Faculty of Aeronautics and Astronautics Department of

ITU Faculty of Aeronautics and Astronautics
Department of Aeronautical Engineering
10837 UCK111E Introduction to Aeronautics and Ethic
2015-2016 Fall Semester
Sample Two
Question 1: Briefly describe who the researchers mentioned below are (short biographical information) and
what their contribution to aeronautics/astronautics has been in two pages maximally.
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Konstantin Eduardovitch Tsiolkovsky
Robert Hutchings Goddard
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Frank Whittle
Hans von Ohain
Question 2: Express the speed of sound in air,
(a) as a function of the air temperature, i.e. 𝑎 = 𝑎(𝑇),
(b) as a function of the air pressure and density, i.e. 𝑎 = 𝑎(𝑝, 𝜌).
(c) Is the airspeed environment dependent? If yes, on which properties of the medium is it
dependent? (propagation of sound waves in a gas).
Question 3: An airplane is performing level flight at V=250 km/h at an altitude h in the troposphere. The
pressure and density at this altitude are 70.12 kPa, and 9.0926×10-1 kg/m3, respectively. On a window of
the airplane the airflow has a velocity of 85 m/s. The normal force exerted by the air on the window is
4141.7 N. Assuming incompressible flow,
(a) find the altitude h the airplane is flying.
(b) Find the total pressure of the airflow.
(c) Find the surface area of the window assuming that the pressure is constant on the window surface.
Now, consider that the airplane ascends to an altitude 1.5h and performs level flight at M=0.27.
(d) What will be the temperature at this altitude?
(e) Calculate the freestream velocity.
Question 4: Consider a 200-ton airplane and its one-seventieth scale test model. Assuming that the average
density of the airplane and the test model are the same,
(a) Find the mass of the test model.
(b) If the wetted area (area of surface exposed to air) of the wing of the test model is 0.208 m 2, find
the wetted area of the airplane.
(c) What will be the aspect ratio of the test model?
(d) If the wing span of the airplane is 60 m, calculate the wingspan of the test model.
Question 5: A flat plate is being tested in a wind tunnel at different angles of attack in the range −5° < 𝛼 <
+5°.
(a) Will the flat plate produce lift at zero angle of attack? Draw the graphic 𝐶𝐿 vs. 𝛼.
(b) Will the drag force measured at zero angle of attack be zero?
(c) How should the flat plate be reshaped in order to generate more lift for 𝛼 > 0?
Question 6: Consider a commercial airliner cruising at a velocity of 885 km/h at a standard altitude of
11582 m, where the freestream pressure and temperature are 2.066×104 N/m2 and 216.66 K, respectively.
A one-fiftieth scale model of the airplane is tested in a wind tunnel where the temperature is −34.26℃.
Calculate the required velocity and pressure of the test airstream in the wind tunnel such that the lift and
drag coefficients measured for the wind-tunnel model are the same as for free flight, i.e. the flows are
dynamically similar. (For this to hold, 𝑀1 = 𝑀2 and 𝑅𝑒1 = 𝑅𝑒2;𝑅𝑒 = 𝜌𝑈𝑐/𝜇). Assume that the air viscosity
𝜇 is proportional to 𝑇 1/2 .
Question 7: Define the following: airfoil, camber, thickness, mean camber line, chord line, leading edge,
trailing edge, angle of attack, planform area, sweep angle. Show these aspects in a figure.
Question 8: How is the critical Mach number defined? Is is possible that Mcr>1? Explain.
Question 9: A 250 ton aircraft is cruising at a velocity of 240 m/s at a an altitude of 11500m (the aircraft is
performing level flight). The aircraft is powered by four engines, each producing 45 kN thrust under the
given flight conditions. The wing area of the aircraft is 525 m2.
(a)
(b)
(c)
(d)
What is the total lift force acting on the aircraft?
What is the total drag force?
Calculate the lift-to-drag ratio L/D.
Calculate the lift and drag coefficients, if the air pressure at the given altitude is 2.099×104 Pa.