# Aerodynamics – Sample Problems About Aircraft Propulsion Systems

Consider a turbojet powered airplane flying at a standard altitude of 20,000 ft at a velocity of 600 fps. The turbojet engine itself has inlet and exit areas of 8 and 5 ft2, respectively. The velocity and pressure of the exhaust gas at the exit are 1500 ft/s and 1240 lb/ft2, respectively. Calculate the thrust.

Consider a turbojet powered airplane flying at a standard altitude of 28,000 ft at a velocity of 650fps. The turbojet engine itself has inlet and exit areas of 6 and 4 ft2, respectively. The velocity and pressure of the exhaust gas at the exit are 1200 ft/s and 700 lb/ft2, respectively. Calculate the thrust of the turbojet.

Calculate the brake horsepower for an engine that develops 600 foot-pounds of torque while turning at 2,700 rpm.

Calculate the indicated horsepower for a six-cylinder engine with a bore of five inches, a stroke of five inches, turning at 2,750 rpm, and with an IMEP of 125 psi per cylinder.

An airplane weighing 5000 lb is flying at standard sea level with a velocity of 200 mi/h. At this velocity, the L/D ratio is a maximum. The wing area and aspect ratio are 200 ft.2 and 8.5, respectively. The Oswald efficiency factor is 0.93. Calculate the total drag on the airplane.

Consider an airplane patterned after the Fairchild Republic A-10, a twin-jet attack aircraft. The airplane has the following characteristics: wing area = 47 m2, aspect ratio = 6.5, Oswald efficiency factor = 0.87, weight = 103,047 N, and parasite drag coefficient =0.032. The airplane is equipped with two jet engines with 40,298 N of static thrusts each at sea level.

Calculate and sketch the power required curve at sea level.

Calculate the maximum velocity at sea level.

Calculate and plot the power required curve at 5 km altitude.

Calculate the maximum velocity at 5 km altitude.

1. Consider an airplane patterned after the Beechcraft Bonanza V-tailed, single engine light private airplane. The characteristics of the airplane are as follows: aspect ratio = 6.2, wing area = 181 ft.2, Oswald efficiency factor = 0.91, weight = 3000 lb, and parasite drag coefficient = 0.027. The airplane is powered by a single piston engine of 345 hp maximum at sea level. Assume the power of the engine is proportional to free stream density. The two-bladed propeller has an efficiency of 0.83.
1. Calculate the power required at sea level.
1. Calculate the maximum velocity at sea level.
1. Calculate the power required at 12,000 ft. altitude.
1. Calculate the maximum velocity at 12,000 ft. altitude.

Consider an airplane patterned after the twin-engine Beechcraft Queen Air executive transport. The airplane weight is 38,220 N, wing area is 27.3 m2, aspect ratio is 7.5. Oswald efficiency factor is 0.9 and parasite drag coefficient CDo = 0.03. Calculate the thrust required to fly at a velocity of 350 km/h at (a) standard sea level and (b) an altitude of 4.5 km.