A frequently quoted rule of thumb in aircraft designs is that wings should produ

Question

A frequently quoted rule of thumb in aircraft designs is that wings should produce about 1000 N of lift per square meter of the wing. ( The fact that a wing has a top and bottom surface does not double its area)

A) At takeoff, an aircraft travels at 58 m/s, so that the air speed relative t the bottom of the wings is 58m/s. Given the sea level density of air to be 1.29 Kg.m^3, how fast must it move over the upper surface to create the ideal lift?

B) How fast must air move over the upper surface at a cruising speed of 240 m/s and at an altitide where air density is one-fourth that at sea level?

Explanation / Answer

given data
force=1000N
aircraft travels at 58 m/s
speed at bottom of the wings is 58m/s
density of air to be 1.29 Kg.m^3

Lift = ½A(U² - V²)

(a) 1000 N = ½ * 1.29kg/m³ * 1m² * (U² - (58m/s)²)
U = 70.10 m/s

(b) 1000 N = ½ * ¼ * 1.29kg/m³ * 1m² * (U² - (58m/s)²)
U = 97.80 m/s

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