The American-made Cessna 172 is the most popular aircraft in the world with a to
ID: 2070303 • Letter: T
Question
The American-made Cessna 172 is the most popular aircraft in the world with a total of over 43,000 of its many variations being constructed since 1956. A typical Cessna 172 has a maximum takeoff mass of 1,157 kg and a total wing area of 16.2 m2. Assuming an air density of 1.225 kg/m3 and that the air over the top surface of the Cessna's wings on average flows 43.0 % faster during takeoff than over the bottom, compute the minimum take-off speed in both m/s and miles per hour. For simplicity, assume that the speed of the plane through the air and the speed of the air over the bottom of the wing are equal.Explanation / Answer
Applying Bernolli equation between a point ovr the wing and another under it,
P1 - P2 = 1/2*(V22 - V12) = 1/2*V12((V2/V1)2-1) = 1/2*1.225*V2(1.432-1) = 0.64*V2
For takeoff, (P1-P2)*A = mg
So, 0.64*V2 * 16.2 = 1157*9.81
So, V = 33.1 m/s = 74 mph
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