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Unformatted text preview: AA311 Atmospheric Flight Mechanics Exam #1 Solutions Problem 1. (10 points) An aircraft pressure sensor reads 54 . 0 kPA. On this day, the sea-level pressure is 100 . 0 kPA, the sea-level temperature is 10 C, and the lapse rate is -7 C per kilometer. Compute the geometric altitude of the aircraft. Solution. Given the pressure P ( h ) = 54 . 0 kPA, we must first find h in the given non-standard conditions: P ( h ) = P SL T SL + Lh T SL- ( g LR ) We know every value in this expression except for h . Solving for h , we find: h = T SL L P ( h ) P SL- LR g- 1 =- 283 . 16 K- . 007 K / m 1- 54 . 0 kPa 100 . 0 kPa- (- . 007 K / m)(287 . 0368 Nm / kgK) 9 . 81 m / s 2 = 4796 m Converting to geometric altitude: h = 4796 m h G = r earth r earth- h h = 4800 m Problem 2. (10 points) An aircraft flies at an altitude of 5000 m. The aircrafts rectangular wing (8 m span, 1.5 m chord) is made up of uniform airfoil elements along the span. Suppose that the pressure distri- bution at some distance along the span takes the form as shown in Figure 1. Calculate the lift coefficient of that airfoil section. Assume that the flow is uniform along the span, and is not affected by wing-tip vortices. The Pitot tube pressure transducer reads a total pressure of p total = 54640 Pa . Calculate the total lift force produced by the wing. How fast is the aircraft flying? Assume the aircraft is flying straighttotal lift force produced by the wing....
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This document was uploaded on 02/05/2012.
- Fall '09