Me 480 Introduction To Aerospace Final Test, Closed Notes, 15 min max.



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ME 480 Introduction To Aerospace

Final Test, Closed Notes, 15 min max.

(20 pts total)
Name____________________________



  1. (3 pts) For any given shape, coefficients of lift, drag, and moment are a function of what three parameters?



  1. (1 pt) Write down the range of maximum coefficient of lift cL for typical airfoils.



  1. (2 pts) What is the physical meaning of Pressure Coefficient?


  1. (3 pts) Write down the three sources of drag for airfoil.



  1. (1 pt) T / F Maximum range and endurance is achieved at sea level for propeller driven aircraft.




  1. (2 pt) Write down the range of typical L/D ratios for aircraft.



  1. (2 pts) Write down the Thrust required for level flight.


  1. (2 pts) Write down the equation for excess power in aircraft.


  1. (2 pts) What is the purpose of the V-n diagram?


  1. (2 pts) For an aircraft at flying at a thrust angle αT in steady flight, write down the equation of equilibrium in the horizontal direction in terms of lift, drag, and thrust.


ME 480 Introduction To Aerospace

Final Test, Fall 2010

Name____________________________


  1. Consider the North American Mustang P-51D (shown in Figure 4.39 in Anderson). Its wingspan is 37 ft, with a wing area of 233.6 ft2. The gross weight is 10, 100 lb. Assume the Oswald efficiency factor is 0.8. The airplane is flying in steady level flight at 300 mph at 5000 ft standard altitude.

  1. Calculate the drag due to lift CD,i.

  2. For the special case of an airplane in subsonic steady level flight, the drag for due to lift Di depends directly on the square of the design parameter W/b (called the span loading) according to:

Di = 1/πeq (W/b)2 Calculate the drag with this formula.


  1. What do you conclude comparing the results of a.) versus b.) ?



Solution, part b)



Solution, part a)


ME 480 Introduction To Aerospace

Final Test, Fall 2010

Name____________________________


  1. (30 pts) In the design of a civil jet transport such as the Boeing 777 (Figure 6.27 in Anderson), the choice of engine size is usually based on having a 300 feet per minute climb capability at the top-of-climb to cruising altitude (basically a safety margin). Assume the following for the 777:

    1. L/D = 18

    2. Altitude = 31,000 ft

    3. M = 0.85

    4. W = 550,000 lb



  1. Obtain an equation for the required engine thrust, assuming the climb angle is so small that L=W

  2. Calculate the engine size (in terms of sea level static thrust) and compare your result with the designers engine choice for the 777, which are two engines with a sea level thrust of 34,000 lb each.

Note: Your intuition might tell you that for such an airplane, the engine should be sized for take-off performance. However, by satisfying the top-of-climb criteria, the engine thrust is usually quite ample for takeoff.


Solution





ME 480 Introduction To Aerospace

Final Test, Fall 2010

Name____________________________



  1. Consider a wing mounted in the test section of a subsonic wind tunnel.

  1. The velocity of the airflow is 160 ft/s. If the velocity at a point on the wing is 195 ft/s, what is the pressure coefficient at that point

  2. Consider the same wing with the air temperature at 519 0R and a flow velocity of 700 ft/s. What is the coefficient of pressure at the same point as in a)?



Solution, part a)






part a)

Solution, part b)




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