Consider the Superrnarine Spitfire shown in Figure 5.19. The first version of the Spitfire was the Mk I. which first flew in 1936. Its maximum velocity is 362 mi/h at an altitude of 18,500 ft. Its weight is 5820 lb, wing area is
a.
The induced drag coefficient of the spitfire at the flight condition of
Answer to Problem 5.9P
The induced drag coefficient of the spitfire at the flight condition of
Explanation of Solution
Given:
The maximum velocity of a spitfire at an altitude of
The expression for the coefficient of drag is given by,
Here,
Substitute
The formula for aspect ratio is given by,
Here,
Substitute
The expression for induced drag coefficient is given by,
Here,
For an elliptic plan-form, the span efficiency factor is
Substitute
Hence, The induced drag coefficient of the spitfire at the flight condition of
b.
The percentage of total drag coefficient as compared to induced drag coefficient.
Answer to Problem 5.9P
The percentage of total drag coefficient as compared to induced drag coefficient is
Explanation of Solution
Given:
The propeller efficiency of the Merlin engine is
The expression for the power generated by the engine is given by
Here,
Substitute
For the steady and level flight, the drag force is equal in magnitude to the thrust produced by impeller,
Here,
The expression for the drag force or thrust for steady flight is given by,
Substitute
The expression for the total drag coefficient is given by,
Substitute
The expression for the percentage of total drag coefficient as compared to induced drag coefficient is given by
Substitute
Hence, the percentage of the total drag coefficient as compared to the induced drag coefficient is
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