i 7 6 



CHAPTER XX. 



GROUND PERFORMANCE. 



Example (l). Getting off a Deck. Take the case of the machine 

 dealt with in Chapter XVIII., examples (l), (2), (3), and (4), 

 page 155, with the propeller dealt with in Chapter XVI I., example 

 (3), page 153. The machine performance curves are plotted on 

 page 157, and from curve (l) we estimate as a reasonable guess 



V=37- 



Now turn to the propeller performance curve which is plotted 

 on page 170, from which we got P T = 162. 



... T = 12,070 = 52,860. 



Now suppose that X = '4 is chosen for the run along the 

 deck, then L/D = 17-63, 



.'. a = 1 1 -4 x -4 x -590 x 52,860 = 142,300 



.-. K - -QQ'495 x 142,300 x 6 9S x 135 + x 



5700 x 150- - 142,300 x 95 

 + '07625 x -4 x -590 x 695 x 5700 x I50 2 = 

 17*63(5700 x 150* - 142,300 x 95) 



B= 1> 



5Q 2 * 37" 



b = V 2 ' 10 + i - i = 760. 



Now we turn to the figures of page 177 where the point A 

 is found in the upper figure and also the inclination of the re- 

 sultant to the wings: this inclination is 11, giving k^ = '536. 



From the lower figure, the total length of leading edges is 

 104 feet, while the total length of leading edges in the circle is 

 18-5 feet. 



.-. S" = l8 ' 5 X 695 = 123-6 square feet. 

 104 



= J 

 \ 



57 



-590(695 - 123-6) 



= 66-6 



