282 H. R. Chaplin 
S 
| 
C = perimeter 
vi ’ 
Ap 
Area 
rea 
AC { Wt 9, AC 
A 
V. — fA : 
Vv 
e 
Simplified Ideal Theory: 
Cruise 
pV, D,AOV, 
=D,_V, 
VD, hC (Ap — Go) 
Fig. 5. Plenum 
Cruise 
ram 0O 
The ram drag (mass flow times flight velocity), propulsive power, and cushion power 
(same as in hovering, except for effect of ram pressure recovery in inlet) are given by 
Dram = PVeDe hCV, 
P, = D, am Vo 
P, = V,D,hC(Ap 
Introducing the dimensionless velocity parameter 
v = ¥/ VE - y2 
and again using the value 0.61 for D, gives 
= 90): 
Vo 
V, 
(5-6) 
(5-7) 
(5-8) 
(5-9) 
