Page 162 - Aeronautical Engineer Data Book
P. 162
Aircraft performance 135
Cruise range
R = L/D(V/sfc) ln(W /W )
1
0
where subscripts ‘0’ and ‘1’ stand for initial and
final weight, respectively.
Cruise fuel
Fuel = W –W = W (e R/k –1)
f
1
0
where k, the range constant, equals L/D(V/sfc)
and R = range.
Cruise speeds
Cruise speed schedules for subsonic flight can
be determined by the following expressions.
), optimum-
Optimum mach number (M DD
altitude cruise
First calculate the atmospheric pressure at
altitude:
W
P =
2
DD
0.7(M )(C L DD )S
2
where M DD = drag divergence Mach number.
Then input the value from cruise-altitude
determination graph for cruise altitude.
Optimum mach number, constant-altitude cruise
Optimum occurs at maximum M(L/D).
� �
�
�
S
3K
W/
M =
�
0 .7P C
D min
where K = parabolic drag polar factor
P = atmospheric pressure at altitude
Landing
Landing distance calculations cover distance
from obstacle height to touchdown and
ground roll from touchdown to a complete
stop.
