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y- CL
3
= 5~30
-. 0.0524 rad
AIRCRAFT PERFORMANCE
C~ = p2S~
2 *5000
= ~25~0~502
- 0.3260
CD - CLy
- 0.326 * 0.0524
- 0.01708
kC~. = CD - CDO
k = O 01708 - 0.015
0 3262
- 0.0196 .
1
A--
k7te
1
=00~96 7r*l
- 16.20
81
2-4 LeveIFlight
The forces acting on an airplane in level :flight are shown in Fig. 2.7. In level
flight, the airplane is at a constant altitude so that h = y = 0. With this, Eqs. (2.7)
and (2.8) take the following form:
/- W _O
T-D-O
(2.61)
(2,62)
\
┏━━━━━━━━━━━━┳━━━━━━━━━━┓
┃ ┃. ┃
┃ -- o- -. ┃ ~ \ Rit ┃
┃ ┃--,- ┃
┃ ┃ ~} ' ┃
┣━━━━━━━━━━━━╋━━━━━━━━━━┫
┃ ┃ a l. ┃
┃ ┃rw ┃
┗━━━━━━━━━━━━┻━━━━━━━━━━┛
Fig.2.7 Airplaneinlevelflight
. Line
FdDO
1/ k
W
11 0 02
82 PERFORMANCE, STABILITY, DYNAMICS, AND CONTROL
can be stated in simple terms as the lift is equal to weight and thrust available is
equal to thrust required. With L - W, the load factor n -. 1 for level flight.
The kinematic equations as given by Eqs. (2.9) and (2.10) assume the form
x - V (2.63)
h-0
(2.64)
A solution ofEqs. (2.61) and (2.62)'gives the velocity V and angle of attack or the
lift coefficient CL for steady, unaccelerated level fiight.
The drag of an airplane in level fiight has an interesting variation with flight
velocity. To understand this,let us proceed as follows:
With L - W, we have
Then,
D = r~p V2S(CDO +kC2)
C~ = p2WS
D = gpl/2S rCDO +
.
4k Wz
p2 \/4S2
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