曝光台 注意防骗
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Recall that when CL = CZ; E - Em, and D - Dnun.ln other words, for a
coordinated turn in a horizontal plane with maximum load factor, the aircraft is
Sharpest sustained turn. Here, we consider the case when the aircraft at-
tempts to make the sharpest possible turn (R = R ) in a horizontal plane with
constant speed. As said before, such a turn holding a constant altitude is called the
SST. From Eq. (2.210), we have
2e = 4ri(z _ t12)
_0
u=J
V=~
134 PERFORMANCE, STABILITY, DYNAMICS, AND CONTROL
Table 2.2' Summary of turning performance ofjet:urcraft
operating at maxunum aerodynamic efficiency or minimum drag condition. The
radius of turn and the rate of turn.for this case are
R ~ g_[Y, ]
g
co = rvR
(2.280)
(2.281)
Table 2.2 summarizes important performance parameters for the above three
special cases of constant-velocity tum in a hor:izontal plane for jet aircraft whose
thrust is independent of velocity. The var:iation of these parameters with nondi-
mensional thrust is shown in Fig. 2.27. From this analysis, we observe that the
turning performance improves with an increase in the thrust-to-weight ratio T/ W,
the aerodynamic efficiency Em, and a decrease in wing loading W/S.
Let us consider a more general case of turning fiight wherein the aircraft may
gain or lose altitude while tunung. We assume that the velocity vector is still
contained in the plane of symmetry so that sideslip is zero. To begin with, let us
consider the tuming fiight of a glider.
Turning f/ight of a gkder. The equations of motion of a glider executing a
constant-velocitjr turn are obtained by substituting T = O in Eqs. (2.190-2.192)
as follows:
D = W siny
(2.282)
(2.283)
(2.284)
!
AIRCRAFT PERFORMANCE
┏━━━━━━━━━━┓
┃ / ┃
┃--/ ┃
┣━━━━━━━━━━┫
┃ -- MSTR ----- ss T ┃
┗━━━━━━━━━━┛
l!
(f; )
i
i
135
Fig.2.27 Variation of turrung performance parameters with nondimensional thrust.
Then,
1
tan y - E~os r.
cos y
n--
cOs /{
V:
V2 cos y
tankt,= Rg
V2 cos y
R--
g tan p4
V cos y
cD -. -
R
g tan ,u,
=~
(2.285)
(2.286)
(2.287)
(2.288)
(2.289)
(2.290)
244 PERFORMANCE, STABIUTY, DYNAMICS, AND CONTROL
and ,
&C/ ),x = c8 - a,+ &C/ )f - -.. (i- L) v,,i,
= 0.30 - 0.24 + 0.1 - (0.08l0.10)(1 - 0.3)0.6 * 0.9
-. -0.1424
For trim with elevator in neutral or stick-fixed position,
Cm = C,no + GC/ ),xc.
0 -. 0.1316 - 0.1424CL
Then,
CL - 0.9242
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