曝光台 注意防骗
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L - W (2.34)
x - V (2.35)
h = Vy (2.36)
Lift and drag forces are given by
L - 21p V 2SCL (2,37)
D = ;p V2SCD
= ~2pl/2' o +kCZ)
_ r2S(CDO. (2.38)
The velocity is given by
'v _
(2.39)
AIRCRAFT PERFORMANCE
The glide angle can be obtained from Eqs. (2.33) and (2.34) as
D
)/ = -W
D
=-L
CD
= - CL
so that
1
= -E
75
(2.40)
Dnun
Ynun - N-
W
1
= - E~ (2.41)
Thus, the fiattest glide (y = Ynun) occurs when the glider fiies at that angle of attack
when the drag per unit weight is minimum or E = Em. Because the weight of a
glider is constant, we can say that the fiattest glide occurs when the drag is at
minimum. We know that when E = Em, CL = C7. =. 7k. The fiight velocity
for the fiattest glide is given by
V --
(2.42)
In other words, the velocity for the fiattest glide is equal to the reference velocity
or u ~ 1.
For a given height, the distance covered with respect to the ground can be
obtained as follows:
dx = V . (2.43)
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