曝光台 注意防骗
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coordinated turn, we mean that the sideslip is zero and the aircraft is correctly
banked so that the lift vector is tilted away from the plane of symmetry to provide
all the centripetal force.
With p = O, Eqs. (2.195-2.197) take the following form:
T - D -.0
Lcosp - W -0
WV2
L si.y,-. -, :O
gR
Then,
1
n -. --
cOs u,
V-
1/2
tan/,. = Rg
R- 1/2
g tan p.
V2
= g ~T"f
g tan /t,
to : -V
gl -f
=~
2rr
t2,r :=: ~
to
27r V
g tan p,
(2.204)
(2.205)
(2.206)
(2.20'7)
(2.208)
(2.209)
(2 210)
(2.211)
(2.212)
126 PERFORMANCE, STABILITY, DYNAMICS, A.ND CONTROL
As said earlier, the parameters that are of special interest in the turning perfor-
mance are the rate of turn co and the radius of turn R. From Eqs. (2.204-2.212),
we observe that the tunung performance improves with increase in load factor, all
the other things being equal.
The load factor is a measure of the strcss to which both the aircraft and the
pilot are subjected. A load factor of 2 means the aircraft structure and the pilot
are stressed twice as much as in steady level flight with a load factor of unity. For
transport airplanes, the value oflimiting load factor nUm is about 2.5 whereas, for
fighter aircraft, it can be as high as 9. However,in most of the cases, this load factor
lirtut of a fighter aircraft becomes more ofalimitation to the pilot rather than to the
machine he is flying.2 As load factor increases, the pilot experiences what is called
"blackout" or "greyout" caused by the blood draining away from his brain; then he
loses color perception. With further increase in load -factor, he will experience loss
of peripheral vision and tunnel vision. Eventually, he will experience a complete
loss of sight Because an attaclang pilot must be in total control of his physical and
mental faculties, he may not be actually able to stress the machine to its limiting
value ifit is as high as 9. He could be unconscious by the time he is pulling 6 g or
7 g. However, a defending pilotis more likely to use all the limiting load factor of
his machine.
A fighter aircraft should bc designed to have a high structural limit load factor.
For air superiority, a fighter aircraft should have a highest possible rate of turn and
a lowest possible radius of turn.ln general, these two conditions do not occur at the
same time. The capability to turn as fast as possible is often preferred compared to
the capability to make the sharpest turn because it is generally known that a fighter
aircrafutahaving a higher rate of tum but not making as sharp turn as its adversary
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