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The time for one complete turn of 2rr radians is given by
27r 2rr V
t27r == -- (2.297)
co = g ~T-_f
Height lost in one complete turn is given by
Ah = (~h) t27r
= (V y)t2,r
2T( T/2y
= g ff//-=l
_ 47rtl2(]
= pg-/~-~) (C/:) (2.298)
For a given load factor n, we observe that the height lost per turn is minimum when
the glider flies at an angle of attack when CDICZ is a minimum, which happens
whe7C, = C~.max-
General turning flight of aircraft. The maximum rate of turn generated by
an airplane in a coordinated, constant-altitude turn is called the MSTR because
the aircraft can produce such a turn rate continuously for some time. However, the
aircraft can generate still higher rates of turn ifit is permitted to lose altitude so that
it can make use ofits height or the potential energy in addition to the aerodynamic
and propulsive forces. The turn rate so generated can be much higher than MSTR
and is called the maximum instantaneous tum rate or the maximum attainable tum
rate (MATR). A high value of MATR is a good measure of the air superiority of
AIRCRAFT PERFORMANCE
137
combat aircraft because it is of crucial importance in close encounters where a
pilot getting first point-and-shoot capability has a better chance to win. Because
the aircraft will rapidly lose altitude during this maneuver,it is necessary for a pilot
to have enough height margin before he initiates this maneuver.ln the following,
we will study this t)rpe of tunung flight, assuming that the sideslip is zero and
the flight velocity is approximately constant. We will consider only the jet aircraft
here. A similar approach can be used for propeller aircraft.
Equations (2.190-2.192) take the following form:
We have
Then,
T-D- Wsiny =O
L cos p, - W cos y - 0
WV2COS2y = 0
L sin ,r. -
gR
D=2Vg (,2+-,)
V cos y
co= R
, T-D
smy= W
cos y
n -.:
COS /,L
f/2 cos )t
tan/r,- Rg
-
cos y
co = gc-;-
R= _, . _
lV =
(2.299)
(2.300)
(2.301)
(2.302)
(2.303)
(2.304)
(2.305)
(2.306)
(2.307)
(2.308)
(2.309)
90 PERFORMANCE, STABILITY, DYNAMICS, AND CONTROL
\f min
V
\f mai
hrust
blc
ttling
Ilg.2.13 Concept oflerrelthght at any desired speed.
Example 2.3
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