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discussion of compressor stall and airstart emergency
procedures.
II.6 HIGH ANGLE OF ATTACK FLIGHT
CHARACTERISTICS
Several characteristics of the F-14 affect its behavior
in high AOA flight. Among these are directional stability,
dihedral effect, stores loading, the stability augmentation
system, and maneuver flaps/slats.
11.6.1 Directional Stability. Directional stability
is the tendency of the aircraft to return to trimmed, zero
sideslip when disturbed. At low AOA, the aircraft exhibits
positive directional stability and, ifsideslip is generated
by a control input or turbulence, the aircraft will
return to the trimmed, zero-sideslip condition.
As AOA increases, directional stability begins to
drop and, for a clean aircraft, becomes negative at approximately
20 to 22 units AOA. At high AOA with
negative directional stability, the aircrat? becomes more
difftcult to fly becauset he pilot must maintain the zerosideslip
condition with rudder inputs.
11.6.2 Dihedral Effect. Dihedral effect is the tendency
of the aircraft to roll in reaction to sideslip being
generated. The F-14 exhibits positive dihedral effect
throughout the positive-AOA envelope (tending to roll
away from sideslip) but negative dihedral effect at negative
AOA. This tendency is borne out by the aircraft
responsefr om a rudder input. When right rudder is applied
from a straight-and-level flight condition, the aircraft
sees sideslip from the left and so rolls to the right
or away from the sideslip. Positive dihedral effect is a
stabilizing influence in the area of reduced directional
stability (high-AOA flight).
11.6.3 Stores. As external stores are added to the
aircraft, the high-AOA flying qualities degrade because
of a decrease in directional stability. Flight tests have
shown that no one store is significant by itself. Rather,
eachs torec ausesa small decreasein directional stability
that accumulates as additional stores are loaded. In addition
to degrading directional stability, external stores
increase aircraft basic weight. As aircraft weight is increased,
more AOA is required to produce the same
normal acceleration or g. As AOA increases above 12
to 14 units AOA, directional stability decreasesT. herefore,
external stores may have a twofold effect on directional
stability. Flight test has shown store loadings up
to and including 3C3 (four AIM-54s, two AIM-7s, two
AIM-9s. and two tanks) can be safely flown to the limits
ofthe basic aircraft with roll SAS offas long as the cruise
configuration maneuveringl imits presentedin Chapter
4 are complied with. No significant change in flying
qualities occurs because of aft cg location.
Maneuvering with significant external
store loadings should be approachedw ith
caution if the pilot is used to maneuvering
the clean or nearly clean aircraft, since the
high-AOA flying qualities will be degraded
from the clean aircraft.
11.6.4 Stability Augmentation System. The effect
of the SAS on aircraft high-AOA flight characteristics
ranges from minor to very significant. With the
pitch SAS off, the nose will be slightly more sensitive
during close controlled tasks such as gunsight tracking.
During large amplitude maneuvers, slightly higher
AOA may be reached. In general, pitch SAS on or off
will not significantly influence departurec haracteristics
or recovety and no limitations concerning its use are
necessaryT. urning the yaw SAS off significantly decreases
the departure resistance of the aircraft. High-
AOA maneuvering should not be conducted with the
yaw SAS off. All discussion on high-AOA flight characteristics
in this section assumes that the yaw SAS is
engaged and operating. Roll SAS has the opposite effect.
With the roll SAS on, maximum differential tail
authority commanded by lateral stick (*12’) is nearly
doubled from that commanded with roll SAS off (i7”).
Additionally, engagement of roll SAS enables the roll
rate feedback circuitry, which will attempt to arrest aircraft
roll commanded with no lateral stick inputs (as
when rolling the aircraft with rudders only at high AOA)
with differential tail opposite the roll. This inadvertent
crossc ontrol alone can caused eparturesfr om controlled
flight. High-AOA maneuvering shall not be conducted
with the roll SAS on. Unless otherwise stated, the following
discussiona ssumest he roll SAS is off.
II.65 Maneuvering Flaps and Slats. Maneuver
flaps and slats extension delays buffet onset below 0.7
Mach, reduces the intensity of the buffet, reduces the
effects of adverse yaw at high AOA through increased
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F-14D 飞行手册 Flight Manual 2(60)
