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is slightly positive (forward stick is required for increasing
speeds, aft stick is required for decreasing
speeds). At speeds where the wings are automatically
sweeping aft, static stability becomes neutral
to slightly negative.
In the transonic region, from Mach 0.8 to 1.5, static
longitudinal stability is essentially neutral. There is,
however, a minor reversal in the stick force gradient
(forward stick force may have to be relaxed to maintain
level flight when accelerating) at approximately Mach
0.95. Above Mach 1.5, the stick force gradient becomes
neutral. Since the engine line of thrust is below the
aircraft cg, reducing power causes a slight nosedown
pitch; power addition causes a noseup pitch.
11.3.2 Dynamic Longitudinal Response Characteristics.
The initial response of the aircraft to a
longitudinal stick input is greatly dependento n the dynamic
longitudinal response or “short period” characteristics.
Dynamic longitudinal response to pilot inputs
is somewhat sluggish in cruise and approach contigurations
when compared to most other modem day fighters.
In cruise configuration this may not be evident until high
gain, close coupled tasks, such as tine gunsight tracking,
are attempted. Here, the pilot’s tendency is to overdrive
the aircraft with the control stick resulting in a slight
porpoising of the nose. This can be avoided by applying
a longitudinal stick input and waiting for a nose response
before applying a further correction.
In approach configurations, the sluggish nose responsew
ill be most noticeabled uring approachesw ithout
DLC, as more nose movement must accompany the
larger power adjustments required to maintain onspeed
AOA when flying the ball.
11.3.3 Maneuvering Stick Force. Maneuvering
stick force, or stick force per g of the aircraft, is predictable
throughout most of the flight envelope. That is, an
increase in force commands a corresponding increase in
g (approximately 4 pounds per g). The stick force per g
generally changes very little with altitude, airspeed,
loading, or cg position.
Stickdisplacementsrequiredduringmaneuveringare
relatively large and may be uncomfortable to some pilots.
While the stick forces are not especially high, the
stick must be placed relatively close to the pilot’s torso
to attain a given g. This gives the pilot less leverage with
his arm and is more tiring, especially at lower airspeeds
and higher AOA, where stick force per g can be as high
as 10 pounds per g.
11.3.4 Roll Performance. The roll performance
(maximum roll rate attainable) is generally satisfactory,
particularly ath igh airspeedsA. t lower speedsh, owever,
the high-aspect ratio and roll inertia of the aircraft restrict
its time to roll to considerably less than that of
smaller, more nimble tactical aircraft (A-4, F-16). The
sluggish maximum roll rate at low airspeeds and high
AOA are definite tactical limitations.
ORIGINAL 11-2
NAVAIR Ol-Fl4AAD-1
Large aft stick inputs applied with lateral stick during
supersonicro lling maneuversr esult in increaseda dverse
sideslip and should be avoided. High Mach number,
high-altitude rolling maneuvers may result in oscillatory
sideslipa nd roll ratchetingd uring aggressivem aneuvering
with roll SAS off. Depending on the phasing of
these dynamics, centering lateral stick may be insufficient
to stop the rolling motion and opposite lateral stick
may be required in order to terminate roll.
11.3.5 Roll Response. The roll responseto control
inputs is good with three exceptions. First, at high airspeeds,
the roll-rate limiting feature of the roll SAS
causes marked variations in roll acceleration during the
initial lateral stick input, which results in a roll-rate oscillation.
Natural pilot compensation for this characteristic
may lead to a lateral pilot induced oscillation
during maximum roll-rate maneuvers at high airspeeds.
Additionally, at high airspeeds, roll response to small
inputs is overly sensitive, primarily because of low
breakout forces and a nonlinearity caused by an abrupt
increasein roll rate when the stick is displacedl aterally
just enough to break out the spoilers. This can result in
bank angle overshoots during maneuvering flight.
Lastly, at high angles of attack, at all airspeeds, the
cumulative effect of several phenomena results in a lateral
control reversal in which the aircraft rolls in a direction
opposite to the lateral control input. This
characteristic is further amplified in paragraph 11.6.6,
Lateral Control Reversal.
11.3.6 Dutch Roll. Although large lateral stick inputs
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F-14D 飞行手册 Flight Manual 2(57)
