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can excite the dutch roll mode of the aircraft in
cruise configuration, the most severe degradation in flying
qualities from the dutch roll is in approach contiguration.
During an approach, the dutch roll is
characterizedbyawallowing,snakeymotionofthenose
thats everelyd egradesli neup control. The period on this
motion is quite long, and has the unfortunate result that
the pilot perceives a heading error when referenced to
centerline, when in fact the flightpath is correct. More
consistent lineup control can be gained by coordinating
lateral stick inputs with rudder.
11.3.7 Trim Characteristics. The trim rate in pitch
is slow. During acceleration runs in MAX power at low
altitude, trim may have to be run nearly continuously to
maintain longitudinal stick force at or near zero. Lateral
control authority and roll rates at slow speeds will be
reduced by almost one-half with full stick deflection in
the direction of full lateral trim because of decreased
spoiler deflection (see spoiler gearing curves in Chapter
2). Therefore, when maximum lateral control authority
is required, such as during an asymmetric flap condition,
trim in the direction of stick displacement should be
avoided. Runaway trim in any axis is controllable. During
field landings, the aircraft can be recovered safely
with runaway trim; however, carrier approachesw ith
full runaway pitch trim may be difficult.
Trimming the aircraft to level flight can be broken
down into two areas. At airspeeds slower than those
using automatic wing-sweep programming, the aircraft
is relatively easy to trim to level flight because it has
positive longitudinal static stability. At airspeedsw here
the wings automatically move with a change in airspeeds,
it becomesv ery difficult to achievea hands-off
trim. Because of the change in aircraft pitching moment
caused by movement of the wings, the nose tends to
pitch further down with each increase in speed or further
up with each decreasein speed.
Changes in thrust settings normally require a trim
change, particularly in the approach configurations. A
reduction in power causes a slight nosedown pitch.
11.4 ASYMMETRIC THRUST FLIGHT
CHARACTERISTICS IN COMBAT
AND CRUISE CONFIGURATION
11.4.1 General. With one engine inoperative, flight
characteristics are considerably affected by the thrust
asymmetry generatedb y the operatinge ngine.T he distance
of the engines from the aircraft centerline produces
flight control requirements and flying qualities
not present in centerline thrust aircraft. Flight control
requirements are a function of the thrust setting on the
operating engine. The thrust required to maintain flight,
and therefore the magnitude of the thrust asymmetry, is
a function of the following.
11.4.1.1 Gross Weight. Heavier gross weights require
higher thrust settings to maintain level flight and,
therefore, larger control deflections to counter the
greater asymmetric thrust.
11.4.1.2 Configuration. Aircraft configuration varies
the amount of thrust required at a particular flight
condition. At cruise contiguration airspeedsc, ontrol requirements
will be significantly reduced compared to
landing configurations, which will require significantly
higher thrust settings and in turn larger control forces to
maintain desired flightpath.
11.4.1.3 Airspeed. At maximum endurance airspeeds,
minimum thrust is required to maintain level
flight; therefore, the smallest asymmetric moment is
produced.H igher or lower airspeedsw ill requireh igher
power settings and, therefore, increased control forces.
At airspeeds above maximum endurance, the greater
asymmetry will be offset largely by the additional control
power available. Minimum control speed is reached
11-3 ORIGINAL
NAVAIR 01-Fl4AAD-1
at the point when maximum rudder deflection is no
longer sutlicient to maintain directional control.
11.4.1.4 Altitude. Net thrust is strongly dependent
on altitude. For a constant throttle setting, the asymmetric
thrust is considerably higher at sea level than at
higher altitudes. The FllO produces considerably more
thrust than the TF-30 powered F-14A. At maximum
afterburner,t he F 11O ’st hrusta t 10,000f eeti s equivalent
to that of the TF-30 at sea level.
11.4.1.5 Bank Angle. Bank angle increases induced
drag and, therefore, requires higher thrust settings
to maintain level flight. The higher thrust setting demands
increased rudder deflection in a turn compared
to thatr equired in level flight at the same airspeedT. urn
direction, into or away from the failed engine, signiticandy
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F-14D 飞行手册 Flight Manual 2(58)
