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within the shortest possible distance consistent with
safety and controllability. If the proper approach speed
has been maintained, resulting in minimum float
during the roundout, and the touchdown made at
minimum control speed, minimum braking will be
required.
Common errors in the performance of short-field
approaches and landings are:
• Failure to allow enough room on final to set up
the approach, necessitating an overly steep
approach and high sink rate.
• Unstabilized approach.
• Undue delay in initiating glidepath corrections.
• Too low an airspeed on final resulting in inability
to flare properly and landing hard.
• Too high an airspeed resulting in floating on
roundout.
• Prematurely reducing power to idle on roundout
resulting in hard landing.
• Touchdown with excessive airspeed.
• Excessive and/or unnecessary braking after
touchdown.
• Failure to maintain directional control.
SOFT-FIELD APPROACH
AND LANDING
Landing on fields that are rough or have soft surfaces,
such as snow, sand, mud, or tall grass requires unique
procedures. When landing on such surfaces, the
objective is to touch down as smoothly as possible,
and at the slowest possible landing speed. The pilot
must control the airplane in a manner that the wings
support the weight of the airplane as long as practical,
to minimize drag and stresses imposed on the
landing gear by the rough or soft surface.
The approach for the soft-field landing is similar to the
normal approach used for operating into long, firm
landing areas. The major difference between the two is
Figure 8-23. Unstabilized approach.
Unstabilized
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that, during the soft-field landing, the airplane is held
1 to 2 feet off the surface in ground effect as long as
possible. This permits a more gradual dissipation of
forward speed to allow the wheels to touch down gently
at minimum speed. This technique minimizes the
nose-over forces that suddenly affect the airplane at
the moment of touchdown. Power can be used
throughout the level-off and touchdown to ensure
touchdown at the slowest possible airspeed, and the
airplane should be flown onto the ground with the
weight fully supported by the wings. [Figure 8-24]
The use of flaps during soft-field landings will aid in
touching down at minimum speed and is recommended
whenever practical. In low-wing airplanes, the flaps
may suffer damage from mud, stones, or slush thrown
up by the wheels. If flaps are used, it is generally inadvisable
to retract them during the after-landing roll
because the need for flap retraction is usually less
important than the need for total concentration on
maintaining full control of the airplane.
The final approach airspeed used for short-field landings
is equally appropriate to soft-field landings. The
use of higher approach speeds may result in excessive
float in ground effect, and floating makes a smooth,
controlled touchdown even more difficult. There is,
however, no reason for a steep angle of descent unless
obstacles are present in the approach path.
Touchdown on a soft or rough field should be made at
the lowest possible airspeed with the airplane in a
nose-high pitch attitude. In nosewheel-type airplanes,
after the main wheels touch the surface, the pilot
should hold sufficient back-elevator pressure to keep
the nosewheel off the surface. Using back-elevator
pressure and engine power, the pilot can control the
rate at which the weight of the airplane is transferred
from the wings to the wheels.
Field conditions may warrant that the pilot maintain a
flight condition in which the main wheels are just
touching the surface but the weight of the airplane is
still being supported by the wings, until a suitable taxi
surface is reached. At any time during this transition
phase, before the weight of the airplane is being supported
by the wheels, and before the nosewheel is on
the surface, the pilot should be able to apply full
power and perform a safe takeoff (obstacle clearance
and field length permitting) should the pilot elect to
abandon the landing. Once committed to a landing,
the pilot should gently lower the nosewheel to the
surface. A slight addition of power usually will aid in
easing the nosewheel down.
The use of brakes on a soft field is not needed and
should be avoided as this may tend to impose a heavy
load on the nose gear due to premature or hard contact
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(93)
