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related to the performance of flight at minimum
controllable airspeeds.
8-17
Effective Runway
Length
Obstacle Clearance
Figure 8-20. Landing over an obstacle.
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To land within a short-field or a confined area, the pilot
must have precise, positive control of the rate of
descent and airspeed to produce an approach that will
clear any obstacles, result in little or no floating during
the roundout, and permit the airplane to be stopped in
the shortest possible distance.
The procedures for landing in a short-field or for landing
approaches over obstacles, as recommended in the
AFM/POH, should be used. A stabilized approach is
essential. [Figures 8-22 and 8-23] These procedures
generally involve the use of full flaps, and the final
approach started from an altitude of at least 500 feet
higher than the touchdown area. A wider than normal
pattern should be used so that the airplane can be
properly configured and trimmed. In the absence of
the manufacturer’s recommended approach speed, a
speed of not more than 1.3 VSO should be used. For
example, in an airplane that stalls at 60 knots with
power off, and flaps and landing gear extended, the
approach speed should not be higher than 78 knots. In
gusty air, no more than one-half the gust factor should
be added. An excessive amount of airspeed could result
in a touchdown too far from the runway threshold or
an after-landing roll that exceeds the available landing
area.
After the landing gear and full flaps have been
extended, the pilot should simultaneously adjust the
power and the pitch attitude to establish and maintain
the proper descent angle and airspeed. A coordinated
combination of both pitch and power adjustments is
required. When this is done properly, very little change
in the airplane’s pitch attitude and power setting is
necessary to make corrections in the angle of descent
and airspeed.
The short-field approach and landing is in reality an
accuracy approach to a spot landing. The procedures
previously outlined in the section on the stabilized
approach concept should be used. If it appears that
the obstacle clearance is excessive and touchdown
will occur well beyond the desired spot, leaving
insufficient room to stop, power may be reduced
while lowering the pitch attitude to steepen the
descent path and increase the rate of descent. If it
appears that the descent angle will not ensure safe
clearance of obstacles, power should be increased
while simultaneously raising the pitch attitude to
shallow the descent path and decrease the rate of
descent. Care must be taken to avoid an excessively
low airspeed. If the speed is allowed to become too
slow, an increase in pitch and application of full power
Non-Obstacle Clearance Effective Runway Length
Figure 8-21. Landing on a short-field.
Figure 8-22. Stabilized approach.
8-18
Stabilized
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may only result in a further rate of descent. This occurs
when the angle of attack is so great and creating so
much drag that the maximum available power is
insufficient to overcome it. This is generally referred
to as operating in the region of reversed command
or operating on the back side of the power curve.
Because the final approach over obstacles is made at a
relatively steep approach angle and close to the airplane’s
stalling speed, the initiation of the roundout or
flare must be judged accurately to avoid flying into the
ground, or stalling prematurely and sinking rapidly. A
lack of floating during the flare, with sufficient control
to touch down properly, is one verification that the
approach speed was correct.
Touchdown should occur at the minimum controllable
airspeed with the airplane in approximately the pitch
attitude that will result in a power-off stall when the
throttle is closed. Care must be exercised to avoid closing
the throttle too rapidly before the pilot is ready for
touchdown, as closing the throttle may result in an
immediate increase in the rate of descent and a hard
landing.
Upon touchdown, the airplane should be held in this
positive pitch attitude as long as the elevators remain
effective. This will provide aerodynamic braking to
assist in deceleration.
Immediately upon touchdown, and closing the throttle,
appropriate braking should be applied to minimize the
after-landing roll. The airplane should be stopped
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(92)
