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The 90° power-off approach usually begins from a rectangular
pattern below normal pattern altitude as long as this point is
above 500 feet AGL. The before-landing checklist should
be completed on the downwind leg.
After a medium-banked turn onto the base leg is completed
and key position obtained, the throttle should be completely
reduced to idle and the airspeed set to approach speed.
[Figure 11-32] At this position, the intended landing spot
appears to be on a 45° angle from the aircraft’s nose.
The pilot can determine the strength and direction of the
wind from the amount of crab necessary to hold the desired
ground track on the base leg. This helps in planning the turn
onto the fi nal approach. The base-to-fi nal turn should be
planned and accomplished so that upon rolling out of the
turn the aircraft is aligned with the runway centerline. Slight
adjustments in pitch attitude may be necessary to control
the glide angle and airspeed. However, never try to stretch
the glide to reach the desired landing spot. After the fi nal
approach glide has been established, full attention is given
to making a good, safe landing rather than concentrating on
the selected landing spot. In any event, it is better to execute
a good landing 200 feet from the spot than to make a poor
landing precisely on the spot.
180° Power-Off Approach
The 180° power-off approach is executed by gliding with
the power off from a given point on a downwind leg to a
preselected landing spot. [Figure 11-33] It is an extension
of the principles involved in the 90° power-off approach
just described. Its objective is to further develop judgment
in estimating distances and glide ratios, in that the aircraft
is fl own without power from a higher altitude and through
a 90° turn to reach the base-leg position at a proper altitude
for executing the 90° approach.
The 180° power-off approach requires more planning and
judgment than the 90° power-off approach. In the execution
of 180° power-off approaches, the aircraft is fl own on a
downwind heading parallel to the landing runway. The
altitude from which this type of approach should be started
in the downwind leg is at a normal pattern altitude. This
power-off approach should be the normal procedure except
for normal light wind landings, the throttle can be brought
back to idle between the downwind leg key position and the
turn onto the base leg depending on the height and distance
from the runway. When abreast of or opposite the desired
landing spot or a location closer to the turn onto base if the
WSC is further from the runway, the throttle should be closed
and the WSC aircraft set to the best glide speed. The point at
which the throttle is closed is the downwind key position.
11-24
36
Power Reduced to Idle
After Turn to Base Leg
at Base Reference Position
45°
Reference Position
Figure 11-32. 90° power-off approach showing 45° reference position.
36
18
90°
Reference Position
Downwind Leg Key Position
Close Throttle Normal Glide Speed
Figure 11-33. 180° power-off approach example.
11-25
36
18
Reference Position
Reference Position
Normal Glide Speed Close Throttle
Normal Glide Speed
Figure 11-34. 360° power-off approach.
The turn from the downwind leg to the base leg should be
a uniform turn with a medium or slightly steeper bank. The
degree of bank and amount of this initial turn depends upon
the glide angle of the aircraft and the velocity of the wind.
Again, the base leg should be positioned as needed for the
altitude or wind condition. Position the base leg to conserve
or dissipate altitude to reach the desired landing spot. The
turn onto the base leg should be made at an altitude high
enough and close enough to permit the aircraft to glide
to what would normally be the base key position in a 90°
power-off approach.
Although the key position is important, it must not be
overemphasized or considered as a fi xed point on the ground.
Many inexperienced pilots have the false understanding of it
as a particular landmark, such as a tree, crossroad, or other
visual reference to be reached at a certain altitude. This leaves
the pilot at a total loss any time such objects are not present.
Both altitude and geographical location should be varied as
much as practical to eliminate any such conception. After
reaching the base key position, the approach and landing are
the same as in the 90° power-off approach.
360° Power-Off Approach
　
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本文鏈接地址：Weight-Shift Control Aircraft Flying Handbook(128)