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时间:2010-05-09 10:13来源:1 作者:admin
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speed of other airplanes in the pattern.
When entering the traffic pattern at an airport without
an operating control tower, inbound pilots are expected
to observe other aircraft already in the pattern and to
conform to the traffic pattern in use. If other aircraft
are not in the pattern, then traffic indicators on the
ground and wind indicators must be checked to determine
which runway and traffic pattern direction should
be used. [Figure 7-2] Many airports have L-shaped
traffic pattern indicators displayed with a segmented
circle adjacent to the runway. The short member of the
L shows the direction in which the traffic pattern turns
should be made when using the runway parallel to the
long member. These indicators should be checked
while at a distance well away from any pattern that
might be in use, or while at a safe height well above
generally used pattern altitudes. When the proper traffic
pattern direction has been determined, the pilot
should then proceed to a point well clear of the pattern
before descending to the pattern altitude.
When approaching an airport for landing, the traffic pattern
should be entered at a 45° angle to the downwind
leg, headed toward a point abeam of the midpoint of the
runway to be used for landing. Arriving airplanes should
be at the proper traffic pattern altitude before entering
the pattern, and should stay clear of the traffic flow until
established on the entry leg. Entries into traffic patterns
while descending create specific collision hazards and
should always be avoided.
The entry leg should be of sufficient length to provide
a clear view of the entire traffic pattern, and to allow
the pilot adequate time for planning the intended path
in the pattern and the landing approach.
The downwind leg is a course flown parallel to the
landing runway, but in a direction opposite to the
intended landing direction. This leg should be
approximately 1/2 to 1 mile out from the landing runway,
and at the specified traffic pattern altitude.
During this leg, the before landing check should be
completed and the landing gear extended if
retractable. Pattern altitude should be maintained
until abeam the approach end of the landing runway.
At this point, power should be reduced and a descent
begun. The downwind leg continues past a point
abeam the approach end of the runway to a point
approximately 45° from the approach end of the runway,
and a medium bank turn is made onto the base
leg.
The base leg is the transitional part of the traffic pattern
between the downwind leg and the final approach
leg. Depending on the wind condition, it is established
at a sufficient distance from the approach end of the
landing runway to permit a gradual descent to the
intended touchdown point. The ground track of the airplane
while on the base leg should be perpendicular to
the extended centerline of the landing runway,
although the longitudinal axis of the airplane may not
be aligned with the ground track when it is necessary
to turn into the wind to counteract drift. While on the
base leg, the pilot must ensure, before turning onto the
final approach, that there is no danger of colliding with
another aircraft that may be already on the final
approach.
The final approach leg is a descending flightpath starting
from the completion of the base-to-final turn and
extending to the point of touchdown. This is probably
the most important leg of the entire pattern, because
here the pilot’s judgment and procedures must be the
sharpest to accurately control the airspeed and descent
angle while approaching the intended touchdown
point.
As stipulated in 14 CFR part 91, aircraft while on
final approach to land or while landing, have the
right-of-way over other aircraft in flight or operating
on the surface. When two or more aircraft are
approaching an airport for the purpose of landing, the
aircraft at the lower altitude has the right-of-way.
Pilots should not take advantage of this rule to cut in
front of another aircraft that is on final approach to
land, or to overtake that aircraft.
The upwind leg is a course flown parallel to the landing
runway, but in the same direction to the intended
landing direction. The upwind leg continues past a
point abeam of the departure end of the runway to
where a medium bank 90° turn is made onto the
crosswind leg.
The upwind leg is also the transitional part of the traffic
pattern when on the final approach and a go-around
Figure 7-2.Traffic pattern indicators. is initiated and climb attitude is established. When a
 
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