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compensate for the drift, the amount of turn will be
more than 90°.
The rollout from this turn must be such that as the
wings become level, the airplane is turned slightly
toward the field and into the wind to correct for drift.
The airplane should again be the same distance from
the field boundary and at the same altitude, as on other
legs. The base leg should be continued until the upwind
leg boundary is being approached. Once more the pilot
should anticipate drift and turning radius. Since drift
correction was held on the base leg, it is necessary to
turn less than 90° to align the airplane parallel to the
upwind leg boundary. This turn should be started with
a medium bank angle with a gradual reduction to a
shallow bank as the turn progresses. The rollout should
be timed to assure paralleling the boundary of the field
as the wings become level.
While the airplane is on the upwind leg, the next field
boundary should be observed as it is being approached,
to plan the turn onto the crosswind leg. Since the wind
is a headwind on this leg, it is reducing the airplane’s
groundspeed and during the turn onto the crosswind
leg will try to drift the airplane toward the field. For
this reason, the roll-in to the turn must be slow and the
bank relatively shallow to counteract this effect. As the
turn progresses, the headwind component decreases,
allowing the groundspeed to increase. Consequently,
the bank angle and rate of turn are increased gradually
to assure that upon completion of the turn the crosswind
ground track will continue the same distance
from the edge of the field. Completion of the turn with
the wings level should be accomplished at a point
aligned with the upwind corner of the field.
Simultaneously, as the wings are rolled level, the
proper drift correction is established with the airplane
turned into the wind. This requires that the turn be less
than a 90° change in heading. If the turn has been made
properly, the field boundary will again appear to be
one-fourth to one-half mile away. While on the crosswind
leg, the wind correction angle should be adjusted
as necessary to maintain a uniform distance from the
field boundary.
As the next field boundary is being approached, the
pilot should plan the turn onto the downwind leg. Since
a wind correction angle is being held into the wind and
away from the field while on the crosswind leg, this
next turn will require a turn of more than 90°. Since
the crosswind will become a tailwind, causing the
groundspeed to increase during this turn, the bank initially
should be medium and progressively increased
as the turn proceeds. To complete the turn, the rollout
must be timed so that the wings become level at a point
aligned with the crosswind corner of the field just as
the longitudinal axis of the airplane again becomes
parallel to the field boundary. The distance from the
field boundary should be the same as from the other
sides of the field.
Usually, drift should not be encountered on the upwind
or the downwind leg, but it may be difficult to find a
situation where the wind is blowing exactly parallel to
the field boundaries. This would make it necessary to
use a slight wind correction angle on all the legs. It is
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important to anticipate the turns to correct for groundspeed,
drift, and turning radius. When the wind is
behind the airplane, the turn must be faster and steeper;
when it is ahead of the airplane, the turn must be
slower and shallower. These same techniques apply
while flying in airport traffic patterns.
Common errors in the performance of rectangular
courses are:
• Failure to adequately clear the area.
• Failure to establish proper altitude prior to
entry. (Typically entering the maneuver while
descending.)
• Failure to establish appropriate wind correction
angle resulting in drift.
• Gaining or losing altitude.
• Poor coordination. (Typically skidding in turns
from a downwind heading and slipping in turns
from an upwind heading.)
• Abrupt control usage.
• Inability to adequately divide attention between
airplane control and maintaining ground track.
• Improper timing in beginning and recovering
from turns.
• Inadequate visual lookout for other aircraft.
S-TURNS ACROSS A ROAD
An S-turn across a road is a practice maneuver in
which the airplane’s ground track describes semicircles
of equal radii on each side of a selected straight
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(66)
