Shallowest Bank
Points of
Steepest Bank
WIND
Figure 9-16. S-turns across a road.
9-17
the helicopter is being crabbed into the wind just as it is
when trying to maintain a straight ground track. The
amount of crab depends upon the wind velocity and
how nearly the helicopter is to a crosswind position.
The stronger the wind, the greater the crab angle at any
given position for a turn of a given radius. The more
nearly the helicopter is to a crosswind position, the
greater the crab angle. The maximum crab angle should
be at the point of each half circle farthest from the
reference line.
Astandard radius for S-turns cannot be specified, since
the radius depends on the airspeed of the helicopter,
the velocity of the wind, and the initial bank chosen
for entry.
TURNS AROUND A POINT
This training maneuver requires you to fly constant
radius turns around a preselected point on the ground
using a bank of approximately 30°, while maintaining
a constant altitude. [Figure 9-17] Your objective, as in
other ground reference maneuvers, is to develop the
ability to subconsciously control the helicopter while
dividing attention between the flight path and ground
references, while still watching for other air traffic in
the vicinity.
The factors and principles of drift correction that are
involved in S-turns are also applicable in this maneuver.
As in other ground track maneuvers, a constant
radius around a point will, if any wind exists, require
a constantly changing angle of bank and angles of
wind correction. The closer the helicopter is to a
direct downwind heading where the groundspeed is
greatest, the steeper the bank, and the faster the rate
of turn required to establish the proper wind correction
angle. The more nearly it is to a direct upwind
heading where the groundspeed is least, the shallower
the bank, and the slower the rate of turn required to
establish the proper wind correction angle. It follows,
then, that throughout the maneuver, the bank and rate
of turn must be gradually varied in proportion to the
groundspeed.
The point selected for turns around a point should be
prominent and easily distinguishable, yet small enough
to present a precise reference. Isolated trees, crossroads,
or other similar small landmarks are usually suitable.
The point should be in an area away from communities,
livestock, or groups of people on the ground to prevent
possible annoyance or hazard to others. Since the
maneuver is performed between 600 and 1,000 feet
AGL, the area selected should also afford an opportunity
for a safe emergency autorotation in the event it
becomes necessary.
To enter turns around a point, fly the helicopter on a
downwind heading to one side of the selected point
at a distance equal to the desired radius of turn. When
any significant wind exists, it is necessary to roll into
the initial bank at a rapid rate so that the steepest
bank is attained abeam the point when the helicopter
is headed directly downwind. By entering the maneuver
while heading directly downwind, the steepest
bank can be attained immediately. Thus, if a bank of
30° is desired, the initial bank is 30° if the helicopter
is at the correct distance from the point. Thereafter,
the bank is gradually shallowed until the point is
reached where the helicopter is headed directly
upwind. At this point, the bank is gradually steepened
until the steepest bank is again attained when heading
downwind at the initial point of entry.
Just as S-turns require that the helicopter be turned
into the wind in addition to varying the bank, so do
turns around a point. During the downwind half of the
circle, the helicopter’s nose must be progressively
turned toward the inside of the circle; during the
upwind half, the nose must be progressively turned
toward the outside. The downwind half of the turn
around the point may be compared to the downwind
side of the S-turn, while the upwind half of the turn
around a point may be compared to the upwind side
of the S-turn.
As you become experienced in performing turns
around a point and have a good understanding of the
effects of wind drift and varying of the bank angle
and wind correction angle as required, entry into the
maneuver may be from any point. When entering
this maneuver at any point, the radius of the turn
UPPER HALF OF CIRCLE
DOWNWIND HALF OF CIRCLE
Shallowest
Bank
Steeper
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