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direction.
4. If on an east or west heading, acceleration results in
a north turn indication; deceleration results in a south
turn indication.
5. When maintaining a north or south heading, no error
results from diving, climbing, or changing airspeed.
With an angle of bank between 15° and 18°, the amount of
lead or lag to be used when turning to northerly or southerly
headings varies with, and is approximately equal to, the
latitude of the locality over which the turn is being made.
When turning to a heading of north, the lead for roll-out must
include the number of degrees of change of latitude, plus the
lead normally used in recovery from turns. During a turn to
a south heading, maintain the turn until the compass passes
south the number of degrees of latitude, minus normal rollout
lead. [Figure 5-35]
For example, when turning from an easterly direction to
north, where the latitude is 30°, start the roll-out when the
compass reads 37° (30° plus one-half the 15° angle of bank,
or whatever amount is appropriate for the rate of roll-out).
When turning from an easterly direction to south, start the
roll-out when the magnetic compass reads 203° (180° plus
30° minus one-half the angle of bank). When making similar
turns from a westerly direction, the appropriate points at
which to begin the roll-out would be 323° for a turn to north,
and 157° for a turn to south.
When turning to a heading of east or west from a northerly
direction, start the roll-out approximately 10° to 12° before
the east or west indication is reached. When turning to an
east or west heading from a southerly direction, start the
rollout approximately 5° before the east or west indication
is reached. When turning to other headings, the lead or lag
must be interpolated.
Abrupt changes in attitude or airspeed and the resulting erratic
movements of the compass card make accurate interpretations
of the instrument very difficult. Proficiency in compass turns
depends on knowledge of compass characteristics, smooth
control technique, and accurate bank-and-pitch control.
Steep Turns
For purposes of instrument flight training in conventional
airplanes, any turn greater than a standard rate is considered
steep. [Figure 5-36] The exact angle of bank at which a
normal turn becomes steep is unimportant. What is important
is learning to control the airplane with bank attitudes in
excess of those normally used on instruments. Practicing
steep turns will not only increase proficiency in the basic
instrument flying skills, but also enable smooth, quick, and
confident reactions to unexpected abnormal flight attitudes
under instrument flight conditions.
Pronounced changes occur in the effects of aerodynamic
forces on aircraft control at progressively greater bank
attitudes. Skill in cross-check, interpretation, and control is
increasingly necessary in proportion to the amount of these
changes, though the techniques for entering, maintaining, and
recovering from the turn are the same in principle for steep
turns as for shallower turns.
Enter a steep turn in the same way as a shallower turn, but
prepare to cross-check rapidly as the turn steepens. Because
of the greatly reduced vertical lift component, pitch control
is usually the most difficult aspect of this maneuver. Unless
5-23
Figure 5-36. Steep Left Turn.
30.0
29.9
29.8
Figure 5-37. Diving Spiral.
for pitch changes, smooth, steady back elevator pressure
will maintain constant altitude. However, overbanking
to excessively steep angles without adjusting pitch as the
bank changes occur, requires increasingly stronger elevator
pressure. The loss of vertical lift and increase in wing loading
finally reach a point at which further application of backelevator
pressure tightens the turn without raising the nose.
How does a pilot recognize overbanking and low pitch
attitude? What should a pilot do to correct them? If a rapid
downward movement of the altimeter needle or vertical speed
needle, together with an increase in airspeed, is observed
despite application of back elevator pressure, the airplane is in
a diving spiral. [Figure 5-37] Immediately shallow the bank
with smooth and coordinated aileron and rudder pressures,
hold or slightly relax elevator pressure, and increase the crosscheck
of the attitude indicator, altimeter, and VSI. Reduce
power if the airspeed increase is rapid. When the vertical
speed trends upward, the altimeter needle will move slower
as the vertical lift increases. When the elevator is effective in
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Instrument Flying Handbook仪表飞行手册上(90)
