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Level Off
The level off from a constant airspeed descent may be
made at descending airspeed or at cruise airspeed, if this is
higher than descending airspeed. As in a climb level off, the
amount of lead depends on the rate of descent and control
technique. For a level off at descending airspeed, the lead
should be approximately 10 percent of the vertical speed. At
the lead altitude, simultaneously increase power to the setting
necessary to maintain descending airspeed in level flight. At
this point, the altimeter becomes primary for pitch, and the
airspeed indicator becomes primary for power.
To level off at an airspeed higher than descending airspeed,
increase the power approximately 100 to 150 feet prior to
reaching the desired altitude. The power setting should be that
which is necessary to maintain the desired airspeed in level
flight. Hold the vertical speed constant until approximately
50 feet above the desired altitude. At this point, the altimeter
becomes primary for pitch and the airspeed indicator becomes
primary for power. The level off from a constant rate descent
should be accomplished in the same manner as the level off
from a constant airspeed descent.
Common Errors During Straight Climbs and
Descents
1. Failure to maintain heading
2. Improper use of power
3. Poor control of pitch attitude
4. Failure to maintain proper pedal trim
5. Failure to level off on desired altitude
Turns
Turns made by reference to the flight instruments should
be made at a precise rate. Turns described in this chapter
are those not exceeding a standard rate of 3° per second
as indicated on the turn-and-slip indicator. True airspeed
determines the angle of bank necessary to maintain a standard
rate turn. A rule of thumb to determine the approximate angle
of bank required for a standard rate turn is to use 15 percent
of the airspeed. A simple way to determine this amount is
to divide the airspeed by 10 and add one-half the result. For
example, at 60 knots approximately 9° of bank is required
(60 ÷ 10 = 6, 6 + 3 = 9); at 80 knots approximately 12° of
bank is needed for a standard rate turn.
To enter a turn, apply lateral cyclic in the direction of the
desired turn. The entry should be accomplished smoothly,
using the attitude indicator to establish the approximate bank
angle. When the turn indicator indicates a standard rate turn,
it becomes primary for bank. The attitude indicator now
becomes a supporting instrument. During level turns, the
altimeter is primary for pitch, and the airspeed indicator is
primary for power. Primary and supporting instruments for a
stabilized standard rate turn are illustrated in Figure 6-14. If
an increase in power is required to maintain airspeed, slight
forward cyclic pressure may be required since the helicopter
tends to pitch up as collective pitch is increased. Apply pedal
trim, as required, to keep the ball centered.
To recover to straight-and-level flight, apply cyclic in the
direction opposite the turn. The rate of roll-out should be the
same as the rate used when rolling into the turn. As the turn
recovery is initiated, the attitude indicator becomes primary
for bank. When the helicopter is approximately level, the
heading indicator becomes primary for bank as in straightand-
level flight. Cross-check the airspeed indicator and ball
closely to maintain the desired airspeed and pedal trim.
Turn to a Predetermined Heading
A helicopter turns as long as its lateral axis is tilted;
therefore, the recovery must start before the desired heading
is reached. The amount of lead varies with the rate of turn
and piloting technique.
As a guide, when making a 3° per second rate of turn, use a
lead of one-half the bank angle. For example, if using a 12°
bank angle, use half of that, or 6°, as the lead point prior to the
desired heading. Use this lead until the exact amount required
by a particular technique can be determined. The bank angle
should never exceed the number of degrees to be turned.
As in any standard rate turn, the rate of recovery should be
the same as the rate of entry. During turns to predetermined
headings, cross-check the primary and supporting pitch, bank,
and power instruments closely.
Timed Turns
A timed turn is a turn in which the clock and turn-and-slip
indicator are used to change heading a definite number of
degrees in a given time. For example, using a standard rate
turn, a helicopter turns 45° in 15 seconds. Using a half6-
14
Figure 6-14. Flight Instrument Indications in a Standard-Rate Turn to the Left.
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Instrument Flying Handbook仪表飞行手册下(3)
