Wednesday, August 27, 2008

Straight Climbs and Descents

For a given power setting and load condition, there is only one attitude
that will give the most efficient rate of climb. The airspeed and the climb
power setting that will determine this climb attitude are given in the
performance data found in your POH/AFM. Details of the technique for
entering a climb vary according to airspeed on entry and the type of climb
(constant airspeed or constant rate) desired. (Heading and trim control are
maintained as discussed under straight-and-level flight.)

To enter a constant-airspeed climb from cruising airspeed, raise the
miniature aircraft to the approximate nose-high indication for the
predetermined climb speed. The attitude will vary according to the type of
airplane you are flying. Apply light back-elevator pressure to initiate and
maintain the climb attitude. The pressures will vary as the airplane
decelerates. Power may be advanced to the climb power setting
simultaneously with the pitch change, or after the pitch change is
established and the airspeed approaches climb speed. If the transition from
level flight to climb is smooth, the vertical speed indicator will show an
immediate trend upward, continue to move slowly, then stop at a rate
appropriate to the stabilized airspeed and attitude. (Primary and
supporting instruments for the climb entry are shown in figure 5-25.)

(See attached file: 5-25 Climb entry for constant-airspeed climb.jpg)

Once the airplane stabilizes at a constant airspeed and attitude, the
airspeed indicator is primary for pitch and the heading indicator remains
primary for bank. [Figure 5-26] You will monitor the tachometer or manifold
pressure gauge as the primary power instrument to ensure the proper climb
power setting is being maintained. If the climb attitude is correct for the
power setting selected, the airspeed will stabilize at the desired speed.
If the airspeed is low or high, make an appropriate small pitch correction.

(See attached file: 5-26 Stabilized climb at constant airspeed.jpg)

To enter a constant-airspeed climb, first complete the airspeed reduction
from cruise airspeed to climb speed in straight-and-level flight. The climb
entry is then identical to entry from cruising airspeed, except that power
must be increased simultaneously to the climb setting as the pitch attitude
is increased. Climb entries on partial panel are more easily and accurately
controlled if you enter the maneuver from climbing speed.

The technique for entering a constant-rate climb is very similar to that
used for entry to a constant-airspeed climb from climb airspeed. As the
power is increased to the approximate setting for the desired rate,
simultaneously raise the miniature aircraft to the climbing attitude for
the desired airspeed and rate of climb. As the power is increased, the
airspeed indicator is primary for pitch control until the vertical speed
approaches the desired value. As the vertical-speed needle stabilizes, it
becomes primary for pitch control and the airspeed indicator becomes
primary for power control. [Figure 5-27]

(See attached file: 5-27 Stabilized climb at constant rate.jpg)

Pitch and power corrections must be promptly and closely coordinated. For
example, if the vertical speed is correct, but the airspeed is low, add
power. As the power is increased, the miniature aircraft must be lowered
slightly to maintain constant vertical speed. If the vertical speed is high
and the airspeed is low, lower the miniature aircraft slightly and note the
increase in airspeed to determine whether or not a power change is also
necessary. [Figure 5-28] Familiarity with the approximate power settings
helps to keep your pitch and power corrections at a minimum.

(See attached file: 5-28 Airspeed low and vertical high-reduce pitch.jpg)

Leveling Off
To level off from a climb and maintain an altitude, it is necessary to
start the level off before reaching the desired altitude. The amount of
lead varies with rate of climb and pilot technique. If your airplane is
climbing at 1,000 fpm, it will continue to climb at a decreasing rate
throughout the transition to level flight. An effective practice is to lead
the altitude by 10 percent of the vertical speed shown (500-fpm/ 50-foot
lead, 1,000 fpm/100-foot lead).

To level off at cruising airspeed, apply smooth, steady forward-elevator
pressure toward level-flight attitude for the speed desired. As the
attitude indicator shows the pitch change, the vertical-speed needle will
move slowly toward zero, the altimeter needle will move more slowly, and
the airspeed will show acceleration. [Figure 5-29] Once the altimeter,
attitude indicator, and vertical speed indicator show level flight,
constant changes in pitch and torque control will have to be made as the
airspeed increases. As the airspeed approaches cruising speed, reduce power
to the cruise setting. The amount of lead depends upon the rate of
acceleration of your airplane.

(See attached file: 5-29 Level-off at cruising speed.jpg)

To level off at climbing airspeed, lower the nose to the pitch attitude
appropriate to that airspeed in level flight. Power is simultaneously
reduced to the setting for that airspeed as the pitch attitude is lowered.
If your power reduction is at a rate proportionate to the pitch change, the
airspeed will remain constant.

A descent can be made at a variety of airspeeds and attitudes by reducing
power, adding drag, and lowering the nose to a predetermined attitude.
Sooner or later the airspeed will stabilize at a constant value. Meanwhile,
the only flight instrument providing a positive attitude reference, by
itself, is the attitude indicator. Without the attitude indicator (such as
during a partial-panel descent) the airspeed indicator, the altimeter, and
the vertical speed indicator will be showing varying rates of change until
the airplane decelerates to a constant airspeed at a constant attitude.
During the transition, changes in control pressure and trim, as well as
cross-check and interpretation, must be very accurate if you expect to
maintain positive control.

The following method for entering descents is effective either with or
without an attitude indicator. First, reduce airspeed to your selected
descent airspeed while maintaining straight-and-level flight, then make a
further reduction in power (to a predetermined setting). As the power is
adjusted, simultaneously lower the nose to maintain constant airspeed, and
trim off control pressures.

During a constant-airspeed descent, any deviation from the desired airspeed
calls for a pitch adjustment. For a constant rate descent, the entry is the
same, but the vertical-speed indicator is primary for pitch control (after
it stabilizes near the desired rate), and the airspeed indicator is primary
for power control. Pitch and power must be closely coordinated when
corrections are made, as they are in climbs. [Figure 5-30]

(See attached file: 5-30 Constant airspeed descent.jpg)

Leveling Off
The level off from a descent must be started before you reach the desired
altitude. The amount of lead depends upon the rate of descent and control
technique. With too little lead, you will tend to overshoot the selected
altitude unless your technique is rapid. Assuming a 500-fpm rate of
descent, lead the altitude by 100–150 feet for a level off at airspeed
higher than descending speed. At the lead point, add power to the
appropriate level-flight cruise setting. [Figure 5-31] Since the nose will
tend to rise as the airspeed increases, hold forward-elevator pressure to
maintain the vertical speed at the descending rate until approximately 50
feet above the altitude, then smoothly adjust the pitch attitude to the
level flight attitude for the airspeed selected.

(See attached file: 5-31 Level-off airspeed higher than descent

To level-off from a descent at descent airspeed, lead the desired altitude
by approximately 50 feet, simultaneously adjusting the pitch attitude to
level flight and adding power to a setting that will hold the airspeed
constant. [Figure 5-32] Trim off the control pressures and continue with
the normal straight-and-level flight cross-check.

(See attached file: 5-32 Level-off at descent airspeed.jpg)

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