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capable of depicting the aircraft attitude is the attitude
indicator displayed on the PFD. The attitude and heading
reference system (AHRS) is the engine that drives the attitude
display. The AHRS unit is capable of precisely tracking
minute changes in the pitch, bank, and yaw axes, thereby
making the PFD very accurate and reliable. The AHRS unit
determines the angle between the aircraft’s longitudinal
axis and the horizon line on initialization. There is no need
4-22
Figure 4-30. Pitch of the Aircraft.
Figure 4-31. Supporting Instruments.
or means for the pilot to adjust the position of the yellow
chevron which represents the nose of the aircraft.
Straight-and-Level Flight
In straight-and-level flight, the pilot maintains a constant
altitude, airspeed and, for the most part, heading for
extended periods of time. To achieve this, three primary
instruments need to be referenced in order to maintain these
three variables.
Primary Pitch
When the pilot is maintaining a constant altitude, the primary
instrument for pitch is the altimeter. As long as the aircraft
maintains a constant airspeed and pitch attitude, the altitude
should remain constant.
Two factors that cause the altitude to deviate are turbulence
and momentary distractions. When a deviation occurs,
a change in the pitch needs to be made on the attitude
indicator. Small deviations require small corrections while
large deviations require larger corrections. Pilots should
avoid making large corrections that result in rapid attitude
changes, for this may lead to spatial disorientation. Smooth,
timely corrections should be made to bring the aircraft back
to the desired attitude.
Pay close attention to indications on the PFD. An increase in
pitch of 2.5° produces a climb rate of 450 feet per minute (fpm).
Small deviations do not require large attitude changes.
A rule of thumb for correcting altitude deviations is to establish
a change rate of twice the altitude deviation, not to exceed 500
fpm. For example, if the aircraft is off altitude by 40 feet, 2 x
40 = 80 feet, so a descent of approximately 100 fpm allows
the aircraft to return to the desired altitude in a controlled,
timely fashion.
In addition to the primary instrument, there are also
supporting instruments that assist the pilot in cross-checking
the pitch attitude. The supporting instruments indicate trend,
but they do not indicate precise attitude indications. Three
instruments (vertical speed, airspeed, and altitude trend
tape) indicate when the pitch attitude has changed and that
the altitude is changing. [Figure 4-31] When the altitude is
constant, the VSI and altitude trend tape are not shown on
the PFD. When these two trend indicators are displayed, the
pilot is made aware that the pitch attitude of the aircraft has
changed and may need adjustment.
The instrument cross-check necessitates utilizing these
supporting instruments to better manage altitude control.
The VSI and trend tape provide the pilot with information
regarding the direction and rate of altitude deviations. The
pilot is thus able to make correction to the pitch attitude
4-23
Figure 4-32. Primary Bank.
moving through the air with the longitudinal axis of the
aircraft aligned with the relative wind.
Primary Power
The primary power instrument for straight-and-level flight is
the airspeed indicator. The main focus of power is to maintain
a desired airspeed during level flight. No other instrument
delivers instantaneous indication.
Learning the primary and supporting instruments for
each variable is the key to successfully mastering attitude
instrument flying. At no point does the primary and supporting
method devalue the importance of the attitude indicator or the
power instruments. All instruments (control, performance,
primary, and supporting) must be utilized collectively.
Fundamental Skills of Attitude Instrument
Flying
When first learning attitude instrument flying, it is very
important that two major skills be mastered. Instrument crosscheck
and instrument interpretation comprise the foundation
for safely maneuvering the aircraft by reference to instruments
alone. Without mastering both skills, the pilot will not be able
to maintain precise control of aircraft attitude.
before a large deviation in altitude occurs. The airspeed
indicator depicts an increase if the pitch attitude is lowered.
Conversely, when the pitch attitude increases, the pilot should
note a decrease in the airspeed.
Primary Bank
When flying in instrument meteorological conditions, pilots
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Instrument Flying Handbook仪表飞行手册上(74)
