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The last step in mastering elevator control is trim. Trimming
the aircraft to relieve any control pressures is essential
for smooth attitude instrument flight. To accomplish this,
momentarily release the control yoke. Note which way the
aircraft pitch attitude wants to move. Grasp the control yoke
again and then reapply the pressure to return the attitude
to the previous position. Apply trim in the direction of the
control pressure. Small applications of trim will make large
changes in the pitch attitude. Be patient and make multiple
changes to trim, if necessary.
Once the aircraft is in trim, relax on the control yoke as
much as practicable. When pressure is held on the yoke,
unconscious pressures are applied to the elevator and ailerons
which displaces the aircraft from its desired flight path. If the
aircraft is in trim, in calm, non-turbulent air, a pilot should be
able to release the control yoke and maintain level flight for
extended periods of time. This is one of the hardest skills to
learn prior to successfully flying in instrument meteorological
conditions (IMC).
5-36
Altimeter
At constant power, any deviation from level flight (except
in turbulent air) must be the result of a pitch change. If the
power is constant, the altimeter gives an indirect indication
of the pitch attitude in level flight. Since the altitude should
remain constant when the airplane is in level flight, any
deviation from the desired altitude signals the need for a
pitch change. For example, if the aircraft is gaining altitude,
the nose must be lowered.
In the PFD, as the pitch starts to change, the altitude trend
indicator on the altitude tape will begin to show a change
in the direction of displacement. The rate at which the trend
indicator grows and the altimeter numbers change aids the
pilot in determining how much of a pitch change is necessary
to stop the trend.
As a pilot becomes familiar with a specific aircraft’s
instruments, he or she learns to correlate pitch changes,
altimeter tapes, and altitude trend indicators. By adding the
altitude tape display and the altitude trend indicator into the
scan along with the attitude indicator, a pilot starts to develop
the instrument cross-check.
Partial Panel Flight
One important skill to practice is partial panel flight by
referencing the altimeter as the primary pitch indicator.
Practice controlling the pitch by referencing the altitude
tape and trend indicator alone without the use of the attitude
indicator. Pilots need to learn to make corrections to altitude
deviations by referencing the rate of change of the altitude
tape and trend indicator. When operating in IMC and in a
partial panel configuration, the pilot should avoid abrupt
changes to the control yoke. Reacting abruptly to altitude
changes can lead to large pitch changes and thus a larger
divergence from the initial altitude.
When a pilot is controlling pitch by the altitude tape and
altitude trend indicators alone, it is possible to overcontrol the
aircraft by making a larger than necessary pitch correction.
Overcontrolling will cause the pilot to move from a nosehigh
attitude to a nose-low attitude and vice versa. Small
changes to pitch are required to insure prompt corrective
actions are taken to return the aircraft to its original altitude
with less confusion.
When an altitude deviation occurs, two actions need to be
accomplished. First, make a smooth control input to stop
the needle movement. Once the altitude tape has stopped
moving, make a change to the pitch attitude to start back to
the entry altitude.
During instrument flight with limited instrumentation, it is
imperative that only small and precise control inputs are
made. Once a needle movement is indicated denoting a
deviation in altitude, the pilot needs to make small control
inputs to stop the deviation. Rapid control movements will
only compound the deviation by causing an oscillation effect.
This type of oscillation can quickly cause the pilot to become
disoriented and begin to fixate on the altitude. Fixation on
the altimeter can lead to a loss of directional control as well
as airspeed control.
As a general rule of thumb, for altitude deviations less than
100 feet, utilize a pitch change of 1°, which equates to 1/5 of
the thickness of the chevron. Small incremental pitch changes
will allow the performance to be evaluated and will eliminate
overcontrolling of the aircraft.
Instrumentation needs to be utilized collectively, but
failures will occur which leave the pilot with only limited
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Instrument Flying Handbook仪表飞行手册上(99)
