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required on the rudder during straight-and-levelflight,
the airplane must be held level. One of the
most common faults of beginning students is the
tendency to concentrate on the nose of the airplane
and attempting to hold the wings level by observing
the curvature of the nose cowling. With this method,
the reference line is very short and the deviation,
particularly if very slight, can go unnoticed. Also, a
very small deviation from level, by this short reference
line, becomes considerable at the wingtips and
results in an appreciable dragging of one wing. This
attitude requires the use of additional rudder to
maintain straight flight, giving a false conception of
neutral control forces. The habit of dragging one
wing, and compensating with rudder pressure, if
allowed to develop is particularly hard to break, and
if not corrected will result in considerable difficulty
in mastering other flight maneuvers.
For all practical purposes, the airspeed will remain constant
in straight-and-level flight with a constant power
setting. Practice of intentional airspeed changes, by
increasing or decreasing the power, will provide an
excellent means of developing proficiency in maintaining
straight-and-level flight at various speeds.
Significant changes in airspeed will, of course, require
considerable changes in pitch attitude and pitch trim to
maintain altitude. Pronounced changes in pitch attitude
and trim will also be necessary as the flaps and landing
gear are operated.
Common errors in the performance of straight-andlevel
flight are:
• Attempting to use improper reference points on
the airplane to establish attitude.
• Forgetting the location of preselected reference
points on subsequent flights.
• Attempting to establish or correct airplane attitude
using flight instruments rather than outside visual
reference.
• Attempting to maintain direction using only rudder
control.
• Habitually flying with one wing low.
• “Chasing” the flight instruments rather than
adhering to the principles of attitude flying.
• Too tight a grip on the flight controls resulting in
overcontrol and lack of feel.
• Pushing or pulling on the flight controls rather
than exerting pressure against the airstream.
• Improper scanning and/or devoting insufficient
time to outside visual reference. (Head in the
cockpit.)
• Fixation on the nose (pitch attitude) reference
point.
• Unnecessary or inappropriate control inputs.
• Failure to make timely and measured control
inputs when deviations from straight-and-level
flight are detected.
• Inadequate attention to sensory inputs in developing
feel for the airplane.
TRIM CONTROL
The airplane is designed so that the primary flight
controls (rudder, aileron, and elevator) are streamlined
with the nonmovable airplane surfaces when
the airplane is cruising straight-and-level at normal
weight and loading. If the airplane is flying out of
that basic balanced condition, one or more of the
control surfaces is going to have to be held out of its
streamlined position by continuous control input.
The use of trim tabs relieves the pilot of this requirement.
Proper trim technique is a very important and
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often overlooked basic flying skill. An improperly
trimmed airplane requires constant control pressures,
produces pilot tension and fatigue, distracts the pilot
from scanning, and contributes to abrupt and erratic
airplane attitude control.
Because of their relatively low power and speed, not
all light airplanes have a complete set of trim tabs
that are adjustable from the cockpit. In airplanes
where rudder, aileron, and elevator trim are available,
a definite sequence of trim application should
be used. Elevator/stabilator should be trimmed first
to relieve the need for control pressure to maintain
constant airspeed/pitch attitude. Attempts to trim the
rudder at varying airspeed are impractical in propeller
driven airplanes because of the change in the
torque correcting offset of the vertical fin. Once a
constant airspeed/pitch attitude has been established,
the pilot should hold the wings level with aileron
pressure while rudder pressure is trimmed out.
Aileron trim should then be adjusted to relieve any
lateral control yoke pressure.
A common trim control error is the tendency to
overcontrol the airplane with trim adjustments. To
avoid this the pilot must learn to establish and hold
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(26)
