Common Errors in Straight-and-Level Flight

Pitch
Pitch errors usually result from the following faults:

Improper adjustment of the attitude indicator's miniature aircraft to
the wings-level attitude. Following your initial level-off from a climb,
check the attitude indicator and make any necessary adjustment in the
miniature aircraft for level flight indication at normal cruise
airspeed.
Insufficient cross-check and interpretation of pitch instruments. For
example, the airspeed indication is low. Believing you are in a
nose-high attitude, you react with forward pressure without noting that
a low power setting is the cause of the airspeed discrepancy. Increase
your cross-check speed to include all relevant instrument indications
before you make a control response.
Uncaging the attitude indicator (if it has a caging feature) when the
airplane is not in level flight. The altimeter and heading indicator
must be stabilized with airspeed indication at normal cruise when you
pull out the caging knob, if you expect the instrument to read
straight-and-level at normal cruise airspeed.
Failure to interpret the attitude indicator in terms of the existing
airspeed.
Late pitch corrections. Pilots commonly like to leave well enough alone.
When the altimeter shows a 20-foot error, there is a reluctance to
correct it, perhaps because of fear of overcontrolling. If
overcontrolling is the error, the more you practice small corrections
and find out the cause of overcontrolling, the closer you will be able
to hold your altitude. If you tolerate a deviation, your errors will
increase.
Chasing the vertical-speed indications. This tendency can be corrected
by proper cross-check of other pitch instruments, as well as by
increasing your understanding of the instrument characteristics.
Using excessive pitch corrections for the altimeter evaluation. Rushing
a pitch correction by making a large pitch change usually aggravates the
existing error and saves neither time nor effort.
Failure to maintain established pitch corrections. This is a common
error associated with cross-check and trim errors. For example, having
established a pitch change to correct an altitude error, you tend to
slow down your crosscheck, waiting for the airplane to stabilize in the
new pitch attitude. To maintain the attitude, you must continue to
cross-check and trim off the pressures you are holding.
Fixations during cross-check. After initiating a heading correction, for
example, you become preoccupied with bank control and neglect to notice
a pitch error. Likewise, during an airspeed change, unnecessary gazing
at the power instrument is common. Bear in mind that a small error in
power setting is of less consequence than large altitude and heading
errors. The airplane will not decelerate any faster if you stare at the
manifold pressure gauge than if you continue your cross-check.

Trim: Adjusting the aerodynamic forces on the control surfaces so that the
aircraft maintains the set attitude without any control input.

Uncaging: Unlocking the gimbals of a gyroscopic instrument, making it
susceptible to damage by abrupt flight maneuvers or rough handling.

Heading
Heading errors usually result from the following faults:

Failure to cross-check the heading indicator, especially during changes
in power or pitch attitude.
Misinterpretation of changes in heading, with resulting corrections in
the wrong direction.
Failure to note, and remember, a preselected heading.
Failure to observe the rate of heading change and its relation to bank
attitude.
Overcontrolling in response to heading changes, especially during
changes in power settings.
Anticipating heading changes with premature application of rudder
control.
Failure to correct small heading deviations. Unless zero error in
heading is your goal, you will find yourself tolerating larger and
larger deviations. Correction of a 1° error takes a lot less time and
concentration than correction of a 20° error.
Correcting with improper bank attitude. If you correct a 10° heading
error with a 20° bank correction, you can roll past the desired heading
before you have the bank established, requiring another correction in
the opposite direction. Do not multiply existing errors with errors in
corrective technique.
Failure to note the cause of a previous heading error and thus repeating
the same error. For example, your airplane is out of trim, with a left
wing low tendency. You repeatedly correct for a slight left turn, yet do
nothing about trim.
Failure to set the heading indicator properly, or failure to uncage it.

Power
Power errors usually result from the following faults:

Failure to know the power settings and pitch attitudes appropriate to
various airspeeds and airplane configurations.
Abrupt use of throttle.
Failure to lead the airspeed when making power changes. For example,
during an airspeed reduction in level flight, especially with gear and
flaps extended, adjust the throttle to maintain the slower speed before
the airspeed reaches the desired speed. Otherwise, the airplane will
decelerate to a speed lower than that desired, resulting in further
power adjustments. How much you lead the airspeed depends upon how fast
the airplane responds to power changes.
Fixation on airspeed or manifold pressure instruments during airspeed
changes, resulting in erratic control of both airspeed and power.

Trim
Trim errors usually result from the following faults:

Improper adjustment of seat or rudder pedals for comfortable position of
legs and feet. Tension in the ankles makes it difficult to relax rudder
pressures.
Confusion as to the operation of trim devices, which differ among
various airplane types. Some trim wheels are aligned appropriately with
the airplane's axes; others are not. Some rotate in a direction contrary
to what you expect.
Faulty sequence in trim technique. Trim should be used, not as a
substitute for control with the wheel (stick) and rudders, but to
relieve pressures already held to stabilize attitude. As you gain
proficiency, you become familiar with trim settings, just as you do with
power settings. With little conscious effort, you trim off pressures
continually as they occur.
Excessive trim control. This induces control pressures that must be held
until you retrim properly. Use trim frequently and in small amounts.
Failure to understand the cause of trim changes. If you do not
understand the basic aerodynamics related to the basic instrument
skills, you will continually lag behind the airplane.