Continue lowering the nose to set the attitude of 2° down and trim left rudder, nose up. When
stable, reset P.A.T. and continue to scan for wings level descent.
How to Trim. The generally accepted sequence for trimming the aircraft is: rudder,
elevator, and aileron. The rudder trim is usually initiated first because it seems
difficult for most pilots to hold the ball centered with rudder for an extended period
and secondly, yaw affects both nose and aileron trim. Thus, if rudder were trimmed
last, both nose and aileron would have to be retrimmed to some extent.
To trim, first set a maneuvering attitude on the gyro and center the ball using light
pressures on the controls. Use peripheral vision to note ball centered. Note the
pressures needed to hold this new balanced attitude and move the trim tabs smoothly
until the pressures are removed. Relax hand and foot pressure on controls to see if
the attitude remains. Do not let go of the stick; simply relax. If the aircraft needs
further "fine" trimming, you will feel the attitude wanting to change and can then trim
out the final pressures. Note that most students tend to undertrim and move tabs too
slowly. Do not be afraid of overtrimming slightly. Fine or final trim will also correct
This trimming sequence will take much less time than it does to read about it and it is
the key to precision flight.
Confirming Attitude With Crosscheck Scan
Once we have established an attitude and trimmed it, we must crosscheck it with the proper
instruments to verify correct attitude.
Aircraft instruments are not absolutely accurate. The attitude gyro is subject to precessional
errors in turns and accelerations and must be crosschecked with other instruments. In addition,
the small size of the gyro makes it difficult to see small changes in attitude.
To explain the scan sequence, we shall use an analogy. Compare attitude flying with the tuning
with the station selector buttons. Neither is necessarily perfect, so we crosscheck the attitude
with other instruments, just as we would dial back and forth across a frequency range for best
reception. Then we "fine tune" by checking performance in the aircraft, for example, a little
more power for airspeed in straight and level. Just as we would adjust volume prior to receiving
the best signal, it is likewise useless to check performance instruments prior to establishing and
crosschecking an attitude.
In order to determine the aircraft's attitude quickly and effectively, you must know what
instruments to scan for a particular maneuver. The following section lists the correct instruments
or scan "pattern" for every situation. It is mandatory that the student commits these patterns to
BASIC INSTRUMENTS GENERAL PROCEDURES 2-5