BASIC INSTRUMENT PROCEDURES
instruments and indicate the aircraft's performance regardless of whether the pilot is referring to
the earth's horizon, the attitude indicator, or both, to control the aircraft attitude (Figure 1-6).
During instrument flight, attention must be divided between the control, performance,
and position instruments. Proper division of attention and the sequence of checking
the instruments (scan) differ throughout the various phases of flight. There is no one
set order for scanning the instruments; the type of maneuver to be executed
determines which instruments are of prime importance. The pilot should become
familiar with the factors to be considered in dividing their attention between
instruments properly, and symptoms, which enable recognition of correct and
incorrect, scan technique.
Experiments in scanning, have shown that a pilot whose instrument flying proficiency
is at a high level, scans the instruments, much more often than a pilot whose
proficiency is at a lower level. In fact, the lack of precision in instrument flying can
often be traced back to slow and/or inaccurate scan. The best way to improve
proficiency is through practice. Listed below are the most common faults in
Omitting an instrument entirely from the scan.
Placing too much emphasis on a single instrument.
A major factor influencing scan technique is the characteristic manner in which
instruments respond to attitude and power changes. The control instruments provide
a direct and immediate indication of attitude and power changes, but indications on
the performance instruments have an inherent lag. Lag will not appreciably affect the
tolerances within which the pilot controls the aircraft. However, at times, a slight
unavoidable delay in knowing the results of attitude and/or power changes will occur.
When the attitude and power are smoothly controlled, the lag factor is negligible and
the indications on the performance instruments will stabilize or change smoothly. Do
not make abrupt control movements in response to the lagging indications on the
performance instruments without first checking the control instruments. Failure to do
so leads to erratic aircraft maneuvers, which will cause additional fluctuations and lag
in the performance instruments. Frequent scanning of the control instruments assists
in maintaining smooth aircraft control. The attitude indicator is the instrument that
should be scanned most frequently. The majority of the pilot's time should be spent
on the control of the aircraft attitude by referencing the VGI supported by the power
BASIC INSTRUMENT PROCEDURES 1-19