Instrument Scan - P-8210031

BASIC INSTRUMENT PROCEDURES

CHAPTER ONE

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).

Instrument Scan

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

instrument scanning:

Omitting an instrument entirely from the scan.

ii.

Placing too much emphasis on a single instrument.

Scan Technique

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

instruments.

BASIC INSTRUMENT PROCEDURES 1-19