Aircraft flight instruments are divided into three categories according to their specific function: control
instruments, performance instruments, and position instruments.
The control instruments enable you to provide a proper combination of pitch, roll, yaw (attitude), and
power control to achieve the desired aircraft performance. These instruments include: the ADI, RPM
gauge, fuel flow gauge, and the slip indicator.
ATTITUDE DIRECTOR INDICATOR (ADI)
This instrument is the primary control instrument. It provides your primary indication for the aircrafts
attitude using the horizon bar, bank pointer, pitch reference scale, and the attitude sphere. Whenever a
deviation from a desired performance is indicated on one of the performance instruments, the correction
should be made referencing the ADI. A standby attitude indicator is provided as an alternate attitude
indicator in the event of failure of the primary ADI, and as a cross- check attitude instrument.
FUEL FLOW AND RPM GAUGES
These instruments both provide a reference to the proper control of the aircrafts engine. In many of the
different maneuvers a specified rpm or fuel flow can be set to allow for the proper thrust to complete the
maneuver. In some cases a range can be used to allow for other possible variables.
The performance instruments indicate how the aircraft is performing as a result of control changes. These
instruments include: the airspeed indicator, the various heading indicators (magnetic compass, HSI, and
ADI), vertical speed indicator, angle of attack indicator, clock, and turn needle. Although the altimeter is
primarily used as a position instrument, in some maneuvers it can be used as a cross-check on aircraft
The position instruments convey the aircrafts location in space and will determine what control changes
are required to achieve the desired aircraft performance. These instruments include: the altimeter,
number 1 and number 2 bearing pointers on the HSI, course deviation indicator (CDI), range indicator
(DME) on the HSI, and the ILS azimuth and glideslope indicators in both the ADI and HSI.
During instrument flight, the pilot must divide his attention between the control, performance, and position
instruments. Proper division of attention and the sequence of checking the instruments varies throughout
the various phases of flight. There is no one set order for scanning the instruments; it depends on the
type of maneuver to be executed as to which instruments are of prime importance. The pilot should
become familiar with the factors to be considered when dividing his attention between instruments. The
pilot should know the indications which will enable him to identify correct and incorrect scan techniques.
The best way to improve proficiency is through practice. Some common errors in instrument scanning
include the following: having no instrument scan pattern plan, omitting an instrument entirely from the
scan, fixating on a single instrument, or misusing an instrument and its indication.