Chapter Two Introduction to Air Craft Flight Instruments

CHAPTER TWO

INTRODUCTION TO AIRCRAFT FLIGHT INSTRUMENTS

200. INTRODUCTION

Aircraft flight instruments are divided into three categories according to their specific function.

The attitude instrument indicates the aircraft's attitude in relation to the Earth's surface, the

position instruments convey the aircraft's location in space, and the performance instruments

indicate how the aircraft is performing as a result of attitude changes.

For information concerning a specific aircraft's instrument, consult the applicable NATOPS

flight manual.

201. ATTITUDE INSTRUMENT

The primary flight instrument in all naval aircraft is the attitude indicator. It provides the pilot

with a substitute for the Earth's horizon as a reference in instrument flight. The instrument

shows a horizontal bar representing the horizon upon which a miniature aircraft is superimposed.

There are graduated scales on the instrument's face to indicate Angle of Bank (AOB) and pitch.

The combined indications provide a constant visual presentation of the aircraft's flight attitude as

it relates to longitudinal, vertical, and horizontal information. Some aircraft installations may

have additional information displayed on the instrument, such as heading, glideslope

information, turn and bank, yaw, and course deviation. Aircrews should refer to the appropriate

NATOPS flight manual for detailed operation of a particular system.

202. PERFORMANCE INSTRUMENTS

Compasses provide magnetic heading information. Some magnetic compasses are not gyro-

stabilized and are subject to some errors while the gyro-stabilized compasses largely eliminate

these errors. Only non-gyro-stabilized (standby) compasses will be discussed in this section.

Gyro-stabilized compasses will be discussed later.

The standby magnetic compass is simple in construction. It contains two steel magnetized

needles mounted on a float, around which is mounted the compass card. The needles are

parallel, with their north-seeking ends pointed in the same direction. The needles react to the

Earth's magnetic field and cause the compass card to indicate magnetic heading relative to

magnetic north. The compass card has letters for cardinal headings and numbers every 30 in

between. The last zero of the degree indication is omitted. Between these numbers, the card is

graduated for each 5.

The standby compass is used for training or cross-check purposes or when any kind of failure

renders the gyro-stabilized compass useless. One of the principal reasons for the reduced

importance of the standby compass is the large and variable amount of heading deviation

present. Variable electrical loads, armament, and the position of the nose landing gear create

deviation errors for which compass correction cards cannot provide sufficient tolerance. The

gyro-stabilized compasses largely eliminate these errors.

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