Lesson 16 Aircraft Instrument Systems Classification Of Instruments

Lesson 16: Aircraft Instrument Systems

Classification Of Instruments • Flight Instruments • Engine Instruments • Auxiliary Instruments

Flight Instruments • Those that help visualize the attitude, location and speeds of the aircraft. • Those which indicate the relationship to the air through which we are flying • Those which relate to our position in space without considering the air.

Pitot-static System • Dynamic Air Pressure - Pressure caused by moving air. • Ambient Static Air Pressure - Pressure of nonmoving air just outside the aircraft.

Pitot-static System

Pitot Head

Pitot Head

Flush Static Port

Airspeed Indicator • Differential pressure gauge that measures the difference between dynamic and ambient static air pressure.

Airspeed Indicator • Indicated airspeed • The speed of an aircraft as shown on the airspeed indicator. • True airspeed • The speed at which an aircraft is moving relative to the surrounding air. • Calibrated airspeed • Indicated airspeed of an aircraft, corrected for installation and instrument errors.

Altimeter • A barometer that measures the absolute pressure of the air.

Altimeter • Indicated Altitude • The altitude shown by an altimeter set to current altimeter setting. • Pressure Altitude • Height above the standard pressure level of 29. 92 in. Hg. • Density Altitude • Pressure altitude corrected for nonstandard temperature variations.

Altimeter • True Altitude • The actual height of an abject above mean sea level. • Absolute Altitude • Actual height above the surface of the earth, either land or water.

Vertical Speed Indicator • The rate of climb indicator • Serves only as a backup for the altimeter and airspeed indicator as a pitch indicating instrument. • Helps the pilot establish a rate of climb or descent.

Blockage Of The Pitot-Static System • Pitot Tube • Affects only the airspeed indicator, but a clogged static system affects all three pitotstatic instruments. • If the pitot tube is blocked and its drain hole remains open, the airspeed reading will drop to zero. • If both pitot tube and the drain hole clog, the airspeed indicator will react like an altimeter.

Blockage Of The Pitot-Static System • Static port • The indicated airspeed increases as the airplane descends and decreases when it climbs. • The altimeter: air pressure in the system will not change and neither will your indicated altitude. • VSI continually indicates Zero.

Gyroscopic Instruments

Gyroscopic Instruments • Turn coordinator • Attitude indicator • Heading indicator

Gyroscopic Instruments • Rigidity In Space – Once a gyroscope is spinning, it tends to remain in a fixed position in space and resist external forces applied to it.

Gyroscopic Instruments • Precession – The tilting or turning of a gyro in response to pressure. • The reaction to this force occurs in the direction of rotation, approximately 90° ahead of the point where the force was applied.

Sources Of Power • Gyroscopes may be operated by electrical power or by a vacuum (suction) system.

Sources Of Power

Attitude Indicator • Vacuum powered instrument which senses pitching and rolling movements about the airplanes lateral and longitudinal axes.

Attitude Indicator

Attitude Indicator

Directional Gyro • Vacuum powered instrument which senses yaw movement of the airplane about the vertical axis. • Horizontal card directional gyro

Directional Gyro • Vertical card directional gyro

Rate Gyros • Turn And Slip Indicator • Turn Coordinator • Inclinometer

Rate Gyros

Turn Coordinator

Floating Magnet-type Magnetic Compass

Engine Instruments

Engine Instruments