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 non-moving 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 pitot-static 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