Aircraft Instruments Prelim Review

Vocabulary flashcards covering classification, primary flight instruments, pitot-static systems, gyroscopic principles, and pressure measurement devices (Weeks 1-5).

Aircraft Instruments

Cockpit instruments that provide the pilot with essential information regarding flight condition, performance, attitude, navigation, and engine operation to ensure safe and efficient control.

Flight Instruments

Instruments delivering information on the aircraft's attitude, altitude, airspeed, direction, and vertical movement.

Navigation Instruments

Instruments providing position, course, bearing, distance, and guidance data to reach a destination safely.

Engine Instruments

Instruments used to monitor the operating condition and performance of the engine and related systems within safe limits.

Pitot-Static Instruments

A category of flight instruments that operate on air pressure, specifically measuring ram pressure and atmospheric static pressure.

Gyroscopic Instruments

Flight instruments that operate based on the principles of rigidity in space and precession of a rapidly spinning rotor.

Direct Sensing

A sensing method where the measuring element is built into the instrument itself, measuring parameters directly without a separate transmitter.

Remote Sensing

A sensing method where the element sits away from the cockpit and sends an electrical signal from a transmitter to the cockpit indicator.

Six-Pack

The standard arrangement of the six primary flight instruments: Airspeed Indicator, Altimeter, Vertical Speed Indicator, Attitude Indicator, Heading Indicator, and Turn Coordinator.

Basic-T

The standardized instrument panel layout where the Attitude Indicator is top-center, Airspeed is to its left, Altimeter is to its right, and Heading is below it.

Indicated Altitude

The altitude read directly from the altimeter when it is set to the current local altimeter setting.

True Altitude

The actual vertical distance of the aircraft above mean sea level ($\text{MSL}$).

Absolute Altitude

The vertical distance of the aircraft above the terrain, often expressed as above ground level ($\text{AGL}$).

Pressure Altitude

The altitude indicated when the barometric scale is set to $\text{29.92\,in.\,Hg}$; it is the height above the standard datum plane.

Density Altitude

Pressure altitude corrected for nonstandard temperature; it is the primary driver of aircraft performance.

Vertical Speed Indicator ($\text{VSI}$)

An instrument that displays the rate of climb or descent in $\text{feet\,per\,minute\,(fpm)}$.

Lag

The time period (typically $\text{6-9\,seconds}$) from the initial change in rate of climb until the $\text{VSI}$ displays an accurate stabilized indication.

Airspeed Indicator ($\text{ASI}$)

A differential pressure gauge that measures the difference between pitot (impact) pressure and static pressure.

Indicated Airspeed ($\text{IAS}$)

The direct reading from the $\text{ASI}$, uncorrected for instrument or system errors.

Calibrated Airspeed ($\text{CAS}$)

Indicated airspeed corrected for installation and instrument errors, which are typically largest at low speeds.

True Airspeed ($\text{TAS}$)

Calibrated airspeed corrected for altitude and nonstandard temperature.

Groundspeed ($\text{GS}$)

The actual speed of the aircraft over the ground, calculated by adjusting $\text{TAS}$ for wind.

White Arc

The flap operating range on an $\text{ASI}$, extending from $\text{V}_{s0}$ to $\text{V}_{fe}$.

Green Arc

The normal operating range on an $\text{ASI}$, extending from $\text{V}_{s1}$ to $\text{V}_{no}$.

Yellow Arc

The caution range on an $\text{ASI}$, allowed only in smooth air, between $\text{V}_{no}$ and $\text{V}_{ne}$.

Red Radial Line

The never-exceed speed ($\text{V}_{ne}$), representing the maximum speed for all operations.

Turn Coordinator

A gyroscopic instrument that displays both the rate and direction of a turn, as well as the initial rate of roll.

Slipping Turn

A turn where centrifugal force is less than horizontal lift, causing the aircraft to move toward the inside of the turn.

Skidding Turn

A turn where centrifugal force is greater than horizontal lift, causing the aircraft to move toward the outside of the turn.

Attitude Indicator ($\text{AI}$)

An instrument providing an instantaneous picture of the aircraft's pitch and bank relative to the artificial horizon.

Heading Indicator

A gyroscopic instrument that provides a steady directional reference, designed to supplement the magnetic compass.

Static Pressure

Ambient atmospheric pressure that is present whether the aircraft is moving or at rest.

Dynamic Pressure

Pressure caused by the forward motion of the aircraft through the air.

Pitot Tube

A forward-facing tube used to sense total pressure, which consists of both static and dynamic pressure.

Alternate Static Source

A backup source of static pressure, usually located inside the cockpit, used if the primary static ports become blocked.

Rigidity in Space

The principle that a spinning rotor resists any force attempting to change the direction of its spin axis.

Precession

The principle where the effect of a force applied to a spinning gyro is manifested $\text{90}^\circ$ later in the direction of rotation.

Absolute Pressure

Pressure measured relative to a perfect vacuum, such as manifold pressure or altimetry.

Gauge Pressure

Pressure measured relative to the ambient atmosphere, such as oil or hydraulic pressure.

Differential Pressure

The difference between two independent pressures, such as airspeed (pitot minus static).

International Standard Atmosphere ($\text{ISA}$)

A standard reference model with a sea-level pressure of $\text{29.92\,in.\,Hg}$ and a temperature of $\text{15\,}^\circ\text{C}$, with a lapse rate of $\text{2\,}^\circ\text{C}$ per $\text{1,000\,ft}$.

Bourdon Tube

A curved metal tube that tends to straighten under internal pressure; used for high-pressure measurements like oil or fuel.

Diaphragm

A thin, flexible disc that deflects with pressure differences; common in airspeed indicators and low-pressure gauges.

Bellows

An accordion-like capsule that provides longer travel for sensitive, low-pressure measurements.

Aneroid

A sealed, evacuated capsule that expands as external pressure falls; it is the sensing element for absolute pressure in altimeters.

Solid-state Transducer

A $\text{MEMS}$ sensor that converts pressure or movement into an electrical signal for digital displays and $\text{ADAHRS}$.