Avionics and Flight Instruments Review

Vocabulary practice flashcards covering aircraft communication, navigation, surveillance, flight director, autopilot, flight recorders, proximity warning, and instrument display systems.

DME (Distance Measuring Equipment)

A navigation system paired with VOR/LOC stations that provides slant distance in nautical miles, transmits on frequencies between $962\text{--}1150\,\text{MHz}$, handles up to $100$ aircraft at once, and features a $50\,\mu\text{s}$ delay between transmit and receive.

Radar Mile

A standard radar time measurement equivalent to $12.36\,\mu\text{s}$.

Secondary Radar

The component of the Air Traffic Control (ATC) radar system that interrogates on $1030\,\text{MHz}$ and receives replies on $1090\,\text{MHz}$ to identify individual aircraft.

Mode A Transponder

An ATC transponder mode that transmits coded aircraft identification only.

Mode C Transponder

An ATC transponder mode that transmits coded aircraft identification plus altitude data.

Mode S Transponder

An advanced transponder mode that transmits squitter pulses containing enhanced digital coded data.

7000 Series ATC Codes

The specific series of transponder squawk codes that must never be entered into an ATC control panel.

Framing Pulses

The designation given specifically to the P1 and P3 pulses in transponder interrogations and replies.

Suppression Cable

An avionics interconnection cable that allows only one onboard transmitter/system to transmit at the same time to prevent cross-system damage or interference.

TCAS (Traffic Collision Avoidance System)

An airborne traffic monitoring system utilizing directional antennas to provide range, bearing, Traffic Advisories (TA), and Resolution Advisories (RA) displayed on dedicated displays, the Navigation Display (ND), or Primary Flight Display (PFD).

TCAS Symbology

Display icons indicating traffic threat levels: open white diamond (no threat), solid white diamond (intruder within $\pm 1200\text{ ft}$ and $6\,\text{NM}$ range), yellow circle (potential threat / TA), and red square (collision threat / RA).

Autopilot Basis of Operation

The principle of continuous error correction, implemented either through position-based or rate-based methods.

Autopilot Position Sensors

Sensors used to detect displacement for autopilot feedback, specifically Synchro, LVDT (Linear Variable Differential Transformer), and RVDT (Rotary Variable Differential Transformer).

ADIRU (Air Data Inertial Reference Unit)

Modern navigation and attitude reference units that replace older mechanical Vertical Gyros (pitch information) and Directional Gyros (heading information) in autopilot systems.

Three-Channel Autopilot

An autopilot system where each flight axis controls a specific primary flight surface: roll controls ailerons, pitch controls elevator, and yaw controls rudder.

Stability Augmentation

The main operational purpose of an aircraft Autopilot system, using servos that are electrically controlled and hydraulically operated.

Yaw Damper

An automatic flight control sub-system designed to stabilize the yaw axis and protect against Dutch roll.

Mach Tuck

A high-speed aerodynamic phenomenon occurring around $0.7\,\text{M}$ where an aircraft displays a nose-down tendency because the center of lift over the wing moves aft as speed increases.

Flight Director (FD)

A flight guidance system that computes and displays visual steering commands/cues on the flight instruments, which can be disengaged independently.

Electronic Engine Control (EEC)

The engine management computer that limits the authority of the Auto Throttle computer (which operates from take-off to touchdown) and provides protection against over-temp, over-boost, and over-speed conditions.

ADF (Automatic Direction Finder)

A low-to-medium frequency navigation receiver that operates in the range of $190\,\text{kHz}$ to $1750\,\text{kHz}$ using amplitude-modulated (AM) radio signals to provide bearing information.

ADF Antennas

A two-antenna setup consisting of a directional loop antenna and an omnidirectional sense antenna; the sense antenna resolves the inherent $180^\circ$ ambiguity of the loop antenna alone.

CVR (Cockpit Voice Recorder)

A crash-survivable audio recorder located in the tail of the aircraft that begins recording $4$ audio channels as soon as aircraft power is turned ON, retaining $30\text{ minutes}$ up to $120\text{ minutes}$ of audio.

CVR Erase Conditions

The two mandatory safety interlocks required to bulk-erase recorded cockpit audio: engines must be OFF and the parking brake must be set.

ULB (Underwater Locating Beacon)

An acoustic pinger mounted to flight recorders that activates upon water immersion and transmits continuously for $30\text{ days}$, or up to $90\text{ days}$ on newer models.

FDR (Flight Data Recorder)

A tail-mounted recorder that automatically begins recording mandatory flight parameters whenever aircraft engines are running or the aircraft enters flight mode.

HUMS (Health Usage and Monitoring Systems)

Specialized sensor and recording systems installed on helicopters to monitor mechanical reliability, structural health, and component usage.

GPWS (Ground Proximity Warning System)

A safety alerting system enabled below $2500\text{ feet}$ radio altitude that issues visual and aural alerts across $7$ distinct modes to prevent Controlled Flight Into Terrain (CFIT).

GPWS Mode Overrides and Priorities

Specific GPWS operational rules where Mode 4 and Mode 5 can be manually overridden, while Mode 7 possesses the highest warning priority.

FMS Navigation Performance (ANP & RNP)

Actual Navigation Performance (the current measured navigation accuracy) and Required Navigation Performance (the accuracy required for a given airspace or procedure).

FMS Database Update Cycle

An onboard aeronautical database that operates on a $28\text{-day}$ cycle and is updated by a dataloader using CD-ROM or USB to refine raw IRS position data using DME or VOR signals.

INS (Inertial Navigation System)

A totally self-contained dead-reckoning navigation system using accelerometers and gyroscopes that requires no external navigational aids to align, typically completing alignment in $10\text{ minutes}$.

Dithering Motor

A mechanical vibratory motor incorporated into ring laser gyroscopes (which contain $2$ lasers) to prevent laser lock at low angular rotation rates.

Strap Down System

An inertial navigation layout where laser gyros and accelerometers are mounted directly to the rigid structural case of the INS unit rather than on a movable $3\text{-gyroscope}$ gimbal platform.

INS Power Warning

An audible horn that sounds when the INS is left powered ON while main aircraft electrical power is turned OFF.

EICAS (Engine Indicating and Crew Alerting System)

An avionics instrumentation system where aircraft system pages are housed, categorizing alerts into $4$ levels: warning, caution, advisory, and memos.

EFIS (Electronic Flight Instrument System)

An integrated cockpit screen suite typically utilizing $6$ display units, including dedicated screens like the Primary Flight Display (PFD) which primarily shows aircraft attitude information.

GPS Constellation

A space-based navigation network consisting of $28$ Earth-orbiting satellites ($24$ operational and $4$ active spares) arranged so that at least $4$ satellites are visible in the sky at all times.

GPS Segments

The three architecture divisions comprising the Global Positioning System: the space (satellite) segment, the user segment, and the ground (control) segment.

Standard Positioning Service (SPS)

The civilian tier of GPS providing a positioning accuracy of $100\text{ meters}$, transmitting time-based signals on L1 ($1575.42\,\text{MHz}$) and L2 ($1227.60\,\text{MHz}$) frequencies and requiring a minimum lock of $4$ satellites to enter navigation mode.

VOR (VHF Omnidirectional Range)

A ground-based navigation aid transmitting Morse code and radials oriented to magnetic north across $108.00\text{--}111.85\,\text{MHz}$ (even tenths) and $112.00\text{--}118.00\,\text{MHz}$, displayed on CDIs, HSIs, or RMIs via a tail-mounted antenna.

VOR Phase Signals

The two signals generated by a VOR ground station used to determine bearing based on position: an AM-modulated variable phase signal and an FM-modulated reference phase signal.

VOR CDI Deflection

Course deviation indicator scaling where each displayed dot represents $2^\circ$ of angular deviation, giving a total full-scale needle deflection of $10^\circ$.

ILS Localizer (LOC)

The horizontal guidance element of an ILS transmitting on $108.10\text{--}111.95\,\text{MHz}$ (odd tenths) via a tail antenna, using overlapping $90\,\text{Hz}$ (left) and $150\,\text{Hz}$ (right) lobes with a sensitivity of $0.5^\circ$ per dot ($2.5^\circ$ total).

ILS Glideslope (G/S)

The paired vertical guidance element of an ILS using a nose-mounted antenna to establish a $3^\circ$ descent path, using overlapping $90\,\text{Hz}$ (top) and $150\,\text{Hz}$ (bottom) lobes with a sensitivity of $0.35^\circ$ per dot ($1.4^\circ$ total).

Marker Beacons

A system of three airway/approach marker transmitters operating on $75\,\text{Hz}$ with distinct light indicators and aural tones: Outer Marker (blue light, $400\,\text{Hz}$ tone), Middle Marker (amber light, $1300\,\text{Hz}$ tone), and Inner Marker (white light, $3000\,\text{Hz}$ tone).