Avionics Electronic Technician (AET) Exam — Questions and Answers

Question 1: What is the meaning of Design Assurance Level (DAL) A in DO-178C?

Software requiring no testing
Software whose failure would cause or contribute to a catastrophic failure condition (Correct answer)
Software used only in simulation
Software that has no safety impact

Correct answer: Software whose failure would cause or contribute to a catastrophic failure condition

DAL A is the highest software assurance level, applied to software where a failure could cause a catastrophic failure condition that would prevent continued safe flight and landing.

Question 2: Which regulation governs avionics communication equipment approval in the US?

TSO (Technical Standard Order) standards (Correct answer)
FAR Part 23 only
RTCA DO-178 exclusively
FCC Part 97

Correct answer: TSO (Technical Standard Order) standards

FAA Technical Standard Orders (TSOs) define minimum performance standards that aviation communication equipment must meet for approval and installation.

Question 3: What is the function of a Ground Proximity Warning System (GPWS)?

Alert the crew when aircraft flight parameters indicate dangerous proximity to terrain (Correct answer)
Detect runway incursions
Warn about icing conditions
Monitor fuel quantity near ground

Correct answer: Alert the crew when aircraft flight parameters indicate dangerous proximity to terrain

GPWS monitors parameters like sink rate, terrain clearance, gear/flap configuration, and airspeed to generate aural and visual warnings before controlled flight into terrain (CFIT).

Question 4: Which instrument is used to measure current flow in an aircraft circuit?

Ammeter (Correct answer)
Ohmmeter
Voltmeter
Wattmeter

Correct answer: Ammeter

An ammeter measures the flow of electric current in amperes and must be connected in series with the circuit.

Question 5: Which system allows for ground-based navigation using radio signals?

Cabin pressurization
ELT
Hydraulic gear extension
VOR navigation system (Correct answer)

Correct answer: VOR navigation system

The VOR (VHF Omnidirectional Range) navigation system is a ground-based radio navigation aid that transmits signals providing bearing information to aircraft. Pilots use these signals to determine their position relative to the VOR station and navigate along specific radial courses.

Question 6: What is the function of an aircraft's hydraulic system?

Operate flight and landing systems (Correct answer)
Fuel delivery
Ventilate the cabin
Distribute electrical power

Correct answer: Operate flight and landing systems

An aircraft's hydraulic system uses pressurized fluid to transmit force and motion, enabling the operation of heavy-duty components. Its primary function is to power critical flight control surfaces (like flaps and spoilers), landing gear retraction/extension, and braking systems. These systems require significant force and precise control, which hydraulics efficiently provide.

Question 7: Why is redundancy critical in aircraft navigation systems?

To lower equipment costs
To simplify maintenance
To reduce aircraft weight
To maintain navigation reliability and safety (Correct answer)

Correct answer: To maintain navigation reliability and safety

Redundancy in aircraft navigation systems means having multiple independent systems or backup components. This ensures that if one navigation system fails, another can immediately take over, preventing loss of navigation capability and maintaining the safety of flight, especially during critical phases.

Question 8: What is the function of a Flux Valve (flux detector) in an aircraft compass system?

Sense the direction of the Earth's magnetic field to provide a slaved magnetic heading (Correct answer)
Measure atmospheric pressure
Detect lightning strikes
Generate aircraft heading from engine data

Correct answer: Sense the direction of the Earth's magnetic field to provide a slaved magnetic heading

A flux valve (also called a flux gate) detects the horizontal component of the Earth's magnetic field to provide an accurate magnetic heading signal to the heading indicator or AHRS.

Question 9: What type of fault occurs when a conductor contacts the aircraft structure unintentionally?

Open circuit
Short to ground (Correct answer)
High resistance fault
Capacitive fault

Correct answer: Short to ground

A short to ground (or ground fault) occurs when an uninsulated conductor touches the aircraft's metallic structure, creating an unintended current path.

Question 10: Which tool is most appropriate for decoding and analyzing traffic on an ARINC 429 bus?

Digital multimeter
Analog oscilloscope only
ARINC 429 protocol bus analyzer (Correct answer)
Generic Ethernet network protocol analyzer

Correct answer: ARINC 429 protocol bus analyzer

An ARINC 429 bus analyzer decodes each 32-bit word into its label, data, SSM, and parity fields in human-readable format, making it the correct tool for protocol-level analysis.

Question 11: What is the specified characteristic impedance of a MIL-STD-1553 bus cable?

100 ohms
50 ohms
120 ohms
70 ohms (Correct answer)

Correct answer: 70 ohms

MIL-STD-1553 specifies a bus characteristic impedance of 70 ohms (±0.5 ohm) for the shielded twisted pair cable.

Question 12: What does a glide slope transmitter provide to an aircraft?

Passenger seat status
Air conditioning control
Vertical descent path information (Correct answer)
Fuel quantity data

Correct answer: Vertical descent path information

The glide slope transmitter, part of the ILS system, provides vertical guidance to the aircraft, indicating the correct angle of descent to the runway. It ensures the aircraft maintains the optimal vertical path for a safe and stable approach, especially in instrument meteorological conditions.

Question 13: Which encoding scheme is used by ARINC 429?

Non-Return to Zero (NRZ)
Bipolar Return to Zero (BPRZ) (Correct answer)
4B/5B encoding
Manchester II Biphase

Correct answer: Bipolar Return to Zero (BPRZ)

ARINC 429 uses Bipolar Return to Zero (BPRZ) encoding with three voltage states: HIGH (+10 V), NULL (0 V), and LOW (−10 V).

Question 14: ARINC 664 Part 7 (AFDX) is derived from which commercial networking standard?

ATM (Asynchronous Transfer Mode)
Switched Ethernet (IEEE 802.3) (Correct answer)
Token Ring (IEEE 802.5)
FDDI (Fiber Distributed Data Interface)

Correct answer: Switched Ethernet (IEEE 802.3)

AFDX (Avionics Full-Duplex Switched Ethernet) is based on switched Ethernet (IEEE 802.3) with deterministic enhancements for avionics use.

Question 15: Under FAR Part 43, who is authorized to perform preventive maintenance on an aircraft?

Only FAA-approved repair stations
Certificated pilots who own or operate the aircraft (for limited items listed in Part 43 Appendix A) (Correct answer)
Any person with basic mechanical skills
Only certificated A&P mechanics

Correct answer: Certificated pilots who own or operate the aircraft (for limited items listed in Part 43 Appendix A)

FAR Part 43 allows certificated pilots who own or operate aircraft not used in air carrier service to perform certain preventive maintenance items listed in Appendix A.

Question 16: What does BIT stand for in avionics system testing?

Built-In Test (Correct answer)
Backup Initialization Timer
Binary Input Test
Bus Interface Terminal

Correct answer: Built-In Test

Built-In Test (BIT) is a self-test capability designed into avionics LRUs to detect and isolate faults during power-up or continuous operation.

Question 17: What type of navigation aid is an Instrument Landing System (ILS)?

Autobrake system
Precision approach navigation aid (Correct answer)
Fuel management system
Cabin control system

Correct answer: Precision approach navigation aid

An Instrument Landing System (ILS) is a ground-based precision approach system that provides pilots with both horizontal and vertical guidance during instrument approaches to a runway. It allows for safe landings in low visibility conditions by guiding the aircraft precisely to the touchdown zone.

Question 18: What is the purpose of FAA Advisory Circular AC 43.13-1B?

Define pilot training requirements
Define ATC communication procedures
Establish airline operating minimums
Provide acceptable methods, techniques, and practices for aircraft inspection and repair (Correct answer)

Correct answer: Provide acceptable methods, techniques, and practices for aircraft inspection and repair

AC 43.13-1B provides acceptable maintenance and repair methods for aircraft structures, systems, and powerplants, serving as a key reference for A&P and avionics technicians.

Question 19: What is the function of a multiplexer (MUX) in an avionics data system?

Amplify multiple signals simultaneously
Convert digital data to analog
Select one of several input signals to route to a single output (Correct answer)
Distribute one signal to multiple outputs

Correct answer: Select one of several input signals to route to a single output

A multiplexer selects one of multiple input signals based on control inputs and routes it to a single output, enabling shared use of a communication channel.

Question 20: What is the purpose of a pitot heater in the aircraft instrument system?

Warm the cockpit instruments
Prevent ice formation in the pitot tube that would cause false airspeed readings (Correct answer)
Defrost the windshield
Heat the static ports

Correct answer: Prevent ice formation in the pitot tube that would cause false airspeed readings

The pitot heater electrically warms the pitot tube to prevent ice accumulation that could block the pressure sensing port and cause erroneous airspeed indications.

Question 21: What does a flip-flop circuit do in digital avionics systems?

Amplifies digital signals
Stores a single bit of data (Correct answer)
Converts analog to digital
Generates clock pulses

Correct answer: Stores a single bit of data

A flip-flop is a bistable multivibrator that stores one bit of digital information, maintaining its output state until triggered to change.

Question 22: In aircraft DC systems, which wire color typically indicates a ground return?

Green
Red
Black or bare (Correct answer)
Blue

Correct answer: Black or bare

In aircraft wiring, black or bare/uninsulated wires typically designate ground returns per MIL-W-5088 standards.

Question 23: What document must accompany an avionics component to prove it is airworthy and approved for installation?

Manufacturer warranty card
Flight manual supplement only
Purchase invoice
FAA Form 8130-3 (Airworthiness Approval Tag) (Correct answer)

Correct answer: FAA Form 8130-3 (Airworthiness Approval Tag)

FAA Form 8130-3 is the Airworthiness Approval Tag that certifies a part or component has been inspected and meets airworthiness requirements for installation.

Question 24: When troubleshooting an ARINC 429 bus with no output signal, what should a technician check first?

Power supply voltage to the transmitter LRU (Correct answer)
Number of receivers connected to the bus
Label coding of individual data words
Parity setting of the receiving units

Correct answer: Power supply voltage to the transmitter LRU

No signal on an ARINC 429 bus most commonly indicates a loss of power to the transmitter, so verifying power supply voltage is the logical first step.

Question 25: What is the primary reason for using torque specifications when tightening fasteners?

To prevent over- or under-tightening (Correct answer)
To balance load distribution
To measure vibration
For aesthetic alignment

Correct answer: To prevent over- or under-tightening

Torque specifications are essential in avionics maintenance to ensure fasteners are tightened to the precise force required. Over-tightening can strip threads, deform components, or cause material fatigue, while under-tightening can lead to fasteners loosening due to vibration. Adhering to these specifications guarantees the structural integrity, reliable operation, and safety of aircraft systems by preventing both types of damage.

Question 26: Why is it important to reference schematic legends when reading diagrams?

To check pricing information
To locate missing parts
To confirm manufacturing dates
To interpret symbols and abbreviations correctly (Correct answer)

Correct answer: To interpret symbols and abbreviations correctly

Schematic legends provide a key to all the symbols, abbreviations, and conventions used within a particular diagram. Referencing the legend is vital for technicians to accurately understand the function of each component and the meaning of various notations, ensuring correct interpretation and troubleshooting.

Question 27: What type of sensor is used to measure outside air temperature (OAT) in avionics systems?

Bimetallic strip
Thermocouple
Thermistor only
Platinum resistance thermometer (PRT/TAT probe) (Correct answer)

Correct answer: Platinum resistance thermometer (PRT/TAT probe)

Aviation OAT/TAT probes typically use platinum resistance thermometers (PRTs), which provide accurate temperature measurement based on resistance change.

Question 28: What does a Supplemental Type Certificate (STC) authorize?

A mechanic to perform annual inspections
A pilot to fly a new aircraft type
An airline to operate new routes
Modification of a certificated aircraft or installation of non-original equipment (Correct answer)

Correct answer: Modification of a certificated aircraft or installation of non-original equipment

An STC is issued by the FAA to approve a modification to a type-certificated aircraft that was not included in the original Type Certificate.

Question 29: What is the purpose of a bus bar in an aircraft electrical system?

To distribute power to multiple circuits (Correct answer)
To measure resistance
To convert AC to DC
To amplify voltage

Correct answer: To distribute power to multiple circuits

A bus bar serves as a common distribution point that supplies power from the main source to multiple branch circuits.

Question 30: How many bits are contained in a standard ARINC 429 data word?

24 bits
16 bits
32 bits (Correct answer)
64 bits

Correct answer: 32 bits

An ARINC 429 data word is 32 bits long, consisting of an 8-bit label, SDI, data field, SSM, and a parity bit.

Question 31: What is the impedance of a standard aviation VHF antenna system?

75Ω
600Ω
300Ω
50Ω (Correct answer)

Correct answer: 50Ω

Aviation VHF antenna systems are designed for 50-ohm impedance to match standard coaxial cables and transceiver output stages.

Question 32: Why are wire numbers included in an aircraft schematic?

Indicate wire color
Show insulation material
Provide unique identification for each wire (Correct answer)
Mark component serial numbers

Correct answer: Provide unique identification for each wire

Wire numbers are assigned to individual wires in an aircraft schematic to give each one a unique identifier. This numbering system is essential for technicians to accurately trace specific wires through complex harnesses, diagnose faults, and ensure correct connections during installation or repair.

Question 33: What AFDX mechanism ensures deterministic, guaranteed bandwidth for each avionics data stream?

Token passing protocol
Quality-of-Service DSCP marking
Virtual Links with Bandwidth Allocation Gaps (BAGs) (Correct answer)
Priority queuing with preemption

Correct answer: Virtual Links with Bandwidth Allocation Gaps (BAGs)

AFDX uses Virtual Links (VLs), each with a defined Bandwidth Allocation Gap (BAG), to guarantee deterministic delivery for every data stream.

Question 34: Which component in an ILS system provides lateral guidance to the runway centerline?

Localizer (Correct answer)
Cabin PA system
Glide slope
Marker beacon

Correct answer: Localizer

The localizer component of an ILS system transmits radio signals that provide lateral guidance, indicating the aircraft's position relative to the runway centerline. It helps the pilot align the aircraft horizontally with the runway during an instrument approach, ensuring proper alignment.

Question 35: What is the primary purpose of coupling transformers used in a MIL-STD-1553 bus installation?

Convert Manchester encoding to NRZ for internal processing
Increase the data transfer speed of the bus
Filter out RF interference from nearby avionics
Provide electrical isolation and impedance matching between terminal and bus (Correct answer)

Correct answer: Provide electrical isolation and impedance matching between terminal and bus

Coupling transformers provide galvanic isolation between the bus and each terminal while simultaneously matching impedance for proper signal integrity.

Question 36: What is the typical aircraft standard DC bus voltage in most general aviation aircraft?

24V
28V (Correct answer)
12V
115V

Correct answer: 28V

Most aircraft use a 28V DC system, which provides adequate power while keeping wire weight practical.

Question 37: What FAA form is used to record a Major Alteration or Major Repair?

FAA Form 8710-1
FAA Form 337 (Correct answer)
FAA Form 8130-3
FAA Form 8060-5

Correct answer: FAA Form 337

FAA Form 337 (Major Repair and Alteration) must be completed and filed with the FAA for any major repair or alteration performed on a certificated aircraft.

Question 38: Why is redundancy built into critical aircraft systems?

Ensure system reliability and safety during failure (Correct answer)
Reduce aircraft weight
Reduce maintenance frequency
Limit system control

Correct answer: Ensure system reliability and safety during failure

Redundancy in critical aircraft systems means having duplicate or backup components. This design philosophy ensures that if one component or system fails, a backup can immediately take over, preventing a catastrophic failure and maintaining the aircraft's safe operation and reliability.

Question 39: Which component prevents accidental re-energizing of a system during maintenance?

Flight data recorder
Fuselage doubler
Circuit breaker label
Lockout/tagout device (Correct answer)

Correct answer: Lockout/tagout device

A lockout/tagout device is a critical safety tool used to prevent accidental re-energizing of equipment during maintenance. It physically secures energy-isolating devices, such as circuit breakers, in the 'off' or 'safe' position. This ensures that the system remains de-energized and safe for technicians to work on, protecting them from unexpected startup or release of hazardous energy.

Question 40: Which logic family is commonly used in modern avionics FPGAs and ASICs due to its low power consumption?

CMOS (Complementary Metal-Oxide Semiconductor) (Correct answer)
RTL (Resistor-Transistor Logic)
ECL (Emitter-Coupled Logic)
TTL (Transistor-Transistor Logic)

Correct answer: CMOS (Complementary Metal-Oxide Semiconductor)

CMOS technology is dominant in modern avionics integrated circuits because of its very low static power consumption and high noise immunity.

Question 41: Why is logging maintenance actions in aircraft records mandatory?

To increase flight hours
To ensure airworthiness and compliance (Correct answer)
To reduce insurance costs
To modify aircraft paint color

Correct answer: To ensure airworthiness and compliance

Logging all maintenance actions in aircraft records is a mandatory regulatory requirement. These detailed records provide a complete history of the aircraft's upkeep, demonstrating its continued airworthiness, compliance with regulations, and ensuring traceability for future inspections and maintenance.

Question 42: What regulation specifies the VOR accuracy check requirements for IFR operations?

FAR 91.409
FAR 91.413
FAR 91.207
FAR 91.171 (Correct answer)

Correct answer: FAR 91.171

FAR 91.171 requires VOR equipment used for IFR flight to be checked for accuracy within the preceding 30 days and the check logged.

Question 43: What does AHRS stand for and what sensors does it use?

Avionics Hub Relay System — databus
Altitude and Heading Reference System — altimeters only
Attitude and Heading Reference System — gyros, accelerometers, and magnetometers (Correct answer)
Aircraft Horizontal Reference System — GPS only

Correct answer: Attitude and Heading Reference System — gyros, accelerometers, and magnetometers

AHRS (Attitude and Heading Reference System) uses solid-state gyroscopes, accelerometers, and magnetometers to compute aircraft attitude and magnetic heading.

Question 44: What does EMF stand for in electrical systems?

Electromotive Force (Correct answer)
Electromagnetic Frequency
Electrical Modulation Factor
Electronic Magnetic Force

Correct answer: Electromotive Force

EMF stands for Electromotive Force, which is the energy per unit charge supplied by a source such as a battery.

Question 45: What is the primary function of an audio control panel (ACP) in an aircraft?

Amplify RF signals
Select and route audio between radios, navigation receivers, and crew headsets (Correct answer)
Generate audio tones
Control autopilot audio alerts

Correct answer: Select and route audio between radios, navigation receivers, and crew headsets

The Audio Control Panel allows crew members to select which radio or nav receiver audio they hear and which microphone/radio they transmit on.

Question 46: What is the fixed data transfer rate of MIL-STD-1553?

100 Mbps
100 kbps
10 Mbps
1 Mbps (Correct answer)

Correct answer: 1 Mbps

MIL-STD-1553 operates at a fixed data rate of exactly 1 Mbps.

Question 47: Which type of circuit has all components connected end-to-end in a single path?

Resonant circuit
Bridge circuit
Series circuit (Correct answer)
Parallel circuit

Correct answer: Series circuit

In a series circuit, current follows one continuous path through all components.

Question 48: Which law states that the algebraic sum of all currents entering and leaving a node equals zero?

Faraday's Law
Kirchhoff's Current Law (Correct answer)
Ohm's Law
Fleming's Rule

Correct answer: Kirchhoff's Current Law

Kirchhoff's Current Law (KCL) states that the total current entering a junction equals the total current leaving it.

Question 49: According to Ohm's Law, if voltage is 24V and resistance is 6Ω, what is the current?

144A
2A
4A (Correct answer)
6A

Correct answer: 4A

Using Ohm's Law (I = V/R), 24V ÷ 6Ω = 4 amperes.

Question 50: Why is proper wire routing critical in avionics maintenance?

To increase signal strength
To minimize insulation costs
To simplify cabin cleaning
To prevent interference and physical damage (Correct answer)

Correct answer: To prevent interference and physical damage

Proper wire routing in avionics is vital to prevent electromagnetic interference (EMI) between wires, which can degrade signal quality and system performance. Additionally, incorrect routing can lead to physical damage such as chafing, pinching, or excessive bending, causing insulation breakdown, short circuits, or open circuits. Adhering to routing standards ensures the reliability and safety of critical aircraft systems.

Question 51: Which document outlines the correct maintenance procedures for aircraft systems?

Passenger manifest
Flight plan
Aircraft Maintenance Manual (AMM) (Correct answer)
Weather report

Correct answer: Aircraft Maintenance Manual (AMM)

The Aircraft Maintenance Manual (AMM) is the authoritative document that contains detailed instructions, procedures, and specifications for all maintenance, repair, and overhaul tasks on an aircraft. Adhering to the AMM ensures that maintenance is performed correctly, safely, and in compliance with regulatory standards.

Question 52: What causes a parity error in an ARINC 429 data word?

Label field mismatch between transmitter and receiver configuration
The total count of logic-1 bits in the 32-bit word is not odd (Correct answer)
Data transmitted at incorrect bus speed
Bus voltage level falling outside the ±10 V specification

Correct answer: The total count of logic-1 bits in the 32-bit word is not odd

ARINC 429 uses odd parity; a parity error occurs when the total number of 1-bits across the 32-bit word is even rather than odd, indicating a transmission error.

Question 53: What is the purpose of a transponder in an aircraft?

Control landing lights
Vent cabin air
Transmit ID and altitude to ATC radar (Correct answer)
Fuel measurement

Correct answer: Transmit ID and altitude to ATC radar

A transponder is an electronic device in an aircraft that responds to interrogations from ground-based air traffic control (ATC) radar. It transmits a unique identification code and the aircraft's pressure altitude back to ATC, allowing controllers to track the aircraft's position and manage air traffic effectively. This system is essential for air traffic management and collision avoidance.

Question 54: According to FAR 91.413, ATC transponders must be tested within how many calendar months?

6 months
12 months
36 months
24 months (Correct answer)

Correct answer: 24 months

FAR 91.413 requires ATC transponders to be tested and inspected in accordance with FAR Part 43 Appendix F within the preceding 24 calendar months.

Question 55: Which avionics data bus standard supports data rates up to 100 Mbps and is used in modern commercial aircraft such as the A380 and Boeing 787?

RS-422
MIL-STD-1553B
ARINC 429
ARINC 664 (AFDX) (Correct answer)

Correct answer: ARINC 664 (AFDX)

ARINC 664 Part 7 (AFDX) supports data rates up to 100 Mbps and is the high-speed backbone network used in the A380 and Boeing 787.

Question 56: Which FAA authorization allows an avionics technician to approve aircraft for return to service after maintenance?

Sport Pilot Certificate
Airframe and Powerplant (A&P) Certificate with Inspection Authorization (IA) for major repairs (Correct answer)
Aircraft Dispatcher Certificate
Private Pilot Certificate

Correct answer: Airframe and Powerplant (A&P) Certificate with Inspection Authorization (IA) for major repairs

An A&P mechanic may return aircraft to service after maintenance; an Inspection Authorization (IA) is additionally required for annual inspections and major repairs/alterations.

Question 57: Under FAR Part 91.411, altimeter systems must be tested and inspected within what period for IFR flight?

Every 500 hours
Every 12 calendar months
Every 100 hours
Every 24 calendar months (Correct answer)

Correct answer: Every 24 calendar months

FAR 91.411 requires altimeter systems and altitude reporting equipment to be tested and inspected within the preceding 24 calendar months for IFR operations.

Question 58: What is the unit of electrical resistance?

Watt
Ampere
Volt
Ohm (Correct answer)

Correct answer: Ohm

Resistance is measured in ohms (Ω), named after Georg Simon Ohm.

Question 59: Which system allows aircraft to determine bearing and distance using ground-based radio signals?

HF comm system
VOR/DME system (Correct answer)
Pressurization system
ADF system

Correct answer: VOR/DME system

The VOR/DME system combines the capabilities of VHF Omnidirectional Range (VOR) for bearing information and Distance Measuring Equipment (DME) for slant range distance. Together, they allow aircraft to determine their precise position (bearing and distance) relative to a ground station, enabling comprehensive navigation.

Question 60: What is the maximum number of receivers that can be connected to a single ARINC 429 transmitter?

5
10
50
20 (Correct answer)

Correct answer: 20

A single ARINC 429 transmitter can drive up to 20 receivers on one unidirectional bus.

Question 61: In aircraft interphone systems, what is the purpose of a hot microphone (hot mic) mode?

Boost microphone gain for weak signals
Allow continuous open-mic communication without PTT (Correct answer)
Record all crew conversations to CVR
Enable passenger PA announcements

Correct answer: Allow continuous open-mic communication without PTT

Hot microphone mode keeps the microphone continuously active so crew can communicate hands-free without pressing the push-to-talk switch.

Question 62: What tool is essential for verifying electrical continuity in avionics systems?

Torque wrench
Hydraulic pump
VOR receiver
Multimeter (Correct answer)

Correct answer: Multimeter

A multimeter is an essential diagnostic tool for avionics technicians, capable of measuring voltage, current, and resistance. It is crucial for verifying electrical continuity, troubleshooting open or short circuits, and confirming proper power supply in avionics systems, ensuring their correct operation.

Question 63: What does an arrowhead in a wiring schematic typically indicate?

Wire insulation rating
Direction of signal or current flow (Correct answer)
Part manufacturer
Fuse amperage

Correct answer: Direction of signal or current flow

An arrowhead in a wiring schematic is commonly used to indicate the intended direction of signal or current flow within a circuit. This helps technicians understand the logical progression of electrical energy or data and diagnose issues related to incorrect signal paths.

Question 64: What is the primary function of an aircraft's pitot-static system?

Fuel distribution control
Flight data for speed, altitude, and climb rate (Correct answer)
Cabin lighting control
Electrical system protection

Correct answer: Flight data for speed, altitude, and climb rate

The pitot-static system is a crucial aircraft instrument system that provides essential flight data. It measures air pressure differences using pitot tubes and static ports to calculate airspeed, altitude, and vertical speed (climb/descent rate). This information is vital for safe navigation, flight control, and accurate performance monitoring.

Question 65: What does the DME system measure?

Distance to a ground station (Correct answer)
Battery voltage
Vertical speed
Altitude

Correct answer: Distance to a ground station

The DME (Distance Measuring Equipment) system works in conjunction with VOR or ILS stations to provide pilots with a precise slant range distance to the ground station. This information is crucial for accurate navigation and position awareness, complementing other navigation aids.

Question 66: What is the first step before performing maintenance on any aircraft system?

Disconnect and secure system power (Correct answer)
Adjust seat positions
Check cabin lighting
Test fire suppression system

Correct answer: Disconnect and secure system power

Before performing any maintenance on an aircraft system, it is paramount to disconnect and secure its power source. This critical safety step prevents accidental activation, electrical shock, or damage to components, ensuring the safety of the technician and the aircraft.

Question 67: Enhanced GPWS (EGPWS) adds which major capability over basic GPWS?

Wind shear detection only
A worldwide terrain database for look-ahead terrain alerting (Correct answer)
Improved sink rate sensors
Better radio altimeter

Correct answer: A worldwide terrain database for look-ahead terrain alerting

EGPWS adds a worldwide terrain elevation database to provide look-ahead terrain alerting, warning of obstacles ahead of the aircraft before they are sensed by reactive modes.

Question 68: Which instrument typically displays navigation signals from ILS, VOR, and GPS sources?

Autopilot controller
Horizontal Situation Indicator (HSI) (Correct answer)
Fuel management panel
Landing gear position light

Correct answer: Horizontal Situation Indicator (HSI)

The Horizontal Situation Indicator (HSI) is a primary flight instrument that combines a directional gyro with navigation information from various sources like VOR, ILS, and GPS. It graphically displays the aircraft's heading, course deviation, and bearing to navigation aids in a single, intuitive presentation.

Question 69: Which component is typically represented by a zigzag line in a schematic?

Transformer
Resistor (Correct answer)
Battery
Switch

Correct answer: Resistor

In electrical schematics, a zigzag line is the standard symbol used to represent a resistor. A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element, used to reduce current flow, adjust signal levels, or divide voltages.

Question 70: Which FAA regulation governs the certification of avionics equipment for installation in aircraft?

FAR Part 135
FAR Part 21 and applicable TSOs (Correct answer)
FAR Part 61
FAR Part 91 only

Correct answer: FAR Part 21 and applicable TSOs

FAR Part 21 governs certification procedures for products and parts, while Technical Standard Orders (TSOs) define minimum performance standards for specific avionics equipment.

Question 71: Which type of memory loses its data when power is removed?

Flash memory
EEPROM
RAM (Correct answer)
ROM

Correct answer: RAM

RAM (Random Access Memory) is volatile and loses all stored data when power is removed from the device.

Question 72: What component converts mechanical energy to electrical energy in an aircraft?

Fuel pump
Inverter
Hydraulic actuator
Generator (Correct answer)

Correct answer: Generator

A generator is a device that converts mechanical energy into electrical energy. In an aircraft, generators are typically driven by the engines and produce the electrical power needed to operate the aircraft's various systems. These systems include avionics, lighting, environmental controls, and other essential electrical components, making the generator fundamental to the aircraft's operation.

Question 73: Which instrument displays a combination of attitude, heading, and navigation information on a single screen?

TCAS display
EFIS/PFD (Primary Flight Display) (Correct answer)
ADI only
EICAS

Correct answer: EFIS/PFD (Primary Flight Display)

A Primary Flight Display (PFD) on an EFIS-equipped aircraft combines attitude, airspeed, altitude, heading, and navigation data on one integrated screen.

Question 74: When is a functional test typically performed after maintenance?

After maintenance, before aircraft release (Correct answer)
Before shutdown procedures
During passenger boarding
After in-flight use

Correct answer: After maintenance, before aircraft release

A functional test is a crucial step performed after maintenance to verify that the repaired or replaced component, and the overall system, operates correctly and safely. This test ensures that all work has been completed to specifications and that the aircraft is airworthy before it is returned to service. Performing it before aircraft release prevents potential in-flight issues and confirms the effectiveness of the maintenance performed.

Question 75: What is the primary purpose of an aircraft's VOR system?

Measure airspeed
Provide azimuth navigation information (Correct answer)
Monitor fuel levels
Display cabin temperature

Correct answer: Provide azimuth navigation information

The VOR (VHF Omnidirectional Range) system is a ground-based radio navigation aid that transmits signals in all directions. Aircraft receivers interpret these signals to determine their magnetic bearing (azimuth) relative to the VOR station, allowing for precise course guidance.

Question 76: What does the 8-bit 'label' field in an ARINC 429 word identify?

The identity of the source transmitter
The type or parameter of data being transmitted (Correct answer)
The error correction code appended to the word
The destination receiver address

Correct answer: The type or parameter of data being transmitted

The 8-bit label field identifies the type of data or avionics parameter (e.g., airspeed, altitude) contained in that word.

Question 77: What does EICAS stand for and what is its primary function?

Engine Instrument and Checklist Advisory System
Electronic Integrated CAS
Electronic Instrument Control and Alert System
Engine Indication and Crew Alerting System (Correct answer)

Correct answer: Engine Indication and Crew Alerting System

EICAS (Engine Indication and Crew Alerting System) displays engine parameters and generates crew alert messages for abnormal aircraft system conditions.

Question 78: What is the binary equivalent of the decimal number 13?

1010
1110
1011
1101 (Correct answer)

Correct answer: 1101

Decimal 13 = 8+4+1 = 1101 in binary (8=1, 4=1, 2=0, 1=1).

Question 79: At what height AGL does the radio altimeter Decision Height (DH) alert typically trigger during an ILS approach?

At the pilot-set DH/DA value, typically 200 ft AGL for a Cat I ILS (Correct answer)
At 1,000 ft AGL always
Only at touchdown
At the outer marker

Correct answer: At the pilot-set DH/DA value, typically 200 ft AGL for a Cat I ILS

The radio altimeter triggers the DH alert at the crew-selected decision height — typically 200 ft AGL for a Category I ILS approach.

Question 80: What system assists pilots by automatically maintaining altitude and heading?

Anti-icing system
Auxiliary fuel system
Autopilot system (Correct answer)
Lighting system

Correct answer: Autopilot system

The autopilot system is specifically designed to assist pilots by automatically controlling the aircraft's flight path, including maintaining a set altitude and heading. It uses various sensors and control surfaces to keep the aircraft stable and on course, significantly reducing pilot workload during flight.

Question 81: What type of gyroscope is used in modern Inertial Reference Systems instead of mechanical gyros?

Ring Laser Gyro (RLG) or Fiber Optic Gyro (FOG) (Correct answer)
Mechanical spinning gyro
Vibrating beam gyro
Pneumatic gyro

Correct answer: Ring Laser Gyro (RLG) or Fiber Optic Gyro (FOG)

Modern IRS units use Ring Laser Gyros (RLGs) or Fiber Optic Gyros (FOGs), which have no moving parts and measure rotation via the Sagnac effect.

Question 82: What does an Air Data Computer (ADC) primarily compute?

Magnetic heading and drift
Fuel quantity and flow
Engine RPM and EGT
Airspeed, altitude, vertical speed, and Mach number from pitot-static data (Correct answer)

Correct answer: Airspeed, altitude, vertical speed, and Mach number from pitot-static data

An ADC processes pitot and static pressure inputs to compute calibrated airspeed, altitude, vertical speed, Mach number, and outside air temperature.

Question 83: What is a Major Alteration in aviation regulatory terms?

An alteration not listed in the aircraft specifications that might affect airworthiness (Correct answer)
Any alteration to wiring
Replacing a radio with an identical model
Painting the aircraft

Correct answer: An alteration not listed in the aircraft specifications that might affect airworthiness

A Major Alteration is one that might appreciably affect structural strength, flight characteristics, or other airworthiness qualities, not listed in the aircraft specifications.

Question 84: Which maintenance practice ensures that tools and parts are accounted for after a job?

Tool control checklist and inventory (Correct answer)
Painting inventory numbers
Labeling hangar equipment
Posting safety posters

Correct answer: Tool control checklist and inventory

Tool control checklists and inventory systems are essential maintenance practices, especially in aviation, to prevent foreign object debris (FOD) hazards. By meticulously accounting for every tool and part before, during, and after a job, technicians ensure that no items are left behind in critical aircraft systems. This systematic approach minimizes the risk of tools or parts interfering with aircraft operation, which could lead to catastrophic failures.

Question 85: Which system ensures continuous power to critical avionics during engine failure?

Landing gear system
Emergency power system (Correct answer)
Hydraulic accumulator
De-icing system

Correct answer: Emergency power system

The emergency power system in an aircraft is designed to provide backup electrical power to critical avionics and essential systems in the event of a primary engine or generator failure. This ensures that vital instruments, communication systems, and flight controls remain operational. Having an emergency power source is crucial for maintaining control and safely managing an in-flight emergency.

Question 86: Which component converts a synchro signal to a DC voltage for use in digital avionics?

Synchro-to-digital converter (SDC) (Correct answer)
Flux valve
Resolver
Comparator circuit

Correct answer: Synchro-to-digital converter (SDC)

A Synchro-to-Digital Converter (SDC) translates the three-wire AC synchro signal from angular position sensors into a digital word for avionics computers.

Question 87: In avionics software, what does DO-178C define?

Hardware qualification requirements
Software development and assurance levels for airborne systems (Correct answer)
ARINC data word formats
EMI testing procedures

Correct answer: Software development and assurance levels for airborne systems

RTCA DO-178C defines the software development and verification processes required for airborne software to meet FAA certification levels (DAL A–E).

Question 88: What information does the SSM (Sign/Status Matrix) field provide in an ARINC 429 word?

Data sign and equipment operational status (Correct answer)
Serial signal modulation type
Secondary system monitor readings
Signal synchronization timing

Correct answer: Data sign and equipment operational status

The SSM field provides the sign of the numeric data and indicates the operational status (e.g., normal, failure warning) of the transmitting equipment.

Question 89: What does the term 'LRU' stand for in avionics maintenance?

Low Range Unit
Line Replaceable Unit (Correct answer)
Load Regulation Unit
Local Radio Unit

Correct answer: Line Replaceable Unit

LRU (Line Replaceable Unit) is an avionics component designed to be quickly removed and replaced at the flight line without depot-level maintenance.

Question 90: What does ACARS stand for?

Aircraft Communication Addressing and Reporting System (Correct answer)
Aviation Communication Archive and Relay Service
Automatic Circuit Alert and Response System
Airborne Communication and Radar System

Correct answer: Aircraft Communication Addressing and Reporting System

ACARS (Aircraft Communication Addressing and Reporting System) is a digital datalink system for transmitting short messages between aircraft and ground stations.

Question 91: What is the purpose of a relay depicted in a schematic?

Indicate fuel quantity
Store electrical energy
Act as a remotely operated switch (Correct answer)
Measure temperature

Correct answer: Act as a remotely operated switch

A relay is an electromechanical switch that uses a small electrical current to control a larger current or circuit. In a schematic, it represents a component that can be activated remotely to open or close contacts, allowing for control of high-power circuits with low-power signals.

Question 92: What type of signal does an ADC (Analog-to-Digital Converter) produce?

Sinusoidal AC signal
Modulated RF carrier
Continuous analog waveform
Discrete binary number representing the sampled analog value (Correct answer)

Correct answer: Discrete binary number representing the sampled analog value

An ADC samples an analog signal at regular intervals and converts each sample into a binary number proportional to the analog voltage level.

Question 93: Which system manages cabin pressure and air circulation in modern aircraft?

Hydraulic system
Autopilot system
Avionics cooling system
Environmental control system (Correct answer)

Correct answer: Environmental control system

The Environmental Control System (ECS) in modern aircraft is responsible for maintaining a comfortable and safe cabin environment. It manages cabin pressure, temperature, humidity, and air circulation, ensuring a continuous supply of fresh, conditioned air for passengers and crew at various altitudes. This system is critical for occupant comfort and physiological well-being during flight.

Question 94: What word length does ARINC 429 use for each data transmission?

32 bits (Correct answer)
16 bits
8 bits
64 bits

Correct answer: 32 bits

Each ARINC 429 word is 32 bits long, containing a label, source/destination identifier, data, sign/status matrix bits, and a parity bit.

Question 95: What is the function of a data concentrator unit (DCU) in a modern avionics suite?

Provide electrical power conversion
Generate navigation data
Control autopilot servos
Collect, process, and route data from multiple avionics sensors to display systems (Correct answer)

Correct answer: Collect, process, and route data from multiple avionics sensors to display systems

A DCU aggregates data from multiple avionics buses and sensors, formats it, and distributes it to cockpit display systems and other LRUs.

Question 96: What frequency does the emergency guard channel operate on in aviation?

156.8 MHz
131.8 MHz
121.5 MHz (Correct answer)
108.0 MHz

Correct answer: 121.5 MHz

121.5 MHz is the international aviation emergency (guard) frequency monitored continuously by ATC and rescue services.

Question 97: What altitude is typically displayed on the TCAS/RA display relative to own aircraft?

Relative altitude in hundreds of feet above or below own aircraft (Correct answer)
Altitude above terrain
Altitude in meters
Absolute altitude MSL

Correct answer: Relative altitude in hundreds of feet above or below own aircraft

TCAS traffic symbols display relative altitude in hundreds of feet above (+) or below (−) the own aircraft's current altitude.

Question 98: A capacitor in an AC circuit acts primarily as which of the following?

Short circuit
Inductor
Resistor
Reactance element blocking DC (Correct answer)

Correct answer: Reactance element blocking DC

A capacitor blocks DC and presents capacitive reactance to AC signals, allowing AC to pass while blocking DC.

Question 99: In MIL-STD-1553, what is a 'stub'?

A parity error flagged in a status word
An unused RT address reserved for future use
An unanswered command left pending by the Bus Controller
A short cable connecting a terminal to the main bus (Correct answer)

Correct answer: A short cable connecting a terminal to the main bus

A stub is the short branch cable that connects a Remote Terminal or other device to the main MIL-STD-1553 bus cable, with maximum lengths defined by coupling type.

Question 100: What is the function of a zener diode in an avionics circuit?

Frequency modulation
Resistance measurement
Voltage regulation (Correct answer)
Amplification

Correct answer: Voltage regulation

A zener diode maintains a constant reference voltage by conducting in reverse at its breakdown voltage, making it useful for voltage regulation.

Avionics Electronic Technician (AET) Exam

The Avionics Electronic Technician (AET) certification validates the knowledge and skills required to install, troubleshoot, and repair aircraft electronic systems.

100

Questions

120 min

Time Limit

70%

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