ASTM NCATT AET – Aircraft Electronics Technician — Questions and Answers

Question 1: ACARS (Aircraft Communications Addressing and Reporting System) primarily uses which communication medium for airborne data link?

DME interrogation/reply channels
ATC radar secondary surveillance
HF voice channels
VHF Data Link (VDL) or SATCOM (Correct answer)

Correct answer: VHF Data Link (VDL) or SATCOM

ACARS uses VHF Data Link (typically 129.125 MHz and others) for short-range digital messaging and SATCOM for oceanic areas beyond VHF coverage.

Question 2: What type of modulation is used by HF aviation voice transceivers?

Pulse amplitude modulation
AM double sideband
FM
Single Sideband (SSB) (Correct answer)

Correct answer: Single Sideband (SSB)

HF aviation radios use Single Sideband (SSB) modulation because it is more power-efficient and occupies less bandwidth than double-sideband AM.

Question 3: What is the purpose of the Aircraft Communications Addressing and Reporting System (ACARS)?

Provide cabin passenger Wi-Fi
Transmit digital data messages between aircraft and ground stations (Correct answer)
Encrypt cockpit voice communications
Control engine thrust automatically

Correct answer: Transmit digital data messages between aircraft and ground stations

ACARS is a digital datalink system that transmits short messages between aircraft and airline operations or ATC ground stations.

Question 4: A strobe light on an aircraft fails to flash but the power supply capacitor charges correctly. The fault most likely lies in the:

Aircraft bus voltage
Flash tube or trigger circuit (Correct answer)
Main generator
Power supply rectifier

Correct answer: Flash tube or trigger circuit

If the capacitor charges correctly but the light fails to flash, the flash tube, trigger transformer, or trigger circuit is likely faulty.

Question 5: What is the maximum theoretical range error caused by Selective Availability (SA) in GPS before it was disabled?

±500 meters
±100 meters (Correct answer)
±15 meters
±5 meters

Correct answer: ±100 meters

Selective Availability intentionally degraded civilian GPS accuracy to approximately ±100 meters (95%) until it was disabled by presidential order in May 2000.

Question 6: A technician is testing an aircraft transponder on the bench. What hazard does the transponder's RF output present?

Electromagnetic radiation hazard to personnel and potential interference with ATC (Correct answer)
Risk of data corruption to nearby avionics
Fire risk from the antenna port
Damage to the bench power supply

Correct answer: Electromagnetic radiation hazard to personnel and potential interference with ATC

Active transponders emit RF energy that can cause electromagnetic radiation hazards to nearby personnel and interfere with ATC radar systems.

Question 7: A technician connects a data bus analyzer to an ARINC 429 bus. The analyzer shows no valid words being decoded. Which condition is least likely to cause this?

A short circuit between the A and B bus lines
The transmitting LRU is in normal operational mode (Correct answer)
Reversed A and B differential pair connections
Incorrect bit rate selected on the analyzer (12.5 kbps vs. 100 kbps)

Correct answer: The transmitting LRU is in normal operational mode

A transmitting LRU in normal operational mode should be producing valid data; the other options would all prevent proper decoding.

Question 8: A Supplemental Type Certificate (STC) grants approval for what type of modification?

Software update to existing certified systems
Major alteration that changes the type design (Correct answer)
Minor repair to existing equipment
Routine inspection of avionics

Correct answer: Major alteration that changes the type design

An STC approves a major alteration to an aircraft's type design that is not covered by the original Type Certificate, allowing installation of new or modified equipment.

Question 9: Why is it important to document all maintenance activities performed on aircraft electronic systems?

To reduce the amount of paperwork required for future inspections
To assist in scheduling future maintenance without prior records
To track the cost of maintenance
To ensure compliance with regulatory requirements and provide a history of work performed (Correct answer)

Correct answer: To ensure compliance with regulatory requirements and provide a history of work performed

Documenting all maintenance activities on aircraft electronic systems is essential for several reasons. It ensures compliance with stringent regulatory requirements, provides a comprehensive historical record of all work performed, and is crucial for future troubleshooting, maintenance planning, and ensuring aircraft safety.

Question 10: In a twin-engine aircraft with two generators, what component automatically connects both generators to share the electrical load?

Voltage regulator
Bus tie relay (BTR) or bus tie breaker (Correct answer)
Current transformer
Load controller unit

Correct answer: Bus tie relay (BTR) or bus tie breaker

A bus tie relay (BTR) or bus tie breaker connects the two main AC or DC buses together, allowing both generators to share the total electrical load equally.

Question 11: What does a high VSWR reading on an antenna analyzer indicate about an aircraft antenna installation?

The antenna is properly matched to the transmission line
The antenna gain is above specification
The coaxial feedline has excessive capacitance
There is a significant impedance mismatch causing reflected power (Correct answer)

Correct answer: There is a significant impedance mismatch causing reflected power

A high Voltage Standing Wave Ratio means reflected power is returning to the transmitter, indicating an impedance mismatch in the antenna system.

Question 12: When analyzing data from an avionics test set, which of the following is a crucial aspect to verify?

The date and time settings of the test set
The color of the display screen
The brand of the test set used
The accuracy of the measurements and comparison with expected values (Correct answer)

Correct answer: The accuracy of the measurements and comparison with expected values

When analyzing data from an avionics test set, the most crucial aspect is to verify the accuracy of the measurements and compare them with expected values or specifications. This ensures that the aircraft's electronic systems are functioning within their designed parameters and meet safety and performance standards. Any deviation from expected values indicates a potential fault that requires further investigation and corrective action.

Question 13: What quality metrics are most important in Avionics Systems?

Measurable outcomes, process compliance, and stakeholder satisfaction (Correct answer)
Only financial metrics
No metrics are needed
Only speed of completion

Correct answer: Measurable outcomes, process compliance, and stakeholder satisfaction

Quality in Avionics Systems is measured through multiple dimensions including outcomes, processes, and satisfaction.

Question 14: How should risk be managed in Electrical Troubleshooting?

Through identification, assessment, mitigation strategies, and ongoing monitoring of potential risks (Correct answer)
By avoiding all risk entirely
Risk management is not necessary
By ignoring potential problems

Correct answer: Through identification, assessment, mitigation strategies, and ongoing monitoring of potential risks

Effective risk management involves a systematic process of identifying, evaluating, and addressing potential threats.

Question 15: Within a microprocessor, which unit is responsible for performing arithmetic and logic operations?

Control Unit
Program Counter
ALU (Arithmetic Logic Unit) (Correct answer)
Memory Management Unit

Correct answer: ALU (Arithmetic Logic Unit)

The ALU executes all arithmetic (addition, subtraction) and logical (AND, OR, NOT) operations in a microprocessor.

Question 16: What is the purpose of a Repair Station's Capability List (CL)?

Specifies the articles the repair station is authorized to maintain, repair, or alter (Correct answer)
Documents customer complaints and resolutions
Lists all employees and their certifications
Tracks inventory of spare parts

Correct answer: Specifies the articles the repair station is authorized to maintain, repair, or alter

A Repair Station's Capability List details the specific articles and functions the station is authorized to perform under its certificate.

Question 17: An aircraft circuit breaker trips immediately upon reset. The FIRST troubleshooting step should be to:

Disconnect loads progressively to find the fault (Correct answer)
Check generator output voltage
Increase the breaker amperage rating
Replace the circuit breaker

Correct answer: Disconnect loads progressively to find the fault

Progressively disconnecting loads isolates the faulty component causing the overcurrent condition before replacing the breaker.

Question 18: When troubleshooting a SATCOM system showing 'no log-on' status, the technician should FIRST check:

VHF radio interference on the SATCOM data bus
The HPA (High Power Amplifier) bias current
The audio codec board for bit errors
Antenna pointing, obstructions, and satellite network log-on status (Correct answer)

Correct answer: Antenna pointing, obstructions, and satellite network log-on status

A 'no log-on' indication most often results from physical blockage, antenna attitude error, or a lapsed network subscription before any internal hardware fault.

Question 19: When an autopilot system's pitch channel fails to hold altitude and continually pitches nose-up, the most logical first diagnostic step is to check:

The fuel quantity indication system
The landing gear position switches
The VHF communication system frequency
The pitch attitude signal from the AHRS and the elevator servo feedback signal (Correct answer)

Correct answer: The pitch attitude signal from the AHRS and the elevator servo feedback signal

A pitch channel that drives nose-up continuously suggests a runaway condition likely caused by incorrect AHRS pitch attitude data or a faulty elevator servo feedback/position sensor.

Question 20: A logic analyzer shows that a data bus has valid framing and clock, but all data bits read as logic '1'. The most likely cause is:

The analyzer probe impedance is loading the bus
An open circuit on the data line causing it to float to the pull-up rail (Correct answer)
The clock frequency is too high
The power supply is 10% over nominal

Correct answer: An open circuit on the data line causing it to float to the pull-up rail

An open data line with a pull-up resistor will float to the positive supply (logic '1'), causing all bits to read as '1' regardless of what the driver is transmitting.

Question 21: How many bits are contained in each ARINC 429 data word?

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

Correct answer: 32 bits

Each ARINC 429 transmission consists of a 32-bit word, divided into a label field (bits 1–8), a source/destination identifier (bits 9–10), data field (bits 11–28), sign/status matrix (bits 29–30), and a parity bit (bit 32).

Question 22: When performing an ARINC 664 (AFDX) network test, a technician uses a network analyzer. Which parameter is most critical to verify for proper avionics bus operation?

Total network cable length
Bandwidth allocation gap (BAG) timing and jitter of virtual links (Correct answer)
Cable impedance at DC
Power spectral density of ambient RF noise

Correct answer: Bandwidth allocation gap (BAG) timing and jitter of virtual links

AFDX relies on deterministic scheduling via BAGs; excessive jitter can cause data to arrive outside its time window, disrupting avionics communication.

Question 23: What is the purpose of a squelch circuit in an aviation receiver?

Mute the receiver when no signal is present (Correct answer)
Amplify weak signals
Reduce transmitter power
Filter harmonics

Correct answer: Mute the receiver when no signal is present

The squelch circuit silences the audio output when received signal strength falls below a set threshold, eliminating background noise between transmissions.

Question 24: What quality metrics are most important in Electrical Troubleshooting?

Only financial metrics
No metrics are needed
Only speed of completion
Measurable outcomes, process compliance, and stakeholder satisfaction (Correct answer)

Correct answer: Measurable outcomes, process compliance, and stakeholder satisfaction

Quality in Electrical Troubleshooting is measured through multiple dimensions including outcomes, processes, and satisfaction.

Question 25: When checking a shorted wiring harness, a technician should use a/an:

High-voltage megohmmeter at 500V
Clamp-on ammeter around the harness
Standard ohmmeter to check pin-to-pin resistance (Correct answer)
Frequency counter

Correct answer: Standard ohmmeter to check pin-to-pin resistance

A standard ohmmeter can detect pin-to-pin shorts within a harness by revealing unexpectedly low resistance between conductors that should be isolated.

Question 26: What information must be included in a maintenance record entry per 14 CFR 43.9?

Aircraft serial number, owner name, and part numbers used
Only the technician's name and date
Work order number, cost, and supervisor approval
Description of work, date, aircraft total time, and certificated person's signature and certificate number (Correct answer)

Correct answer: Description of work, date, aircraft total time, and certificated person's signature and certificate number

14 CFR 43.9 requires the description of work, date, aircraft total time, and the certificated person's signature and certificate number.

Question 27: A CVR (Cockpit Voice Recorder) is required to retain audio from the last:

30 minutes of flight
4 hours of operation
2 hours of flight (Correct answer)
6 hours from wheels-off

Correct answer: 2 hours of flight

Current regulations (14 CFR 91.609) require CVRs to retain at least 2 hours of the most recent audio to capture enough data for accident investigation.

Question 28: An aircraft HF radio is being checked and exhibits low output power but correct frequency. The MOST likely cause is:

Defective PA (power amplifier) stage (Correct answer)
Failed frequency synthesizer
Faulty squelch circuit
Incorrect antenna coupler setting

Correct answer: Defective PA (power amplifier) stage

Low output power with correct frequency typically points to a failure in the PA stage, since frequency generation is handled separately by the synthesizer.

Question 29: Thermal runaway in a NiCd aircraft battery is dangerous because it can result in:

Increased battery capacity
A self-sustaining charging reaction that generates heat, gas, and potential fire (Correct answer)
Reduced avionics noise
Lower battery voltage output

Correct answer: A self-sustaining charging reaction that generates heat, gas, and potential fire

Thermal runaway occurs when heat from charging increases the battery's ability to accept charge, generating more heat in a feedback loop that can lead to fire, explosion, and toxic gas release.

Question 30: What is the purpose of an overvoltage protection relay in an aircraft electrical system?

To reset tripped circuit breakers automatically
To disconnect the alternator from the bus if output voltage rises above a safe threshold (Correct answer)
To regulate battery charging current
To balance load between two generators

Correct answer: To disconnect the alternator from the bus if output voltage rises above a safe threshold

The overvoltage protection relay monitors alternator output and automatically disconnects the alternator from the bus if voltage rises above approximately 31–32V (28V system) to protect sensitive avionics from damage.

Question 31: A technician uses a curve tracer to evaluate a transistor from an aircraft avionics power supply. Compared to a known-good device, the curves show early saturation at low collector voltage. This indicates:

The transistor has a higher-than-normal beta (gain)
The transistor's collector-emitter breakdown voltage is reduced, suggesting a damaged junction (Correct answer)
The base resistor in the circuit is too high
Normal transistor behavior under high temperature conditions

Correct answer: The transistor's collector-emitter breakdown voltage is reduced, suggesting a damaged junction

Early saturation at low collector voltage on a curve trace is a classic sign of reduced breakdown voltage, indicating junction damage.

Question 32: Under FAA regulations, who is authorized to approve avionics maintenance work for return to service on a certificated aircraft?

Any FAA-certificated mechanic
An FAA-certificated repairman with appropriate ratings or an A&P mechanic with IA (Correct answer)
Any person supervised by a licensed engineer
Only an FAA-certificated repairman with an avionics rating

Correct answer: An FAA-certificated repairman with appropriate ratings or an A&P mechanic with IA

Return-to-service approval for avionics maintenance requires a certificated repairman with appropriate ratings or an Airframe & Powerplant mechanic holding an Inspection Authorization (IA).

Question 33: Which Federal Aviation Regulation (FAR) part governs the installation and airworthiness of aircraft communication equipment?

FAR Part 43 and Part 91 (Correct answer)
FAR Part 65
FAR Part 121 only
FAR Part 61

Correct answer: FAR Part 43 and Part 91

FAR Part 43 covers maintenance and alteration of avionics, while Part 91 (and 121/135 as applicable) specifies equipment requirements and operational rules.

Question 34: What does the term 'double-break switching' mean in aircraft avionics maintenance safety context?

Applying two independent lock-out tags
Interrupting both the hot and return sides of a circuit simultaneously (Correct answer)
Using two circuit breakers in series for redundancy
Breaking the circuit at two physical locations

Correct answer: Interrupting both the hot and return sides of a circuit simultaneously

Double-break switching interrupts both the positive (hot) and return conductors simultaneously, ensuring complete circuit isolation during maintenance.

Question 35: On a glass cockpit aircraft, what does the magenta triangle on the navigation display (ND) typically represent?

Airport of departure
Traffic alert from TCAS
Top-of-descent point
Active waypoint or TO waypoint (Correct answer)

Correct answer: Active waypoint or TO waypoint

The magenta triangle on the ND indicates the active TO waypoint that the flight management system is currently navigating toward.

Question 36: The hexadecimal number 0xAF converted to decimal is:

185
155
165
175 (Correct answer)

Correct answer: 175

0xAF = (10 × 16) + 15 = 160 + 15 = 175 in decimal.

Question 37: A technician finds that an avionics connector pin is recessed (pushed back) in its housing. The CORRECT repair procedure is to:

Apply epoxy to secure the pin in position
Replace the entire connector assembly immediately
Use the approved extraction and insertion tool for that connector series (Correct answer)
Re-insert the pin using needle-nose pliers

Correct answer: Use the approved extraction and insertion tool for that connector series

Approved extraction and insertion tools must be used to prevent damage to the connector housing, pin contacts, and adjacent pins during repair.

Question 38: Which system in an aircraft is responsible for providing real-time navigation information to the pilot?

Flight Management System (FMS)
Engine Control Unit (ECU)
Inertial Navigation System (INS) (Correct answer)
Radar Altimeter

Correct answer: Inertial Navigation System (INS)

The Inertial Navigation System (INS) uses gyroscopes and accelerometers to continuously calculate an aircraft's position, orientation, and velocity. It provides independent, real-time navigation information to the pilot without relying on external signals, making it a critical system for flight.

Question 39: What does CRC stand for in the context of digital data communications?

Circuit Reset Command
Clock Rate Control
Carrier Reference Clock
Cyclic Redundancy Check (Correct answer)

Correct answer: Cyclic Redundancy Check

CRC (Cyclic Redundancy Check) is an error-detection algorithm that generates a checksum to verify data integrity during transmission.

Question 40: What are the key regulatory requirements affecting Electrical Troubleshooting?

Only federal regulations apply
There are no regulations
Regulations are optional guidelines
Compliance with applicable laws, industry standards, and licensing requirements specific to the field (Correct answer)

Correct answer: Compliance with applicable laws, industry standards, and licensing requirements specific to the field

Practitioners must comply with all applicable regulations, which may include federal, state, and industry-specific requirements.

Question 41: A Supplemental Type Certificate (STC) for a new avionics installation specifies a specific antenna placement. A technician installs the antenna 2 inches from the approved location. This action constitutes a:

Deviation acceptable within manufacturing tolerances
No violation if the system passes bench testing
Minor alteration requiring only logbook entry
Major alteration requiring FAA Form 337 (Correct answer)

Correct answer: Major alteration requiring FAA Form 337

Deviating from STC installation instructions constitutes a major alteration requiring FAA Form 337, as the STC defines the approved data for the installation.

Question 42: What fundamental gyroscopic property allows an attitude indicator (artificial horizon) to maintain a reference to the earth's horizon?

Precession — the gyro tilts 90° from an applied force
Resonance — the gyro vibrates at the earth's natural frequency
Rigidity in space — a spinning gyro resists any change to its orientation (Correct answer)
Pendulosity — the gyro is weighted to seek the gravitational vertical

Correct answer: Rigidity in space — a spinning gyro resists any change to its orientation

Gyroscopic rigidity in space (also called gyroscopic inertia) means that a rapidly spinning mass tends to maintain its plane of rotation in a fixed orientation relative to inertial space. The attitude indicator exploits this to keep the gyro aligned with the true horizon as the aircraft maneuvers around it.

Question 43: What is the maximum length of time a calibration sticker on a test instrument can be expired before the instrument must be recalibrated before use on an aircraft?

No grace period — any instrument with an expired calibration sticker must NOT be used on aircraft (Correct answer)
30 days grace period is standard
90 days if stored in a controlled environment
6 months for digital instruments

Correct answer: No grace period — any instrument with an expired calibration sticker must NOT be used on aircraft

Instruments with expired calibration certificates must not be used on aircraft; there is no grace period because calibration accuracy cannot be guaranteed after expiration.

Question 44: Which organization is primarily responsible for setting aviation safety regulations in the United States?

Federal Aviation Administration (FAA) (Correct answer)
NASA
International Civil Aviation Organization (ICAO)
National Transportation Safety Board (NTSB)

Correct answer: Federal Aviation Administration (FAA)

The Federal Aviation Administration (FAA) is the primary governmental authority responsible for regulating all aspects of civil aviation in the United States. Its mission includes ensuring the safety of air travel by setting and enforcing aviation safety regulations and standards.

Question 45: Which of the following best describes a 'red tag' on an avionics component?

The part is serviceable and ready for installation
The part is on order from the manufacturer
The part is unserviceable and must not be installed (Correct answer)
The part requires lubrication before installation

Correct answer: The part is unserviceable and must not be installed

A red tag indicates an unserviceable part that must not be installed on an aircraft until it has been inspected, repaired, or replaced.

Question 46: An aircraft bus bar shows 26V on one side and 24V on the other side under load. The technician should suspect:

Excessive generator voltage
A high-resistance connection or corroded bus bar (Correct answer)
Normal operation within tolerance
A faulty voltmeter

Correct answer: A high-resistance connection or corroded bus bar

A 2V drop across a bus bar indicates a high-resistance fault such as corrosion, loose hardware, or oxidation at the connection point.

Question 47: What is the primary purpose of standardized procedures in Navigation Equipment?

To ensure consistency, safety, and quality across all practitioners (Correct answer)
To create unnecessary bureaucracy
To slow down work processes
To benefit only management

Correct answer: To ensure consistency, safety, and quality across all practitioners

Standardized procedures ensure that all practitioners deliver consistent, safe, and high-quality outcomes.

Question 48: What is the output of an XOR gate when both of its inputs are logic HIGH?

LOW (Correct answer)
HIGH
Depends on the clock signal
Undefined — depends on propagation delay

Correct answer: LOW

An XOR (Exclusive OR) gate outputs LOW when both inputs are the same state (both HIGH or both LOW).

Question 49: A 4-bit binary counter has a modulus of:

32
16 (Correct answer)
8
4

Correct answer: 16

A 4-bit counter can represent 2^4 = 16 unique states (0 through 15), giving it a modulus of 16.

Question 50: When testing a VOR receiver, an approved VOR test facility (VOT) should produce what indication on a correctly functioning receiver?

000° radial with TO flag and centered CDI (Correct answer)
090° radial with FROM flag and full-scale CDI deflection
360° radial with FROM flag and centered CDI
180° radial with TO flag and centered CDI

Correct answer: 000° radial with TO flag and centered CDI

A VOT transmits the 360° radial omnidirectionally; a properly functioning receiver tuned to a VOT should show 000° (or 360°) with a TO flag and a centered CDI within ±4°.

Question 51: Which frequency band does a typical radio altimeter operate in?

VHF (108–118 MHz)
Ka-band (35 GHz)
C-band (4.2–4.4 GHz) (Correct answer)
UHF (329–335 MHz)

Correct answer: C-band (4.2–4.4 GHz)

Radio altimeters operate in the C-band at 4.2–4.4 GHz, transmitting FM continuous-wave signals toward the ground to measure altitude above terrain.

Question 52: A technician performing a functional test notices an avionics unit fails its self-test only when the aircraft is at operating temperature. The best diagnostic strategy is to:

Use a thermal camera or temperature-sensitive spray to identify heat-sensitive components while monitoring with a digital multimeter (Correct answer)
Increase the cooling airflow and retest without further investigation
Test the unit only at room temperature and clear the fault code
Replace the unit immediately since intermittent faults are not repairable

Correct answer: Use a thermal camera or temperature-sensitive spray to identify heat-sensitive components while monitoring with a digital multimeter

Thermal imaging or temperature spray helps isolate components whose electrical characteristics shift with temperature, causing the intermittent failure.

Question 53: Which instrument is used to measure insulation resistance between an aircraft wire and its shield or conduit?

Multimeter on resistance setting
Megohmmeter (megger) (Correct answer)
Oscilloscope
Clamp-on ammeter

Correct answer: Megohmmeter (megger)

A megohmmeter applies high voltage to reveal insulation degradation that a standard ohmmeter cannot detect.

Question 54: What type of memory is typically used to store the boot firmware in an avionics Line Replaceable Unit (LRU)?

Magnetic core memory
DRAM
Flash (EEPROM) (Correct answer)
SRAM

Correct answer: Flash (EEPROM)

Flash (EEPROM) is non-volatile and retains firmware without power, making it standard for avionics LRU boot code storage.

Question 55: The purpose of performing a 'split-half' troubleshooting method on a long wiring run is to:

Efficiently isolate the fault location by testing the midpoint first (Correct answer)
Test both ends of the wiring simultaneously
Verify wire gauge is consistent throughout the run
Replace half the wiring at a time to reduce cost

Correct answer: Efficiently isolate the fault location by testing the midpoint first

Testing the midpoint of a circuit first eliminates half the possible fault locations with each measurement, minimizing total tests required.

Question 56: How should risk be managed in Navigation Equipment?

Risk management is not necessary
By avoiding all risk entirely
Through identification, assessment, mitigation strategies, and ongoing monitoring of potential risks (Correct answer)
By ignoring potential problems

Correct answer: Through identification, assessment, mitigation strategies, and ongoing monitoring of potential risks

Effective risk management involves a systematic process of identifying, evaluating, and addressing potential threats.

Question 57: In ARINC 429 digital data bus, data words are transmitted:

Simultaneously on 32 parallel lines
As analog voltage levels on a single wire
Via optical fiber at 100 Mbps
Serially, one bit at a time on a differential pair (Correct answer)

Correct answer: Serially, one bit at a time on a differential pair

ARINC 429 uses serial transmission of 32-bit words over a shielded twisted-pair differential bus.

Question 58: What does SELCAL stand for in aircraft communication systems?

Self-Calibrating Amplifier Loop
Selective Calling System (Correct answer)
Satellite Electronic Communication Link
Sequential Electronic Link Call

Correct answer: Selective Calling System

SELCAL (Selective Calling System) allows ground stations to alert a specific aircraft over HF/VHF without requiring continuous radio monitoring by the crew.

Question 59: Which logic gate produces a HIGH output only when all inputs are HIGH?

OR gate
AND gate (Correct answer)
NAND gate
NOR gate

Correct answer: AND gate

An AND gate output is HIGH only when every input is simultaneously HIGH.

Question 60: What is the primary function of a Traffic Collision Avoidance System (TCAS)?

Track cargo weight and balance
Monitor ATC radar returns
Issue resolution advisories to avoid mid-air collisions (Correct answer)
Provide terrain proximity warnings

Correct answer: Issue resolution advisories to avoid mid-air collisions

TCAS interrogates transponders of nearby aircraft and issues resolution advisories (RAs) to pilots to prevent mid-air collisions.

Question 61: A technician signs off on an annual inspection. Where must the inspection sign-off entry appear?

In the FAA registry database directly
In the aircraft's maintenance records (logbooks) (Correct answer)
Only in the shop's work order file
On the aircraft's instrument panel placard

Correct answer: In the aircraft's maintenance records (logbooks)

Annual inspection results must be entered in the aircraft maintenance records (logbooks) per 14 CFR 43.11.

Question 62: A technician discovers an in-service failure of an avionics component that could affect airworthiness. Under 14 CFR 121.703, who is responsible for filing the Service Difficulty Report?

The FAA district office directly
The aircraft owner/operator (Correct answer)
The NTSB
The original equipment manufacturer

Correct answer: The aircraft owner/operator

Under 14 CFR 121.703, air carriers (owner/operators) are responsible for reporting safety-of-flight malfunctions and failures to the FAA via Service Difficulty Reports.

Question 63: Under 14 CFR Part 145, a certificated repair station must make its maintenance records available for inspection by the FAA for how long?

Six months
Five years
One year
Two years (Correct answer)

Correct answer: Two years

14 CFR Part 145 requires certificated repair stations to retain and make maintenance records available to the FAA for at least two years.

Question 64: How should ethical dilemmas be handled in Avionics Systems?

Ignore ethical concerns
Make decisions based solely on personal preference
Follow established ethical guidelines, consult with supervisors, and prioritize stakeholder welfare (Correct answer)
Always choose the cheapest option

Correct answer: Follow established ethical guidelines, consult with supervisors, and prioritize stakeholder welfare

Ethical decision-making requires following professional guidelines and prioritizing the welfare of all stakeholders.

Question 65: What test instrument is used to verify antenna VSWR (Voltage Standing Wave Ratio) in aircraft communications?

Wattmeter/SWR meter (Correct answer)
Multimeter
Oscilloscope
Spectrum analyzer only

Correct answer: Wattmeter/SWR meter

A wattmeter or SWR meter measures forward and reflected RF power to calculate VSWR, confirming antenna system impedance matching.

Question 66: What is the primary function of a capacitor in an electronic circuit?

To store electrical energy temporarily (Correct answer)
To convert alternating current to direct current
To amplify electrical signals
To measure electrical current

Correct answer: To store electrical energy temporarily

A capacitor's primary function in an electronic circuit is to store electrical energy temporarily in an electric field. It can then release this energy back into the circuit, making it crucial for filtering, timing, and power supply smoothing applications.

Question 67: What is 'latent ESD damage' in an avionics component?

Surface pitting on connector pins caused by repeated discharge events
Damage that occurs only during an actual lightning strike on the aircraft
Partial damage that does not cause immediate functional failure but degrades the component so it fails prematurely during service (Correct answer)
Damage detectable only by electron microscope imaging immediately after the ESD event

Correct answer: Partial damage that does not cause immediate functional failure but degrades the component so it fails prematurely during service

Latent ESD damage is the most dangerous form because the component passes all functional checks immediately after the ESD event but has weakened semiconductor junctions. The component then fails in service — often in a mission-critical situation — long after the original handling error.

Question 68: Which approach is most effective for problem-solving in Electrical Troubleshooting?

Always asking someone else
Systematic analysis followed by evidence-based decision making (Correct answer)
Ignoring the problem until it resolves itself
Random trial and error

Correct answer: Systematic analysis followed by evidence-based decision making

Systematic, evidence-based approaches lead to more reliable solutions than ad hoc methods.

Question 69: When an AET completes an avionics repair, the return-to-service entry must be signed by a person holding which certificate?

Powerplant Mechanic
Flight Engineer
Airframe and Powerplant Mechanic or Repairman (Correct answer)
Private Pilot

Correct answer: Airframe and Powerplant Mechanic or Repairman

Only an FAA-certificated Airframe and Powerplant (A&P) mechanic, Repairman, or authorized repair station representative may approve an aircraft for return to service after maintenance.

Question 70: What is a common symptom of a broken coaxial antenna feed line in a VHF COM system?

Excessive audio distortion
Very short transmission range and reduced receive sensitivity (Correct answer)
Stuck squelch
No power to the radio

Correct answer: Very short transmission range and reduced receive sensitivity

A broken or high-VSWR coaxial feed line causes significant signal loss, resulting in greatly reduced transmit range and receive sensitivity.

Question 71: Which test instrument captures and simultaneously displays multiple digital signal states to aid in troubleshooting microprocessor-based avionics?

Logic analyzer (Correct answer)
Impedance bridge
Function generator
Multimeter

Correct answer: Logic analyzer

A logic analyzer captures multi-channel digital signals and displays them as timed waveforms, making it ideal for debugging data bus and microprocessor faults.

Question 72: A technician performs a major repair on an avionics system. Within how many days must FAA Form 337 be submitted to the FAA Aircraft Registry?

30 days (Correct answer)
60 days
90 days
No submission required if kept with the aircraft

Correct answer: 30 days

A copy of Form 337 for a major repair or alteration must be forwarded to the FAA Aircraft Registry in Oklahoma City within 48 hours—commonly cited as 30 days for record submission to the FSDO.

Question 73: What type of pressure does the pitot tube sense?

Dynamic (impact) pressure only
Total ram air pressure (static + dynamic) (Correct answer)
Differential pressure between the upper and lower wing surfaces
Static atmospheric pressure only

Correct answer: Total ram air pressure (static + dynamic)

The pitot tube is forward-facing and captures total (ram) air pressure — the sum of static atmospheric pressure and dynamic pressure created by the aircraft's forward motion. The airspeed indicator then subtracts static pressure (from the static port) to derive dynamic pressure, from which airspeed is calculated.

Question 74: What is the primary function of a watchdog timer in an avionics microprocessor system?

Reset the processor if software fails to respond within a defined time interval (Correct answer)
Monitor and log bus voltage levels to detect power anomalies
Track total elapsed flight hours for maintenance scheduling
Synchronize timing across multiple ARINC 429 data buses

Correct answer: Reset the processor if software fails to respond within a defined time interval

A watchdog timer resets the CPU if the running software fails to periodically reset the timer, preventing the system from being stuck in a software fault state.

Question 75: An FAA-certificated avionics technician may legally perform a major alteration on a certificated aircraft only if the work is performed in accordance with:

Any published aviation industry standard
The technician's best professional judgment
Manufacturer's service manual only
FAA-approved data such as an STC, AD, or FAA-approved engineering order (Correct answer)

Correct answer: FAA-approved data such as an STC, AD, or FAA-approved engineering order

Major alterations must be performed in accordance with FAA-approved data, which includes STCs, ADs, FAA-approved engineering orders, or other data acceptable to the FAA.

Question 76: When using a pitot-static test set to perform an altimeter check, the technician must ensure the aircraft's static system is:

Leak-free, as leaks will cause the altimeter to read incorrectly (Correct answer)
Pressurized to twice the maximum altitude to be tested
Connected only to the primary altimeter during the test
Vented to ambient before applying test pressure

Correct answer: Leak-free, as leaks will cause the altimeter to read incorrectly

Any leak in the static system will allow ambient air to enter, preventing the test set from maintaining the correct simulated altitude.

Question 77: Which modulation type is used by standard VHF aviation communication radios for voice transmissions?

DSB-SC (Double Sideband Suppressed Carrier)
SSB (Single Sideband)
FM (Frequency Modulation)
AM (Amplitude Modulation) (Correct answer)

Correct answer: AM (Amplitude Modulation)

Aviation VHF communication uses AM because it allows multiple signals to coexist on the same frequency and is compatible with legacy ground infrastructure.

Question 78: Which type of data transmission sends bits one at a time sequentially over a single channel?

Synchronous burst transmission
Multiplex transmission
Serial transmission (Correct answer)
Parallel transmission

Correct answer: Serial transmission

Serial transmission sends data bit-by-bit over a single wire, as used in avionics buses like ARINC 429 and RS-232.

Question 79: What is the maximum civil penalty that can be assessed for a single violation of an FAA regulation under 49 U.S.C. § 46301?

$1,000
$25,000 (Correct answer)
$10,000
$50,000

Correct answer: $25,000

Under 49 U.S.C. § 46301, the FAA may assess a civil penalty of up to $25,000 per violation for individuals who violate aviation safety regulations.

Question 80: What makes a professional competent in Navigation Equipment?

A combination of education, practical experience, ongoing learning, and adherence to professional standards (Correct answer)
Only certifications matter
Only experience matters
Only formal education matters

Correct answer: A combination of education, practical experience, ongoing learning, and adherence to professional standards

Competence requires the integration of knowledge, skills, experience, and professional conduct.

Question 81: Which instrument is the correct tool for verifying the output frequency of an aircraft inverter?

Megohmmeter
Frequency counter or oscilloscope (Correct answer)
Capacitance bridge
Digital multimeter set to AC volts

Correct answer: Frequency counter or oscilloscope

A frequency counter or oscilloscope directly measures the cycles per second of an inverter's AC output.

Question 82: A voltage drop test across a switch shows 1.8 volts while the circuit is operating. This indicates:

An open circuit downstream
Reverse polarity in the circuit
High resistance in the switch contacts (Correct answer)
Normal switch operation

Correct answer: High resistance in the switch contacts

Excessive voltage drop across a closed switch indicates high contact resistance due to corrosion, pitting, or wear.

Question 83: An aircraft Transformer Rectifier Unit (TRU) converts:

400 Hz AC to 60 Hz AC for ground equipment
115V AC three-phase to 28V DC (Correct answer)
28V DC to 115V AC for large loads
DC battery power to AC for avionics

Correct answer: 115V AC three-phase to 28V DC

A TRU uses a transformer to step down voltage and a rectifier bridge to convert three-phase 115V AC aircraft power into 28V DC for DC-powered systems.

Question 84: What role does continuing education play in Navigation Equipment?

Only beneficial for management
It is optional and rarely helpful
Only required for new practitioners
Keeping practitioners current with evolving best practices and new developments (Correct answer)

Correct answer: Keeping practitioners current with evolving best practices and new developments

Continuing education ensures practitioners stay current with advances in their field.

Question 85: A ground power unit (GPU) is connected to an aircraft for maintenance. What precaution must be taken before connecting the GPU to avoid damage to avionics?

Run the aircraft engine simultaneously
Ensure all avionics master switches are ON
Set all transponders to STANDBY mode only
Verify GPU voltage and polarity match aircraft requirements before connecting (Correct answer)

Correct answer: Verify GPU voltage and polarity match aircraft requirements before connecting

Before connecting a GPU, technicians must verify that the GPU output voltage and polarity are correct for the aircraft system to prevent damage to sensitive avionics and electrical components.

Question 86: An aircraft has multiple avionics units failing simultaneously. The technician should first suspect:

Software corruption in each unit
A common power bus, ground, or power supply fault (Correct answer)
EMI interference from an external source
Individual component failures in each unit

Correct answer: A common power bus, ground, or power supply fault

Simultaneous failure of multiple units sharing a common bus or ground points to a single upstream fault rather than multiple independent component failures.

Question 87: What does 'BITE' stand for in avionics maintenance contexts?

Binary Interface Test Engine
Bus Isolation and Test Electronics
Built-In Test Equipment (Correct answer)
Basic Integrated Test Equipment

Correct answer: Built-In Test Equipment

BITE stands for Built-In Test Equipment, onboard self-test circuitry that monitors LRU health and stores fault codes for maintenance retrieval.

Question 88: What does the term 'EFIS' stand for in modern avionics?

Encoded Flight Indicator Standard
Enhanced Flight Information Software
Electronic Flight Instrument System (Correct answer)
Electronic Frequency Integration System

Correct answer: Electronic Flight Instrument System

EFIS stands for Electronic Flight Instrument System, replacing traditional electromechanical gauges with digital displays.

Question 89: What is the nominal frequency of AC power produced by most commercial aircraft generators?

50 Hz
400 Hz (Correct answer)
60 Hz
800 Hz

Correct answer: 400 Hz

Aircraft AC generators produce power at 400 Hz, which allows smaller, lighter transformers and motors compared to the 60 Hz used in commercial ground power.

Question 90: What role does continuing education play in Avionics Systems?

It is optional and rarely helpful
Keeping practitioners current with evolving best practices and new developments (Correct answer)
Only beneficial for management
Only required for new practitioners

Correct answer: Keeping practitioners current with evolving best practices and new developments

Continuing education ensures practitioners stay current with advances in their field.

Question 91: During an interphone system check, audio is heard in the cockpit but not at the forward attendant station. Which component is MOST suspect?

Interphone amplifier serving the forward cabin zone (Correct answer)
Cockpit audio control panel
Audio frequency oscillator
Volume control in the cockpit

Correct answer: Interphone amplifier serving the forward cabin zone

If only one station is silent, the amplifier or wiring serving that specific zone is the most likely fault rather than a shared component.

ASTM NCATT AET – Aircraft Electronics Technician

The ASTM NCATT AET certification exam validates the knowledge and skills of aircraft electronics technicians in areas including AC/DC fundamentals, digital techniques, RF energy, test equipment, avionics systems, and aviation safety regulations.

Questions

120 min

Time Limit

73%

To Pass

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