ASTM NCATT AET – Aircraft Electronics Technician — Questions and Answers

Question 1: A SATCOM system on an aircraft provides communication primarily via:

UHF line-of-sight links
Geostationary or LEO satellites (Correct answer)
HF sky-wave propagation
Ground-based VHF repeaters

Correct answer: Geostationary or LEO satellites

SATCOM uses geostationary (e.g., Inmarsat) or low Earth orbit satellites to relay voice and data communications globally, including over oceans.

Question 2: During an aircraft battery capacity check, what indicates a serviceable NiCd battery?

Battery temperature stays below ambient during a 1-hour discharge
Individual cells measure exactly 1.2V under full charge with no variation
Battery delivers rated ampere-hour capacity to a specified end-cell voltage (Correct answer)
Battery maintains charge indefinitely with no load applied

Correct answer: Battery delivers rated ampere-hour capacity to a specified end-cell voltage

A NiCd battery passes a capacity check when it can deliver its rated ampere-hour capacity while maintaining voltage above the minimum end-cell cutoff voltage.

Question 3: An airborne weather radar system operating in X-band operates at approximately:

3 GHz
9.3–9.5 GHz (Correct answer)
1 GHz
35 GHz

Correct answer: 9.3–9.5 GHz

Airborne weather radar X-band systems operate at approximately 9.3–9.5 GHz, which provides good precipitation detection while keeping antenna size manageable.

Question 4: In an Inertial Reference System (IRS), what sensors are used to measure angular rate?

Ring laser gyroscopes or fiber optic gyroscopes (Correct answer)
Barometric sensors
GPS receivers
Magnetometers

Correct answer: Ring laser gyroscopes or fiber optic gyroscopes

Modern IRS units use ring laser gyroscopes (RLGs) or fiber optic gyroscopes (FOGs) to measure angular rate without moving parts.

Question 5: In a typical general aviation aircraft, what is the primary function of the aircraft's alternator?

To charge the battery and power the electrical bus during engine operation (Correct answer)
To power the landing gear actuators
To provide emergency lighting only
To start the engine

Correct answer: To charge the battery and power the electrical bus during engine operation

The alternator charges the battery and supplies electrical power to the aircraft's bus systems whenever the engine is running above a threshold RPM.

Question 6: Aircraft wiring that shows discoloration (brown or black insulation) most likely indicates:

Normal aging of the insulation material
Exposure to hydraulic fluid
Overheating due to excessive current or poor connection (Correct answer)
Correct wire gauge for the application

Correct answer: Overheating due to excessive current or poor connection

Discolored or charred insulation is a sign of overheating, caused by overcurrent, high-resistance connections, or incorrect wire gauge.

Question 7: Which of the following is the CORRECT way to handle a suspected counterfeit avionics part discovered in the supply chain?

Quarantine the part and report it to the FAA via a Suspected Unapproved Parts (SUP) notification (Correct answer)
Install it and monitor for discrepancies
Return it to the supplier for a refund
Destroy it immediately to prevent misuse

Correct answer: Quarantine the part and report it to the FAA via a Suspected Unapproved Parts (SUP) notification

Suspected counterfeit or unapproved parts must be quarantined and reported to the FAA via the Suspected Unapproved Parts program to protect the fleet.

Question 8: After completing avionics maintenance, a technician notices the aircraft skin has several small scratches near the avionics bay access panel. The CORRECT action is to:

Ignore scratches smaller than 1/8 inch
Document the damage in the maintenance record and defer to sheet metal inspection (Correct answer)
Polish the scratches with abrasive compound and return to service
Apply touch-up paint immediately to prevent corrosion

Correct answer: Document the damage in the maintenance record and defer to sheet metal inspection

Any new airframe damage found during maintenance must be documented and assessed by qualified personnel before return to service.

Question 9: Under 14 CFR Part 39, an Airworthiness Directive (AD) is legally classified as:

A recommendation that operators should follow
An advisory from the manufacturer only
A Federal Regulation with the force of law (Correct answer)
An optional upgrade program

Correct answer: A Federal Regulation with the force of law

Airworthiness Directives issued under 14 CFR Part 39 are Federal Regulations and must be complied with; non-compliance renders the aircraft unairworthy.

Question 10: What does the term 'EFIS' stand for in modern avionics?

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

Correct answer: Electronic Flight Instrument System

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

Question 11: Which avionics component converts analog sensor signals to digital format for processing by the flight management computer?

Remote Data Concentrator (RDC)
Analog-to-Digital Converter (ADC) (Correct answer)
Digital-to-Analog Converter (DAC)
Signal Multiplexer

Correct answer: Analog-to-Digital Converter (ADC)

An Analog-to-Digital Converter (ADC) translates analog sensor voltages into digital data that avionics computers can process.

Question 12: TCAS II issues Resolution Advisories (RAs) by coordinating with the intruder aircraft via:

VHF voice communication
ACARS messaging
ATC radar instructions
Mode S data link at 1030/1090 MHz (Correct answer)

Correct answer: Mode S data link at 1030/1090 MHz

TCAS II units coordinate complementary RAs between aircraft using the Mode S transponder data link on 1030 MHz (interrogation) and 1090 MHz (reply) frequencies.

Question 13: Which Federal Aviation Regulation (FAR) part governs the installation and airworthiness of aircraft communication equipment?

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

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 14: What is the correct first step when active corrosion is discovered on an aircraft structure during inspection?

Seal the corroded area with epoxy topcoat to exclude oxygen
Apply a penetrating oil to neutralize the corrosion and prevent further spread
Apply a zinc chromate primer directly over the corroded area to seal it
Remove all corrosion mechanically or chemically before applying any corrosion-inhibiting treatment or primer (Correct answer)

Correct answer: Remove all corrosion mechanically or chemically before applying any corrosion-inhibiting treatment or primer

Primer and sealant applied over active corrosion trap moisture and corrosion products against the metal, allowing the corrosion to continue undetected underneath. The corroded material must be fully removed first, the base metal restored, and then primer and protective coatings applied.

Question 15: In ARINC 629 multi-transmitter data bus used on the Boeing 777, how is bus access controlled?

Priority levels are hard-wired into each LRU at manufacture
A central bus controller grants access tokens to each LRU
Time-division multiplexing assigns fixed slots to each transmitter
Each terminal uses a decentralized CSMA/CA protocol with periodic and aperiodic transmission (Correct answer)

Correct answer: Each terminal uses a decentralized CSMA/CA protocol with periodic and aperiodic transmission

ARINC 629 uses a decentralized protocol where each terminal autonomously manages periodic and aperiodic data transmission without a central bus controller.

Question 16: What is the frequency range of the aviation VHF communication band?

108.0–117.95 MHz
406.0–420.0 MHz
225.0–399.975 MHz
118.0–136.975 MHz (Correct answer)

Correct answer: 118.0–136.975 MHz

Aviation VHF communication operates from 118.0 to 136.975 MHz, while 108–117.95 MHz is reserved for VOR/ILS navigation.

Question 17: Which type of corrosion is characterized by a white or gray powdery deposit on aluminum aircraft structures?

Uniform surface oxidation (aluminum oxide formation) (Correct answer)
Stress corrosion cracking
Galvanic corrosion
Pitting corrosion

Correct answer: Uniform surface oxidation (aluminum oxide formation)

When aluminum oxidizes, it forms aluminum oxide (Al₂O₃) — a white or gray powdery film. Unlike iron rust, aluminum oxide forms a tight adherent layer that can slow further corrosion, but the powdery appearance is a clear visual indicator of surface oxidation.

Question 18: Which type of fire extinguisher is approved for use on an avionics bench fire involving energized electrical equipment?

Class C dry chemical or CO2 extinguisher (Correct answer)
Class D metal-powder extinguisher
Class B foam extinguisher
Class A water-based extinguisher

Correct answer: Class C dry chemical or CO2 extinguisher

Class C extinguishers (CO2 or dry chemical) are rated for energized electrical equipment fires because they use non-conductive extinguishing agents.

Question 19: 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 20: An ammeter is connected in series with an aircraft circuit to check current flow. When the circuit is activated, the meter reads zero. This indicates:

Normal low-current operation
An open circuit between the power source and the load (Correct answer)
Correct operation at idle
A short circuit in the wiring

Correct answer: An open circuit between the power source and the load

Zero current in an energized series circuit indicates an open that prevents current from flowing through the ammeter and load.

Question 21: What does a RAIM (Receiver Autonomous Integrity Monitoring) function do in a GPS receiver?

Detects faulty satellite data using redundant satellites (Correct answer)
Amplifies weak satellite signals
Corrects for ionospheric delay errors
Switches to INS when GPS is unavailable

Correct answer: Detects faulty satellite data using redundant satellites

RAIM uses extra visible satellites beyond the minimum required to self-check GPS integrity and alert crew if a satellite is providing erroneous data.

Question 22: What does the term 'squelch' refer to in an aviation radio receiver?

A circuit that mutes the receiver output in the absence of a valid signal (Correct answer)
A device that boosts weak incoming signals
A filter that removes sideband noise
A modulator that encodes audio before transmission

Correct answer: A circuit that mutes the receiver output in the absence of a valid signal

Squelch suppresses receiver output when signal strength falls below a threshold, preventing the cockpit from being flooded with static noise between transmissions.

Question 23: What frequency range is used by the ADF system's NDB ground stations?

108–117.95 MHz VHF
190–1750 kHz LF/MF (Correct answer)
960–1215 MHz L-band
329–335 MHz UHF

Correct answer: 190–1750 kHz LF/MF

Non-Directional Beacons (NDB) transmit in the low frequency/medium frequency range of 190–1750 kHz, which ADF receivers tune to determine bearing.

Question 24: In a microcontroller used in aircraft fuel management, what is the purpose of a watchdog timer?

To measure fuel flow rate electronically
To delay startup until all systems are initialized
To reset the processor if software fails to service the timer within a set interval (Correct answer)
To synchronize the fuel pump motor speed

Correct answer: To reset the processor if software fails to service the timer within a set interval

A watchdog timer automatically resets the microcontroller if the main program becomes stuck and fails to periodically 'kick' (service) the timer.

Question 25: Which component in an aircraft’s electronic system converts electrical energy into mechanical movement?

Diode
Relay (Correct answer)
Transformer
Capacitor

Correct answer: Relay

A relay is an electrically operated switch that uses an electromagnet to open or close contacts. When an electrical current flows through its coil, it creates a magnetic field that moves a lever, converting electrical energy into a mechanical switching action to control other circuits.

Question 26: What is the purpose of an overvoltage protection relay in an aircraft electrical system?

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
To reset tripped circuit breakers automatically

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 27: How should an Aircraft Electronics Technician handle discrepancies found during an inspection?

Ignore them if they seem minor
Fix them without documenting the changes
Record them thoroughly and report them to the relevant authority (Correct answer)
Wait until the end of the day to document all discrepancies

Correct answer: Record them thoroughly and report them to the relevant authority

Discrepancies found during an inspection, regardless of their perceived severity, must be thoroughly recorded and reported to the relevant authority. This ensures that all potential issues are documented, assessed, and addressed appropriately, maintaining the aircraft's airworthiness and safety standards. Ignoring or undocumented fixes can lead to serious safety hazards, regulatory non-compliance, and compromise the integrity of the aircraft.

Question 28: 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 29: Which of the following best describes the function of a BITE (Built-In Test Equipment) system?

Onboard self-test circuitry that monitors and reports system faults automatically (Correct answer)
An external bench tester used to qualify LRUs before installation
A dedicated oscilloscope built into the aircraft instrument panel
A handheld tool used to inject test signals into avionics buses

Correct answer: Onboard self-test circuitry that monitors and reports system faults automatically

BITE is embedded within avionics units to continuously or on-command perform self-tests and store fault codes for maintenance retrieval.

Question 30: 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.

Question 31: 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 32: What resistance value should a properly functioning ESD wrist strap measure when tested with a wrist strap checker?

Approximately 1 megohm (1 MΩ) (Correct answer)
Less than 10 ohms
Greater than 100 megohms (open circuit)
0 ohms (dead short to ground)

Correct answer: Approximately 1 megohm (1 MΩ)

A correctly functioning ESD wrist strap contains a 1 MΩ resistor in series. This provides enough resistance to protect the technician from electrical shock while still allowing static charge to drain safely to ground. A dead short (0 Ω) would create a shock hazard.

Question 33: An aircraft inverter converts aircraft DC power into AC power primarily to supply which type of equipment?

AC-powered instruments and avionics that require 115V 400 Hz AC (Correct answer)
Landing lights
Engine ignition systems
DC motors and actuators

Correct answer: AC-powered instruments and avionics that require 115V 400 Hz AC

Inverters convert 28V DC bus power to 115V 400 Hz AC to power AC instruments, gyros, and some avionics in aircraft that do not have AC generators.

Question 34: A Technical Standard Order (TSO) authorization indicates that avionics equipment meets which standard?

Manufacturer's internal quality standard
Minimum FAA performance standard (Correct answer)
Military performance specification
RTCA DO-178C software standard only

Correct answer: Minimum FAA performance standard

A TSO authorization means the equipment meets the minimum performance standards specified in the applicable TSO, ensuring baseline airworthiness for installation.

Question 35: What type of information can an oscilloscope display that is critical for diagnosing electronic circuit issues?

Electrical resistance values
Temperature changes over time
The color of electrical signals
Voltage and current waveforms over time (Correct answer)

Correct answer: Voltage and current waveforms over time

An oscilloscope is a vital diagnostic tool that graphically displays voltage signals as a function of time, allowing technicians to visualize their waveforms. This capability is critical for diagnosing electronic circuit issues because it reveals the shape, amplitude, and timing of signals. By observing these characteristics, technicians can identify anomalies, distortions, or incorrect timing that indicate faults, providing a dynamic view of circuit behavior.

Question 36: Why is it essential for an Aircraft Electronics Technician to maintain detailed records of all maintenance activities?

To avoid the need for further inspections
To meet personal job performance goals
To ensure compliance with aviation regulations and provide a history of work performed (Correct answer)
To improve personal time management

Correct answer: To ensure compliance with aviation regulations and provide a history of work performed

Maintaining detailed records of all maintenance activities is crucial for an Aircraft Electronics Technician to ensure compliance with stringent aviation regulations and provide a comprehensive history of work performed. These records serve as vital documentation for airworthiness, traceability, and accountability, supporting future troubleshooting, inspections, and regulatory audits. Accurate documentation is fundamental to aircraft safety and operational integrity.

Question 37: Which Boolean expression correctly represents the output of an XNOR gate with inputs A and B?

A ⊕ B
A + B
NOT(A ⊕ B) (Correct answer)
A · B

Correct answer: NOT(A ⊕ B)

An XNOR gate is the complement of XOR, producing HIGH when inputs are equal: output = NOT(A ⊕ B).

Question 38: In a twin-engine aircraft with two generators, what component automatically connects both generators to share the electrical load?

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

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

Mute the receiver when no signal is present (Correct answer)
Reduce transmitter power
Amplify weak signals
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 40: Which approach is most effective for problem-solving in Electrical Troubleshooting?

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

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

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

Question 41: A VOR receiver measures the phase difference between which two signals?

9960 Hz subcarrier and 30 Hz variable signals
AM reference and FM variable signals
UHF pulse and VHF carrier signals
30 Hz reference and 30 Hz variable signals (Correct answer)

Correct answer: 30 Hz reference and 30 Hz variable signals

VOR bearing is determined by comparing the phase of the 30 Hz omnidirectional reference signal against the 30 Hz variable phase signal.

Question 42: When an avionics maintenance task requires working at night in the aircraft hangar, which lighting requirement applies to ensure safety and work quality?

Any available lighting is acceptable as long as the technician can see the work area
Only aircraft-mounted lighting may be used to prevent electrostatic hazards
Lighting must meet a minimum of 30 foot-candles at the work surface per OSHA 1910.303 guidelines (Correct answer)
Natural daylight must supplement artificial lighting for color-critical wire identification

Correct answer: Lighting must meet a minimum of 30 foot-candles at the work surface per OSHA 1910.303 guidelines

OSHA standards require a minimum illumination level at work surfaces to ensure technicians can accurately read wiring colors, labels, and torque marks.

Question 43: When using a clamp-on ammeter to measure AC current in an aircraft wiring harness, the technician should ensure which of the following?

Only one conductor passes through the clamp jaw (Correct answer)
The circuit breaker is pulled before clamping
The meter is set to DC mode before clamping
All conductors in the bundle pass through the clamp jaw

Correct answer: Only one conductor passes through the clamp jaw

A clamp-on ammeter measures the magnetic field produced by a single conductor; placing multiple conductors cancels their fields and gives a false reading.

Question 44: An ARINC 664 (AFDX) network in a modern aircraft serves as a replacement for which older avionics data bus architecture?

MIL-STD-1553 dual-redundant bus
ARINC 429 point-to-point buses (Correct answer)
RS-232 serial links
CSDB (Collins Serial Data Bus)

Correct answer: ARINC 429 point-to-point buses

AFDX (Avionics Full-Duplex Switched Ethernet, ARINC 664 Part 7) was developed to replace the many point-to-point ARINC 429 links with a higher-bandwidth switched network.

Question 45: 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
Power supply rectifier
Flash tube or trigger circuit (Correct answer)
Main generator

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 46: Which FAA form is used to record a major repair or major alteration performed on an aircraft?

FAA Form 337 (Correct answer)
FAA Form 8130-3
FAA Form 8060-4
FAA Form 8110-3

Correct answer: FAA Form 337

FAA Form 337 (Major Repair and Alteration) must be completed in duplicate and submitted to the FAA for any major repair or major alteration performed on an aircraft.

Question 47: An HF antenna coupler (ATU) is required because:

The HF transceiver output is balanced and the antenna is unbalanced
Antenna impedance varies widely across HF frequencies and must be matched to the transmitter (Correct answer)
HF signals cannot propagate without impedance transformation to 600 ohms
HF frequencies require circular polarization

Correct answer: Antenna impedance varies widely across HF frequencies and must be matched to the transmitter

HF antennas are electrically short relative to the wavelength at many HF frequencies, so the ATU performs impedance matching to maximize power transfer.

Question 48: 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 VHF communication system frequency
The fuel quantity indication system
The landing gear position switches
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 49: What test instrument is used to verify antenna VSWR (Voltage Standing Wave Ratio) in aircraft communications?

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

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 50: What is the primary purpose of the Marker Beacon system in an ILS approach?

Transmit weather minima to the cockpit
Control glide slope transmitter power
Provide lateral guidance corrections
Indicate specific distance-to-threshold fix points via audio and visual signals (Correct answer)

Correct answer: Indicate specific distance-to-threshold fix points via audio and visual signals

Marker beacons (outer, middle, inner) transmit upward-directed 75 MHz signals that trigger distinct audio tones and cockpit lights at known distance points along the ILS approach path.

Question 51: What does the ESD (Electrostatic Discharge) symbol on an avionics component packaging indicate?

The component emits electromagnetic radiation during operation
The component must be stored at a controlled temperature
The component requires external power before installation
The component is sensitive to static electricity and requires ESD-safe handling procedures (Correct answer)

Correct answer: The component is sensitive to static electricity and requires ESD-safe handling procedures

The ESD symbol warns that static electricity can damage the component's sensitive circuits, requiring ESD-safe work surfaces, wrist straps, and handling procedures.

Question 52: Which standard defines the ARINC 429 data bus commonly used to interconnect avionics including communication management units?

ARINC 664 (AFDX)
RS-485
ARINC 429 (DITS) (Correct answer)
MIL-STD-1553B

Correct answer: ARINC 429 (DITS)

ARINC 429 (Digital Information Transfer System) is a unidirectional serial data bus standard widely used on commercial aircraft to pass data between avionics LRUs.

Question 53: In ARINC 429 digital data bus, data words are transmitted:

Simultaneously on 32 parallel lines
Via optical fiber at 100 Mbps
As analog voltage levels on a single wire
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 54: Which of the following test equipment is specifically designed to verify the accuracy of an aircraft's transponder Mode C altitude encoding?

ILS ramp tester
Pitot-static test set used in conjunction with an encoding altimeter check (Correct answer)
VOR test set
TCAS test unit only

Correct answer: Pitot-static test set used in conjunction with an encoding altimeter check

Mode C altitude encoding is verified by applying known simulated altitudes via a pitot-static test set while monitoring the transponder's Gillham code output.

Question 55: When analyzing data from an avionics test set, which of the following is a crucial aspect to verify?

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

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 56: When troubleshooting an ARINC 429 bus fault, a technician finds all labels on that bus are missing. The most likely cause is:

Incorrect baud rate on a single receiver
Transmitter output failure in the source LRU or open wire on the bus pair (Correct answer)
Receiver card failure in one LRU
Software version mismatch on one listener

Correct answer: Transmitter output failure in the source LRU or open wire on the bus pair

Since ARINC 429 is unidirectional with one transmitter feeding multiple receivers, a transmitter failure or open bus wire eliminates all labels for every listener on that bus.

Question 57: A VOR receiver indicates a 'TO' flag with full left CDI deflection. The aircraft is flying directly TOWARD the station. What is the most likely cause?

The VOR station is transmitting an alarm signal
The OBS is set 90° off from the inbound course (Correct answer)
The receiver AGC circuit has failed
The aircraft is on the correct course and the CDI is calibrated correctly

Correct answer: The OBS is set 90° off from the inbound course

A full CDI deflection with a TO flag while flying toward the station indicates the OBS course selector is set approximately 90° off from the actual bearing to the station.

Question 58: What is the primary purpose of a voltage regulator in an aircraft electrical system?

Convert AC to DC power
Increase generator output frequency
Protect against reverse current flow
Maintain constant output voltage despite load variations (Correct answer)

Correct answer: Maintain constant output voltage despite load variations

A voltage regulator maintains a constant output voltage from the generator regardless of changes in engine speed or electrical load.

Question 59: What does a 'split bus' configuration provide in an aircraft electrical power system?

Faster load shedding during generator failure
Direct connection of all generators to a single master bus
Higher voltage output for engine start
Electrical isolation between buses so a single fault cannot affect all systems simultaneously (Correct answer)

Correct answer: Electrical isolation between buses so a single fault cannot affect all systems simultaneously

A split bus configuration isolates major electrical buses from each other so that a failure or fault on one bus does not propagate to and disable other buses.

Question 60: On a horizontal situation indicator (HSI), what does the course deviation indicator (CDI) needle represent when centered?

Aircraft is on the selected VOR radial or localizer course (Correct answer)
Aircraft heading matches the runway bearing
Aircraft is on the selected magnetic heading
Aircraft has reached the DME fix distance

Correct answer: Aircraft is on the selected VOR radial or localizer course

A centered CDI needle on the HSI indicates the aircraft is on the selected VOR radial or localizer centerline course.

Question 61: 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 62: If the static port becomes completely blocked during a climb, what indication will the altimeter display?

It will freeze at the altitude where the blockage occurred (Correct answer)
It will under-read, showing lower altitude than actual
It will fluctuate rapidly and become unreliable
It will over-read, showing higher altitude than actual

Correct answer: It will freeze at the altitude where the blockage occurred

A blocked static port traps the air pressure inside the static system at the value present when the blockage occurred. Since no new pressure reference can enter the system, the altimeter, VSI, and airspeed indicator are all frozen at their last readings. The altimeter will not change as the aircraft climbs or descends.

Question 63: When testing a VOR receiver, an approved VOR test facility (VOT) should produce what indication on a correctly functioning receiver?

360° radial with FROM flag and centered CDI
000° radial with TO flag and centered CDI (Correct answer)
090° radial with FROM flag and full-scale CDI deflection
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 64: When performing a continuity check on an aircraft wiring harness, the technician should FIRST:

Disconnect power and verify the circuit is de-energized before testing (Correct answer)
Use an RF signal injector for better accuracy
Apply 28 VDC to the circuit and measure with a voltmeter
Remove the harness from the aircraft for bench testing

Correct answer: Disconnect power and verify the circuit is de-energized before testing

Before any continuity test, the circuit must be completely de-energized to protect equipment and prevent inaccurate readings from back-EMF sources.

Question 65: An aircraft's Master Minimum Equipment List (MMEL) is approved by the FAA and forms the basis for an operator's:

Weight and Balance Manual
Aircraft Flight Manual (AFM)
Minimum Equipment List (MEL) (Correct answer)
Approved Maintenance Program

Correct answer: Minimum Equipment List (MEL)

Operators develop their own Minimum Equipment List (MEL) from the FAA-approved MMEL, allowing certain equipment to be inoperative under specified conditions while maintaining airworthiness.

Question 66: Which fastener material used in aluminum aircraft skin would create the greatest risk of galvanic corrosion?

Stainless steel (300-series) fasteners
Uncoated carbon steel fasteners (Correct answer)
2024 aluminum alloy rivets
Titanium fasteners

Correct answer: Uncoated carbon steel fasteners

Uncoated carbon steel and aluminum are far apart in the galvanic series, creating a large electrochemical potential difference that drives aggressive galvanic corrosion. Aluminum and titanium are much closer in the galvanic series, making titanium an acceptable fastener in aluminum structure.

Question 67: Which type of battery is most commonly used as a primary backup power source in modern transport-category aircraft?

Silver-zinc
Lithium-ion
Lead-acid
Nickel-cadmium (NiCd) (Correct answer)

Correct answer: Nickel-cadmium (NiCd)

Nickel-cadmium batteries are preferred in transport-category aircraft for their high discharge rate capability, long cycle life, and reliability under extreme temperatures.

Question 68: What modulation type is used by VHF aviation voice communication radios?

SSB
FM
AM (Correct answer)
DSB

Correct answer: AM

VHF aviation communications use Amplitude Modulation (AM) because it allows simultaneous reception from multiple stations and simulates 'breaking squelch' when multiple transmitters key at once.

Question 69: During an ILS approach, a glideslope pointer above center on the ADI/flight director indicates the aircraft is:

Below the glideslope — fly up (Correct answer)
Above the glideslope — fly down
On the glideslope — maintain current rate
Glideslope signal unreliable — go around

Correct answer: Below the glideslope — fly up

A glideslope deviation pointer above center means the glideslope beam is above the aircraft, so the aircraft is below the glideslope and must climb (fly up) to intercept it.

Question 70: 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 71: When filling out a squawk sheet, which entry is most critical for the next technician to understand the fault?

A clear, specific description of the observed symptom and conditions when it occurred (Correct answer)
The part number of all components checked
The cost estimate for repair
The pilot's name and flight hours

Correct answer: A clear, specific description of the observed symptom and conditions when it occurred

A precise symptom description including conditions of occurrence allows the next technician to efficiently troubleshoot and reproduce the fault.

Question 72: Which FAA Advisory Circular provides guidance on the installation of electronic flight display systems in certificated aircraft?

AC 25.1309
AC 43.13-1B
AC 91-21
AC 20-165 (Correct answer)

Correct answer: AC 20-165

AC 20-165 addresses airworthiness approval of automatic dependent surveillance-broadcast (ADS-B) out systems, including electronic flight display installations.

Question 73: What are the key regulatory requirements affecting Electrical Troubleshooting?

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

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 74: An avionics technician installs a replacement VHF comm radio. Which document provides the approved data confirming the replacement is authorized?

The shop's internal work order
The technician's logbook entry
FAA-approved data such as STC, AML, or aircraft manufacturer data (Correct answer)
The Pilot's Operating Handbook only

Correct answer: FAA-approved data such as STC, AML, or aircraft manufacturer data

Approved data such as an STC, AML listing, or aircraft manufacturer's maintenance manual must authorize avionics installations.

Question 75: A technician uses an oscilloscope to observe a 400 Hz aircraft power bus waveform and notices the top of the sine wave is flattened. This condition is called:

Frequency modulation
Phase shift
Hysteresis
Clipping or waveform clipping (Correct answer)

Correct answer: Clipping or waveform clipping

Clipping occurs when a signal exceeds the linear range of a component or supply, causing the peaks to be cut flat.

Question 76: What is the purpose of IRS (Inertial Reference System) alignment and why must it be performed stationary?

To zero out accumulated drift errors from the previous flight
To calibrate barometric sensors against a known field elevation
To synchronize the IRS clock with GPS time signals
To establish a precise north reference and initial position before computing navigation (Correct answer)

Correct answer: To establish a precise north reference and initial position before computing navigation

IRS alignment uses Earth's rotation sensed by the gyros to determine true north and must be done stationary because any movement during alignment introduces position and heading errors.

Question 77: When using a Manufacturer's Service Bulletin (SB) as maintenance guidance, what determines whether compliance is mandatory?

The technician's judgment
The service bulletin's issue date
The aircraft owner's preference
Whether an Airworthiness Directive (AD) has been issued mandating the SB (Correct answer)

Correct answer: Whether an Airworthiness Directive (AD) has been issued mandating the SB

A service bulletin becomes mandatory only when the FAA issues an Airworthiness Directive that specifically requires compliance with that bulletin.

Question 78: When troubleshooting a faulty fuel quantity indicator, a technician should verify the sender resistance by:

Measuring voltage at the indicator terminals
Replacing the indicator first, then the sender
Applying full power and observing indicator deflection
Disconnecting the sender and measuring resistance at the sender connector pins (Correct answer)

Correct answer: Disconnecting the sender and measuring resistance at the sender connector pins

Disconnecting the sender and measuring its resistance directly verifies whether the sender or indicator is faulty before replacing components.

Question 79: 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 NTSB
The original equipment manufacturer
The FAA district office directly
The aircraft owner/operator (Correct answer)

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 80: What distinguishes a microcontroller from a standalone microprocessor?

A microcontroller has a wider data bus than a microprocessor
A microcontroller operates at a faster clock speed
A microcontroller integrates CPU, memory, and I/O peripherals on a single chip (Correct answer)
A microcontroller uses only RISC architecture

Correct answer: A microcontroller integrates CPU, memory, and I/O peripherals on a single chip

A microcontroller combines the CPU, RAM, ROM, and I/O ports onto one chip, making it a self-contained computing system suitable for embedded avionics control.

Question 81: In aircraft wiring, what is the primary reason for twisting wire pairs used for sensitive avionics circuits?

Cancel electromagnetic interference through opposing field cancellation (Correct answer)
Reduce wire weight by eliminating shielding
Improve insulation resistance at high altitudes
Increase current-carrying capacity of the conductors

Correct answer: Cancel electromagnetic interference through opposing field cancellation

Twisting wire pairs causes their magnetic fields to cancel each other, greatly reducing susceptibility to electromagnetic interference (EMI) pickup.

Question 82: What is the preferred method for splicing aircraft wiring according to FAA Advisory Circular 43.13-1B?

Soldering with rosin-core solder and electrical tape
Heat-activated butt connectors from automotive supply
Mechanical screw-type wire nuts
Approved crimp splices with calibrated crimp tools (Correct answer)

Correct answer: Approved crimp splices with calibrated crimp tools

Crimp splices using approved tools and correct positioners are the preferred method for aircraft wiring splices. They produce consistent, reliable connections without the risk of cold solder joints or flux contamination associated with soldering.

Question 83: What is the decimal equivalent of the binary number 1010?

12
10 (Correct answer)
14
8

Correct answer: 10

Binary 1010 equals (1×8) + (0×4) + (1×2) + (0×1) = 10 in decimal.

Question 84: Which instrument is best suited for measuring the frequency of a signal in an aircraft's electronic system?

Multimeter
Frequency counter (Correct answer)
Signal generator
Oscilloscope

Correct answer: Frequency counter

A frequency counter is a specialized electronic instrument designed specifically to measure the frequency of an oscillating electronic signal with high precision. While an oscilloscope can display waveforms from which frequency can be estimated, a frequency counter provides a direct, accurate digital readout. This makes it the best tool for obtaining exact frequency measurements in complex aircraft electronic systems.

Question 85: What is the primary advantage of ARINC 664 (AFDX — Avionics Full-Duplex Switched Ethernet) over ARINC 429 in modern aircraft?

Vastly higher bandwidth and bidirectional data flow on a single connection (Correct answer)
Better immunity to electromagnetic interference than twisted-pair buses
Lower installation cost due to use of standard CAT5 cable
Direct compatibility with consumer Ethernet switches and routers

Correct answer: Vastly higher bandwidth and bidirectional data flow on a single connection

ARINC 664/AFDX provides 10/100 Mbps full-duplex bandwidth, supporting bidirectional communication over a single connection — a dramatic improvement over ARINC 429's 12.5 kbps or 100 kbps unidirectional bus. It is used in aircraft such as the Airbus A380 and Boeing 787.

Question 86: When a technician makes an error in a maintenance logbook entry, what is the correct procedure?

Remove the page and rewrite it
Draw a single line through the error, initial and date it, then write the correct entry (Correct answer)
Completely black out the error so it is unreadable
Use white-out to cover the error and rewrite the correct information

Correct answer: Draw a single line through the error, initial and date it, then write the correct entry

Errors in maintenance records must be corrected with a single line through the mistake, initialed and dated, so the original entry remains legible.

Question 87: A MIL-STD-1553B data bus uses which physical medium and topology?

Twisted shielded pair with transformer coupling in a bus topology at 1 Mbps (Correct answer)
Coaxial cable ring topology at 10 Mbps
Fiber optic star topology at 1 Gbps
CAT5 Ethernet at 100 Mbps

Correct answer: Twisted shielded pair with transformer coupling in a bus topology at 1 Mbps

MIL-STD-1553B uses a shielded twisted pair bus with transformer-coupled stubs, operating at 1 Mbps in a command/response protocol with one Bus Controller and up to 31 Remote Terminals.

Question 88: What is the importance of communication skills in Avionics Systems?

Communication skills cannot be learned
Communication is only important for managers
Technical skills are sufficient without communication
Clear communication prevents errors, builds relationships, and ensures understanding among all parties (Correct answer)

Correct answer: Clear communication prevents errors, builds relationships, and ensures understanding among all parties

Effective communication is essential for coordination, error prevention, and stakeholder relationships.

Question 89: How does technology impact modern practices in Avionics Systems?

Technology replaces all human judgment
Technology improves efficiency, accuracy, and access to information while requiring new skills (Correct answer)
Technology has no impact on this field
Technology is only useful for record keeping

Correct answer: Technology improves efficiency, accuracy, and access to information while requiring new skills

Technology enhances capabilities while also requiring practitioners to develop new competencies.

Question 90: In an aircraft bus tie system, what is the function of a Bus Tie Breaker (BTB)?

Regulate voltage between two AC buses
Protect the bus against overvoltage conditions
Convert AC bus power to DC for avionics
Connect or isolate AC buses to allow power transfer between sources (Correct answer)

Correct answer: Connect or isolate AC buses to allow power transfer between sources

A Bus Tie Breaker connects two AC buses together, allowing one generator to power both buses if one generator fails.

Question 91: Which type of analog-to-digital converter (ADC) is preferred in avionics for highest accuracy at lower sample rates, such as pressure sensor digitization?

Delta-sigma ADC (Correct answer)
Successive approximation ADC
Ramp (single-slope) ADC
Flash ADC

Correct answer: Delta-sigma ADC

Delta-sigma ADCs achieve very high resolution through oversampling and noise shaping, making them ideal for slow but precise measurements like pressure.

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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