NCATT AET & AEIT ENDORSEMENT EXAM
COMPREHENSIVE TEST BANK - 300 QUESTIONS
WITH ANSWERS AND RATIONALES National Center for
Aerospace and Transportation Technologies (NCATT) |
2026-2027 Edition | Most Recent Edition
EXAM OVERVIEW
The NCATT Aircraft Electronics Technician (AET) certification and Aircraft Electronics Integrated
Technician (AEIT) endorsements are designed to validate the knowledge and skills of aviation
electronics technicians . The AET certification covers fundamental electronic principles, while
endorsements such as Radio Communication Systems, Onboard Communication and Safety
Systems, Dependent Navigation Systems, and Autonomous Navigation Systems require additional
specialized knowledge .
This test bank covers all core domains including electromagnetic interference (EMI), grounding and
bonding, wire identification and installation, technical standard orders (TSO), parts manufacturer
approval (PMA), and aircraft wiring practices . All Answers are based on AC 43.13-1B Chapter 11
and other applicable FAA regulations and industry standards .
SECTION 1: ELECTROMAGNETIC INTERFERENCE (EMI) (Questions 1-50)
1. What is the primary mechanism by which EMI affects avionics systems?
A) Thermal heating of conductors
B) Unwanted coupling of electromagnetic energy into sensitive circuits
C) Galvanic corrosion of connectors
D) Electrostatic discharge from human touch
Answer: B) Unwanted coupling of electromagnetic energy into sensitive circuits
Rationale: EMI occurs when electromagnetic energy from a source couples (via radiated or
conducted paths) into a victim circuit, causing noise, false data, or malfunction . This unwanted
coupling can degrade system performance and cause intermittent failures.
2. Which frequency range is most susceptible to radiated EMI from aircraft communication
antennas?
,A) 10Hz – 1 kHz
B) 100 kHz – 30 MHz
C) 30 MHz – 1 GHz
D) Above 10 GHz
Answer: C) 30 MHz – 1 GHz
Rationale: The 30 MHz – 1 GHz frequency range is most susceptible to radiated EMI from aircraft
communication antennas . This range includes VHF and UHF communication bands used in
aviation.
3. What does "EMI" stand for in aviation maintenance?
A) Engine Malfunction Indicator
B) Electromagnetic Interference
C) Electronic Maintenance Inspection
D) Emergency Mode Indicator
Answer: B) Electromagnetic Interference
Rationale: EMI is the standard acronym in avionics for Electromagnetic Interference . It refers to
the disturbance caused by electromagnetic radiation from one electronic device affecting another.
4. Which shielding effectiveness improvement would best reduce radiated EMI at 400 MHz?
A) Increasing conductor gauge
B) Using aluminum foil with 90% coverage
C) Applying ferrite beads only
D) Using a solid copper shield with <5% openings
Answer: D) Using a solid copper shield with <5% openings
Rationale: Shield effectiveness at RF depends on conductivity, thickness, and low porosity. Solid
copper provides high attenuation and reduces radiated EMI .
5. What is the dominant coupling mechanism for EMI between two parallel wires in a bundle?
A) Radiated
B) Inductive and capacitive
C) Galvanic
D) Common impedance
Answer: B) Inductive and capacitive
,Rationale: Proximity allows magnetic (inductive) and electric (capacitive) field coupling between
parallel wires . This is the primary coupling mechanism in wire bundles.
6. What is the typical frequency range of conducted EMI in aircraft DC power systems?
A) 0-150 kHz
B) 1-30 MHz
C) 30-100 MHz
D) >1 GHz
Answer: A) 0-150 kHz
Rationale: Conducted EMI on DC lines (ripple, switching noise, harmonics) usually spans audio to
low RF (kHz to ~150 kHz) .
7. What is the primary difference between radiated and conducted EMI?
A) Radiated travels through space; conducted travels via conductors
B) Conducted only occurs at power line frequencies
C) Radiated is always worse
D) There is no difference
Answer: A) Radiated travels through space; conducted travels via conductors
Rationale: Radiated EMI travels through space as electromagnetic waves, while conducted EMI
travels via conductors such as wires and cables . The coupling path distinguishes them.
8. What is the primary difference between differential-mode and common-mode conducted EMI?
A) Differential mode flows between line and neutral; common mode flows on both lines in same
direction
B) Common mode only occurs in AC systems
C) Differential mode cannot be filtered
D) Common mode requires 3-wire systems
Answer: A) Differential mode flows between line and neutral; common mode flows on both lines in
same direction
Rationale: Differential mode is normal circuit current; common mode is parasitic current seeking
ground return . Understanding this distinction is essential for proper filtering.
9. A ferrite core around a cable suppresses EMI by:
, A) Reflecting energy back to source
B) Absorbing high-frequency energy
C) Increasing cable resistance
D) Shielding the cable
Answer: B) Absorbing high-frequency energy
Rationale: Ferrite cores absorb high-frequency energy and dissipate it as heat . They are effective at
suppressing common-mode EMI on cables.
10. Which of the following is a conducted EMI path?
A) Antenna radiation
B) Crosstalk via shared power return
C) Magnetic field induction through air
D) Electrostatic discharge spark
Answer: B) Crosstalk via shared power return
Rationale: Conducted EMI travels via wires; shared returns allow coupling . This is a common path
for conducted interference.
11. A VOR receiver shows bearing errors only when the electric hydraulic pump operates. What is
the first step in troubleshooting?
A) Replace the VOR antenna
B) Check VOR receiver bench test
C) Check pump motor for EMI suppression
D) Replace the hydraulic pump
Answer: C) Check pump motor for EMI suppression
Rationale: The pump motor is likely generating EMI that is coupling into the VOR receiver. This is
a common scenario where EMI from a high-current motor affects sensitive avionics .
12. After installing a new comm radio, the ADF needle swings wildly during transmit. The radio
passes bench test. Most likely cause:
A) TSO mismatch
B) Antenna proximity – radiated EMI
C) PMO not updated
D) Poor bonding of radio chassis
COMPREHENSIVE TEST BANK - 300 QUESTIONS
WITH ANSWERS AND RATIONALES National Center for
Aerospace and Transportation Technologies (NCATT) |
2026-2027 Edition | Most Recent Edition
EXAM OVERVIEW
The NCATT Aircraft Electronics Technician (AET) certification and Aircraft Electronics Integrated
Technician (AEIT) endorsements are designed to validate the knowledge and skills of aviation
electronics technicians . The AET certification covers fundamental electronic principles, while
endorsements such as Radio Communication Systems, Onboard Communication and Safety
Systems, Dependent Navigation Systems, and Autonomous Navigation Systems require additional
specialized knowledge .
This test bank covers all core domains including electromagnetic interference (EMI), grounding and
bonding, wire identification and installation, technical standard orders (TSO), parts manufacturer
approval (PMA), and aircraft wiring practices . All Answers are based on AC 43.13-1B Chapter 11
and other applicable FAA regulations and industry standards .
SECTION 1: ELECTROMAGNETIC INTERFERENCE (EMI) (Questions 1-50)
1. What is the primary mechanism by which EMI affects avionics systems?
A) Thermal heating of conductors
B) Unwanted coupling of electromagnetic energy into sensitive circuits
C) Galvanic corrosion of connectors
D) Electrostatic discharge from human touch
Answer: B) Unwanted coupling of electromagnetic energy into sensitive circuits
Rationale: EMI occurs when electromagnetic energy from a source couples (via radiated or
conducted paths) into a victim circuit, causing noise, false data, or malfunction . This unwanted
coupling can degrade system performance and cause intermittent failures.
2. Which frequency range is most susceptible to radiated EMI from aircraft communication
antennas?
,A) 10Hz – 1 kHz
B) 100 kHz – 30 MHz
C) 30 MHz – 1 GHz
D) Above 10 GHz
Answer: C) 30 MHz – 1 GHz
Rationale: The 30 MHz – 1 GHz frequency range is most susceptible to radiated EMI from aircraft
communication antennas . This range includes VHF and UHF communication bands used in
aviation.
3. What does "EMI" stand for in aviation maintenance?
A) Engine Malfunction Indicator
B) Electromagnetic Interference
C) Electronic Maintenance Inspection
D) Emergency Mode Indicator
Answer: B) Electromagnetic Interference
Rationale: EMI is the standard acronym in avionics for Electromagnetic Interference . It refers to
the disturbance caused by electromagnetic radiation from one electronic device affecting another.
4. Which shielding effectiveness improvement would best reduce radiated EMI at 400 MHz?
A) Increasing conductor gauge
B) Using aluminum foil with 90% coverage
C) Applying ferrite beads only
D) Using a solid copper shield with <5% openings
Answer: D) Using a solid copper shield with <5% openings
Rationale: Shield effectiveness at RF depends on conductivity, thickness, and low porosity. Solid
copper provides high attenuation and reduces radiated EMI .
5. What is the dominant coupling mechanism for EMI between two parallel wires in a bundle?
A) Radiated
B) Inductive and capacitive
C) Galvanic
D) Common impedance
Answer: B) Inductive and capacitive
,Rationale: Proximity allows magnetic (inductive) and electric (capacitive) field coupling between
parallel wires . This is the primary coupling mechanism in wire bundles.
6. What is the typical frequency range of conducted EMI in aircraft DC power systems?
A) 0-150 kHz
B) 1-30 MHz
C) 30-100 MHz
D) >1 GHz
Answer: A) 0-150 kHz
Rationale: Conducted EMI on DC lines (ripple, switching noise, harmonics) usually spans audio to
low RF (kHz to ~150 kHz) .
7. What is the primary difference between radiated and conducted EMI?
A) Radiated travels through space; conducted travels via conductors
B) Conducted only occurs at power line frequencies
C) Radiated is always worse
D) There is no difference
Answer: A) Radiated travels through space; conducted travels via conductors
Rationale: Radiated EMI travels through space as electromagnetic waves, while conducted EMI
travels via conductors such as wires and cables . The coupling path distinguishes them.
8. What is the primary difference between differential-mode and common-mode conducted EMI?
A) Differential mode flows between line and neutral; common mode flows on both lines in same
direction
B) Common mode only occurs in AC systems
C) Differential mode cannot be filtered
D) Common mode requires 3-wire systems
Answer: A) Differential mode flows between line and neutral; common mode flows on both lines in
same direction
Rationale: Differential mode is normal circuit current; common mode is parasitic current seeking
ground return . Understanding this distinction is essential for proper filtering.
9. A ferrite core around a cable suppresses EMI by:
, A) Reflecting energy back to source
B) Absorbing high-frequency energy
C) Increasing cable resistance
D) Shielding the cable
Answer: B) Absorbing high-frequency energy
Rationale: Ferrite cores absorb high-frequency energy and dissipate it as heat . They are effective at
suppressing common-mode EMI on cables.
10. Which of the following is a conducted EMI path?
A) Antenna radiation
B) Crosstalk via shared power return
C) Magnetic field induction through air
D) Electrostatic discharge spark
Answer: B) Crosstalk via shared power return
Rationale: Conducted EMI travels via wires; shared returns allow coupling . This is a common path
for conducted interference.
11. A VOR receiver shows bearing errors only when the electric hydraulic pump operates. What is
the first step in troubleshooting?
A) Replace the VOR antenna
B) Check VOR receiver bench test
C) Check pump motor for EMI suppression
D) Replace the hydraulic pump
Answer: C) Check pump motor for EMI suppression
Rationale: The pump motor is likely generating EMI that is coupling into the VOR receiver. This is
a common scenario where EMI from a high-current motor affects sensitive avionics .
12. After installing a new comm radio, the ADF needle swings wildly during transmit. The radio
passes bench test. Most likely cause:
A) TSO mismatch
B) Antenna proximity – radiated EMI
C) PMO not updated
D) Poor bonding of radio chassis
