NCATT AET & AEIT Endorsement Exam - 170 Questions and
Answers Already Graded A+ Premium Exam Tested And
Verified
Subject Area Avionics Engineering Technology (AET) and Avionics Electronics Installation
(AEIT)
Description This exam assesses advanced knowledge in avionics systems engineering,
installation practices, troubleshooting, and regulatory compliance for
FAA-certified avionics technicians. Covers aircraft electrical systems,
communication/navigation systems, radar, autopilots, and safety wiring.
Expected Grade A+
Total Questions 170
Duration 3 hours
Learning Outcomes 1. Analyze complex avionics system interactions and diagnose faults using
schematics and test equipment.
2. Evaluate installation procedures for compliance with FAA AC 43.13-1B and
manufacturer data.
3. Synthesize knowledge of digital data buses (ARINC 429, MIL-STD-1553) and
system integration.
4. Apply advanced troubleshooting strategies for radar, GPS, and flight
management systems.
Accreditation NCATT (National Center for Aerospace & Transportation Technologies)
Endorsement Exam - US University Standards
Page 1
,1. An aircraft experiences intermittent loss of GPS position data during turns.
The GPS antenna is a top-mounted blade, and the receiver is an ARINC 743A
unit. The installer used RG-400 coax with BNC connectors. During
troubleshooting, you measure VSWR at the antenna connector as 1.8:1 at the
GPS L1 frequency. Which of the following is the most likely cause of the
intermittent loss?
Answer: VSWR exceeding 1.5:1 causing receiver desensitization
GPS receivers typically require VSWR < 1.5:1 for reliable operation. A VSWR of
1.8:1 indicates a mismatch that can cause receiver desensitization, especially
during turns when the antenna pattern shifts. RG-400 is suitable for GPS;
RG-142 is stiffer but similar loss. Antenna polarization is fixed; blade antennas
are vertically polarized. A loose connector would cause intermittent loss but
VSWR would vary; a steady 1.8:1 suggests a fixed mismatch.
2. During installation of a new VHF COM radio, you must bond the radio
chassis to the aircraft ground. Per AC 43.13-1B, which of the following
bonding methods is acceptable for a radio mounted on a shock tray?
Answer: Use a flat braided copper strap (tinned) from the radio chassis to the
shock tray, with the strap length less than 6 inches and secured with stainless
steel hardware.
AC 43.13-1B recommends using a flat braided copper strap (tinned) for bonding
radio equipment to minimize RF impedance. The strap should be as short as
possible (typically <6 inches) and secured with corrosion-resistant hardware. A
#20 AWG wire may be insufficient for RF bonding. Relying on mounting screws
is unreliable due to vibration and corrosion. Using the coax shield as the only
ground is improper; a separate bond is required.
Page 2
,3. A technician is troubleshooting an ARINC 429 data bus issue where the
system indicates a 'no data' condition on a particular label. Using an
oscilloscope, the technician observes that the data lines (A and B) show a
differential voltage of ±5V during normal operation, but for the suspect label,
the differential voltage is only ±1V. What is the most likely cause?
Answer: A missing termination resistor at the far end of the bus
ARINC 429 uses a differential voltage of ±5V for logic 1 and 0. A missing
termination resistor can cause reflections and reduced voltage levels, especially
for specific labels if the bus is unterminated. A short between A and B would
result in near-zero differential voltage. An open return would cause
common-mode issues but not necessarily low differential voltage. Excessive
loading would reduce voltage across all labels, not just one.
4. When installing a new weather radar system, the antenna is mounted in the
nose radome. The radome is made of a fiberglass composite with a lightning
diverter strip. The technician must ensure the antenna is properly grounded.
Which of the following is the correct grounding method for the radar antenna?
Answer: Bond the antenna base directly to the aircraft structure using a
braided strap, and ensure the radome diverter strip is bonded to the same
ground.
Radar antennas must be bonded to aircraft structure to provide a low-impedance
path for lightning and static discharge. The antenna base should be bonded with
a braided strap, and the radome diverter strip must also be bonded to the same
ground to ensure lightning currents are safely conducted. Using coax shield alone
is insufficient. Isolation could cause arcing. #10 AWG wire may have higher
impedance at radar frequencies.
Page 3
, 5. A technician is calibrating a pitot-static system after installing a new air data
computer (ADC). The aircraft is equipped with a digital air data system
(DADS). Using a pitot-static test set, the technician applies a static pressure
equivalent to 10,000 ft altitude. The ADC displays 10,050 ft. Which of the
following is the most appropriate corrective action?
Answer: Adjust the ADC static pressure correction factor via the
manufacturer's software; the error is within typical tolerance.
A 50 ft error at 10,000 ft is within acceptable tolerance for many ADCs (typically
±50 ft). The technician should adjust the correction factor in the ADC software as
per manufacturer instructions. A static port blockage would cause larger errors
and would not be compensated by correction factor. A leak would cause unstable
readings. Temperature effects are minimal at this altitude.
6. During an autopilot system checkout, the roll axis servo exhibits a slow
oscillation when engaged. The servo is a linear actuator with a potentiometer
feedback. The technician measures the servo motor voltage and finds it varying
between +5V and -5V at a frequency of 0.5 Hz. The command signal is steady.
Which of the following is the most likely cause?
Answer: Excessive gain in the autopilot roll channel
Slow oscillation (0.5 Hz) with motor voltage alternating suggests a control loop
instability due to excessive gain. The command is steady, so the oscillation is
likely a limit cycle. A worn potentiometer would cause erratic, not sinusoidal,
variations. Mechanical binding would cause sluggish response, not oscillation.
Low hydraulic pressure would cause reduced force, not oscillation.
Page 4
Answers Already Graded A+ Premium Exam Tested And
Verified
Subject Area Avionics Engineering Technology (AET) and Avionics Electronics Installation
(AEIT)
Description This exam assesses advanced knowledge in avionics systems engineering,
installation practices, troubleshooting, and regulatory compliance for
FAA-certified avionics technicians. Covers aircraft electrical systems,
communication/navigation systems, radar, autopilots, and safety wiring.
Expected Grade A+
Total Questions 170
Duration 3 hours
Learning Outcomes 1. Analyze complex avionics system interactions and diagnose faults using
schematics and test equipment.
2. Evaluate installation procedures for compliance with FAA AC 43.13-1B and
manufacturer data.
3. Synthesize knowledge of digital data buses (ARINC 429, MIL-STD-1553) and
system integration.
4. Apply advanced troubleshooting strategies for radar, GPS, and flight
management systems.
Accreditation NCATT (National Center for Aerospace & Transportation Technologies)
Endorsement Exam - US University Standards
Page 1
,1. An aircraft experiences intermittent loss of GPS position data during turns.
The GPS antenna is a top-mounted blade, and the receiver is an ARINC 743A
unit. The installer used RG-400 coax with BNC connectors. During
troubleshooting, you measure VSWR at the antenna connector as 1.8:1 at the
GPS L1 frequency. Which of the following is the most likely cause of the
intermittent loss?
Answer: VSWR exceeding 1.5:1 causing receiver desensitization
GPS receivers typically require VSWR < 1.5:1 for reliable operation. A VSWR of
1.8:1 indicates a mismatch that can cause receiver desensitization, especially
during turns when the antenna pattern shifts. RG-400 is suitable for GPS;
RG-142 is stiffer but similar loss. Antenna polarization is fixed; blade antennas
are vertically polarized. A loose connector would cause intermittent loss but
VSWR would vary; a steady 1.8:1 suggests a fixed mismatch.
2. During installation of a new VHF COM radio, you must bond the radio
chassis to the aircraft ground. Per AC 43.13-1B, which of the following
bonding methods is acceptable for a radio mounted on a shock tray?
Answer: Use a flat braided copper strap (tinned) from the radio chassis to the
shock tray, with the strap length less than 6 inches and secured with stainless
steel hardware.
AC 43.13-1B recommends using a flat braided copper strap (tinned) for bonding
radio equipment to minimize RF impedance. The strap should be as short as
possible (typically <6 inches) and secured with corrosion-resistant hardware. A
#20 AWG wire may be insufficient for RF bonding. Relying on mounting screws
is unreliable due to vibration and corrosion. Using the coax shield as the only
ground is improper; a separate bond is required.
Page 2
,3. A technician is troubleshooting an ARINC 429 data bus issue where the
system indicates a 'no data' condition on a particular label. Using an
oscilloscope, the technician observes that the data lines (A and B) show a
differential voltage of ±5V during normal operation, but for the suspect label,
the differential voltage is only ±1V. What is the most likely cause?
Answer: A missing termination resistor at the far end of the bus
ARINC 429 uses a differential voltage of ±5V for logic 1 and 0. A missing
termination resistor can cause reflections and reduced voltage levels, especially
for specific labels if the bus is unterminated. A short between A and B would
result in near-zero differential voltage. An open return would cause
common-mode issues but not necessarily low differential voltage. Excessive
loading would reduce voltage across all labels, not just one.
4. When installing a new weather radar system, the antenna is mounted in the
nose radome. The radome is made of a fiberglass composite with a lightning
diverter strip. The technician must ensure the antenna is properly grounded.
Which of the following is the correct grounding method for the radar antenna?
Answer: Bond the antenna base directly to the aircraft structure using a
braided strap, and ensure the radome diverter strip is bonded to the same
ground.
Radar antennas must be bonded to aircraft structure to provide a low-impedance
path for lightning and static discharge. The antenna base should be bonded with
a braided strap, and the radome diverter strip must also be bonded to the same
ground to ensure lightning currents are safely conducted. Using coax shield alone
is insufficient. Isolation could cause arcing. #10 AWG wire may have higher
impedance at radar frequencies.
Page 3
, 5. A technician is calibrating a pitot-static system after installing a new air data
computer (ADC). The aircraft is equipped with a digital air data system
(DADS). Using a pitot-static test set, the technician applies a static pressure
equivalent to 10,000 ft altitude. The ADC displays 10,050 ft. Which of the
following is the most appropriate corrective action?
Answer: Adjust the ADC static pressure correction factor via the
manufacturer's software; the error is within typical tolerance.
A 50 ft error at 10,000 ft is within acceptable tolerance for many ADCs (typically
±50 ft). The technician should adjust the correction factor in the ADC software as
per manufacturer instructions. A static port blockage would cause larger errors
and would not be compensated by correction factor. A leak would cause unstable
readings. Temperature effects are minimal at this altitude.
6. During an autopilot system checkout, the roll axis servo exhibits a slow
oscillation when engaged. The servo is a linear actuator with a potentiometer
feedback. The technician measures the servo motor voltage and finds it varying
between +5V and -5V at a frequency of 0.5 Hz. The command signal is steady.
Which of the following is the most likely cause?
Answer: Excessive gain in the autopilot roll channel
Slow oscillation (0.5 Hz) with motor voltage alternating suggests a control loop
instability due to excessive gain. The command is steady, so the oscillation is
likely a limit cycle. A worn potentiometer would cause erratic, not sinusoidal,
variations. Mechanical binding would cause sluggish response, not oscillation.
Low hydraulic pressure would cause reduced force, not oscillation.
Page 4
