Aviation Electrical Troubleshooting
Certification Exam Practice Questions
And Correct Answers (Verified Answers)
Plus Rationale 2026 Q&A| Instant
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1. In an aircraft electrical troubleshooting scenario, a technician is
investigating a DC bus that shows normal voltage with no load but
drops significantly when several electrical consumers are energized.
The battery has recently passed a capacity test, the generator output
is within specification at the source, and the circuit protection devices
show no signs of tripping. Voltage measurements taken progressively
along the feeder indicate an increasing voltage drop across a particular
connection. Which condition most directly explains the observed
symptom, and what troubleshooting action is most appropriate?
A. An open circuit in the feeder, requiring replacement of the entire wire
bundle
B. A high-resistance connection, requiring inspection, cleaning, tightening,
or replacement in accordance with the maintenance data
,C. An excessive generator frequency, requiring adjustment of the generator
speed
D. A short circuit downstream, requiring immediate removal of every
electrical load from the aircraft
Answer: B. A high-resistance connection, requiring inspection, cleaning,
tightening, or replacement in accordance with the maintenance data
A high-resistance connection can produce acceptable voltage with little or
no current flow but develop a substantial voltage drop when current
increases. Progressive voltage-drop testing under the appropriate
energized conditions helps isolate the defective connection or conductor.
2. During troubleshooting of an aircraft 28-volt DC electrical system, a
technician measures 28.2 volts directly at the generator output
terminal but only 24.6 volts at a remote equipment bus while a high-
current load is operating. The aircraft wiring diagram shows several
connectors and circuit-protection devices between the generator and
the bus. Which troubleshooting technique provides the most useful
information for locating the excessive resistance?
A. Measure resistance of the entire aircraft wiring system with all loads
energized
B. Measure voltage drop across individual sections, connectors, switches,
and protective devices while the circuit carries its normal load
,C. Disconnect the battery and measure generator frequency at the bus
D. Replace the generator before performing any additional tests
Answer: B. Measure voltage drop across individual sections, connectors,
switches, and protective devices while the circuit carries its normal load
Voltage-drop testing under load identifies unwanted resistance that may
not be apparent during an unloaded continuity or resistance test.
Measuring across individual circuit sections allows the technician to
progressively isolate the defective component or connection.
3. An aircraft circuit breaker repeatedly trips shortly after a particular
cabin electrical device is switched on. The breaker rating corresponds
to the aircraft wiring requirements, and the same circuit previously
operated normally. What should the technician generally do first when
following an approved troubleshooting procedure?
A. Install a circuit breaker with a higher current rating
B. Reset the breaker repeatedly until the equipment operates
C. Determine whether an abnormal current condition or fault exists and
isolate the affected circuit or equipment according to the maintenance
procedure
D. Permanently bypass the circuit breaker to prevent nuisance tripping
, Answer: C. Determine whether an abnormal current condition or fault
exists and isolate the affected circuit or equipment according to the
maintenance procedure
Repeated circuit-breaker operation is an indication that a fault or
abnormal load may exist. Increasing the breaker rating or bypassing
protection can create an electrical fire or wiring-damage hazard and is not
an acceptable substitute for troubleshooting the underlying problem.
4. A technician is troubleshooting an aircraft lighting circuit in which the
lamp does not illuminate. The lamp has been verified serviceable, and
the circuit breaker is closed. A schematic indicates that the lamp
receives power through a switch and connector. Which sequence is
generally most effective for systematic troubleshooting?
A. Replace every component in the circuit until the lamp operates
B. Begin making random resistance measurements without reference to the
wiring diagram
C. Verify the applicable power source, protection, switching, wiring,
grounding, and load in a logical sequence using approved documentation
D. Disconnect all aircraft electrical systems and replace the lamp again
Answer: C. Verify the applicable power source, protection, switching,
wiring, grounding, and load in a logical sequence using approved
documentation
Certification Exam Practice Questions
And Correct Answers (Verified Answers)
Plus Rationale 2026 Q&A| Instant
Download Pdf
1. In an aircraft electrical troubleshooting scenario, a technician is
investigating a DC bus that shows normal voltage with no load but
drops significantly when several electrical consumers are energized.
The battery has recently passed a capacity test, the generator output
is within specification at the source, and the circuit protection devices
show no signs of tripping. Voltage measurements taken progressively
along the feeder indicate an increasing voltage drop across a particular
connection. Which condition most directly explains the observed
symptom, and what troubleshooting action is most appropriate?
A. An open circuit in the feeder, requiring replacement of the entire wire
bundle
B. A high-resistance connection, requiring inspection, cleaning, tightening,
or replacement in accordance with the maintenance data
,C. An excessive generator frequency, requiring adjustment of the generator
speed
D. A short circuit downstream, requiring immediate removal of every
electrical load from the aircraft
Answer: B. A high-resistance connection, requiring inspection, cleaning,
tightening, or replacement in accordance with the maintenance data
A high-resistance connection can produce acceptable voltage with little or
no current flow but develop a substantial voltage drop when current
increases. Progressive voltage-drop testing under the appropriate
energized conditions helps isolate the defective connection or conductor.
2. During troubleshooting of an aircraft 28-volt DC electrical system, a
technician measures 28.2 volts directly at the generator output
terminal but only 24.6 volts at a remote equipment bus while a high-
current load is operating. The aircraft wiring diagram shows several
connectors and circuit-protection devices between the generator and
the bus. Which troubleshooting technique provides the most useful
information for locating the excessive resistance?
A. Measure resistance of the entire aircraft wiring system with all loads
energized
B. Measure voltage drop across individual sections, connectors, switches,
and protective devices while the circuit carries its normal load
,C. Disconnect the battery and measure generator frequency at the bus
D. Replace the generator before performing any additional tests
Answer: B. Measure voltage drop across individual sections, connectors,
switches, and protective devices while the circuit carries its normal load
Voltage-drop testing under load identifies unwanted resistance that may
not be apparent during an unloaded continuity or resistance test.
Measuring across individual circuit sections allows the technician to
progressively isolate the defective component or connection.
3. An aircraft circuit breaker repeatedly trips shortly after a particular
cabin electrical device is switched on. The breaker rating corresponds
to the aircraft wiring requirements, and the same circuit previously
operated normally. What should the technician generally do first when
following an approved troubleshooting procedure?
A. Install a circuit breaker with a higher current rating
B. Reset the breaker repeatedly until the equipment operates
C. Determine whether an abnormal current condition or fault exists and
isolate the affected circuit or equipment according to the maintenance
procedure
D. Permanently bypass the circuit breaker to prevent nuisance tripping
, Answer: C. Determine whether an abnormal current condition or fault
exists and isolate the affected circuit or equipment according to the
maintenance procedure
Repeated circuit-breaker operation is an indication that a fault or
abnormal load may exist. Increasing the breaker rating or bypassing
protection can create an electrical fire or wiring-damage hazard and is not
an acceptable substitute for troubleshooting the underlying problem.
4. A technician is troubleshooting an aircraft lighting circuit in which the
lamp does not illuminate. The lamp has been verified serviceable, and
the circuit breaker is closed. A schematic indicates that the lamp
receives power through a switch and connector. Which sequence is
generally most effective for systematic troubleshooting?
A. Replace every component in the circuit until the lamp operates
B. Begin making random resistance measurements without reference to the
wiring diagram
C. Verify the applicable power source, protection, switching, wiring,
grounding, and load in a logical sequence using approved documentation
D. Disconnect all aircraft electrical systems and replace the lamp again
Answer: C. Verify the applicable power source, protection, switching,
wiring, grounding, and load in a logical sequence using approved
documentation
