AS9120B, ISO 9001:2015, and FAA AC 0056B Accredited
Posted on April 28, 2025 Berry Allen Aviation
Within the aircraft industry, countless electrical systems necessitate the use of circuit breakers as protective elements to prevent the risks associated with overloads and short circuits. The correct operation of these trip switches depends on routine maintenance and testing, which necessitates basic knowledge on common forms of servicing and care. In this blog, we will give you ten essential steps for maintaining and testing circuit breakers, ensuring that you can uphold safe electrical operations for your aircraft.
As one of the most basic means of upholding circuit breaker health, operators should regularly check for any evidence of deterioration, physical damage, and heat issues through regular visual checks. They should also check equipment for loose connections and observe the condition of the casing for any signs of physical damage.
The trip functionality of circuit breakers requires regular testing to ensure that circuits can be interrupted as necessary in the instance of overloads and short circuits. In order to verify such functionality, one should use a calibrated test set to perform a simulation of overloading or short circuits. If the circuit breaker is operating as intended, the simulated current should activate the tripping feature within designated time limits.
Checks for insulation resistance are done using an inspection method that involves applying a direct current voltage and measuring the amount of resistance insulation provides between two points. This is necessary for determining how durable and clean insulation is. A megohmmeter is the most common tool for conducting such measurements, allowing for different contacts to be checked.
Testing contact resistance plays an essential role in detecting excessive resistance between the electrical contacts of circuit breakers. The contact resistance of main and auxiliary contacts should be measured with a micro-ohmmeter, as performance and temperature stability will suffer in the face of excessive contact resistance.
Thermal Inspections help personnel discover any overheating sections in circuit breakers, which may arise as a result of poor connections or excessive load use. Thermal imaging on the circuit breaker should reveal temperature anomalies when using a thermal camera, with immediate solutions being necessary for any hot spots to prevent circuit breaker damage.
A circuit breaker operates and lasts longer when moving parts are properly lubricated. The moving parts of a circuit breaker require lubrication to prevent damage as a result of friction and sliding, where mechanism contacts and springs need to be protected through the use of manufacturer recommended substances. Proper lubrication results in an extended lifespan for a circuit breaker, reducing the need for maintenance and costly expenditures.
The protection settings of a circuit breaker need to be calibrated from time to time for proper operational behavior. A relay test should be used to set protection parameters, including overcurrent levels, short circuit, and ground fault settings. Failure to calibrate equipment properly could result in malfunctions that prevent correct functionality during electrical faults.
The regular cleaning of circuit breakers remains an important step of maintenance, as the operation of contacts and mechanisms requires free operation without debris and dust accumulation impeding functions. A soft brush combined with compressed air tools should be used to clean both the internal and external parts of circuit breakers, while solvents and abrasive materials should be avoided with their potential to damage components.
The personnel who handle circuit breaker maintenance and testing operations need training to develop all necessary skills for safe handling. For example, employees must receive training that includes learning correct inspection skills, operational testing methods, safety risks, and proper equipment use.
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