What Circuit Protection Devices Do Aircraft Employ?

The direct short in a circuit can bring about damaging results along a network and its included wiring. This event occurs when voltage present in a system comes in direct contact with the ground or return side of the circuit, resulting in a path of current which contains little to no resistance. In such circumstances, current with very minimal resistance can lead to the rapid generation of heat which can result in melted wiring, damaged equipment, and the potential opening of the circuit. While aircraft primarily employ small gauge wiring with a limited carrying capacity, the size of wiring is ultimately chosen based on how much current the wires are expected to carry under normal operating conditions. To ensure aircraft circuits remain unperturbed from direct shorts, it is compulsory that circuit protection devices like fuses, current limiters, and circuit breakers be installed to protect different networks against overcurrent conditions.


Fuses are designed to allow all current in a circuit to pass through its assembly. Manufactured to prevent the flow of excess current during any given situation, most fuses are constructed with a thin strip of metal made from an alloy of tin and bismuth. This metal strip, housed within a casing encapsulating the fuse component, is designed to melt and open the circuit if current surpasses a desired limit. Once the link within the fuse has broken, the component will need to be replaced.

When replacing a blown fuse, the new item must align with the circuit's defined capacitance values. As fuses applied for aircraft are available in plug-in holder and clip-type holder variations, it is crucial that the correct type of fuse is installed to avoid premature part failure.

Current Limiter

Similar in function to a fuse, current limiters are built with a link that is meant to open when overcurrent conditions exceed a certain threshold. As current limiters are designed to withstand excess amounts of current for a short period of time, they only activate to separate bonds when a surge in current ceases to subside. Current limiters are often applied to a marginalized section within an aircraft to sectionalize a circuit.

Circuit Breaker

A circuit breakers is a common component often used in lieu of a fuse; however, unlike a fuse, a circuit breaker can be reset. As such, circuit breakers work by disconnecting internal contacts to terminate current if it is surpassing a predetermined value in a system. After a circuit breaker has separated its internal contacts, it can often be easily reset with the flip of a switch by hand. Common circuit breakers generally used in aircraft systems consist of magnetic or thermal overload types, among others.

Each unique in design depending on their application, parts like a fuse, current limiter, and circuit breaker are subject to failure if kept operational without proper maintenance.  However, to further facilitate current traveling between connecting parts, modern equipment like circuit protection devices and health monitoring systems are available. Installed in select networks, typically among those that require constant observation, circuit protection devices and  health monitoring systems work in tandem by operating around a database which has been created to establish pre-made operational characteristics. If these operational characteristics are recognized as exceeding their limits, the system will cause the circuit protection device to trip, terminating connections to ensure that the device, and all other parts, are kept from harm.

To protect your aircraft electrical systems from damage caused by excess current, it is vital that circuit protection devices are used. Serving the common purpose of keeping aircraft safe, ASAP Axis is here to streamline and expedite any one of your orders for immediate procural. As a leading distributor of tools essential for vehicle maintenance, we feature a diverse catalog of components necessary for aircraft safety, including circuit breaker actuators, circuit breaker adapters, and various other circuit breaker accessories. Due to our quality control and export compliance, we operate with AS9120B, ISO 9001:2015, and FAA AC 00-56B certification and accreditation, alongside our NO CHINA sourcing pledge. If you would like to request a quote for your comparisons, you can submit an RFQ form as provided on our website. Upon receipt, a dedicated account manager will quickly review and respond with a personalized solution to your needs in just 15 minutes or less, 24/7x365.


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