What is RCR in Aviation? (Reverse Current Relay)

A reverse current relay (RCR) is an important component in aviation electrical systems. It is designed to protect electrical equipment from damage caused by reverse current flow. In simple terms, when electrical current flows in the opposite direction than intended, the RCR detects this abnormality and takes corrective action to prevent potential harm.

Understanding the Function of Reverse Current Relay

The reverse current relay plays a crucial role in aviation by safeguarding various electrical devices and systems such as generators, motor-driven pumps, and batteries. It is primarily used to prevent damage to these systems when the direction of current flow is reversed.

The RCR functions by continuously monitoring the current flow in the system it is installed in. When the current flows in the opposite direction, indicating a potential fault or malfunction, the relay triggers a response to disconnect the affected equipment from the circuit. This disconnection prevents backfeed, which can cause overheating, damage, or failure of the equipment.

The reverse current relay is especially critical in aviation applications where the electrical system operates in complex and interdependent networks. A fault in one component can have a domino effect, leading to widespread damage and possible system failure. The RCR acts as an early warning mechanism, alerting operators to any reverse current issues before they escalate.

RCRs are typically designed as electromechanical devices, consisting of a coil, armature, and contacts. The coil produces a magnetic field when energized, which attracts the armature. In normal current flow, the armature is held in place due to the strength of the magnetic field. However, if the current flow is reversed, the armature loses its magnetism and moves away from the contacts, causing the relay to open and disrupt the circuit.

It is worth noting that RCRs are not foolproof and can experience failures or malfunctions like any other electrical component. Regular maintenance, testing, and inspection are crucial to ensure their proper functioning. Aviation maintenance personnel follow specific guidelines and procedures to ensure the reliability and effectiveness of reverse current relays.

Applications of Reverse Current Relay in Aviation

The reverse current relay finds applications in various aviation systems where protecting against reverse current flow is of utmost importance. Let’s explore some common applications:

1. Generator Protection

In aviation, generators are essential for providing electrical power to various aircraft systems. The reverse current relay is used to protect generators from reverse current flow, which can occur due to a malfunctioning battery or a damaged circuit. By quickly detecting and isolating the faulty generator, the relay prevents further damage to the electrical system and ensures the continuous and reliable supply of power.

2. Motor-driven Pump Protection

Motor-driven pumps are used in aircraft to perform various functions such as fuel transfer, hydraulic system operation, and cooling. The reverse current relay helps protect these pumps from damage caused by reverse flow, which may occur due to leaks or failures in the associated systems. By interrupting the circuit, the relay prevents potential damage to the pump and ensures its proper functionality.

3. Battery Protection

Batteries play a critical role in aviation, providing backup power during emergencies or when the main power source is unavailable. The reverse current relay is employed to protect batteries from reverse current flow, which can occur when external power sources are connected incorrectly or when there is a fault in the charging system. By isolating the battery from the circuit when reverse current is detected, the relay prevents damage to the battery and ensures its optimal performance.


The reverse current relay, or RCR, is a vital component in aviation electrical systems. It serves to protect various equipment, such as generators, motor-driven pumps, and batteries, from damage caused by reverse current flow. By monitoring the direction of current, the RCR can detect any abnormality and take corrective action to prevent further harm. Its applications in aviation are diverse and encompass crucial systems that rely on the integrity of electrical circuits. Therefore, it is essential to perform regular maintenance, testing, and inspection to ensure the reliability and effectiveness of reverse current relays in aviation.

For More: What is FDM in Aviation? (Flight Data Monitoring)