What is ELCU on Boeing 737? (Electrical Load Control Unit)

The Electrical Load Control Unit, or ELCU, is an essential component of the Boeing 737 aircraft’s electrical system. It is responsible for efficiently distributing and controlling the electrical loads throughout the aircraft, ensuring that all systems and equipment receive the necessary power to operate safely and effectively. The ELCU plays a crucial role in managing the electrical power supply, monitoring the power usage, and protecting the electrical system from overloads or faults.

As the aircraft’s electrical demand increases or decreases during the flight, the ELCU adjusts the power distribution accordingly, ensuring that the power is allocated efficiently to different systems such as avionics, lighting, sensors, and various electronic components. It acts as a control interface between the aircraft’s power sources, such as generators and batteries, and the electrical loads, ensuring a steady and reliable power supply to all critical systems.

Let’s dive deeper into the functionality and significance of the Electrical Load Control Unit on the Boeing 737 aircraft.

The Role of the Electrical Load Control Unit

The Electrical Load Control Unit is essentially the brain that oversees the distribution and management of electrical loads on the Boeing 737. Its primary role is to ensure that the electrical power generated by the aircraft’s generators is allocated efficiently to all the systems and equipment on board.

One of the key responsibilities of the ELCU is load shedding. Load shedding refers to the process of selectively disconnecting non-essential electrical loads from the system in the event of a power overload or under certain conditions, such as during engine start. The ELCU intelligently identifies the non-critical electrical loads and temporarily removes power from them to maintain the operation of vital systems.

For instance, during an engine start sequence where a significant power surge is required, the ELCU prioritizes critical systems like the engine start pumps, ignition systems, and hydraulic pumps. It temporarily disconnects lower-priority loads, such as cabin lighting or passenger entertainment systems, to ensure sufficient power availability for the critical components.

In addition to load shedding, the ELCU also performs load monitoring. It constantly monitors the power usage of individual electrical loads and provides feedback to the aircraft’s electrical system. This feedback helps identify potential issues like excessive power consumption or abnormal behavior in electrical components. With this information, maintenance crews can diagnose and rectify electrical faults in a timely manner, ensuring the reliability and safety of the aircraft.

The ELCU and Power Distribution

The Electrical Load Control Unit is responsible for managing the distribution of electrical power from the generators to the loads. It ensures that each system and component receives an appropriate and stable power supply, optimizing their performance.

The ELCU regulates the voltage and frequency of the electrical power based on the load requirements. It maintains the voltage within specified limits to prevent damage to sensitive equipment and ensures compatibility with different electrical systems onboard. By regulating the power, the ELCU provides a stable and consistent electrical supply to various aircraft systems, contributing to the overall efficiency and reliability of the Boeing 737.

The Electrical Load Control Unit also plays a vital role in the automatic power management of the aircraft. It allows for the automatic control of various electrical functions, such as the deployment of flaps, landing gears, and other mechanisms that require electrical power. By automating these processes, the ELCU enhances operational efficiency, reducing pilot workload and ensuring accurate and timely power distribution.


The Electrical Load Control Unit, or ELCU, is an integral part of the Boeing 737 aircraft’s electrical system. It manages the distribution and control of electrical loads, ensuring efficient power supply to different systems and components onboard. The ELCU’s role in load shedding, load monitoring, and power distribution optimization contributes to the aircraft’s safety, reliability, and performance.

As an essential component of the Boeing 737, the ELCU exemplifies the sophistication and engineering excellence behind modern aircraft electrical systems. Its intelligent and reliable operation helps maintain the electrical system’s integrity, enabling the successful and safe operation of the aircraft throughout its lifespan.

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