Home Boeing Boeing 737 What is AOC on Boeing 737? (Air/Oil Cooler)

What is AOC on Boeing 737? (Air/Oil Cooler)

The Air/Oil Cooler (AOC) is an essential component of the Boeing 737 aircraft, playing a crucial role in maintaining the optimal operating temperature of the aircraft’s engine oil. As the name suggests, the AOC serves to cool the oil that circulates within the engine, ensuring its efficient and reliable functioning during flight. It is a critical part of the aircraft’s lubrication system, ensuring that the engine oil remains within the acceptable temperature range to maximize its performance and durability.

The AOC is located in the engine area, typically attached to the engine or near the oil tank. It consists of a series of fins or tubes through which air is forced to flow. The engine oil, in turn, flows through these heat-exchanging fins or tubes, allowing the heat to transfer from the oil to the surrounding air. This process effectively cools down the oil, preventing it from becoming too hot and potentially causing engine damage or performance issues.

How Does the Air/Oil Cooler Work?

The Air/Oil Cooler operates based on the principle of heat transfer. As the engine runs, the oil becomes heated due to friction and other factors. The heated oil flows from the engine to the AOC, entering through an inlet port. Inside the cooler, the oil passes through numerous small tubes or fins that have a large surface area. As the air is forced to flow over the outside of these tubes or fins, the heat from the oil is transferred to the air, effectively cooling down the oil.

Equipped with a cooling fan, the AOC ensures that a constant flow of air passes over the cooling fins, enhancing the cooling efficiency. The fan draws in air from the surrounding atmosphere and directs it towards the cooler, allowing for optimal heat dissipation. The cooled oil then exits the AOC through an outlet port and returns to the engine, repeating the cycle.

The Importance of Air/Oil Cooler

The Air/Oil Cooler plays a critical role in maintaining the engine oil temperature within the acceptable range. Maintaining the ideal oil temperature is essential for several reasons:

1. Optimal Lubrication: Engine oil serves to lubricate the moving parts within the engine, reducing friction and wear. However, if the oil becomes too hot, its lubricating properties may deteriorate, leading to increased friction and potential damage to the engine components. The AOC ensures that the oil remains at a temperature that allows it to provide the necessary lubrication consistently.

2. Cooling the Engine: In addition to cooling the oil, the AOC also indirectly contributes to cooling the engine itself. By removing excess heat from the oil, the AOC helps to maintain the overall temperature of the engine at optimum levels, preventing it from overheating. This efficient cooling system is essential for the engine’s performance, longevity, and reliability.

3. Energy Efficiency: The AOC plays a significant role in optimizing the energy efficiency of the aircraft. By cooling down the oil, the AOC prevents energy loss due to excessive friction and heat dissipation. This ensures that the engine operates at its peak efficiency, reducing fuel consumption and enhancing the aircraft’s overall performance.

4. Safety and Reliability: The Air/Oil Cooler is crucial for ensuring the safe and reliable operation of the Boeing 737 aircraft. It helps to prevent engine overheating, reducing the risk of engine failure or performance degradation during flight. By maintaining the optimal oil temperature, the AOC contributes to the overall safety and reliability of the aircraft.


The Air/Oil Cooler is a vital component of the Boeing 737 aircraft, playing a crucial role in maintaining the optimal temperature of the engine oil. By cooling the oil, the AOC ensures efficient lubrication, contributes to engine cooling, enhances energy efficiency, and promotes safety and reliability. Understanding the importance and functionality of the AOC is essential for pilots, maintenance personnel, and aviation enthusiasts alike.

For More: What is ACARS on Boeing 737? (Aircraft Communications Addressing And Reporting System)

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