Jet engine bleed, do you know how it works?

Summary

In this video, the presenter provides a detailed walkthrough of the high-pressure bleed system on the CFM56-5B engine, which powers the A320 aircraft. Key concepts like the bleed air source, pressure regulation, cooling, and the steps for replacing the high-pressure bleed valve are discussed. The process is broken down into clear steps, including safety precautions, component removal, installation, and testing for leaks. The presenter emphasizes the importance of following proper procedures, including using the correct tools and referencing the latest documentation. The video ends with the aircraft being prepared for run-up after completing the valve replacement.

Takeaways

• 😀 The CFM56-5B engine on the A320 uses bleed air from both high pressure stage 5 and stage 9 to supply aircraft systems like air conditioning and anti-ice.
• 😀 At low speed operation, bleed air is taken from stage 9 due to insufficient pressure from stage 5.
• 😀 The bleed air pressure is controlled by the Bleed Pressure Regulating Valve, which operates pneumatically and is electrically controlled by the bleed monitory computer.
• 😀 An overpressure valve is used downstream of the Bleed Pressure Regulating Valve to protect the system from damage caused by overpressure.
• 😀 The air from the engine is cooled using fan air from the engine's cold stream through a precooler, which reduces the temperature of the bleed air.
• 😀 When the engine is operating at higher speeds, the bleed air from stage 5 is sufficient, and the high-pressure valve closes.
• 😀 The system includes a check valve that prevents the high-pressure air from escaping when the high-pressure valve is closed.
• 😀 Safety precautions are critical during maintenance, including pulling all CBS (Circuit Breakers) to prevent damage to components like the leading edge and reversers.
• 😀 During replacement of the high-pressure bleed valve, it is essential to inspect seals and components, and ensure the correct installation of the new valve.
• 😀 Lubrication is applied to connectors, and torque specifications for clamps and connections must be followed carefully to ensure a proper seal and function.
• 😀 To check for leaks after installation, a dry developer (powder) is applied, which can reveal any air leaks by showing a white line where the air escapes.
• 😀 The final steps involve a full inspection, closing the reversers, and preparing the aircraft for engine run-up and testing of the bleed air system.

Q & A

What is ATA 36, and why is it important for the CFM56-5B engine on the A320?

ATA 36 is a chapter in the aircraft maintenance manual that covers bleed air systems. For the CFM56-5B engine on the A320, bleed air is crucial for powering aircraft systems like air conditioning, anti-ice, and engine control systems.

Where does the bleed air come from in the CFM56-5B engine?

Bleed air is taken from two places in the engine: the high-pressure Stage 5 and Stage 9. Stage 9 is used during low-speed operation when the pressure from Stage 5 is insufficient.

Why is Stage 9 used during low-speed operation of the engine?

Stage 9 is used during low-speed operation because the air pressure from Stage 5 is not sufficient to supply the aircraft systems like air conditioning or anti-ice systems.

What components control and regulate the bleed air pressure?

The bleed air pressure is controlled by the Bleed Pressure Regulating Valve (BPRV) and the Overpressure Valve. The BPRV is controlled pneumatically and electrically by the Bleed Monitoring Computer, ensuring the correct pressure for the aircraft systems.

How does the cooling of bleed air occur in the system?

The bleed air is cooled using a fan-air belt that brings cooler air from the cold stream of the engine, passing through a precooler to cool the hot bleed air before it enters the aircraft systems.

What happens when the engine reaches higher operation limits?

When the engine reaches higher operation limits (idle), the pressure from Stage 5 becomes sufficient, causing the high-pressure valve to close. This allows the system to be supplied by Stage 5 pressure, reducing the need for Stage 9.

What is the function of the high-pressure valve in the bleed air system?

The high-pressure valve controls the supply of bleed air from Stage 5 or Stage 9. It opens or closes based on the pressure requirements of the aircraft systems, ensuring that the correct pressure is provided.

What kind of valve is the high-pressure valve, and how does it operate?

The high-pressure valve is a butterfly-type valve that is spring-loaded to the closed position. This ensures that the valve closes in case of failure, preventing uncontrolled airflow.

What is the importance of torque specifications during the valve installation process?

Torque specifications are important during valve installation to ensure that the clamps holding the valve are secured tightly without being over-tightened, which could cause damage. Following the correct torque ensures a proper seal and safe operation.

How is the leak check performed after the valve installation?

A dry developer powder is applied to the joints and components after installation. If there is a leak, the air will blow away the powder, revealing the location of the leak during the inspection.