Pressurization Control & Operation - Pneumatics - Airframes & Aircraft Systems #42

Summary

This lesson explores different types of pressurization controllers in aircraft, focusing on their evolution from pneumatic to electronic systems. It discusses the controller's functions, including cabin altitude control, rate of change, and maximum differential pressure limitation. The script explains how modern aircraft use electronic controllers for automatic pressurization, with pilots setting cruise and landing altitudes. It also covers manual control and the necessary instruments for monitoring cabin pressure, altitude, and differential pressure, ensuring passenger comfort and safety.

Takeaways

• 😀 Pressurization systems use various types of controllers, including pneumatic, electropneumatic, and electronic controllers.
• 🛫 Controllers manage cabin altitude, rate of change, and limit maximum differential pressure to ensure passenger comfort and aircraft integrity.
• 🔑 Older generation jets use electropneumatic controllers, while modern aircraft rely on electronic controllers for pressurization.
• ✈️ On Boeing 737 aircraft, pilots set cruise altitude and landing airfield elevation during pre-flight preparation, which the controller uses to manage cabin pressure.
• 🚀 Airbus types typically operate without pilot input, with the controller receiving altitude data from flight management computers.
• 📊 The pressurization control system in modern aircraft includes automatic controllers with inputs from static pressure sensing systems and cabin pressure sensors.
• 🔄 In case of a controller failure, a standby controller automatically takes over to ensure continued pressurization.
• 📉 The minimum required indications for pressurization systems are cabin altitude, vertical speed, and differential pressure, displayed on gauges or LCD screens.
• 🔧 In manual mode, pilots can control the outflow valve position to directly manage cabin pressure, altitude, and rate of climb or descent.
• ⚠️ Cabin pressurization rates should be carefully monitored, with typical limits of 500 feet per minute climb and 300 feet per minute descent to prevent discomfort.

Q & A

What are the main types of controllers used in pressurization systems?

Pressurization systems use various types of controllers including purely pneumatic for small aircraft, electropneumatic for older generation jets, and electronically operated for most modern aircraft.

What are the three primary functions of a pressurization controller?

A pressurization controller controls the cabin altitude, the rate of change of cabin altitude, and limits the maximum differential pressure.

How does an old generation controller differ from a modern electronic controller in terms of pilot interaction?

Old generation controllers require the pilot to manually select the desired cabin altitude and rate of change, while modern electronic controllers automate these tasks based on received altitude data and an inbuilt program.

What specific actions does the pressurization controller take during the aircraft's pre-flight preparation on a Boeing 737?

On a Boeing 737, the pilot selects the aircraft's cruise altitude and landing airfield elevation during pre-flight preparation, and the controller automatically manages the outflow valve to achieve and maintain the appropriate cabin altitude.

How does the pressurization control system in an Airbus aircraft differ from that in a Boeing 737 during normal operation?

In most Airbus types, the pilot makes no inputs to the pressurization system during normal operation as the controller receives all necessary altitude data from the flight management computers.

What are the minimum indications required for a pressurization system?

The minimum indications required for a pressurization system are cabin altitude, cabin vertical speed, and cabin differential pressure.

What is the purpose of pre-pressurization in aircraft before takeoff?

Pre-pressurization ensures a gradual transition to pressurized flight and prevents surges of pressure on rotation during takeoff.

How does the pressurization controller adjust the cabin pressure during the aircraft's climb and descent?

The controller adjusts the cabin pressure by controlling the rate of cabin climb or descent in proportion to the aircraft's climb or descent rate, maintaining a slightly less than the maximum permitted differential pressure.

What happens when the aircraft reaches its cruise altitude in terms of cabin pressurization?

When the aircraft reaches its cruise altitude, the controller maintains a constant cabin altitude, resulting in a constant mass flow of air through the cabin with the mass of air coming in from the packs equaling the mass leaving through the outflow valve.

How does the pressurization system handle significant changes in the aircraft's altitude during level flight?

In level flight, small changes in aircraft altitude are accommodated without any change in cabin pressure. However, if a significant increase in crew's altitude is required, the flight altitude selection must be reset to prevent exceeding the maximum differential pressure.

What are the normal cabin descent rates during the aircraft's descent and landing?

The normal cabin descent rate during the aircraft's descent is about 300 feet per minute, and it is adjusted to approximately 0.1 psi on touchdown.