AMT 212
Cabin Pressurization Cabin Differential Pressure (CDP)
Cabin Pressurization Cabin Vertical Speed (CVS)
- We need to pressurize the aircraft in order to Cabin Altitude (CA)
ensure adequate passenger comfort and safety. If the outflow valve if closed:
By providing safe environmental pressure, that is • CDP↑ CA↓CVS↓
enough to push oxygen through the human If the outflow valve if open:
bloodstream at flights beyond 8,000 ft. • CDP↓ CA ↑CVS↑
- When an aircraft is flown at a high, it burns less Pressurization Terms
fuel for a given airspeed than it does for the same 1. Cabin altitude
speed at a lower altitude. - It is used to express cabin pressure in
- A cabin pressurization system must accomplish terms of equivalent altitude sea level.
several functions if it is to ensure adequate 2. Cabin differential pressure
passenger comfort and safety. - The difference between the air pressure
1. It must be capable of maintaining a cabin inside the cabin and the air pressure
altitude of approximately 8,000 ft at the outside the cabin.
maximum designed cruising altitude of 3. Cabin rate of climb & descend
the aircraft. - The rate of change of air pressure inside
2. Must be designed to prevent rapid the cabin, expressed in feet per min (fpm)
changes of cabin altitude which may be of cabin altitude change.
uncomfortable or injurious to passengers 4. Aircraft Altitude
and crew. - The actual height above sea level at
3. Cabin air must also be heated or cooled. which an aircraft is flying.
- Compressible seals around doors combine with 5. Ambient Pressure
various other seals, grommets, and sealants to - The pressure in the area immediately
essentially establish an air tight pressure vessel. surrounding the object under discussion.
- A key factor in pressurization is the ability of the 6. Standard Barometric Pressure
fuselage to withstand the forces associated with - The weight of gases in the atmosphere
the increase in pressure inside the structure sufficient to hold up a column of mercury
versus the ambient pressure outside 760 mm high at sea level (14.7 psi). This
- Metal fatigue from repeated pressurization and pressure decreases with altitude.
depressurization weakens the airframe. 7. Gage Pressure
Sea level = 14.7 psi - A measure of the pressure in a vessel,
At 8000ft = 10.92 psi container, or line, as compared to
Time of useful consciousness atmospheric pressure.
At approx.: Pressurization modes
18,000ft = 15 mins • Isobaric Mode
20,000ft = 1-3 mins
- It works to maintain cabin altitude at a
30,000ft = 30-60 secs single pressure despite the change
35,000ft = 15-30 secs altitude of the aircraft.
Pressurize area:
• Constant Differential Mode
• Cockpit
- It works by controlling cabin pressure to
• Avionics bay
maintain a constant pressure difference
• Cabin between the air pressure inside the cabin
• Caro compartments and the ambient air pressure, regardless
2 major components for cabin pressurization of the altitude changes.
• Outflow Valve
- It is located at the right-hand lower
empennage.
- It is used to regulate the amount of air
allowed to escape from the pressurized
Cabin Pressurization Cabin Differential Pressure (CDP)
Cabin Pressurization Cabin Vertical Speed (CVS)
- We need to pressurize the aircraft in order to Cabin Altitude (CA)
ensure adequate passenger comfort and safety. If the outflow valve if closed:
By providing safe environmental pressure, that is • CDP↑ CA↓CVS↓
enough to push oxygen through the human If the outflow valve if open:
bloodstream at flights beyond 8,000 ft. • CDP↓ CA ↑CVS↑
- When an aircraft is flown at a high, it burns less Pressurization Terms
fuel for a given airspeed than it does for the same 1. Cabin altitude
speed at a lower altitude. - It is used to express cabin pressure in
- A cabin pressurization system must accomplish terms of equivalent altitude sea level.
several functions if it is to ensure adequate 2. Cabin differential pressure
passenger comfort and safety. - The difference between the air pressure
1. It must be capable of maintaining a cabin inside the cabin and the air pressure
altitude of approximately 8,000 ft at the outside the cabin.
maximum designed cruising altitude of 3. Cabin rate of climb & descend
the aircraft. - The rate of change of air pressure inside
2. Must be designed to prevent rapid the cabin, expressed in feet per min (fpm)
changes of cabin altitude which may be of cabin altitude change.
uncomfortable or injurious to passengers 4. Aircraft Altitude
and crew. - The actual height above sea level at
3. Cabin air must also be heated or cooled. which an aircraft is flying.
- Compressible seals around doors combine with 5. Ambient Pressure
various other seals, grommets, and sealants to - The pressure in the area immediately
essentially establish an air tight pressure vessel. surrounding the object under discussion.
- A key factor in pressurization is the ability of the 6. Standard Barometric Pressure
fuselage to withstand the forces associated with - The weight of gases in the atmosphere
the increase in pressure inside the structure sufficient to hold up a column of mercury
versus the ambient pressure outside 760 mm high at sea level (14.7 psi). This
- Metal fatigue from repeated pressurization and pressure decreases with altitude.
depressurization weakens the airframe. 7. Gage Pressure
Sea level = 14.7 psi - A measure of the pressure in a vessel,
At 8000ft = 10.92 psi container, or line, as compared to
Time of useful consciousness atmospheric pressure.
At approx.: Pressurization modes
18,000ft = 15 mins • Isobaric Mode
20,000ft = 1-3 mins
- It works to maintain cabin altitude at a
30,000ft = 30-60 secs single pressure despite the change
35,000ft = 15-30 secs altitude of the aircraft.
Pressurize area:
• Constant Differential Mode
• Cockpit
- It works by controlling cabin pressure to
• Avionics bay
maintain a constant pressure difference
• Cabin between the air pressure inside the cabin
• Caro compartments and the ambient air pressure, regardless
2 major components for cabin pressurization of the altitude changes.
• Outflow Valve
- It is located at the right-hand lower
empennage.
- It is used to regulate the amount of air
allowed to escape from the pressurized
