Pressurizarion Flashcards
Overview 1
Bleed air either from the engines or APU is conditioned by the environmental system and sent through ducts into the cabin and cockpit. Conditioned bleed air provides pressurization, ventilation, and air conditioning. Outflow valves in the aft pressure bulkhead control the amount of escaping air to maintain cabin pressurization.
Overview 2
Two outflow valves on the aft pressure bulkhead are controlled automatically or manually. The valves are interconnected and work together. When the outflow valves are open, cabin air pressure escapes into the unpressurized tail cone and cabin pressure decreases, allowing cabin altitude to climb. When the outflow valves partially close, less cabin air pressure escapes and the pressure increase causes cabin altitude to descend.
What does the CABIN DUMP BUTTON do?
The cabin dump button opens both outflow valves to their maximum position.
It requires 28 VDC main electrical power to activate the dump mode.
CABIN ALT TOGGLE LEVER
Commands altitude tor climb, descend, or hold altitude as selected. Holding the toggle lever UP directs regulated vacuum from a dedicated static source to the manual control metering valve on the secondary outflow valve. Both outflow valves open and cabin altitude climbs. When the manual toggle is selected DN, cabin pressure is applied to the secondary outflow valve causing both outflow valves to close and cabin altitude descends.
MANUAL RATE KNOB
The manual RATE knob is below the red manual CABIN ALT toggle lever. The knob operates a needle valve controlling the rate at which the cabin climbs or descends. The MIN and MAX positions allow a rate of change of approximately 300 to 800 fpm.
