PRESSURIZATION & ENVIRONMENTAL
The pressurization system keeps the cabin altitude significantly lower than the aircraft’s actual altitude, ensuring a comfortable and safe environment for occupants. It achieves this by routing a steady flow of conditioned bleed air into the sealed cabin and regulating the outflow of air overboard through an automatic control system, with a manual override available to the pilot when needed.
Note:
The bleed air (compressed, conditioned engine air) maintains the cabin at a much lower cabin altitude, typically around 8,000 ft when the aircraft is at 40,000 ft.
That air is breathable because pressure and oxygen partial pressure are adequate; it’s the same air you’d breathe at 8,000 ft in the mountains.
- The pressurization and environmental system is divided into two zones: cockpit and cabin.
- High-pressure bleed air from the left engine supplies the cockpit, while the right engine provides air to the cabin.
- Each stream is conditioned through heat exchangers, regulated, and distributed via individual vents. If cockpit airflow is interrupted, a check valve automatically redirects cabin air forward.
- Cabin pressurization is fully automatic, maintaining up to 8.3 psi differential, which provides a sea-level cabin up to approximately 21,000 ft, and an 8,000 ft cabin altitude at FL410.
- Control is managed through a digital pressurization controller linked to avionics, with settings entered via the PFD landing elevation input. All system data is shown on the MFD, and additional switches are located on the right-hand tilt panel.
- The air conditioning system provides independent cockpit and cabin temperature control through separate rheostats on the right-hand panel. It uses an electric compressor and dual evaporators for zone cooling.
- The system may operate in flight or on the ground when GPU or engine power is available. If a generator fails in flight, the compressor automatically shuts down to conserve electrical power.
- A fresh-air blower and vent system under the nose provides outside airflow to the cockpit when the aircraft is unpressurized.
SYSTEM CONTROLS:
The pressurization controller operates in two modes: Normal and High Altitude, while automatically managing cabin pressure according to aircraft altitude and flight conditions.
Using ambient air data from the avionics system and pilot-selected inputs, it sends precise electrical commands to the climb and dive solenoid valves to regulate cabin pressure.
In normal operation, the system maintains an 8,000-foot cabin altitude up to 41,000 feet, corresponding to a pressure differential of 8.3 ± 0.1 psid.
Its built-in automatic schedule continuously:
- Controls cabin altitude relative to aircraft altitude.
- Modulates the cabin climb/descent rate to match aircraft transitions.
- Compensates for destination elevation as set by the pilot.
OPERATION
AIR SOURCE SELECT Knob
The AIR SOURCE SELECT knob is a rotary electrical selector that determines the source of air supplied to the cabin and cockpit. It commands the Pressure Regulating and Shutoff Valves (PRSOVs) and Flow Control Valves (FCVs) within the bleed-air system, and also activates the fresh-air fan when the aircraft is unpressurized.
- OFF - Both PRSOVs are energized closed, stopping all bleed-air and fresh-air inflow to the cockpit and cabin.
- BOTH (Both Engines) - Both PRSOVs are de-energized open, allowing temperature-controlled, pressurized bleed air from both engines: left engine for cockpit, right engine for cabin.
- L (Left Engine) - The right PRSOV is energized closed, isolating the right engine bleed supply. Bleed air flows only from the left engine, supplying the cockpit first and then the cabin as air moves aft toward the outflow valves.
- R (Right Engine) - The left PRSOV is energized closed, isolating the left engine bleed source. Bleed air flows only from the right engine, supplying the cabin and then the cockpit through a check valve.
- FRESH AIR - Both PRSOVs are energized closed, halting all pressurized bleed-air inflow. The cabin will gradually depressurize.
MANUAL CABIN PRESSURE DUMP:
- The CABIN DUMP switch can be activated at any time DC or EMERGENCY power is available to rapidly depressurize and ventilate the cabin.
- When engaged, the system opens the outflow path to reduce cabin pressure. However, altitude limit valves automatically override the climb solenoid valves to prevent complete depressurization above approximately 14,300 ± 300 feet, ensuring occupant safety.
COCKPIT TEMP and CABIN TEMP Knobs
The COCKPIT TEMP and CABIN TEMP knobs allow the crew to select and control the desired temperature in the cockpit and passenger cabin zones.
Rotating either knob counterclockwise (COLD) commands the lowest temperature, while turning clockwise (HOT) selects the highest. The normal operating range for both zones is approximately 65°F to 85°F.
- COCKPIT TEMP knob sets the target temperature for the cockpit zone. The left (cockpit) PCB compares the selected temperature with readings from the cockpit zone temperature sensor and the left bleed-air duct temperature sensor. Based on this comparison, the system automatically adjusts bleed-air temperature and cooling flow to achieve the commanded cockpit temperature.
- CABIN TEMP knob determines the desired temperature for the passenger cabin. The right (cabin) PCB compares the knob setting with inputs from the cabin zone temperature sensor and the right bleed-air duct temperature sensor, then modulates bleed-air temperature and cooling rate as needed to maintain the selected cabin environment.
AIR COND Switch
The AIR COND switch engages the vapor-cycle air conditioning system when set to ON, as long as one or both fan switches are in an active position: LOW, HI, or FLOOD. This enables the system to deliver cooled, conditioned air to the cabin and cockpit zones.
OXYGEN SYSTEM
The oxygen system is standby/emergency only.
It provides pure O₂ only to masks (crew and passengers), not to the general cabin atmosphere.
It activates automatically (NORMAL mode) only if cabin pressurization fails and the cabin altitude rises above ~14,800 ft, meaning the cabin air has become too thin to breathe safely.
The oxygen system supplies both the crew and passenger distribution networks. Oxygen is continuously available to the crew, while passenger oxygen is provided automatically when cabin altitude exceeds approximately 14,800 feet, or manually at any altitude through operation of the oxygen control valve.
- The system is designed primarily for emergency use, with limited capability for short-duration non-emergency operation. It delivers low-pressure breathable oxygen (≈70 psi) to crew and passengers through individual masks, supplied from a single oxygen bottle.
- A regulator maintains system pressure, while a shutoff valve controlled by the OXYGEN SUPPLY switch in the cockpit enables or disables oxygen flow. The OXYGEN CONTROL VALVE determines distribution mode, and a cockpit gauge displays bottle pressure (and remaining quantity).
- A CAS alert notifies the crew of insufficient supply; if oxygen is off or system pressure is low, an amber OXYGEN OFF message appears. Each crew mask includes an individual control to adjust oxygen flow.
Oxygen Bottle
The system uses a single oxygen bottle located on the right side of the nose storage compartment. It contains compressed oxygen with a usable capacity of 623 liters (22 cubic feet), or an optional 1,133 liters (40 cubic feet) configuration. Storage pressure ranges from 1,600 to 1,800 psig.
OXYGEN SYSTEM - OPERATION
System Overview
- Single oxygen bottle supplies both crew and passenger masks.
- Normal system pressure: 1,600–1,800 psig.
- Oxygen available for crew at all times, and for passengers automatically or manually as required.
OXYGEN - HOW MANY ‘BREATHERS’
- Each loaded passenger (in the cockpit and in the cabin) is taken into account and being integrated into the oxygen system, in its various modes of operation.
- When oxygen is consumed (intentionally by setting the drop-masks knob or in case of pressurization loss at high altitude), each loaded passenger acts as an active ‘breather’ and increases oxygen consumption rate respectively.
OXYGEN CUTOFF Knob
- Located below the OXYGEN pressure gauge (lower right instrument panel).
- Function: Closes the bottle regulator to shut off oxygen delivery to all users.
- When set to CUTOFF, system line pressure vents overboard.
OXYGEN CONTROL VALVE Knob
- Positioned on the far left edge of the instrument panel.
- Controls passenger oxygen distribution through three selectable modes:
- CREW ONLY: Oxygen available to crew only; passenger supply closed. Operates with or without DC power. Crew masks provide selectable NORMAL / 100% / EMERGENCY oxygen. Crew masks certified for use to 40,000 ft cabin altitude.
- NORMAL: Enables automatic passenger oxygen deployment. Masks drop automatically if cabin altitude >14,800 ft. System shuts off automatically when cabin altitude decreases below ≈11,500 ft. Operates automatically through the passenger oxygen solenoid valve.
- DROP MASK: Manually deploys passenger oxygen masks at any altitude. Functions with or without DC power. Masks immediately drop from overhead compartments when selected. To stop passenger oxygen flow, select CREW ONLY or NORMAL (below 11,500 ft).
MIC Switches (Left / Right)
- Located below and inboard of each control yoke on the tilt panel.
- Two-position switch: HEADSET / OXY MASK.
- HEADSET: Normal crew communication via headset microphone.
- OXY MASK: Switches audio input to the oxygen mask microphone and automatically activates cockpit speaker audio (cannot be turned off). Push-to-talk switch transmits via the selected microphone source.
OXYGEN Pressure Gauge
- Located on the copilot instrument panel, right of the PFD, above the OXYGEN CUTOFF knob.
- Indicates system pressure and bottle volume.
- Range Markings:
- Yellow arc: 0-400 psi - Low / Service required
- Red line: 2,000 psi - Maximum charge limit
- Normal operating range: 1,600-1,800 psig
Pilot Note:
If system pressure is low or oxygen is shut off, a CAS message “OXYGEN OFF” appears. Always verify adequate supply prior to flight in accordance with the AFM procedures.
