Pressurisation System Operation
Before takeoff the cabin altitude selector is selected to Cruise Altitude + 500 ft. This provides for optimum performance from the pressurisation system.
The cabin rate controller is positioned with the arrow pointing straight up. This position generally provides a cabin rate of climb/descent of 500 ft/min.
Select the altitude selector to cruise height + 500ft.
Select the cabin rate selector to point straight up.
For cruising altitudes below values shown on the inner scale of the altitude controller (10 000 ft) always select the destination field elevation + 200 ft. on the outer scale.
Any altitude selections made in flight should be done so slowly so as to reduce occupant discomfort due to the ensuing cabin pressure changes.
If you are concerned about the cabin altitude being too high at any stage of a flight (particularly at high flight levels) selecting a hotter temperature on the manual temperature control switch will reduce the cabin altitude slightly.
This is due to an increase in hot bleed air bypassing the ACM and entering the pressurised cabin quite quickly causing a decrease in cabin altitude.
As the bypass valve opens more hot air will enter the cabin
At top of descent the altitude selector knob should be positioned to an altitude 200 ft above the destination airfield elevation on the outer scale, which will ensure that the aircraft will remain pressurised until the aircraft reaches this altitude.
Below 200 ft AGL at the destination the pressurisation system will open the outflow valve below this altitude to ensure that the aircraft will depressurise prior to landing.
At touch down the right hand main landing gear squat switch energises the cabin dump solenoid to direct vacuum pressure to the outflow and safety valves to ensure that the cabin will not pressurise during ground operations.
Cabin pressurisation is a pneumatic function, independent of electrical control except to dump pressurisation during ground operations through the right hand main landing gear squat switch.
Vacuum pressure is used to open the outflow and safety valves during pressurised flight operations.
Should vacuum pressure be lost, the pressurisation controller will become inoperative causing the outflow valve to close with the cabin pressure being maintained at 6.3 PSI by the pressure differential limit switches.
Pressure Differential Limit switches
Should the cabin pressurisation be lost for any reason the emergency pressurisation can be manually selected on the pressurisation source selector, or, if the ACM fails will automatically be selected allowing unconditioned bleed air from the right engine to enter the cabin.
Cabin temperatures will quickly rise requiring quick action to descend to an altitude so that unpressurised flight can be continued.
Turn the emerg. cabin press. ON/OFF with the PRESS SOURCE selector.
Emergency press. air flows only from the right engine
FLIGHT.ORG AIR has implemented an emergency pressurisation modification to all of its Conquests to increase the safety margin against a failed emergency pressurisation valve should it not be able to be turned off.
This modification utilises a second valve fitted in line with the emergency pressurisation valve incase the standard valve fails in the open position should the ACM fail.
The emergency pressurisation modification also places a manually controlled switch which will close the second valve to shutoff the emergency pressurisation airflow should the first valve fail due to lack of use.
Simply lift the plastic cover and press the button to stop the flow of bleed air into the cabin