1. Climb Rate Indicator
2. Climb Rate Selector
3. Cabin Altitude Limit Selector
4. Outflow Safety Valve Indicators
5. Cabin Altitude Indicator
6. Pressure Control Switch
7. Vacuum Solenoid Pressure/Dump Valve

8. Differential Pressure Indicator
9. Cabin Air Source/Pressure Control
10. Cabin temperature thermostat
11. ECS Mode Selector
12. Emergency Pressure Mode Switch
13. Fan Control
14. Temperature Mode Control

Always check the cabin temperature and cabin differential pressure periodically to insure that the proper comfort level is being maintained.  Cabin temperature can be read on the OAT/Cabin Temp indicator on the main instrument panel.

Although it looks the same, it is not to be confused with the vertical speed of the aircraft. This indicates the actual rate of change in the cabin altitude from the pressurization system.

2. Climb Rate Selector

Use this knob to regulate the rate of change in the cabin pressure from a minimum of 175 FPM to a maximum of 2,500 FPM.

3. Cabin Altitude Limit Selector

The cabin altitude limit selector, in the center of the cabin pressure controller, is used to select the desired cabin altitude for cruise altitude. 

4. Outflow Safety Valve Indicators

The outflow safety valve is mechanically the same as the isobaric valve. It differs in that it is not modulated by the cabin pressure, but rather, it is fully opened and closed. The safety valve opens during landing by the left gear squat switch action and stays open during ground operations to prevent pressurization of the cabin. It is held open during ground operations by vacuum supplied from the pneumatic system.

5. Cabin Altitude Indicator

Cabin pressure is monitored on the cabin altitude pressure gauge. This gauge is calibrated in feet.

6. Pressure Control Switch

This switch controls the isobaric valve and mode of operation of the pressurization system.  There are three positions:

1. Dump - in this position the isobaric valve is open from the pressure vessel to the outside atmosphere. No pressurization is possible in this position.

2. Cabin Press - in this position the isobaric valve is regulated to the outside atmosphere according to the pressurization system control. 

3. Test - use this position to test the system during ground operations. This will temporarily close the outflow safety valve for 5 seconds, and the isobaric valve, allowing for momentary pressurization of the pressure vessel. The outflow safety valve indicator should show Closed and the Vacuum Solenoid Pressure/Dump Valve should show Press during a successful test.

7. Vacuum Solenoid Pressure/Dump Valve

This indicates the position of the outflow isobaric valve, which is a mechanical valve located on the upper aft pressure bulkhead. It is modulated by the cabin pressure controller to regulate the outflow of the pressurized cabin air so as to maintain the cabin altitude desired. When indicating Dump the valve is open to the outside atmosphere. When indicating Press the valve is modulated/regulated by the pressure control system.

8. Differential Pressure Indicator

The difference in pressure between the outside atmosphere and the pressure vessel is monitored on the differential pressure gauge. This gauge is calibrated in pounds per square inch (PSI) pressure differential.

9. Cabin Air Source/Pressure Control

Controls the air source for the cabin. When pressurization is desired, this selector must be set to Press. Otherwise the isobaric valve between the pressure vessel and the outside atmosphere will be open.

10. Cabin temperature thermostat

Controls the comfort level of the cabin. Heating or coolant is applied to either outside air or pressurized cabin air. Works in conjunction with the ECS mode selector [11] and the Temperature Control Mode Selector [14].

11. ECS Mode Selector

This is the main mode of control switch for the entire environmental/pressurization system. There are five (5) positions on this selector:

• Off - shuts down the entire system

• Lo - applies slow heating or cooling to the cabin environment - normal pressurization rate*

• Hi - applies more rapid heating or cooling to the cabin environment - normal pressurization rate*

• Hi Heat - applies rapid cabin heating - normal pressurization rate*

• Emer Press - applies more rapid pressurization to the cabin in case of high cabin altitude readings

* If the Emergency Pressure Mode Switch [12] is set to manual (Man), rapid pressurization can only occur if the ECS Mode Selector is in Emer Press position.

12. Emergency Pressure Mode Switch

Controls the Emergency Pressurization System (EPS). The EPS has two modes of operation:

• Auto - normally recommended.  If cabin altitude exceeds safety limit a more rapid pressurization rate is provided

• Man - Manual mode allows for the very highest pressurization rate. Note that the ECS Mode Selector must be set to EMER PRESS for manual EPS to work!  Otherwise normal pressurization rate is provided.

13. Fan Control

Controls the rate of air circulation in the cabin.

14. Temperature Mode Control

Controls the mode of operation (heating or cooling) of the ECS. There are three (3) modes of operation:

• AUTO - Recommended for normal operations, this position will allow both heating or cooling according to the Thermostat Control [10] setting

• HEAT - Will allow for heating of the cabin only, according to the Thermostat Control [10] setting

• COOL - Will allow for cooling of the cabin only, according to the Thermostat Control [10] setting