(O) May be inoperative provided:
a) Both valves are verified closed,
b) PAC Switches remain OFF,
c) Wemac Boost is operational,
d) Aircraft is operated unpressurized,
e) Aircraft is operated at or below 10,000 MSL, and
f) Baggage compartment remains empty.
(To Verify no air is flowing out of PACs)
Refer to Procedures Guide Appendix page A-3 (Air Distribution Flow Diagram) while performing this
1. Start both engines.
2. Ensure APU is shut down and Wemac Boost is OFF.
3. Position CKPT PAC and CABIN PAC selectors to OFF.
4. Place ISOL VALVE to the CLSD (vertical) position.
5. Close all cabin overhead outlets (Wemacs) and open cockpit overhead air outlets.
a. There should be no airflow from the cockpit overhead air outlets.
6. Switch to manual pressurization and select and hold the manual control toggle (cherry picker) to the DOWN position. No change in cabin rate should be observed on the cabin rate-of-climb indicator.
7. Shut down engines.
8. Place placard adjacent to the environmental control
panel stating, "COCKPIT AND CABIN PAC's INOP."
9. Make appropriate discrepancy report entry.
With both bi-level flow control valves inoperative, the aircraft may be dispatched if both valves are verified in the closed position. No airflow out of either PAC will indicate that both bilevel flow control valves are in the closed position. Using the manual pressurization is a secondary check to ensure the valves are closed and the cabin is not being pressurized. However, presence of airflow indicates one or both valves are stuck in the open position and further troubleshooting should be initiated prior to aircraft dispatch.