Trimec Aviation Inc. - Westwind Wizard

Westwind Wizard

#23 Ground Pressurization Checklist

First, anytime the aircraft is started, the DV window must be open. This is because both bleed switching valves (BSV’S) are failed open, and they require electrical power and bleed air pressure to close. Therefore, air is being pumped into the cabin as soon as the engine is cranked, and not enough vacuum is generated at the venture to open the safety valve.

Second, keep the outflow valves clean. Use mild soap or isopropyl alcohol to wipe the knife edge seal and surrounding area.

Third, spray a little LPS-1 into the vent hole on the outflow valve and push up the valve and spray the shaft area also.

Fourth, use the ground pressurization button. If yours does not work, get it fixed.

GROUND PRESSURIZING THE WESTWIND:

Check the following first before closing the isobaric valve.

The normal valve opens on engine start.
Ground pressurization button used – normal valve closes ¾ -- Safety valve start opening – normal valve closes completely.
Trip the left main landing gear squat switch to flight position – safety valve closes fully and normal valve opens and meters.

INFORMATION ONLY – The manual dump valve only controls the safety valve with vacuum from the ejector on forward pressure bulkhead. You must have the engines running and all doors and DV window shut.

TO PRESSURIZE:

Cut safety wire and close the isobaric valve.
Open the manual dump valve fully.
Start both engines.
Select both on bleed source selector.
Close the DV window slowly.
Pull the LH pressurization circuit breaker.
Fully close the manual dump valve.
You may have to increase engine speed or toggle temp to hot to reach max differential, but it should get there and operate on the limiters of the outflow valves.
Slowly open the manual dump to bleed the cabin to ambient pressure.
Reset all circuit breakers and re-open the isobaric valve and safety wire it.

NOTE: If you want to check your cabin leakage rate, leave the aircraft pressurized and shut down both engines. See how long it takes the aircraft to return to ambient pressure.

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Fort Worth, Texas 76106