Pressurization System Flight Check - Piper Cheyenne IIIA Airplane Maintenance Manual

PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
A. Pressurization Control (continued)
7. Pressurization System Flight Check
The following instructions explain how to perform a pressurization system flight check:
(a) Pre-Flight Procedure
(1.) Ensure cabin door and pilot window are closed and locked.
(2.) Set cabin altitude selector knob so cabin altitude indicates approximately 500 feet above
field altitude.
(3.) Turn cabin rate control knob to NORM position.
(4.) Move cabin air manual control handle to PRESSURIZE position.
CAUTION: CHECK FOR BROKEN OR DISCONNECTED CONTROL CABLE IF LITTLE
EFFORT IS REQUIRED TO MOVE CONTROL HANDLE. DO NOT
CONTINUE FLIGHT CHECK UNTIL INSPECTION OR REPAIRS ARE
COMPLETED.
(5.) Set cabin pressure mode switch to CABIN PRESS position.
(6.) Start engines, set both right and left engine bleed air switches to ON position, ECS
selector switch to HI or LO, as desired, and establish steady cabin air flow.
(7.) Ensure cabin door seal is inflated.
(b) Ascent Procedure
(1.) After lift-off, when selected cabin altitude is attained and cockpit work load permits, select
aircraft cruise altitude plug, 1,000 feet on aircraft altitude dial. Note when safety valve
closes on lift-off, no appreciable increase in cabin pressure exists. The cabin rate of
descent must not exceed 500 FPM from safety valve to outflow valve during transition of
cabin altitude control.
(2.) Cabin altitude automatically climbs to altitude indicated on controller at rate set with cabin
rate control selector knob.
(3.) Monitor differential pressure gauge, cabin altitude gauge, and other pressurization
controls during climb.
(c) Cruise Procedure
(1.) Annunciator/Warning Light Emergency Pressurization System Check:
(a.) With airplane cruising at 10,000 feet, position cabin pressure switch to DUMP position
and allow cabin pressure to stabilize.
(b.) Initiate climb to 11,700 + 200 feet and ensure cabin pressurization warning light and
annunciator have activated. Continue climb to 12,500 feet and ensure emergency
pressurization comes on.
(c.) Repressurize cabin by positioning cabin pressure switch to CABIN PRESSURE
position.
(d) Maximum Positive Differential Relief Test Procedure
(1.) Monitor cabin differential pressure gauge continuously during test so maximum outflow
valve setting is not exceeded.
(2.) Stabilize cabin altitude at 10,500 feet and initiate climb to 16,000 feet at climb power.
NOTE: Leave pressurization controls at 10,000 feet and rate full clockwise.
(3.) When 16,000 feet is reached, establish cruise power. The cabin altitude must stay at
10,000 feet with zero rate of change.
(4.) Perform the following steps while maintaining cruise power at 16,000 feet:
(a) Turn rate knob counterclockwise (decrease).
(b) Select 7,500 feet cabin altitude (outer knob).
(c) Turn rate knob slowly clockwise until comfortable rate of descent is obtained. When
cabin altitude nears 7,500, turn rate knob counterclockwise until 300 FPM descent is
obtained.
(d) Wait until cabin stabilizes.
EFFECTIVITY:
040-999
21-30-00
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21- 30-00
Jan 10/90