extinguishat 70 to 75% Ng speed. (8.) Retard throttles slowly and ensure lights illuminate againat 65 to 70% Ng speed.
NOTE: Ensurethat the BLEED AIR OFF light illuminates when each engine is started and when bleed air switch and ECS switch are in the OFF position.
(h)
Place cabin pressurization/test/dump
switch in the TEST position. Note that the safety valve closes.
(i)
Rotate the cabin altitude controller knob until either the cabin altitude indicates approximately 1,500 feet below field elevationor to full counterclockwise stop position (below sea level), whichever is applicable. Cabinpressurewill increaseduring rate of change operations.
(j)
Rotate rate of change control knob counterclockwise. Note reduction in cabin pressure rate of change.
(k)
Rotate rate of change control knob clockwise. Note increase in cabin rate of change.
(l)
Allowcabin pressure to stabilize at the selected value.
(m)Rotate cabin altitude selector knob until CABIN ALT indicates approximately 500 feet above fieldaltitude.
(n)
Rotatecabin rate control selector knob counterclockwise. Note reduction in cabin pressure rate-of-change.
(o)
Rotate cabin rate control selector knob clockwise. Note increase in cabin pressure rate-of-change. Allow cabin pressureto return to field altitude.
(p)
Monitor cabin rate of climb, cabin differential pressure and the cabin altitude gauges during test. Check for system malfunctionif gauge readings are not acceptable.
(q)
Placecabin pressure switch to cabin pressureposition and permit cabin to depressurize. Note safetyvalve and outflow valve are fully open.
(r)
For positive differential pressure relief check, establish steady cabin air inflow (outlined above) and proceed as follows: (1.) Rotate cabin rate of change control knob fully clockwise. This allows pressure in rate
chamber to remain equal with cabin pressure during checkout procedure. (2.) Rotate cabin altitude selector knob until CABIN ALT indicates approximately500 feet above field altitude. (3.) Place cabin pressure switch in TEST position to simulate flight condition. Ensure safety valve closes and outflow valve moves toward OPEN position. (4.) Behind instrument panel, locate manual test valve in controller vacuum line and cut safety wire to handle. (5.) Slowly move test valve handle toward closed position until cabin pressure starts to increase (indicated on cabin altimeter and rate of change indicator).
(6.) Adjust neutral test valve until comfortable cabin rate of change is established. Allow cabin pressureto increase until positive differential pressure control operation is achieved (shown on cabin-to-atmosphere differentialpressuregauge).
EFFECTIVITY:
21-30-00PAGE
21-30-00 19
Jan10/90
PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL
A. Pressurization Control (continued)
5. Ground Operational Check(continued)
(r) continued
NOTE: When working with manual test valve, opening valve decreasescabin pressure rate of change and closing valveincreases cabin pressure rate of change.
decreases vacuumto controller. The cabin pressure controlsystemmust control cabin pressure during normal positivedifferentialpressureoperation.
(8.) Cap outflowvalve ambient line to ensurepropertransferof differential pressurecontrolto safety valve. The system nowexhibitscontrolatmaximumpositivedifferentialpressure operation,verifyingoperationof outflow andsafety valves.
(9.) Uncap outflow valve ambient line, allowingdifferentialpressurecontrol to return to outflow valve. (10.)Slowlyopenmanual test valve to establish comfortablecabin pressure rate-of-change
while ascending to field altitude. (11.)Whencabin pressure returnsto field altitude, shutengines down. (12.)Lockwiremanualtest valve in OPEN position and ensure adapter fittings are uncapped
and secured open with cotter pins.
(7.) When pressurerate-of-change to zero, close manualtestvalve to shutoff
6. Safety Precautions
The following safetyprecautionsmust be observed:
(a) Uncontrolled Pressurization: (1.) During flight testing of system, continuouslymonitor cabin pressurizationinstrumentsfor overpressurization.
(2.) In case of uncontrolled pressurization,the pilot must stop pressurization or depressurize aircraft as follows: (a.) Move cabinpressure mode switchto DUMP position. (b.) Pull circuit breakerto deactivate inflationof cabin door seal. (c.) Close rightand left engine bleed air valves by placing both bleed air switches in OFF
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