A. PressurizationControl (continued)
2.  
Cabin Pressure Dump In case of an emergency requiring the cabin pressure to be dumped in flight, place the cabin pressure switch in the DUMP position, place the ECS selector switch to OFF position and pull the circuitbreaker for the DOOR SEAL.

3.  
Pressurization Check with Test Unit

NOTE: The ambient lines on the isobaric valves are capped by capping their adapter fittings on the external side of the aft pressure bulkhead. These fittings are accessible by removing the access panel in the tail.
Use the following pressurization test procedure to determine if the aircraft fuselage has an
acceptable leakage rate. A pressurization test unit (Figures 501, 502, 503) is required to perform
the test.
(a)AircraftPreparation (1.) Remove access panel on the right side of the nose section, to permit accessto forward
pressurebulkheadat fuselage station 57.00. (2.) Remove accesspanelson the right and left side of the fuselage tail sectionat station
346.00. (3.) Remove the trim panel at fuselage station 296.00, in front of the outflow and safety valves. Remove the cotter pin and cap ambient lines from the outflow and safety valves. (4.) Place cabin air control in pressurized position. Close pressurization test valve under the instrumentpanel. (5.) Place the cabin air control in the pressurized position. Close the pressurization test valve under the instrument panel.
(6.) Position all circuit breakers except the cabin pressure control, door seal and annunciator/warninglights in the OFF position.
NOTE: If airplane is not on jacks, disconnect electrical power to vacuum relief solenoid.
(7.) disconnect and plug gyro inlet lines at the filter. (Refer to 37-00-00)
(b) Test Unit Hookup (1.) On the right side of the forward pressure bulkhead, remove the cabin pressure test fitting protective cap. Connect the cabin reference line from the test unit to the fitting.
(2.) Remove air supply line from the water separator inlet and install test adapter as shown in Figure 503. Connect air prssure line from the cart to the adapter.
NOTE: Besure that connections do not leak.
(3.) The door seal can either be set up with shop air regulated to 18 psi or through the test cart. Proceed as follows: (a.) Disconnect the line from inlet side of the solenoid valve (left side of fuselage, under
floor, F.S. 203.00).

(b.) Connect the line (hose) to the inlet side of the valve and route it back to the fitting on the upper middle part of rear pressure bulkhead. Attach hose to adapter with tightened hose clamp to prevent leakage.
(c.) Remove access panels on the tail of the aircraft and rach into the tail to unscrew cap from external side of fitting. (d.) Attach the line from the test cart or shop air source to external side of fitting.
EFFECTIVITY: 040-999 PAGE14 21-30-00
Jan10/9021-30-00
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL

A. PressurizationControl(continued)
3. PressurizationCheckwith Test Unit (continued)
3.75
2.50
1.25DIADIA

FabricatedReducerPressureTestAdapter
Figure 501

NOTE: This unit must be purchased
from Piper. Thisunit is
designatedwitha PiperPart
Number 756 344.

NOTE: The flow rate valve must be
set in full pump bypass
beforestarting or stopping
unit.

Cabin Differential CabinReference -Pneumatic Air or Pressure Indicator PresssureAir Rate of Flow IInstrumentAir Indicator Pressure Indicator
Fill Port  Instrument -
Air
0

Indicator  Rateof
Climb -

Indicator Circuit Breaker
-Sta rt B u tto n
Flow Rate

Stop Button

Valve2
Electrical Connection
ShopAir-
Air Regulator
Valve BACK VIEW FRONT VIEW

CabinPressureTest Unit (Typical)
Figure 502

EFFECTIVITY:
040-999
21-30-00Jan10/90
21-30-00 Jan 10/90
PIPER AIRCRAFT

PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. PressurizationControl(continued)
3. PressurizationCheck with Test Unit (continued)
1 1/4 INCH SUPPLY HOSE FROM TEST CART
-CABIN PRESSURE IN

Pressurization Test Hookup 
Figure 503 
EFFECTIVITY: 
040-999 
JanJan 10/90 10/9021-30-0021-30-00 

PIPERAIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL

A.  PressurizationControl(continued)
3. PressurizationCheckwith Test Unit (continued)
(c) TestUnit Operation

TO AVOID HARMING AIRCRAFT,TESTUNITOR PERSONNEL.THE TEST UNITCANNOTBE TURNEDOFFWHENPRESSUREDIFFERENTIALEXISTSIN THE CABIN. IF MACHINE IS UNPLUGGED,RAPIDDEPRESSURIZATIONRESULTS CAUSINGSERIOUSDISCOMFORTTOANYONEINTHECABIN.
WARNING: EXERCISECAUTIONDURINGDEPRESSURIZATION
　
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