(b)
Disconnectthe hose to the cabin pressure controlsystemfromthe tee behind the co-pilots instrument panel. Plug the port on the tee.

(c)
Disconnectvacuumsupply line at the vacuumejectorunder the cabin floor just forwardof F.S.

(d)
Connecta vacuum pumpwhich produces at least 20 in. Hg suction,a test vacuumgauge, and shutoffvalvesin line with the vacuum supply tubing from the gyros. (Figure 501.)

151.30.
NOTE: To eliminate the effectsof instrument case and valve leakage during the system leak test, disconnect the hoses at the inlet and outlet of each gyro, the suction gaugeand the turn and bank adjustment valve. Connectthe two hoses from eachinstrumentand the valve using a piece of tubing beaded on each end and secure.
(e)
Attaina vacuum of 20 in. Hg on the test gauge.

(f)
Maintaina vacuum pressureof 20 in. Hg on the test gauge. Close both test shutoffvalves. The suctiongauge can not decrease more than 1 in. Hg over 5 minutes. If the systemdoes not holdthe vacuum, check for leaks.

(g)
Reinstallall lines, floor panels,seats and hoses removed or capped forthis test.

SuctionGauge

T.& B. Adjustment Valve
Test Vacuum Gauge
0 -30 in. Hg

Cap

DisconnectHose to Cabin DisconnectTubing Pressure Control System at Vacuum Ejector at this Port and Plug Port
Gyro Instruments

Vacuum System Test Setup 
Figure501 
EFFECTIVITY: 
040-999 
Jan 10/9037-10-00 

PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCE MANUAL

A. Distribution
2. VacuumRegulatorAdjustment(Figure502)
NOTE: Do not adjustvacuumregulatorwithoutchangingthecentralair filter. Central air filter mustbe changed every50 hours.
(a)
Start enginesandturn ON left and rightbleedair switches.

(b)
Withone enginepowereddown,setthe other at 75% Ng. Checkvacuumgauge readingand adjustvacuumregulator,if necessary,fornot lessthan4.5 in. Hg.The vacuumregulatorsare locatedabovethe copilot's rudder pedals.

(c)
Observingpropersafetyprecautions,advancepoweron both enginesto a minimum 90%and

ensurevacuumgaugereads5.4 in.Hgminimum.Adjustvacuumregulatoraccordingly,reduce powerand repeatstep (b).

(d)
Afterestablishingaboveparameters,applysufficientpowerestablishinga pressure gaugereadingof 16-20 psig. Cycledeicerbootsand ensuregyro vacuumindicatesa steady4.5 in. Hg, afterdeicerbootcycleis turnedOFF.

(e)
If adjustments of the pneumaticsystemarerequired,referto 36-10-00.

Poppet
DiaphragmAssembly Seat
Vacuum

Air From Source Gyro
AdjustingScrew
VacuumRegulator Figure502

EFFECTIVITY:
040-999
37-10-00 PAGE3
Jan10/90

PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

CHAPTER 51

LIST OF EFFECTIVE PAGES

CHAPTER  CHAPTER 
SECTION  PAGE  DATE  SECTION  PAGE  DATE 
51-EFFECTIVITY  1  Feb 1/98  51-40-00  1  Jan 10/90 
51-CONTENTS  1  Jan 10/90  51-40-00  2  Jan 10/90 
51-CONTENTS  2  Jan 10/90  51-40-00  3  Jan 10/90 
51-00-00  1  Jan 10/90  51-40-00  4  Jan 10/90 
51-10-00  1  Jan 10/90  51-40-00  5  Jan 10/90 
51-10-00  2  Jan 10/90  51-40-00  6  Jan 10/90 
51-10-00  3  Feb 1/98  51-40-00  7  Jan 10/90 
51-10-00  4  Jan 10/90  51-40-00  8  Jan 10/90 
51-10-00  5  Jan 10/90  51-70-00  1  Jan 10/90 
51-10-00  6  Jan 10/90  51-70-00  2  Jan 10/90 
51-10-00  7  Jan 10/90  51-70-00  3  Jan 10/90 
51-10-00  8  Jan 10/90  51-70-00  4  Jan 10/90 
51-10-00  9  Jan 10/90  51-70-00  5  Jan 10/90 
51-10-00  10  Apr 15/91  51-70-00  6  Jan 10/90 
51-10-00  11  Jan 10/90  51-70-00  7  Jan 10/90 
51-10-00  12  Jan 10/90  51-70-00  8  Jan 10/90 
51-10-00  13  Jan 10/90  51-70-00  9  Jan 10/90 
51-10-00  14  Jan 10/90  51-70-00  10  Jan 10/90 
51-10-00  15  Jan 10/90  51-70-00  11  Jan 10/90 
51-10-00  16  Jan 10/90  51-70-00  12  Jan 10/90 
51-10-00  17  Jan 10/90  51-70-00  13  Jan 10/90 
　
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