EFFECTIVITY:
040-999

Jan 10/9035-00-00
Jan 1
PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCE MANUAL

A. Description and Operation (continued)
Fault

No indication of pressure-on pressure gauge.
Pressure indication normal but no oxygen flowing.
Offensive odors in oxygen.
Rupture of green visual indicating disc.
CHART 1

FAULT ISOLATION (OXYGEN SYSTEM)
Cause

Cylinderemptyor leak in systemhasexhaustedpressure.
Pressuregauge defective.
Defectiveregulator.
Oxygen cylinder regulator
assembly defective.

On/ Off control out of adjustment.
Cylinderpressurebelow 50 psig. Foreign matter has entered the systemduringprevious servicing.
Oxygensystemleaking Remedy
If empty, refill. If discharge indicatordisk is ruptured, do not refill. Refer to instructions below.
Replacepressuregauge.
Replaceregulator.
Replace regulator assembly.
Adjust control.
Purgeoxygensystem.
Remove oxygen cylinderand regulatorand returnto qualified overhaulfacility. Replace disc
as required(Figure35-2).

EFFECTIVITY:
040-999 PAGE 3 35-00-00 Jan 10/90
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

A. Maintenance Practices
1. Oxygen System Servicing
(a)
Check that all lines have sufficient clearance between all adjacent structures and are secured in place. Also check the mounting security of the cylinder.

(b)
Check the cylinder for the ICC identification number and date of the last FAA inspection and test.

NOTE: If cylinder is completely empty, it must be completely disassembled and inspected in an FAA approved facility before recharging.

(c)
Replaceany lines that are defective with factory replacements.

(d)
Clean all lines and fittings.

(e)
Use Permacel 412 ribbon dope thread on male ends of fittings only. Wrap thread with a 1/4-inch or more overlap in direction of thread spiral, beginning with the second thread on the fitting. Avoid getting any sealant into the lines. After joint has been made, remove excess sealant.

CHART 1 OXYGEN SYSTEM COMPONENTS LIMITS
PARTS  INSPECTION  ACTION 
Regulator  300 Flight Hours  See Note 
Masks  Each Use  Replace as necessary 
Cylinders (DOT 3HT), steel, 
thin wall  3 Years  Hydrostatictest; Replace every 
24 years or 4,380 filling cycles 
Cylinders (DOT 3AA), steel  5 Years  Hydrostatic test 
Cylinders(DOT E-8162, E-8391), 
composite  3 Years  Hydrostatic test; Replace every 
15 years 

NOTE: Regulatorsused with DOT 3HT (steel, thin wall) cylinders and DOT E-8162, E-8391 (composite) cylinders: Perform a functional check every 3 years and overhaul every 6 years. Regulators used with DOT 3AA (steel) cylinders: Overhaul every 5 years.
2. OverboardDischargeIndicator
WARNING:  REFER TO THE WARNING IN 35-00-00 PRIOR TO PERFORMING ANY MAINTENANCE ON THE OXYGEN SYSTEM.
The green visual indicating disc is located on the belly of the nose section under the baggage compartmentarea (refer to 35-00-00 Figure 1 and 35-10-00 Figure 401).
NOTE: If the cylinder safety disc has ruptured, remove cylinder in accordance with Oxygen Cylinderand Regulator Removal paragraph. Return cylinder and valve assembly to a qualified overhaul depot.
(a) Removal
(1.) Remove snap ring holding visual indicating disc in place and remove disc or any
remaining pieces if disc was blown out. (2.) Check frame and dump outlet for damage if disc was blown out and repair as required. (3.) Flush/purge if required.
EFFECTIVITY:
040-999
PAGE 1
35-10-00 Feb 1/98

PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL

A.  MaintenancePractices(continued)
2.  OverboardDischargeIndicator(continued)
(b) Installation
(1 .) Ensuredumpoutletisclean.
(2.) Insertvisualindicatingdisc into frame.
(3.) Installsnap ring.
(4.) Install cylinder per the sectiontitled Oxygen Cylinderand Regulator Installationif cylinder
was removed.
Visual Indicating Disc Figure401
3. Purging
Purgethe system wheneverthe cylinder pressure falls below 50 psig, or if any lines are left open for any length of time, or whenever there are any offensive odorspresent.
(a)
Park the airplane in a NO SMOKING area and exercise extreme caution.

(b)
Keep all doors and windows open.

(c)
Be sure all electricalsystemsare shut off.

(d)
Connectthe oxygenrechargingunitto the filler valve.

(e)
Turn on the system.