SECTION X
INSTRUMENTS
10-1. GENERAL.
The instrumentation is designed to give a quick and actual indication of the attitude, performance and
condition of the airplane. Maintenance, other than described in these sections shall be done by the instrument
manufacture or an authorized repair station.
The two types of instruments have been classified in this section as non-electrical and electrical. The first
part of this section will pertain to maintenance and troubleshooting of all the instruments and their systems
which depend on non-electrical sources for their operation. The remaining portion of this section is directed to
maintenance and troubleshooting of all the electrically operated instruments.
10-2. NON-ELECTRICAL INSTRUMENTS.
10-3. VACUUM SYSTEM.
10-4. VACUUM SYSTEM AND GYRO PRESSURE SERVICE TIPS.
The following information is intended to acquaint field service personnel with a means to diagnose vacuum
system service symptoms on those components which are serviced by removal and replacement, along with
recommended service practices. These items include hoses, clamps, gyro filters, vacuum regulating valves,
vacuum gauges and vacuum pumps.
a. Hoses and Clamps:
1. These items should be examined periodically and inspected carefully whenever engine maintenance
activities cause hose disconnections to be made at the pump, regulating valve, gyros and/or vacuum gauge.
2. The ends of the hoses should be examined for rubber separation and slivers of rubber on the inside
diameter of the hoses. These slivers can and do become detached. If this happens, the vacuum pump suck these
loose particles and eventually ingest them. This can cause premature pump service.
3. Hose, clamps and fittings should be replaced when broken, damaged or corroded.
—CAUTION—
When replacing any of the threaded fittings, DO NOT USE PIPE DOPE or
any other anti-seize tape or compound. The AIRBORNE fittings are
cadmium plated to avoid the need for any other anti-seize materials.
The reason for this caution is to protect the pump from ingesting any
foreign materials that could cause premature service. If a thread
lubricant is required, use a powdered moly sulfide or graphite in dry
form or in an evaporating vehicle; or employ a silicone spray. Apply
sparingly to external threads of fittings only.
b. Vacuum Gauges:
1. Vacuum gauges seldom require service and usually are replaced when malfunctions occur.
—NOTE—
Vacuum gauge failure in a properly operating vacuum system does not
impair safety of flight.
PIPER AIRCRAFT
PA-28-161 CADET
AIRPLANE MAINTENANCE MANUAL
Issued: FEBRUARY. 28, 1989
I N S T R U M E N T
2B9