Instruments Description - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
SECTION X
INSTRUMENTS
10-1. INTRODUCTION. The purpose of this section is to provide instructions for remedying
difficulties
which may arise in the operation of the various instruments and pneumatic system. The instructions
are
organized so that the mechanic can refer to description, for a basic understanding of the instruments and
pneumatic system; troubleshooting, for a methodical approach in locating the difficulty; corrective
maintenance, for the removal, repair and installation of components; and adjustments and tests, for the
operation of the repaired system.
The instruments have been classified into two types, non-electrical and electrical. Maintenance, other
than that which is described in this section should be accomplished by the instrument manufacturer
or an
authorized repair station.
10-2. GENERAL DESCRIPTION. The instrumentation of the PA-31-350 provides for all conditions
of
flight. The instruments are designed to give a quick and actual indication of attitude, performance, and
condition of the airplane. Some of the instruments are components of indicating systems that indicate
conditions at remote parts of the airplane. A few of the instruments, however, are self-contained and
merely have to be correctly installed to give an indication. Warning lights are installed to indicate
unsatisfactory or dangerous conditions in some systems. Instruments requiring power from the electrical
system are provided with circuit breakers to isolate the individual systems in the event of trouble. For night
operation, each instrument is either individually lighted by shielded post lights or a light incorporated
as
part of the instrument.
The panel has been arranged to accommodate flight instruments in the left side, in front of the pilot.
electronic equipment and some engine instruments in the center, and the remaining engine
and
miscellaneous instruments to the right. A second set of flight instruments may be installed in the
right side
of the panel for use by the copilot. Additional instruments are mounted in a sub-panel located
over the
windshield. Most of the instruments have been shock-mounted to minimize vibration that is transmitted to
the instrument panel.
10-3. INSTRUMENT AIR SYSTEM. (Refer to Figure 10-2.)
The instrument air system consists of a pitot air system and a static air system. Refer to Figure 10-2
for system layout.
Pitot air system consists of a pitot mast located on the bottom side of the nose section, with its'
related plumbing. Impact air pressure entering the pitot head is transmitted through the pitot plumbing
to
the airspeed indicator on the instrument panel.
Static air system consists of two static ports, one on each side of the fuselage, located just aft of
bulkhead station 296.0. These ports are interconnected as shown in Figure 10-2 and the tubing is then
routed forward along the top of the fuselage and down the windshield center post to the back
of the
instrument panel, where it is connected to the airspeed indicator, altimeter and rate of climb indicator. An
alternate static air source is located below the instrument panel in front of the pilot. This alternate
static
source is part of the standard system and has a shutoff valve which closes the port when it is not needed.
10-4. TROUBLESHOOTING. For troubleshooting of the various instruments, refer to the Table
with each
particular instrument.
Revised: 3/11/81
INSTRUMENTS
3A10