Power Plant Description - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
SECTION VII
POWER PLANT
8-1.
INTRODUCTION. This section provides instructions for remedying difficulties which may arise in
the operation of the power plant and its related components. The instructions are organized so the mechanic
can refer to: Description and principles of operation for a basic understanding of the power plant and its various
components; 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
components.
8-2.
DESCRIPTION. The PA-31-350 is powered by two Avco Lycoming TIO-540-J series six cylinder,
direct drive, wet sump, horizontally opposed, fuel injected, turbocharged, air cooled engines with a
compression ratio of 7.3:1, rated at 350 HP at 2575 RPM and designed to operate on 100/130 (minimum)
octane aviation grade fuel.
Cowlings completely enclose the engines and consist of an upper and lower section. The cowling is
cantilever construction attached at the fire wall. Located on both sides of the upper cowl are louvered doors
that hinge upward when their quick fasteners are released, to allow inspection of the accessory section and tur-
bocharger area. A cowl flap door is an integral part of the lower cowl and is operated through mechanical link-
age and an electric motor. Electric indicators are used to show the position of the cowl flaps.
Propellers are Hartzell full feathering, constant speed, each controlled by a governor mounted on the
engine supplying oil through the propeller shaft at various pressures. Oil pressure from the governor moves
the propeller blades into low pitch (high RPM). The centrifugal twisting moment of the blade also tends to
move the blades in low pitch. Opposing these two forces are blade counterweights and the force produced by
compressed air between the cylinder head and the piston in the propeller dome, which tends to move the blades
into high pitch in the absence of governor oil pressure. Thus feathering is accomplished by compressed air.
The induction system consists of a dry type air filter, an alternate air door, a Bendix RSA-IOEDI type fuel
injector and a Lear-Siegler fuel supply pump as an integral part of the fuel injector system. An AiResearch
model TH08A60 turbocharger is mounted as an integral part of the engine. Automatic waste gate control of
the turbocharger provides constant air density at the fuel injector inlet from sea level to critical altitude.
Bendix D-2230 series magnetos are installed with their associated components. Each magneto features
two electrically independent ignition circuits in one housing. Each magneto has two separate breaker cams;
one operates the main breaker for both magneto circuits, while the other operates the retard breaker in the left
magneto circuit. The magnetos are designed to generate and distribute high tension current through high ten-
sion leads to the spark plugs. Also incorporated in these magnetos are pressurized air lines from the engine air
inlet housing, which improve the operation of these magnetos during high altitude operation by maintaining a
high atmospheric pressure within the magnetos, thus insuring good electrical resistance and permitting effi-
cient magneto operation at high altitude.
In addition to the aforementioned components, each engine is equipped with an alternator, geared starter,
hydraulic pump and pneumatic pressure pump. Engine mounts are steel tubing construction attached at the fire
wall and incorporate vibration absorbing dynafocal mounts. The two top exhaust stacks and extensions are
positioned one for the left and one for the right bank of cylinders. From the exhaust stacks, gases are directed
to the turbocharger exhaust plenum, through or around the turbocharger turbine, as required, and overboard at
the bottom of the engine nacelle.
The lubrication system is of the pressure wet sump type. The oil pump, which is located in the accessory
housing, draws oil through a drilled passage leading from the oil suction screen located in the sump. The oil
from the pump then enters a drilled passage in the accessory housing which feeds the oil to a threaded
connection on the rear face of the accessory housing, where a flexible line leads the oil to the external oil cooler.
Revised: 3/31/94 POWER PLANT
2H5