Piper Navajo PA-31 Service Manual page 459

PIPER NAVAJO SERVICE MANUAL
SECTION VIII
POWERPLANT
(PA-31 Turbo)
8-1. DESCRIPTION. The PA-31 is powered by two Avco Lycoming TIO-540-A Series six cylinder, direct
drive, wet sump, horizontally opposed, fuel injected, turbocharged, air cooled engines with a compression
ration of 7.3:1, rated at 310 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 of
cantilever construction attached at the firewall. 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
turbocharger area. A cowl flap door is an integral part of the lower cowl and is operated through
mechanical linkage and an electric motor.
Propellers are Hartzell full feathering, constant speed, each controlled by a governor mounted on the
engine supplying oil through the propeller shaft as various pressures. Oil pressure from the governor moves
the blades into low pitch (high RPM). The centrifugal twisting moment of the blade also tends to move the
blades into low pitch. Opposing these two forces are blade counter weights and the force produced by
compressed air between the cylinder head and the piston, 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-10AD1 type
fuel injector and a Lear-Seigler fuel supply pump as an integral part of the fuel injector system. An
AiResearch model TE0659 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 Scintilla S-1200 series magnetos are installed with their associated components. Each system
consists of a single contact magneto, a dual contact magneto to obtain the retard spark necessary for
starting, a starter vibrator, magneto switches and starter switch. The magnetos are designed to generate and
distribute high tension current through high tension leads to the spark plugs.
In addition to the aforementioned
components, each engine is equipped with an alternator, geared
starter, hydraulic pump and pressure pump. Engine mounts are steel tubing construction attached at the
firewall 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, gasses are
directed to the turbocharger exhaust plenum, through or around the turbo turbine, as required, and over
board 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. Pressure oil from the cooler returns to a second threaded connection on the accessory
housing from which point a drilled passage conducts the oil to the oil pressure filter. In the event that cold
oil or an obstruction should restrict the oil flow to the cooler, an oil cooler by-pass valve is provided to pass
the oil directly from the oil pump to the oil pressure filter.
The oil pressure filter element, located on the accessory housing, is provided as a means to filter from
the oil any solid particles that may have passed through the suction screen in the sump. After being filtered
in the pressure filter, the oil is fed through a drilled passage to the oil pressure relief valve, located in the
upper right side of the crankcase in front of the accessory housing.
Reissued: 10/12/79
POWER PLANT
2H9