Piper Navajo PA-31 Service Manual page 531

PIPER NAVAJO SERVICE MANUAL
SECTION VIIIA
POWERPLANT
(PA-31-300)
8A-1. INTRODUCTION. This section covers powerplants used in the PA-31-300
and is comprised of instructions for the removal, minor repair,
service and in-
stallation of the engine cowling, propeller,
propeller governor, engine, engine
shock mounts, induction system, fuel injector, fuel air bleed nozzle, ignition sys-
tem and lubrication system.
8A-2. DESCRIPTION. The PA-31-300 is powered by two Avco-LycomingIO-540
-M1A5 six cylinder, direct drive, wet sump, horizontally opposed, fuel injected,
air cooled engines with a compression ratio of 8. 7:1, rated at 300 HP at 2700 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. There
are louvered doors on both upper cowls to allow inspection of the accessory sec-
tion.
The 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 at var -
ious pressures.
Oil pressure from the governor moves the blades into low pitch
(high RPM). The centrifugal twistingmoment of the blades also tends to move the
blades into low pitch.
Opposing these two forces are blade counterweights 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 pres-
sure. 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 aLear-Seigler
fuel supplypump as an
integral part of the fuel injector system.
These engines are normally aspirated
with no restrictions
on maximum power output.
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
Reissued:
10/12/79
POWER PLANT
2K9