Piper Navajo PA-31 Service Manual page 541

PIPER NAVAJO SERVICE MANUAL
SECTION VIIIB
POWER PLANT (325 H.P.)
8B-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 cover the removal, minor repair, service and installation of the engine cowling,
propeller, propeller governor, engine, engine shock mounts, induction system, fuel injector,
fuel air bleed nozzle, ignition system and lubrication system.
8B-2. DESCRIPTION. The PA-31-325 is powered by two Avco-Lycoming TIO-540-F 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 325 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 turbocharger area. A cowl flap door is an
integral part of the lower cowl and is operated through mechanical linkage 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-10ED 1 type fuel injector and a Lear-Siegler 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 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 tension
leads to the spark plugs. Also incorporated in these magnetos are pressurized air lines from
the engine air inlet housing, which improves 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 efficient magneto operation at high
altitudes.
Reissued: 10/12/79
POWER PLANT
2K19