Piper COMANCHE PA-24-180 Service Manual page 402

PIPER COMANCHE SERVICE MANUAL
SECTION VIIB
POWER PLANT PA-24400
7B-1. Inrodution. This section coven power plans used in the PA-24400 and is comprued of
inructions for the removal, minor repair, servie nd installtion of the engine cowling, propeller,
propeller governor, engine, engine shock mounts, induction system, ignition system and lubrication system.
7B-2. Description. The PA-24400 Comanche is powered by an Avco-Lycoming 10-720 AIA eight
cylinder, direct drive, wet sump, fuel injected horizontally opposed, air-cooled engine with a compressrn
ratio of 8.7:1 rted it 400 HP at 2650 RPM and designed to operate on 100/130 (minumum) oci
aviation grade fuel. Cowling completely encloses the engine and conssts of an upper, a lower, and a nose
secnon. Side panels lift up to allow access to the engine.
The propeller is a constant speed three blade Hareill unit controlled by a governor mounted on the
engine upplying oil through the propeller shaft a various pressures. Oil pressure from the governor moves
the blades into high pitch (reduced RPM) and centrifugal twiing moment of the blades tend to move them
into low pitch (high RPM) in the absence of governor oil presure.
The induction system consists of a dry type air filter, an alternate air door and a Bendix RSA-1OADI
type fuel injector. This engine is normally aspirted with no resaicnons on maximum power output.
Bendix Scintilla S-700 series magneos are instlled with their associted components. The magnero
system consists of a dual (retard) contact assembly magneto. a single contct asembly magneto. a high
tenson harness assembly, one ransformer assembly mounted on each magneto and two low tension leads. a
starting vibrator, and a combination ignition and starter switch.
In addition to the previously mentioned components, each engine is furnished with a 12-volt starter, a
70-ampere alternator, a vacuum pump drive and fuel pump.
The lubrication system is of the presure 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 enten a drilled passage in te accessory housing, which feeds the oil to a
threaded connection on the rear face of the accessory housing, where 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 oil to the oil pressure screen or filter. In the event that
cold oil or an obstruction should restrict the oil flow to the cooler, an oil by-pass valve is provided to pass
the oil directly from the oil pump to the oil pressure screen or filter.
The oil pressure screen or filter element, located on the accessory housing is provided as a means to
filter from the oil any solid parcles that may have passed through the uction screen m the sump. After
being filtered in the presure screen or filter, the oil is fed through a drilled pssage to the oil pressure relief
valve, located in the upper nght side of the crankcase in front of the accessory housing.
This relief valve regulates the engine oil pressure by allowing excessive oil to return to the sump, while
the balance of the pressure oil is fed to the main oil gallery in the right half of the crankcse. Residual oil is
returned by gravity to the sump where, after passing through a screen. it is again circulated through the
engine.
POWER PLANT
ISSUED:
8/18/72
2 E20