Piper PA-24 Comanche, Service Manual

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PIPER COMANCHE SERVICE MANUAL
04/01/09 VIIA - POWER PLANT
(PA-24-250/260)
2C3
SECTION VIIA
POWER PLANT PA-24-250 AND PA-24-260
7A-1.
Introduction.
This section covers power plants used in the PA-24-250 and PA-24-260 and is comprised of instructions
for the removal, minor repair, service and installation of the engine cowling, propeller, propeller
governor, engine, engine shock mounts, induction system, ignition system and lubrication system
7A-2.
Description.
The PA-24-250 and PA-24-260 Comanches are powered by a Lycoming engine of either 250 or 260
horsepower. (See Table II-I.) Engines are 0-540 series or IO-540 series which are six cylinder direct
drive, wet sump, horizontally opposed, air-cooled, and are designed to operate on 91/96 (minimum)
octane aviation grade fuel.
Cowling completely encloses the engine and consists of an upper and lower section. Side panels lift up
to allow access to the engine.
The propeller may be a constant speed McCauley or Hartzell unit controlled by a governor mounted on
the engine supplying oil through the propeller shaft at various pressures. Oil pressure from the governor
moves the blades into high pitch (reduced RPM) and centrifugal twisting movement of the blades tend to
move them into low pitch (high RPM) in the absence of governor oil pressure.
The induction system consists of a wet type air filter on the early models or a dry type air filter on the
later models and a MA-4-5 Marvel-Schebler carburetor or a Bendix fuel injection unit. The engines are
normally aspirated with no restrictions on maximum power output.
Bendix Scintilla S6LN-20 series and S6LN-200 series magnetos are installed with their associated
components. The S6LN-20 series magnetos incorporate a single breaker and an impulse coupling
installed on the left magneto. The S6LN-200 series magneto system consists of a single contact magneto
on the right side of the engine and a dual contact magneto on the left, to obtain the retard spark
necessary for start. A starting vibrator, magneto switches and starter switch complete the system
In addition to the previously mentioned components, each engine is furnished with a 12-volt starter, a
12-volt, 35-ampere or 50-ampere generator or a 70-ampere alternator; a vacuum pump drive and fuel
pump.
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 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 particles that may have passed through the suction screen in the sump. After
being filtered in the pressure screen or 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.