SECTION 7
CESSNA
AIRPLANE AND SYSTEMS DESCRIPTION
MODEL 172S NAV III
ENGINE
(Continued)
ENGINE LUBRICATION SYSTEM
The engine utilizes a full-pressure, wet-sump type lubrication
system with aviation-grade oil used as the lubricant. The capacity of
the engine sump (located on the bottom of the engine) is eight
quarts. Oil is drawn from the sump through an oil suction strainer
screen into the engine-driven oil pump. From the pump, oil is routed
to a bypass valve. If the oil is cold, the bypass valve allows the oil to
bypass the oil cooler and go directly from the pump to the full flow
oil filter. If the oil is hot, the bypass valve routes the oil out of the
accessory housing and into a flexible hose leading to the oil cooler
on the right, rear engine baffle. Pressure oil from the cooler returns
to the accessory housing where it passes through the full flow oil
filter. The filter oil then enters a pressure relief valve which
regulates engine oil pressure by allowing excessive oil to return to
the sump while the balance of the oil is circulated to various engine
parts for lubrication. Residual oil is returned to the sump by gravity
flow.
An oil filler cap/oil dipstick is located at the right rear of the engine.
The filler cap/ dipstick is accessible through an access door on the
top right side of the engine cowling. The engine should not be
operated on less than five quarts of oil. For extended flight, fill to
eight quarts (dipstick indication only). For engine oil grade and
specifications, refer to Section 8 of this handbook.
IGNITION AND STARTER SYSTEM
Engine ignition is provided by two engine-driven magnetos, and two
spark plugs in each cylinder. The right magneto fires the lower right
and upper left spark plugs, and the left magneto fires the lower left
and upper right spark plugs. Normal operation is conducted with
both magnetos due to the more complete burning of the fuel/air
mixture with dual ignition.
(Continued Next Page)
7-34 U.S.
172SPHAUS-00
