New Engine Break-In And Operation; Engine Oil System; Ignition Starter System; Air Induction System - Cessna Hawk XP R172K Pilot Operating Handbook

SECTION 7
AIRPLANE
&
SYSTEMS DESCRIPTIONS
CESSN/\
MODEL R1721\
':I';SSNA
MODEL R172K
SECTION 7
AIRPLANE & SYSTEMS DESCRIPTIONS
(red line) is 3 PSI, and the maximum (red line) is 17 gallons per hour
(17 PSI).
An economy mixture (EGT) indicator is available for the airplane
and is located on the right side of the instrument panel. A thermocou-
ple probe in the left exhaust collector measures exhaust gas tempera-
ture and transmits it to the indicator. The indicator serves as a visual
aid to the pilot in adjusting cruise mixture. Exhaust gas temperature
varies with fuel-to-air ratio, power, and RPM. However, the difference
between the peak EGT and the EGT at the cruise mixture setting is
essentially constant and this provides a useful leaning aid. The indica-
tor is equipped with a manually positioned peak EGT reference pointer.
NEW ENGINE BREAK-IN AND OPERATION
The engine underwent a run-in at the factory and is ready for the
full range of use. It is, however, suggested that cruising be accomp-
lished at 65% to 80% power until a total of 50 hours has accumulated or
oil consumption has stabilized. This will ensure proper seating of the
rings.
The airplane is delivered from the factory with corrosion preven-
tive oil in the engine. If, during the first 25 hours, oil must be added,
use only aviation grade straight mineral oil conforming to Specifica-
tion No. MIL-L-6082.
ENGINE OIL SYSTEM
Oil for engine lubrication and propeller governor operation is
supplied from a sump on the bottom of the engine. The capacity of the
engine sump is eight quarts (one additional quart is contained in the
engine oil filter, if installed). Oil is drawn from the sump through a
filter screen on the end of a pick-up tube to the engine-driven oil
pump. Oil from the pump passes through a pressure screen (full flow
oil filter, if installed), a pressure relief valve, and a thermostatically
controlled oil cooler. Oil from the cooler is then circulated to the oil
galleries and propeller governor. The engine parts are then lubricated
by oil from the galleries. After lubricating the engine, the oil returns
to the sump by gravity. If a full flow oil filter is installed, the filter is
equipped with a bypass valve which will cause lubri.cating oil to by-
pass the filter in the event the filter becomes plugged, or the oil
temperature is extremely cold.
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An oil filler cap/ oil dipstick is located at the rear of the engine on
1.110 left side. The filler cap/dipstick is accessible through an access
door in the engine cowling. The engine should not be operated on less
uian
six quarts of oil. To minimize loss of oil through the breather, fill
1.0seven quarts for normaL flights of less than three hours. For ex-
tunded flight, fill to eight quarts (dipstick indication only). For engine
uil grade and specifications, refer to Section 8 of this handbook.
An oil quick-drain valve is available to replace the drain plug in
the oil sump drain port and provides quicker, cleaner draining of the
ungine
oil. To drain the oil with this valve, slip a hose over the end of
the valve and push upward on the end of the valve until it snaps into
the open position. Spring clips will hold the valve open. After drain-
ing, use a suitable tool to snap the valve into the extended (closed)
position and remove the drain hose.
IGNITION-STARTER SYSTEM
Engine ignition is provided by two engine-driven magnetos, and
two spark plugs in each cylinder. The right magneto fires the lower
left and upper right spark plugs, and the left magneto fires the lower
right and upper left spark plugs. Normal operation is conducted with
both magnetos due to the more complete burning of the fuel-air mixture
with dual ignition.
Ignition and starter operation is controlled by a rotary type switch
located on the left switch and control panel. The switch is labeled
clockwise, OFF, R, L, BOTH, and START. The engine should be operat-
ed on both magnetos (BOTH position) except for magneto checks. The
Rand L positions are for checking purposes and emergency use only.
When the switch is rotated to the spring-loaded START position, (with
the master switch in the ON position), the starter contactor is energized
and the starter will crank the engine. When the switch is released, it
will automatically return to the BOTH position.
AIR INDUCTION SYSTEM
Ram air entering the openings in the front of the engine cowling
serves as induction air for the engine. The air is drawn through a
cylindrical filter on top of the engine and into the induction airbox.
The induction airbox contains an alternate air door which is spring-
loaded to the closed position. If the induction air filter becomes
blocked, suction created by the engine will open the alternate air door
and draw unfiltered air from inside the cowling. An open alternate air
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