S
ECTION
4: N
ORMAL
P
ROCEDURES
C
IRRUS
D
ESIGN
N
ORMAL
P
ROCEDURES
SR20
4-18
P/N 11934-005
Cruise
Normal cruising is performed between 55% and 85% power. The engine
power setting and corresponding fuel consumption for various altitudes
and temperatures can be determined by using the cruise data in Section 5.
The selection of cruise altitude is made based on the most favorable wind
conditions and the desired power settings. These significant factors should
be considered on every trip to reduce fuel consumption.
• N
OTE
•
Mineral oil should be used for the first 50 hours of engine opera-
tion or until oil consumption stabilizes.
An engine break-in is done to seat the piston rings and stabilize oil
consumption. During the break-in period, it is important to keep
the engine temperatures as cool as reasonably possible, while
operating at a higher power setting. Engine operation at power
settings between 65% and 75% power are recommended. To aid in
keeping engine temperatures cool, it is recommended to operate
the engine at best power fuel flows or slightly richer for the first 50
hours of engine operation, or until oil consumption stabilizes.
During break-in, make sure the engine is operated at 65% or
higher cruise power as much as practical to ensure correct piston
ring seating. Cruise power of 75% for the first hour of flight, and
alternating power settings between 65% and 75% power for the
second hour of flight, is recommended for proper engine break-in.
Engine operation below 65% cruise power during engine break-in
can cause poor engine performance.
Avoid engine operation with low manifold pressure and high
engine RPM. Manifold pressures less than 15 in.Hg with high
engine RPM should be avoided when possible to do so. When
possible avoid rapid changes in the throttle setting. These condi-
tions can cause damage to the counterweights, rollers or bushings,
and cause detuning.
Do not do closed throttle descents which can cause ring flutter and
damage to the cylinders and piston rings.
Operate the engine at cruise power at lower altitudes for engine
break-in. Density altitude in excess of 8,000 feet (2438 m) will
prevent the engine from reaching sufficient cruise power for an
acceptable break-in. An altitude of 5,000 feet (1524 m) is recom-
mended.
(Continued on next page)
Reissue A