Textron Cessna 172S Skyhawk SP, Information Manual

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CESSNA
MODEL 172S
SECTION 4
NORMAL PROCEDURES
75% POWER
65% POWER
. 55% POWER
ALTITUDE
KTAS NMPG KTAS
NMPG KTAS
NMPG
Sea Level
114 11.2
108 12.0
101 12.8
4000 feet 119 11.7
112 12.4
104 13.2
8000 feet
124 12.2 117
12.9 107
13.6
Recommended Lean oer Fioure 4-4.
MIXTURE DESCRIPTION
EXHAUST GAS
TEMPERATURE
RECOMMENDED LEAN
50° Rich of Peak EGT
(Pilot's Operating Handbook)
BEST ECONOMY
Peak EGT
Figure 4-3. Cruise Performance Table
LEANING WITH AN EGT INDICATOR
At or below 75% power in level cruise flight, the exhaust ga~
temperature (EGT) indicator. is used to lean the fuel-air mixture fo
best performance or economy. The Cruise Performance charts i
Section 5 are based on the EGT to adjust the mixture t
I
f
,
f
I
,
Figure 4-4. EGT Table
Use the mixture control vernier adjustment (rotate the knob CCW
to lean the mixture) to .slowly lean, from full rich or maximum RPM
mixture, while monitoring the EGT indicator. As theEGT indication
begins to increase, continue to slowly lean the mixture until an EGT
indication decrease is just detectable. Reverse the adjustment
slowly in the rich direction until an EGT indication decrease is
again just detectable, then set the EGT index pointer to match the
peak indication.
The mixture may be .leaned slightly to return to
peak EGT or may be further richened to Recommended Lean
mixture as desired. Continuous operation at mixture settings
lean of peak EGT is prOhibited. Any change in altitude or throttle
position will require that peak EGT be redetermined and the desired
.mixture be reset Under some condition.s, engine roughness may
occur at peak EGT. In this case, operate at Recommended Lean
mixture.
As noted in Figure 4-4, operation at peak EGT provides the bes
fuel economy. Operation at peak EGT results in .approximately 4%
greater range and approximateiy a 3 knot decrease in airspeed from
the figures shown in the Performance section of this handbook.
Recommended Lean mixture provides best level cruise performance
(gener.ally close to "best power" or maximum RPM):
Revision 4