Cessna SKYHAWK 1976 Pilot Operating Handbook page 54

4-16
SECTION 4
CESSNA
NORMAL PROCEDURES
MODEL 172M
75% POWER 65% POWER
55% POWER
ALTITUDE KTAS NMPG
KTAS
NMPG KTAS
NMPG
Sea Level
4000 Feet
8000 Feet
112
116
120
13.5
14.0
14.5
106
109
112
14.7
15.1
15.6
97
99
102
15.2
15.5
15.9
Standard Conditions
Zero Wind
Figure 4-3. Cruise Performance Table
able winds aloft information, to determine the most favorable altitude and
power setting for a given trip. The selection of cruise altitude on the
basis of the most favorable wind conditions and the use of low power set ­
tings are significant factors that should
be
considered on evexy trip to
reduce fuel consumption.
To achieve the recommended lean mixture fuel consumption figures
shown in Section 5, the mixture should be leaned as follows:
(1) Pull the mixture control out until engine RPM peaks and begins
to falloff.
(2) Enrichen slightly back to peak RPM.
For best fuel economy at 75% power or less, operate at the leanest
mixture that results in smooth engine operation or at 50 RPM on the lean
side of the peak RPM, whichever occurs first. This will result in approxi ­
mately 5% greater range than shown in this handbook.
Carburetor ice, as evidenced by an unexplained drop in RPM, can be
removed by application of full carburetor heat. Upon regaining the origi­
nal RPM (with heat off), use the minimum amount of heat (by trial and
error) to prevent ice from forming. Since the heated air causes a richer
mixture, readjust the mixture setting when carburetor heat is to
be
used
continuously in cruise flight.
The use of full carburetor heat is recommended during flight in heavy
rain to avoid the possibility of engine stoppage due to excessive water in­
gestion or carburetor ice. The mixture setting should
be
readjusted for
smoothest operation.
In extremely heavy rain, the use of partial carburetor heat (control