Normal climbs are performed at 85-95 KIAS with flaps up, 25 In. Hg. or full throttle (whichever is less) and 2500 RPM for the best combination of engine cooling, rate of climb and forward visibility. If it is necessary to climb rapidly to clear mountains or reach favorable winds at high altitudes, the best rate-of-climb speed should be used with maximum power. This speed is 84 KIAS at sea level, decreasing to 77 KIAS at 10,000 feet.
If an obstruction ahead requires a steep climb angle, a best angle-of- climb speed should be used with landing gear and flaps up and maximum power. This speed is 67 KIAS at sea level, increasing to 68 KIAS at 10,000 feet.
The mixture should be full rich
during climb at altitudes up to 3000 feet. Above 3000 feet, the mixture may be
leaned for increased power and smooth engine operation. With the optional Cessna
Economy Mixture Indicator, the mixture may be leaned to maintain the EGT
indication corresponding to full rich at 3000 feet. Without an EGT indicator,
the mixture may be leaned to momentary engine roughness and then enri chened two
full turns at the mixture control knob. Each of these procedures result in
approximately the same mixture and will significantly improve high altitude
Normal cruising is performed between 55% and 75% power. The corresponding power settings and fuel consumption for various altitudes can be determined by using your Cessna Power Computer or the data in Section 5.
Cruising should be done at a minimum of 75% power until a total of 25 hours has accumulated or oil consumption has stabilized. Operation at this higher power will ensure proper seating of the rings and is applicable to new engines, and engines in service following cylinder replacement or top overhaul of one or more cylinders.The Cruise Performance Table, figure 4-3, illustrates the true airspeed and nautical miles per gallon during cruise for various altitudes and percent powers. This table should be used as a guide, along with the available winds aloft information, to determine the most favorable alti tudes 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 settings are significant factors that should be considered on every trip to reduce fuel consumption.
The tachometer is marked with a green arc from 2100 to 2700 RPM with a step at 2500 RPM. The use of 2500 RPM will allow 75% power at altitudes up to 7500 feet on a standard day. For hot day or high altitude conditions, the cruise RPM may be increased to 2700 RPM. Cruise at 2700 RPM permits the use of 75% power at altitudes up to 9000 feet on a standard day. However, for reduced noise levels it is desirable to select the lowest RPM in the green arc range for a given percent power that will provide smooth engine operation.
The cowl flaps should be opened, if necessary, to maintain the cylinder head temperature at approximately two-thirds of the normal operating range (green arc).
Cruise performance data in this handbook and on the power computer is based on a recommended lean mixture setting which maybe established as follows:
1. Lean the mixture until the engine becomes rough.For best fuel economy at 75% power or less, the engine may be operated at the leanest mixture that results in smooth engine operation. This will result in approximately 8% greater range than shown in this handbook accompanied by approximately 3 knots decrease in speed.
2. Enrichen the mixture to obtain smooth engine operation; then further enrichen an equal amount.
Standard Conditions Zero Wind
75% POWER 65% POWER 55% POWER ALTITUDE KTAS NMPG KTAS NMPG KTAS NMPG 3000 132 13.2 124 14.2 114 15.0 6000 136 13.6 127 14.6 116 15.3 9000 140 14.0 130 14.9 118 15.6
Figure 4-3. Cruise Performance Table
Any change in altitude, power or carburetor heat will require a change in the recommended lean mixture setting and a recheck of the EGT setting (if installed).
Carburetor ice, as evidenced by
an unexplained drop in manifold pressure, can be removed by application of full
carburetor heat. Upon regaining the original manifold pressure indication (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
LEANING WITH A CESSNA ECONOMY MIXTURE INDICATOR (EGT)
Exhaust gas temperature (EGT) as shown on the optional Cessna Economy Mixture Indicator may be used as an aid for mixture leaning in cruising flight at 75% power or less. To adjust the mixture, using this indicator, lean to establish the peak EGT as a reference point and then enrichen the mixture by a desired increment based on data in figure 4-4.
As noted in the table, operation at peak EGT provides best fuel economy. This results in approximately 8% greater range than shown in this handbook accompanied by approximately 3 knots decrease in speed.
When leaning the mixture under
some conditions, engine roughness may occur before peak EGT is reached. In this
case, use the EQT corres ponding to the onset of roughness as the reference
point instead of peak EGT.
and Power Computer)
|50 F Rich of Peak EGT|
|BEST ECONOMY||Peak EGT|
Figure 4-4. EGT Table