Cruise; Leaning With A Cessna Economy Mixture Indicator (Egt); Cruise Performance Table; Egt Table - Cessna Hawk XP R172K Pilot Operating Handbook

/~ECTION 4
. / NORMAL PROCEDURES
1/
CRUISE
CESSNA
MODEL R172K
( ~II;HHNA
M()!)L~L H172K
SECTIO~
NOHMAL PROCEDUHES
Normal cruising is performed between 60% and 80% power. The
engine RPM and corresponding fuel consumption for various altitudes
can be determined by using your Cessna Power Computer or the data in
Section 5.
NOTE
Cruising should be done at 80% power until a total of
50 hours has accumulated or oil consumption has sta-
bilized. This is to ensure proper seating of the rings
and is applicable to new engines, and engines in ser-
vice following cylindcr replacement or top overhaul of
one or
more
cylinders.
The Cruise Performance Table, figure 4-3, illustrates the advantage
of higher altitude on both true airspeed and nautical miles per gallon.
In addition, the beneficial effect of lower cruise power on nautical miles
per gallon at a given altitude can be observed. This table should be
used as a guide, along with the available 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 settings are significant fac-
tors that should be considered on every trip to reduce fuel consumption.
For reduced noise levels. it is desirable to select the lowest RPM in
the green arc range for a gi.ven percent power that will provide smooth
engine operation.
The cowl fht.p should
be opened, if necessary, to
maintain the cylinder head temperature at approximately two-thirds of
the normal operating range (green are).
--
-----------,-------
80% POWEH
--
ALTITUDE
KTAS
NMPG K
n~,""~
1---'
3000 Feet
126
11.2 1
6000 Feet
130
11.5
9000 Feet
-
-
- - - -
Standard Conditions
% POWER
60% POWER
,0'_,-'.-
J
NMPG
KTAS
NMPG
-
12.0
110
'12.9
12.3
112
13.1
12.6
114
13.3
Zero Wind
1·'01'
best fuel economy at 70% power or less, the engine may be
operated at one gallon per hour leaner than shown 'in this handbook
and on the power computer. This will result in approximately 8%
greater range than shown in this handbook accompanied by approxi-
mately a 4 knot decrease in speed.
The. f,:e1 injection system employed
on this engine
is considered to
?e non-icmg, In the event that unusual conditions cause the intake air
filter to become clogged or iced over, an alternate intake air valve
opens automatically for the most efficient use of either normal or alter-
nate air depending on the amount of filter blockage.
LEANING WITH A CESSNA ECONOMY MiXTURE INDICATOR
(EGT)
Exhaust gas temperature (EGT) as shown on the optional Cessna
~conom~ Mix:ture Indicator may be used as an aid for mixture leaning
m. cr~.lls~ng fIight at 80% p0",'ler or less. To adjust the mixture, using
th is mdl?ator, lean to estabh.sh the peak EGT as a reference point and
then ennchen the mixture by a desired increment based on figure 4-4.
Continu?us operation at peak EGT is authorized only at 70% power
or less. ThIS best economy mixture setting results in approximately
8% greater range than shown in this handbook accompanied by approx-
Imately
a
4
knot decrease in speed.
NOTE
Operation on the lean side of peak EGT is not approved.
When leaning the mixture, if a distinct peak is not obtained, use the
corresponding maximum EGT as a reference point for enrichening the
m:xture to the desired cruise setting. Any change in altitude or power
Will requrre a recheck of the EGT indication.
MIXTURE
EXHAUST GAS
DESCRIPTiON TEMPERATURE
....
-
---,----
•.
- -~
.....
-
....
---
RECOMMENDED LEAN
(Pilots Operating Handbook 50°F Rich of Peak EGT
and Power Computer)
BEST ECONOMY
(70% Power or Less)
Peak EGT
Figure 4-4. EGT Table
4-17
I
70
TA::-
19
122
125
Figure 4-3. Cruise Performance Table
4-16