Specifications

SECTION 4 CESSNA
NORMAL PROCEDURES MODEL 172R NAV III
GFC 700 AFCS
U.S.
CRUISE (Continued)
LEANING USING EXHAUST GAS TEMPERATURE (EGT)
(Continued)
To aid in leaning the mixture, push the ENGINE, LEAN and ASSIST
softkeys,
ΔPEAK °F will display below the EGT °F numerical value.
Lean the mixture by slowly turning the mixture control knob in the
counterclockwise direction while monitoring EGTs. As EGTs increase,
continue to lean the mixture until the hottest (cyan) cylinder reaches
peak EGT. This is identified by the EGT bar graph for that cylinder
changing to cyan with a hollow bar at the top. Note the
ΔPEAK °F and
FFLOW GPH values for the first peaked cylinder. Peak EGT is
represented by ΔPEAK 0°F, if ΔPEAK °F value is negative (-) the
mixture can be on the lean side of peak. Enrichen the mixture by slowly
turning the mixture control clockwise and monitor both fuel flow and
EGTs until the leanest cylinder returns to peak EGT (
ΔPEAK 0°F) or
desired setting based on the Exhaust Gas Temperature (EGT) Table,
Figure 4-4.
ΔPEAK °F values rich of peak will also be a negative (-) value (-50°F).
The lean assist system calculation is defined such that the peak EGT is
the highest value and any lesser value is represented with a negative (-
) value, whether on the lean or rich side of the peak.
NOTE
The 172R engine manufacturer, Textron Lycoming, has not
approved operation of the engine at fuel flow rates (mixture
settings) less than necessary to reach peak EGT in the
leanest cylinder (the first cylinder to reach peak EGT). Use
FULL RICH mixture when operating the engine above 80%
power.
(Continued Next Page)
172RPHBUS-00
4-36