Mooney M20M, Pilot Operating Handbook

Page: 307 / 377

GI 275 Part 23 AML STC
190-02446-12 Rev. 4
Airplane Flight Manual Supplement Page 67 of 70
7.18.5 Mixture Leaning
GI 275 EIS provides two different lean assist methods, rich of peak or lean of
peak.
Lean assist mode is entered by pressing the Lean Button on the EGT page. Lean
mode automatically detects the EGT peak and indicates peak by using a bar
above the EGT indicator for the cylinder. As the mixture is leaned, the system
will transition from “Rich of Peak” indications to “Lean of Peak” indications
automatically. The system requires fuel quantity indication, fuel flow indication
and EGT indication to function.
Rich of peak leaning detects and indicates the first engine cylinder to peak
during the leaning process. Once the first peak in EGT is detected, the
temperature differential from the recorded maximum EGT of the first cylinder to
peak is displayed.
Lean of peak leaning detects and indicates the last engine cylinder to peak
during the leaning process. Once the last cylinder peak EGT is detected, the
system will display the temperature differential from the recorded maximum
EGT of the last cylinder to peak.
NOTE
The Lean Assist is meant to aid the pilot in detecting the peak
temperatures. Smooth leaning technique is required for the system
to be able to accurately detect the peak temperature.
Caution should be used to ensure that, during the leaning
procedure, the engine is not leaned beyond the engine or aircraft
limitations and that the engine continues to operate smoothly after
setting the mixture. Should any engine roughness occur during
leaning, consult the aircraft POH or AFM for appropriate leaning
of the engine.
The Lean Find functions are calculated using the relationship
between fuel flow and EGTs. If a false EGT peak is observed and
does not automatically reset, disable the Lean Find function, reset
throttle and mixture controls, and reattempt.
It is recommended to set the aircraft power settings for cruise flight
prior to beginning the lean find process.