Cirrus Design Section 7
SR20 Airplane and Systems Description
P/N 21399-004 7-51P/N 21399-004 7-51
Mixture Management
The mixture control needs to be carefully monitored and managed
during all phases of flight to avoid damage to the engine or possible
loss of power.
After engine start, and during taxiing operations, lean the mixture until
maximum engine RPM is attained to prevent possible spark plug
fouling and ensure smooth engine operation.
The engine is equipped with an altitude compensating fuel pump that
automatically provides the proper full rich mixture. Therefore, the
mixture should be set to full rich for takeoff and climb, even at high
altitude airfields. If at any point during the climb CHTs are trending
above 420 °F, verify the mixture is set to full rich and increase climb
speed, terrain and obstacles permitting, to promote engine cooling.
During cruise flight the throttle should be set for 75% power or less
when operating the engine at best power mixture settings, and 65%
power or less when operating at best economy mixture settings.
During best power operations the mixture should be set for 75 °F rich
of peak EGT. During best economy operations the mixture should be
set for 50 °F lean of peak EGT. In lean of peak operations, mixtures
leaner than 50 °F lean of peak EGT may result in rough engine
operation.
If the mixture has been leaned during cruise operations, it will be
necessary to richen the mixture prior to landing. Before the approach
to landing, mixture should be set to full rich to ensure full power
availability in the case of throttle advancement.
If at any time during normal operations, with the mixture set near or at
full rich, a slightly rough running engine is noticed, accompanied by
EGTs less than 1200 °F, this may be a sign that the mixture setting is
too rich for the given conditions. The mixture should be leaned in small
increments until smooth engine operation is again achieved with EGTs
greater than 1200 °F.
Revision A1
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