Cirrus Design
Section 4
SR22T
Normal Procedures
P/N 13772-005
4-21
P/N 13772-005
4-21
Cruise
1. Oxygen ................................................................. AS REQUIRED
2. Cruise Altitude ........................................................ESTABLISHED
3. Power Lever ....................................REDUCE to 30.5 in.Hg or less
4. Fuel Pump ............................................................. AS REQUIRED
5. Mixture .............................................................................. ADJUST
6. Engine Parameters ........................................................ MONITOR
7. Fuel Flow and Balance .................................................. MONITOR
If any CHT’s exceed 420°F:
8. Mixture ........................................... LEAN 0.5 GPH and MONITOR
Amplification
Recommended cruise is at a Lean of Peak / “Best Economy” mixture
setting. Cruise leaning, i.e. leaning below full rich fuel flow, is only
approved with manifold pressure settings of 30.5 in.Hg or less. Once
power is reduced below this level, the green arc expands and a cyan
colored Target Fuel Flow que is displayed on the fuel flow gage. With
higher manifold pressures, the fuel flow gage provides a narrow green
arc which defines full rich fuel flow settings.
Target fuel flow is determined using a calculated engine air flow based
on Engine Speed, Manifold Air Temperature and Manifold Air Pressure
and indicates a fuel flow that will give the approximate air-to-fuel ratio
for best economy operation. Alternatively, the mixture can be set by
finding a fuel flow that provides peak TIT and then leaning until TIT is
50°-75°F less than its peak value.
Target Fuel Flow is advisory only. This indicator or the Peak leaning
method will provide an initial lean point only. As this setting is
dependant on ambient air temperatures, it may not ensure sufficient
cylinder cooling. If any CHT’s are greater than 420°F, lean the mixture
to maintain cylinders below 420°F. As an approximation, a 0.5 GPH
reduction in fuel flow will reduce CHT’s by 15°F.
Running the engine at mixture levels leaner than the target will
improve cooling, but provide lower cruise power because engine
power scales in proportion to fuel flow when the engine is running at
lean of peak. Other than lower cruise power, the only undesirable
affect of an overly lean-of-peak setting is engine misfire. Cruise
mixture should be rich enough to avoid lean misfire, but no richer than
target indicator for cruise.
Original Issue
