Leaning the Engine

WHY

• Better engine performance at high altitudes
• Reduce carbon buildup on spark plugs, increase flight safety
• Fuel Economy

WHEN

• Above 3000ft MSL, enroute climb or cruise
• Taxi on the ground

HOW

Leaning with EGT Indicator

1. Slowly lean the mixture until EGT indication peaks and begins to fall off
2. Mark the peak EGT indication with the yellow EGT index pointer
3. Enrichen the mixture until EGT indication decreased to Peak – 50°F

Note: The EGT indicator requires several seconds to respond to mixture adjustments and changes in exhaust gas temperature.

Leaning with Tachometer

1. Pull the mixture control out until engine RPM peaks and begins to fall off
2. Enrichen slightly back to peak RPM

For Ground Operations

1. set the throttle to 1200 RPM
2. lean the mixture for maximum RPM
3. throttle back to 800 to 1000 RPM for ground operations

 

 

References

FAA Pilot’s Handbook

Cessna 172M PILOT’S OPERATING HANDBOOK

Cessna 172S PILOT’S OPERATING HANDBOOK