Love the One You’re With

Tom Bell

Go Home with the One That Brought You

or

Why Are We Here?

• How we fly the airplane can directly impact the life of the engine, the cost per flying hour, and the safety of our fellow pilots

• In particular talk about leaning as a way to improve engine performance and engine life

Review of Engine Operation

• Air through intake port to carburetor• Mixed with fuel; moves into the combustion

chamber—burning optimized at 1/15 ratio• Four stroke engine—fuel/air ratio in first stroke

determines:– Combustion temperature after the second stroke– Power generated by the third stroke– EGT of discharge gasses in the fourth stroke

• Leaning the engine reduces the amount of fuel mixed with the air in the carburetor

Too Lean

• Too much fuel for the given amount of air

• Engine roughness

• Spark plug fouling from excessive carbon buildup on spark plugs– Due to lower temperature

inside cylinder and incomplete burning of fuel

• Higher engine temperature—not enough fuel for cylinder cooling

• Detonation: explosive ignition of fuel/air mixture inside cylinder– Causes excessive cylinder

temperatures and pressures

– Can quickly lead to failure of piston, cylinder, or valves

Too Rich

From Lycoming Service Instruction 1094D

General Leaning RulesLycoming Service Instruction 1094D

• Observe engine red line during takeoff, climb, and high power cruise

• Lean or enrich the mixture slowly

• Return to FULL RICH before adding power

• Use care not to shock cool the engine (50º change in temperature per minute)

Phases of Flight

• Ground Ops:– Normally FULL RICH

– Consider leaning at high density altitude or to warm engine on cold day

• Takeoff:– Goal is max power (highest RPM)

– Aircraft Information Manual: “The mixture should be FULL RICH, except a minimum amount of leaning is permitted for smooth engine operation when taking off at high elevation.”

– Lycoming 1094D: Use full power for takeoff and climb…except• When DA > 5000 feet, lean to max RPM at full power prior to takeoff

Phases of Flight

• Cruise– Reduce throttle and set pitch (if applicable)

– Lean at any altitude when in the 55% - 75% cruise power range

– Lean at any power setting when above 6000’ DA

From Warrior POH

OK to Lean

Don’t Lean

Lean to Best Power

• Set power approx 35 RPM below desired cruise RPM

• Lean the mixture to peak RPM and airspeed

• Adjust throttle, if necessary, for final RPM setting

• With an EGT gauge (Archer), lean to peak EGT, then enrich mixture until EGT drops 100º

Lean to Best Economy

• Set throttle and mixture full forward

• Begin leaning the mixture

• RPM will increase slightly, then decrease

• Lean until desired RPM is reached– Below 5,000 ft use caution not to remain above 75%

power with a leaned mixture for more than 15 seconds (due to detonation)

– Above 6,000 feet engine cannot generate > 75% power

• With an EGT gauge (Archer), lean to peak EGT

From Warrior POH

Comparison

Power Setting

Range (45 min reserve)

Cruise Airspeed

Fuel Consumption

75% 480 nm 115 KTAS 10.0 gph

65% 495 nm 106 KTAS 8.8 gph

55% 505 nm 96 KTAS 7.8 gph

Best Power Mixture

- Standard Day- 8000 MSL- No wheel fairings

Best Economy Mixture

- 2-3 KTAS slower- 1-2 gph savings- 13% greater range- Less engine wear

Phases of Flight

• Descent– Enrich the mixture slowly during the descent…the

air is getting more dense and needs more fuel to maintain the proper fuel/air ratio

• Pattern/Landing― Mixture to “FULL RICH” as part of Approach/Landing

check

Summary

• Leaning increases performance/decrease wear

• Lean when appropriate– Takeoff / climb when > 6,000 ft DA

– Cruise in 55% - 75% power range

– Richen mixture before power increase

– Richen mixture slowly on descent

• Best power vs. best economy– Tradeoff of speed, fuel used, range, engine wear

• Talk to your instructor for techniques