love the one you’re with tom bell go home with the one that brought you or

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