Engine Intro & Basic Induction

Presented by:Will Miller

Engine Types

Turbine Engine– Found in transport Category aircraft– Relatively costly but extremely

powerful Reciprocating Engine

– Found in general aviation– Economical, but still very reliable

Cessna Engine

Horizontally Opposed

Direct Drive Air Cooled 4 cylinder

Engine Operation

What are the four strokes of an engine?

Four Strokes on an Engine

Intake

When the piston moves away form the cylinder head

Intake valve opens Fuel/Air mixture is drawn into the

combustion chamber

Compression

Piston moves back toward the cylinder head

Intake valve closes Fuel/Air Mixture is compressed

Power

Compression nearly complete Spark plugs fire Compressed mixture is ignited Rapidly expanding gases drive

the piston, providing the power that rotates the crankshaft

Exhaust

Expels the burned gases through the exhaust valve, which opens at the end of the power stroke

Induction System

Brings outside air into the engine, mixes it with fuel in the proper proportion and deliver it to the cylinders where combustion occurs.

Throttle Mixture Intake Port

Throttle

Controls Engine Speed Regulates the amount of fuel/air

mixture that flows into the cylinders

Mixture

Controls the fuel/air ratio

Intake Port

Where outside air enters the induction system

Normally contains an air filter to keep out dust and FOD

Carburetor

Mixes the incoming air with fuel and delivers it to the combustion chamber

Carburetor

Air passes through a venturi, increases velocity and decreases pressure

Fuel enters from a float chamber where it is maintained at a nearly constant level by a float device

Discharge nozzle is located in an area of low pressure created by the venturi

Fuel is forced through the discharge nozzel by the higher atmospheric pressure in the float chamber

Overly Rich Mixture

What does it mean to have a “Rich” mixture?– As altitude increases, the mixture

will get progressively richer due to the decrease in air density.

– Can result in engine roughness: excessive carbon buildup on the spark plug will cause them to foul.

– High elevation airports, climb or cruise at high elevation

Overly Lean Mixture

What does it mean to have a “Lean” mixture?– May result in high engine

temperatures causing excessive wear or even failure

– Enrichen Mixture on descents from high altitudes

– Watch engine temperature

Carburetor Ice

Occurs due to the effect of fuel vaporization and decreasing pressure in the venturi which causes a sharp temperature drop in the carburetor

If water vapor in the air condenses when the carburetor temperature is at or below freezing, ice may form on internal surfaces of the carburetor, including the throttle valve

Likely below 21C (70F), humidity above 80%

Carburetor Ice

Carburetor Ice

Carburetor Ice Indications Why can Carburetor Ice be dangerous? What are some indications of Carb Ice?

– Drop in engine RPM– Engine Roughness– Fuel starvation

What can we do to get rid of carburetor ice or even prevent it from happening in the first place?– Carburetor Heat

Carburetor Heat

Carburetor ice is especially dangerous when operating at low power settings, may go unnoticed until power is added

How does carburetor heat work?– Carburetor heat routes air across a heat source

before it enters the carburetor

How will carb heat affect engine performance?– Causes a slight decrease in engine power (heated

air is less dense)– If ice is present, there will be a decrease followed

by a gradual increase in rpm

Carburetor Heat