Class #3 Powerplant -Principles

Content of lesson Engine operation Fuel essentials Mixture control Carburetor Icing Propeller Engine Cooling

HOMEWORK Gleim 2.9-2.17 Chapter 2 section B http://www.bigbendaviation.com/Engine.ppt

Engine Operation All engines operate because they provide a means of releasing the chemical energy stored in fuel. An Internal combustion engine does this by combining a small amount of fuel with a larger amount of air and compressing them in a chamber.

Basic components of a reciprocating engine Crankcase Carburetor Manifold Valves (Intake/Exhaust) Spark Plugs Cylinder Piston Connecting Rods Wrist Pins Crankshaft Magnetos Accessory Section (Vacuum pump, alternator, Oil pan, Oil pump etc.)

Crankcase (13) Crankcase=housing that encloses the various mechanisms surrounding the crankshaft; hence, it is the foundation of the engine.

Carburetor (127) Defined: a device for automatically metering fuel in the proper proportions with air to produce a combustible mixture. (A perfectly balanced F/A mixture is approx. 15:1 , 15parts air to 1 part fuel)

Intake Manifold (87) The tubes or housings used to conduct the air-fuel mixture to the cylinders.

The four-stroke operating cycle Intake (Fuel/Air mixture in) Compression Power (ignition) Exhaust (Burned gases out)

Cylinder

Four-Stroke Operating Cycle (P64) Firing order 1324 At the exhaust stage all exhaust gases leave the cylinder through the exhaust manifold out the exhaust

Crankshaft (P65) Transforms the reciprocating motion of the piston and connecting rod to rotary motion for turning the propeller

How does an engine work? Fuel and air are mixed together to form a combustible mixture in a carburetor or through fuel injection. The fuel and air mixture then flow through the intake manifold into the engine intake valve at the top or head of the cylinder.

How does an engine work? Inside the cylinder is a piston which is fitted air tight. When a source of ignition is supplied the fuel and air mixture burn and expand rapidly moving the pistion. This expansion begins a mechanical actions that result in the rotation of a shaft, which is then harnessed to accomplish useful work in turning the prop.The goal of the engine is to produce this useful rotary motion, or torque.

Torque Torque is defined as a force that produces or tries to produce rotation. The amount of torque is measured as horsepower.

Lets look at the engine

Engine Classification L=Left hand rotation T=Turbocharged V=Vertical Helicopter H=Horizontal A=Aerobatic I=Fuel Injected G=Geared S=Supercharged O=Opposed Cylinders R=Radial Engine

B-19 Manual (1-9) O-320-E2B O=Opposed type engine 320=320 cubic inch displacement E=E-type crankcase 2=Mode 2 counterweights B=type accessory section 150 Horsepower

Other Classification of engines based on cylinder arrangement

Proper Fuel Essentials Aviation Fuel=aviation gasoline(Avgas) Identified by octane number. The octane number of fuel measures how fast it burns. Higher octanes burns: Slower and in a more controlled manner.

Normal vs Abnormal Combustion (P73) Use the next higher grade if you use a lower grade the fuel will burn rapidly and uncontrolled causing detonation. Fig 3.15

Mixed Fuel Fuel is colored for easy identification. The dyes used to create these colors are designed to cancel each other if different grades of fuel are mixed. An unequal blend will have the color of the predominant fuel but weaker in color Half and half will turn the fuel clear.

Fuel Color What color is Jet Fuel? Clear or straw colored What color is water? Clear or blue What color is mixed fuel half and half? Clear

Fuel Contamination Also want to be looking for particles in the fuel. Such as rubber for bladder cells deterorating. Dirt, rocks, sand as well

Mixture Control Mixture control prevent mixture from becoming too rich at high altitudes conserve fuel provide optimum power

Mixture control Leaning the engine Rule of thumb whenever power is 75% or less or above 5000 feet B-19 lean until engine runs rough enrichen back to peak rpm then a little more C-23 use peak egt then enrichen for 75 degree drop F-33A use peak egt then enrichen for 100 degree drop

Carburetor Icing Also refered to as Carb Ice Carb ice can occur in high humidity between 20 and 70 degrees F Whenever a liquid is vaporized into a gas, as fuel is in a carburetor, it draws heat out of its surroundings. Fuel spilled on hands is cold.

Carb Ice If moist air enters the carburetor, and the temp. drops this liquid can condense into liquid form. If the temp drops further below zero we can get ice Accumulation at low power settings is possible Detection a gradual loss of rpm or manifold pressure

Carb Ice Three kinds of Carb ice Impact ice, Fuel ice, and Throttle ice. Fig 3.22

Carb Heat (P80)

Checking for Carb Ice 1. Pull on carb heat looking for a steady drop. If steady for 15 seconds return to off position should see a rise in RPM 2. If RPM rises with heat on you have carb ice the engine will start to run smoother as ice melts. 3. Leave until ice is melted and RPM stable then return to off

Carburetor Keep in mind with carb heat on you are getting unfiltered air, the density decreases and mixture enrichens thus the drop in rpm Some POH’s state to lean mixture before applying carb heat.

Propeller 2 or more small airfoils spun by the engine to create thrust All propellers have a few things in common including geometric twist Tip rotates faster than the hub Two types of props Fixed Pitch and Constant-speed (Controllable Pitch) Prop

Fixed Pitch Prop

Constant Speed Prop

Multi-Bladed Prop

Propeller Prop blade is basically an airfoil. Angle of attack becomes less the faster you go This is why the engine speeds up the faster you go As increase in altitude rpm increases because less drag caused by less dense air

Propeller (Fixed pitch) Throttle controls rpm Simple to operate Lower cost Less weight Less expensive to overhaul

Propeller (Constant speed or Variable pitch) Constant speed prop controlled by governor Prop governor allows the selection of blade pitch to control engine RPM. (will maintain a constant RPM) Pilot can control the pitch from the cockpit prop control lever

Propeller (Constant speed or Variable pitch) Pitch on Bonanza 12.5 to 34º Longer engine life Less pilot fatigue More efficient operation Can reduce drag in emergency glide configuration

Throttle control Manifold pressure gauge measures pressure in the intake manifold in inches of mercury Control power by reference to this instrument

Engine Cooling Several ways Oil, cowl flaps, baffles, cooling fins, firewall, air intake for engine cooling, rich mixture, lower power higher airspeed. Oil Temp guage, cylinder head temp gauge.

Engine Cooling (P70-71)

Lubrication We use mostly aeroshell 15W-50 Oil pressure should show some indication by 30 seconds in summer and 60 seconds in winter

Oil has 4 purposes 1. cooling, removes heat and reduces friction 2. helps seal between cylinder wall and piston rings 3. cleans 4. prevents corrosion