Powerplant Finals

Metal-to-Metal Friction

When two metallic surfaces move against each other and create friction and heat

Wear and Tear

Excessive wear from metal parts contacting each other

Lubricating Film

Film that separates moving parts to prevent contact

Lubrication

Process of separating moving engine parts

Liquid, solid, gas

Lubricating System Types

- Minimizing powerloss

- Reduced wear and tear of moving parts

- Provides cooling

- Provides cushioning

- Carries out the internal cleaning of engines

- Helps piston rings to seal against high pressure

gases

Results of Lubrication

Oil Sump

Bowl-shaped reservoir that stores engine oil

Oil Pump

Component circulating oil to moving parts

Oil Pump

Component supplying oil to the oil filter

Oil Filter

Final barrier preventing particulate matter from entering bearings

0.002-0.007 mm

Oil Filter Particle Size

Oil Galleries

Passages distributing oil to remote engine locations

Oil Gallery Distribution

Oil passages feeding crankshaft, bearings, camshaft, valves

Viscosity

Oil's resistance to flow

Specific Gravity

Comparison of oil's weight to water at a specific temperature

Oil Color Test

Test for oil color using ASTM Union Colorimeter

Cloud Point

Temperature where oil becomes cloudy

Pour Point

Lowest temperature at which oil can still flow

Flash Point

Temperature where oil releases ignitable vapors

Fire Point

Temperature where oil produces sufficient vapor to sustain flame

Oil Consumption Factors

Oil consumption affected by rpm, temperature, clearances, viscosity

Oil Consumption - High Factors

Higher rpm, high temps, large clearances increase oil consumption

Oil Consumption - Low Viscosity

Lower viscosity causing increased oil consumption

Aircraft Fuel System

System delivering consistent fuel flow at required pressure

Carburetor Type System

Carburetor-based fuel delivery method

Fuel Injection System

Fuel injection-based system with no carburetor

Fuel Tank

Pressurized tank preventing fuel vaporization and pollution

Fuel Tank Vent System

Fuel tank venting through emission control systems

Fuel Pipes

Fuel pipes ensuring optimal fuel passage

Fuel Pipe Construction

Fuel pipes made of steel or plastic secured with clips

Fuel Filter

Filter preventing dirt and fluff from entering fuel pump

Fuel Filter Location

Fuel filter placed on suction side of pump

Fuel Pump - Injection

Pump supplying fuel under high pressure to injection systems

Fuel Pump - Carburetor

Pump supplying fuel under low pressure to carburetor

Air Filter

Device preventing dust from entering the engine

Carburetor

Component atomizing and mixing fuel with air

Fuel Injection Advantage - Icing

Fuel injection advantage of less induction icing

Fuel Injection Advantage - Distribution

Fuel injection providing better fuel distribution

Fuel Injection Advantage - Economy

Fuel injection improving fuel economy

Fuel/Air Control Unit

Component controlling metered fuel pressure and air intake

Gravity-Fed System

System relying on gravity for fuel flow

Gravity-Fed Use Case

Gravity-fed systems used mostly on high-wing aircraft

Gravity System Fuel Verification

Requirement to verify remaining fuel quantity in tank

Pump-Fed System

System relying on pumps instead of gravity

Pump-Fed Use Case

Pump-fed systems required for low-wing aircraft

Pump-Fed Redundancy

Need for primary and auxiliary fuel pumps

Pump Requirement Standard

Each fuel pump must supply 125% of max requirement

Vapor Lock

Interruption of fuel flow due to vapor formation

Vapor Lock Cause - Pressure Drop

Lower pressure causing fuel vaporization

Vapor Lock Cause - Temperature

High fuel temperatures causing vapor lock

Vapor Lock Cause - Turbulence

Excessive turbulence causing vapor lock

Vapor Lock Prevention - Heat

Keeping fuel lines away from heat to prevent vapor lock

Vapor Lock Prevention - Line Routing

Avoiding sharp bends or steep rises in fuel lines

Vapor Lock Prevention - Booster Pumps

Use of booster pumps to reduce vapor lock

Backfiring

Lean mixture burning slowly igniting during intake

After Firing

Rich mixture burning slowly in exhaust system

Ignition System

System generating electrical spark for fuel-air ignition

Ignition Independent Supply

Ignition system separated from aircraft electrical system

Ignition Timing Purpose

Spark timed near TDC during compression stroke

Variable Ignition Timing

Ignition system adjusting timing for speed and load

Battery

Battery providing power for ignition and other functions

Battery Functions

Battery used for ground power and emergency power

Lead-Acid Battery

Battery type for small private aircraft (lead acid)

Nickel-Cadmium Battery

Battery type for commercial aircraft (NiCad)

Battery Type Change

Changing battery type considered major alteration

Ignition Switch

Switch allowing pilot to control ignition on/off

Spark Plug

Spark plug producing arc inside combustion chamber

Spark Plug Function

Spark plug converting electrical energy to combustion

Distributor

Distributor routing spark in correct order

Distributor Function - Current Cycling

Distributor actuating current flow on/off cycles

Distributor Function - High Voltage

Distributor routing high voltage to plug wires

Distributor Function - Timing

Distributor advancing spark timing as speed increases

Magneto

Magnet-driven generator supplying high-voltage spark

Low-Tension Magneto

Low-tension magneto producing low voltage for local coils

High-Tension Magneto

High-tension magneto generating high voltage directly

Firing Order

Sequence in which cylinders fire in correct timing

Firing Order Factors

Firing order affected by vibration, cooling, back pressure

Radial Firing Pattern

Odd cylinders fire first in radial engines

Radial Firing Second Phase

Even cylinders fire after odd cylinders in radial engines

1-3-5-7-2-4-6

Firing order of 7-cylinder radial =

1-3-5-7-9-2-4-6-8

Firing order of 9-cylinder radial =

Double-Row Radial Concept

Double-row radial = two single-row engines sharing crankshaft

Double-Row Firing Balance

Double-row radial balancing by alternating between rows

14-Cylinder Radial Example

14-cylinder double-row starts 1 → 10 order

18-Cylinder Firing Rule

General method: add 11 or subtract 7 for 18-cylinder radial

Four-Stroke Cycle

Cycle consisting of intake, compression, ignition, power, exhaust

Crankshaft Cycle Requirement

Two revolutions of crankshaft per engine cycle

Top Dead Center

Position of piston at highest travel point

Bottom Dead Center

Position of piston at lowest travel point

Bore

Cylinder inside diameter

Stroke

Piston travel distance from TDC to BDC

Piston Displacement

Volume swept by piston between TDC and BDC

Volume Displacement Formula

Product of piston area × stroke × number of cylinders

Clearance Volume

Cylinder volume at TDC

Total Volume

Total cylinder volume including clearance

Valve Timing

Timing describing when valves open/close

Intake Valve Early Opening

Intake valve opens before piston reaches TDC

Intake Valve Purpose

Early intake opening increases fuel-air charge volume

Exhaust Valve Overrun

Exhaust valve remains open past TDC

Valve Lag

Crankshaft degrees exhaust valve stays open past TDC