AGK Flashcards by Charles Parsons

What will a piston engine produce?

Power (horsepower) Rotation (RPM) Torque (Newton Meters)

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Piston Engine Power Formula?

Power = Torque x RPM Or. Power = torque x RPM/5252

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Piston Engine Torque Formula?

Torque = Force x Distance

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Force within torque formula?

Force = pressure x area

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How does torque and speed relate?

Inversely proportional

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What are the piston engine chemical reaction principles?

Chemical energy => Heat Energy => Pressure Energy => Mechanical energy

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What is the vertical (up and down) movement of a piston called?

Reciprocal movement

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What is the lowest and highest point at which a piston reaches called?

TDC (top dead centre) BDC (bottom dead centre)

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What are the 4 stages of a stroke cycle on a piston engine?

Induction 2. Compression 3. Power 4. Exhaust

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What happens within the Induction stroke in a piston engine?

Inlet valve opens
Piston moves down towards BDC
Volume increases, Pressure decreases temp decreases
180 degree crank shaft rotation

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What happens within the Compression stroke in a piston engine?

Both valves are shut
Volume decreases
Temp and pressure increase
Piston moves towards TDC
Crankshaft rotates 180 degrees

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What happens within the Power stroke in a piston engine?

Both valves closed
Piston moves towards BDC
Volume increases
Temp and density decrease
Crankshaft rotates 180 degrees

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What happens within the exhaust stroke in a piston engine?

Exhaust valve opens
Piston moves towards TDC
Volume decreases
Temp and density increase
Crankshaft rotates 180degrees

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Ineffective crank angle?

Small linear movement of piston
Large angle of rotation of crankshaft
Happens at TDC and BDC

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Inlet valve lag?

Inlet valve still open at the start of compression stroke
Due to relatively little piston movement (ineffective crank angle)

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Inlet valve lead?

Inlet valve opens early whilst exhaust valve is still open
Due to little amount of linear piston movement (ineffective crank angle)

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Piston engine optimised cycle?

Ignition happens at 30degree before TDC
Advanced/retarding sparking

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The crank assemble consists of?

Connecting rods
Crank shaft
Pistons

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What is the primary disadvantage of water cooling?

The weight of the coolant

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What is the part of the camshaft that lifts the push rods?

Cams

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The propeller is attached to and driven by?

The crankshaft

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What are hydrologic tappets used for?

Automatically adjust the tappet clearance

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What is tappet clearance?

Maintain the gap between the push rod and the valve rocker despite thermal expansion of the valve stem

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Which component seals the piston skirt?

Piston rings

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What is charge?

Fuel and air(oxygen)

What word means chemically balanced

Stoichiometric

What is the pressure balance duct

YouTube connected back to the pre Venturi airflow

The pressure balance duct helps correct for changes in which speed?

True air speed (TAS)

In theory, combustion happens when?

Start of Power stroke, TDC

What help control fuel flow in a carbretta?

Main jet Idle Jet Diffuser

Where is the mixture in a carbretta controlled?

The diffuser

The rich lean graph (Lycombing mixture graph) shows what?

EGT (exhaust gas temp) CHT (Cylinder head Temp) Power Fuel flow

Which valve is still open as the compression stroke begins? What is this called?

Inlet valve Inlet valve lag

Which valve opens early during exhaust stroke? And what is this called?

Inlet valve Inlet valve lead

Why do we have lead in fuel

Temp control Lubrication Valve strength

Purpose of lubrication

Cleaning Cooling (Control expansion) Lubricating Performing hydronic functions

What does 10W50 mean for oil?

Cold: viscosity rating 10 (10x the viscosity of water) When warm: viscosity rating 50 (50 x the viscosity of water)

What is ineffective crank angle?

Large crank shaft rotation with small linear piston movement

Peek torque is when the crankshaft is at what angle?

90 degrees

What components of the stroke cycle are variable?

Pressure and RPM (By changing the throttle, you increase/decrease airflow(pressure))

What is the correct name for chemically balanced AVGAS? And what is the ratio?

Stoichiometric 15:1

What are the characteristics of AVGAS?

Contains sufficient amount of energy (able to form Vapor and burn quickly and controllably) Burns at 18-24 m/s Produces predictable rise in cylinder pressure Good anti-knock properties (resists detonation) 85% carbon & 15% hydrogen Flashpoint -20 degrees

What is Vapor lock?

Vapour pocket forms which restricts liquid fuel movement

What is the flash point for AVGAS and Jetfuel?

AVGAS = -20 degrees Jet fuel = 37 degrees

Describe AVGAS types and colouring system

AVGAS100LL - Blue - Octain rating 100 - Low lead AVGAS100 - Green - octain rating 100 - leaded fuel AVGAS80 - red - leaded MOGAS - motor gas - no water checks AVGAS82 - purple - unleaded

Describe the difference between AVGAS and MOGAS

AVGAS is more regulated No more than 20-30ppm (parts per million) of water

What is the specific density of AVGAS at 15 degrees

0.72

What is the specific gravity for fuel and water?

Water = 1 AVGAS = 0.72

List the pre-flight fuel checks are

Sample the fuel to test that it is: 1. Clear and bright 2. Free of sediment 3. No entrained water (30ppm max)

In a turbo, there are two components on a single shaft, what are they

Compressor Turbine

What is the ratio for a rich, chemically correct (Stoichiometric), and lean mixture of charge?

Rich = 8:1 Stoichiometric = 15: 1 Lean = 20:1 (Parts of air(oxygen) : fuel)

What fuel mixture would you use for take off and what ratio would be ideal?

Rich mixture 11:1

What fuel mixture would you use for cruise and what would the ideal ratio be?

Lean mixture 17:1

True or false: Engine pressure will always be lower than atmospheric pressure?

TRUE

In a Venturi, what happens to velocity, pressure and temperature as it converges (goes in)?

Velocity = increase Pressure = decrease Temperature = decrease

In a Venturi, what happens to Velocity, Temp & Pressure during the diverging stage (leaving the throat)?

Velocity decreases Pressure increases Temp increases

In the climb with no adjustments, what happens to the mixture?

It gets richer (as you climb the atmosphere gets thinner, there is less oxygen, Same amount of fuel with less oxygen is richer)

What is connected to the float in a carburettor that controls the fuel?

Needle valve

True or false, the butterfly valve when closed (engine idle) still allows a small amount of air through

TRUE

What is the purpose of a main jet within a carburettor?

Narrows and limits fuel flow Controls fuel flow

What is an atomiser and where is it found? (Carburettor)

found about the main jet Turns liquid fuel into vapour

What is the diffuser and when can it be found?

Found: Just after or parallel to the main jet Balences fuel flow to speed and oxygen levels (oxygen levels decrease with altitude) (Glass and straw with 3 holes analogy) (As static pressure increases, more fuel is required) (As static pressure decreases, less fuel is required) Regulates the mixture Aids Atomisation Air from the pressure balance duct is fed to the diffuser

Doubling the mass flow of air through the Venturi would have what effect on the pressure?

4 x drop in pressure (Lead to a large increase in fuel)

What does the mixture control do in the carbretta do?

- overrides the diffuser - makes fuel rich or lean depending on what’s required - it is the red lever on an aircraft

Where is the cylinder head temperature (CHT) measured?

On the hottest cylinder

Stoichiometric (chemically balanced) mixture (15:1) is what temperature?

Peak temperature As seen on the lycombing mixture graph

What is the air:fuel ratios for the following: - start up - take off - cruising (power cruising) - climb - Economy cruise - Peak power

- start up (9:1) (rich) - take off (12:1) (rich) - cruising (power cruising) (17:1) (lean) - climb (14:1) (lean) - Economy cruise (19:1) (lean) - Peak power (14:1) (rich)

A fuel cooled mixture would be?

Rich

An air cooled mixture would be?

Lean

What is an accelerator pump and what does it do?

Prevents lean out Injects a secondary amount of fuel to stop throttle hesitation

What are the three methods of priming?

Accelerator pump (3 pumps of throttle) Priming hand pump Electric pump

Why should you not over prime an engine?

Could cause a build up of liquid fuel Flood the engine Cause a fire

How many carburettors do most engine have

One

What are the two types of Carburettor icing

Refrigerated icing Impact icing

What are some of the effects of refrigerated icing?

Lose power Jam throttle

In reference to piston engines, what is meant by the term swept volume

The volume displaced by the piston during a single stroke

Consider a fuel injection system. Which is the central point from where fuel is distributed to the individual cylinders

Manifold valve

What three valves are within the manifold valve

Metering valve