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Mod 1 > AGK Engines > Flashcards

AGK Engines Flashcards

1
Q

what is 1hp equivalent to?

A

740 watts

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2
Q

what is torque? what does it depend on?

A

a ‘push’ and ‘pull’ > a twist that is forced to rotate an object.

It depends on:
-The force applied
-length of the lever arm connecting to axis
-Angle between the two.

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3
Q

what is the SI unit of torque?

A

Foot lb

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4
Q

what else is torque described as?

A

A moment of force

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5
Q

How does piston engines produce power?

A
  1. Converting chemical energy into mechanical energy.
  2. Fuel is burned to release energy in the form of heat
  3. This results to increase in pressure energy.
  4. Pressure energy is converted to mechanical energy.
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6
Q

What is the function of the crankshaft?

A

converts it linear (up and down motion) to rotary motion (makes it rotate.)

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7
Q

What is the four stroke cycle?

A

Induction: Mixture drawn into the cylinder
Compression: Mixture is compressed increasing pressure
Power: Piston is driven down the cylinder for mechanical power
Exhaust: waste gases are expelled and whole process begins

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8
Q

What happens in induction stroke?

A
  1. Inlet valve opens
  2. Volume > increases
    Static Pressure > reduces
    Temperature > reducing
  3. Piston moves towards Bottom Dead Centre (BDC)
  4. 180 degree crankshaft rotation between TDC and BDC.

this is called a ‘normally aspirated engine’

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9
Q

What happens in Compression stroke?

A
  1. Inlet & outlet valves closed.
  2. Volume > decreases
    Pressure > increasing
    Temperature > increasing towards TDC
  3. 180 degree crankshaft rotation from BDC to TDC.
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10
Q

What happens in Combustion stroke?

A

Ignited by electrically generated spark .
this occurs instantaneously whilst piston is at TDC.

Produces a very large increase in temperature and pressure.

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11
Q

What happens in Power stroke?

A

Rapid rise in pressure makes the piston

  1. Inlet & exhaust valve closed
  2. Volume increasing
    Static Pressure > Reducing
    Temperature reducing
  3. 180 degree crankshaft rotation from BDC to TDC.
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12
Q

What happens in Exhaust stroke?

A

Inlet valve > closed
exhaust valve > open

  1. Volume decreasing
    Static Pressure > increasing
    Temperature increasing
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13
Q

What is it called when both inlet and outlet valve are open at the same time? Which stage does this occur

A

Valve overlap

Occurs between exhaust and induction strokes.

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14
Q

Why do you need to turn the engine over slowly before starting?

A

to stop the oil causing excessive known as ‘hydraulicing’. this can cause the cylinder head to separate from the engine.

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15
Q

Why are there two spark plugs per cylinder?

A

Built in redundancy for safety
Ensures efficient combustion.

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16
Q

What is one rotation equivalent to?

A

2x Throw = 1x Stroke

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17
Q

What is the crankcase?

A

Main structural element of the engine. It is a light, strong heavy steal alloy e.g. magnesium (highly reactive).

They are hollowed to allow cooling and lubricating oil through it.

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18
Q

What is the camshaft?

A

It always rotates at half the speed of the engine crankshaft.

It operates the vales via the push rods.

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19
Q

What are the characteristics of a valve gear?

A

A ‘backfire’ is when an exhaust valve is open when it should be closed.
A ‘popping back’ into the carburetor is when the inlet valve is open when it should be closed.

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20
Q

What are the colours of fuel and their octane rating? (RGB)

A

AVGAS80 = Red (most likely to detonation due inability to reach performance number of 100)
AVGAS100 = Green (anti - detonation)
AVGAS100LL = Blue (anti - detonation)
JETA = Colorless or straw

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21
Q

What is detonation?

A

= knocking = Pinning

After ignition it is the last bit of mixture (end gas) may detonate. This results in a violent and uneven rise in pressure in the cylinder. an EXPLOSION. this is heard as knocking or pinning sound.

22
Q

How do you control detonation?

A

Avoid carburetor heat
high power settings at low RPM
Overheating cylinders, lean mixture

23
Q

What are the colours in relation to fuel usage? (BBR)

A

Throttle = Black

RPM = Blue
High RPM = Fine propeller
Low RPM = Coarse propeller

Mixture = Red

24
Q

What are the mixture ratios?

A

15:1 stoichiometric (chemically correct)
12:1 Rich (Take-off)
18:1 Lean (cruise economy)

25
Q

what does it mean if the ignition happens before TDC (34 deg before) and after TDC (8-10 deg aft)

A

Before TDC - Advanced
After TDC its a Fat retarded spark

26
Q

What is pre ignition?

A

Pre ignition is the ignition before the spark occurs.

27
Q

What is engine fuel supply and how does it work

A

It is controlled by the throttle
Must have the right amount of atomized fuel added to it.
Done by the carburetor or the fuel injection system.

Main fuel jet = upstream the throttle valve
Throttle = Downstream of the main fuel jet

28
Q

Carburettor air is…

A

Hot air and unfiltered

29
Q

Principle operation of the basic float carburettor

A

Float and Needle Valve: The float rises and falls with the fuel level in the float chamber. When the fuel level drops, the float falls, opening the needle valve and allowing more fuel to enter the chamber. When the fuel level rises, the float rises and closes the needle valve, stopping the fuel flow. This maintains a constant fuel level in the float chamber.

Venturi Effect: Air is drawn into the carburetor through the venturi when the engine is running. The venturi is a narrow section that causes the air to speed up and its pressure to drop (Bernoulli’s principle).

Fuel Drawn into Air Stream: The drop in pressure in the venturi creates a suction effect that pulls fuel from the float chamber through the fuel jet into the air stream.

Throttle Valve: The throttle valve controls the amount of air entering the engine. When the throttle is opened, more air flows through the venturi, drawing more fuel and increasing the engine’s power. When the throttle is closed, less air and fuel enter, reducing power.

30
Q

What is the function of the pressure balance?

A

The pressure balance duct is to ensure that the correct mixture ratio is maintained across a range of airspeeds and flight conditions.

31
Q

What is the function of the diffuser?

A

As airflow increases the fuel form main jet needs to be at a lower rate to a maximum mixture.

Without this it would result in the mixture being rich as the engine speed increases.

32
Q

What is the function of mixture control?

A

decrease in air density resulting in richer mixture as air climbs
A manual/automatic valve compensates for this.
mixture controls valve adjusts fuel flow at different altitudes and adjusted for power and economy.

33
Q

What is slow running jet (idle to shut down)?

A

Provides a rich mixture at idle throttle.

Cutoff valve ensure fuel flow to the engines ceases when sbut down

Placed at the end of almost closed butterfly

34
Q

What is Power enrichment in engines?

A

provides a richer mixture at takeoff to cool the cylinders

35
Q

What is an accelerator pump?

A

Accelerates the fuel when the throttle lever is moved rapidly.

caters for the delay in rapid reduction in pressure when power has decreased.

A flat spot is lack of acceleration

36
Q

Thermal efficiency equation

A

(Heat converted to work/heat energy available in the fuel) x 100%

37
Q

What colour illuminates when driving gear is engaged? how long until the illuminate means there is a problem?

A

Amber light

If on more than 30 seconds after engine start, the starter motor must be disengaged, therefore, the the engine must be shut down.

38
Q

What is a primary winding?

A

A low tension (LT) circuit is wound around the stator and comprises a few turns of thick wire.

39
Q

What is a secondary winding?

A

A high tension (HT) circuit is then wound over it. it comprises of many turns of fine wire and also acts as a step-up transformer. A high voltage and lower current will be produced from the primary winding

40
Q

What are the the effects of a contact breaker?

A
  • Converts continuous flow into a series of pulses.
    the collapse of the magnetic field around primary winding produce a surge of energy in the secondary winding.
41
Q

What are fed through high tension cables to the spark plugs?

A

A series of high voltage, low current pulses of electricity. Also is dependent on aircraft battery and electrical system.

42
Q

What will make the magneto circuit live?

A

Switch must be closed (off) to the earth circuit
When switch is open (on) the circuit is live.

When its on the ground, a disconnected wire results in a permanently live circuit.

43
Q

What is a spark plug?

A

compromises of two electrodes by small air gap
When HT voltage is applied to the Centre electrode a strong spark is generated.

44
Q

What is a magneto?

A

A self contained generator and step-up transformer, designed to produce high voltage momentarily

(for petrol engines)

for cap size it must be set accurately
A small cap will cause the spark to be too weak
An oversized cap will not have a spark

45
Q

What are the effects of contact breakers?

A

-Converts continuous flow of alternating currents into a series of pulses.
-Collapse of primary winding creates a surge in secondary.

46
Q

What is the job of a capacitor?

A

Fitted in parallel with contact breaker to prevent arcing and also produces the highest possible voltage induced in secondary circuit.

47
Q

What is the task of hot well?

A

It ensures that the engine oil warms up quickly

48
Q

When must the oil be checked after a dry sump system shut down?

A

Must be checked immediately after shut down. False reading may occur if checked later as oil can start to drain back into the engine.

49
Q

When must the oil be checked after a wet sump system shut down?

A

About 20 minutes after shut down. This is the time allowed for all the oil to drain back into the sump.

50
Q

What’s the difference between wet and dry sump systems?

A

Dry sump > filtered and cooled oil o=in all flight conditions.
Wet sump > Oil disperses round the engine during inverted flight.

51
Q

What is the role of cylinder baffles?

A

Control the flow of air ensuring that each cylinder is evenly cooled.

Mod 1 (6 decks)

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