Engine and Systems

Question 1

What are the 4 strokes to a four stroke reciprocation engine cycle?

Answer 1

4-stroke Cycle

• Intake(suck)
• Compression (squeeze)
• Combustion (bang)
• exhaust (blow)

Question 2

What happens during each stroke of a four-stroke engine cycle? (What is the piston doing, Spark plugs, Valves?)

Intake Stroke

Answer 2

Intake stroke (1st stroke)

• Piston is pulled down in the cylinder by the crankshaft
• This lowers the pressure in the cylinder and allows the air/fuel mixture to be sucked into the cylinder from the carburator through the intake valve
• Intake Valve is open

Question 3

What happens during each stroke of a four-stroke engine cycle? (What is the piston doing, Spark plugs, Valves?)

Compression Stroke

Answer 3

Compression Stroke(2nd stroke)

• Intake valve is closed
• Piston is driven up, and compresses fuel/air mixture increasing its temperature
• As piston reaches top of cylinder, spark plugs ignite the fuel/air mixture
• This ignition begins a controlled burn and the start of the power stroke

Question 4

How is power increased?

Answer 4

Power is increased by increasing the amount of air/fuel mixture that enters the Cylinder during the intake stroke,

Question 5

What happens during each stroke of a four-stroke engine cycle? (What is the piston doing, Spark plugs, Valves?)

Power Stroke

Answer 5

Power Stroke(3rd stroke)

• Fuel/air mixture expands as it burns, forcing the piston to the bottom of the cylinder.
• Just prior to the end of the power stroke, the exhaust valve opens.

Question 6

What happens during each stroke of a four-stroke engine cycle? (What is the piston doing, Spark plugs, Valves?)

Exhaust stroke

Answer 6

• Piston is driven back up to the top of the cylinder, driving the exhaust gases out the exhaust valve
• Exhaust valve is open

Question 7

The power strokes of the cylinders are spaced so that they occur …

Answer 7

The power strokes of the cylinders are spaced so that they occur “at different positions during the revolution of the crankshaft.”

Question 8

Each cylinder provides a power stroke per __ revolutions of the crankshaft, whether it’s a 4 or 6 cylinder engine.

Answer 8

Each cylinder provides a power stroke per 2 revolutions of the crankshaft, whether it’s a 4 or 6 cylinder engine.

Question 9

Exhaust System

Answer 9

Burned gases leave cylinders, then exit the aircraft through the exhaust pipe on the underside of the cowling

Question 10

How is cabin heat and defrost provided on most GA airplanes

Answer 10

• Via the exhaust system
• A shroud around muffler provides heated air for use in cabin heating/defrosting and carburetor heat

Question 11

How is carburetor heat created for use?

Answer 11

A shroud around muffler provides heated air for use in cabin heating/defrosting and carburetor heat

Question 12

What’s a Magneto?

Answer 12

• A magneto is a self-contained generator of electricity used to provide electricity to the spark plugs.
• Mechanically driven by the engine.
• Consists of a magnet that is rotated near a conductor which has a coil of wire around it.
• The rotation induces electrical current to flow in the coil.

Question 13

What do the coils of wire of the Magneto do?

Answer 13

Around this primary coil of wire are many more coils of thinner wire which amplify, or transform, the primary voltage into the higher voltage needed for the spark plugs.

Question 14

What is the arrangement of primary & secondary coils in the magneto called?

Answer 14

• The arrangement of primary & secondary coils in the magneto is called a transformer.
• The higher voltage is what is fed to the spark plugs which ignites the fuel/air mixture

Question 15

What do spark plugs do?

Answer 15

The higher voltage from the magneto is what is fed to the spark plugs which ignites the fuel/air mixture

Question 16

What makes sure the magneto delivers the higher voltage to each spark plug properly?

Answer 16

• a distributor in the magneto delivers the higher voltage to each spark plug at different times
• The distributor has a finger which is geared to crankshaft so it turns only once for every two turns of crankshaft
• .This finger turns once for each 4-stroke cycle

Because of this, the magneto distributes the current to each cylinder in the correct order.

Question 17

Magnetos run __________ of all other electrical sources of power…they only need _____ to rotate the magnet

Answer 17

Magnetos run independently of all other electrical sources of power…they only need engine to rotate the magnet = engine driven.

Question 18

If a lower grade of fuel is used what can happen?

Answer 18

It’s important to use the correct grade of aviation fuel:
If a lower grade is used than needed, it will cause high engine temperatures and detonation.

Question 19

If a higher grade of fuel is used, what can happen?

Answer 19

It’s important to use the correct grade of aviation fuel:

If a higher grade is used than needed, spark plugs can be fouled by lead deposits.

Question 20

What is detonation?

Answer 20

• Detonation is explosive combustion
• When gas is compressed it’s temperature and pressure rises.
• If it rises too high the air/fuel mixture in the cylinder will explode rather than burn evenly.
• Detonation can be very damaging to pistons, valves, & spark plugs

Question 21

What is a sign of detonation?

Answer 21

Excessively high cylinder head temperature is a sign of detonation

Question 22

What causes detonation?

Answer 22

• Lower fuel grade than recommended
• Old fuel (additives evaporate lowering the octane rating)
• Too lean of a mixture = too little fuel mixed with the air for burning in the cylinders.
• Over-heated engine.
• Excessive temperature of air passing through the carburetor

Question 23

What do you do if detonation occurs in flight?

Answer 23

If detonation occurs in flight:

• Richen the fuel/air mixture
• Reduce thrust by pulling back on the throttle (less pressure in the cylinders with less power).
• Increase airspeed to increase airflow to the engine (to cool the cylinders).
• Increasing airspeed without increasing thrust requires a descent.

Question 24

What is pre-ignition?

Answer 24

Ignition of fuel/air mixture before spark plug fires (before the piston reaches TDC)

Question 25

The results of pre-ignition include:

Answer 25

The results of pre-ignition include: * A rough running engine * A sudden rise in cylinder head temperature * Possible backfiring of the engine * Possible engine damage

Question 26

Pre-Ignition can be caused by:

Answer 26

Pre-Ignition can be caused by: * Carbon or lead deposits (hot-spots in cylinder) * Using high power with the fuel/air mixture too lean (no extra fuel available for cooling). * Overheated spark plugs ( possibly due to detonation).

Question 27

What is the carburetor ?

Answer 27

The carburetor mixes the fuel with the air prior to sending this mixture to the cylinders for combustion

Question 28

What is the correct ratio of fuel/air?

Answer 28

The correct ratio of fuel/air is approximately 1 part fuel to 12 parts air by weight

Question 29

What is a rich mixture?

Answer 29

A rich mixture means that the fuel/ air ratio is larger (1:8 maximum).

Question 30

What is a lean mixture?

Answer 30

A lean mixture means that the fuel/air ratio is smaller (1:20 minimum).

Question 31

What is latent heat of vaporization?

Answer 31

I think based on the Jep book... The vaporization of fuel contributes to a temperature decrease in the carburetor

Question 32

What is the first indication of Carb Ice

Answer 32

* A decrease in RPM * Rough running engine

Question 33

What conditions are favorable to the formation of carburetor Ice?

Answer 33

* Tempurature below 70 F * High humidity

Question 34

What's the differnence between rich fuel/air mixture and lean fuel/air mixture? rich fuel/air mixture

Answer 34

With a rich fuel air mixture there will be excess fuel after burning. This can cause * loss of power * rough running engine * high fuel consumption * fouling of spark plufs * formation of lead deposits On a good note, the cylinder head temperatures are cooler

Question 35

What's the differnence between rich fuel/air mixture and lean fuel/air mixture? lean fuel/air mixture

Answer 35

A lean mixture means there is a relative shortage of fuel compared to the air in the fuel/air mixture, so after burning, there will be some oxygen left over. This causes excessively high cylinder head temperatures possibly leading to detonation or pre-ignition

Question 36

Is it better to have a too rich or too lean fuel/air mixture?

Answer 36

A little “too rich” mixture is preferable to a “too lean” mixture

Question 37

When starting a C-172 engine, do both magnetos provide electrical current to all of the spark plugs?

Answer 37

No, the left magneto provides electrical current to 1 spark plug in each cylinder

Question 38

What are the causes of a temperature drop in the carburetor venturi?

Answer 38

* pressure drop * latent heat of vaporization

Question 39

Does application of carburetor heat affect engine performance?

Answer 39

Yes. Causes a reduction of RPM. Heated air is less dense ? To ask Bill: Why would an rich mixture cause a reduction in RPM?

Question 40

What does the throttle do?

Answer 40

The throttle lever in the cockpit allows the pilot to vary the airflow into the carburetor throat by positioning the throttle plate (butterfly valve). Why does that matter? The greater the amount of airflow, the greater the pressure differential between the carburetor throat and the float chamber, and the more fuel/air mixture provided to the cylinders. The more fuel/air mixture to the cylinders = more power = more thrust

Question 41

The greater the amount of airflow to the carburetor means what?

Answer 41

The greater the amount of airflow, the greater the pressure differential between the carburetor throat and the float chamber, and the more fuel/air mixture provided to the cylinders. The more fuel/air mixture to the cylinders = more power = more thrust

Question 42

Engine Controls in the cockpit Mixture

Answer 42

Mixture: used to adjust the metered weight of fuel to be mixed with air in the carburetor

Question 43

Engine Controls in the cockpit Throttle

Answer 43

Throttle: used to adjust the amount of fuel/air mixture to be delivered to the cylinders = increases/decreases power = adjusts thrust

Question 44

Engine Controls in the cockpit Tachometer

Answer 44

Tachometer: engine instrument used to adjust/monitor engine rpm.

Question 45

What type of fuel systems are typical on high wing, small aircraft and why?

Answer 45

Gravity fed systems are typical on high wing, small aircraft, because they are simple!

Question 46

Fuel Systems What are located under each wing and are used to check for fuel contamination during pre-flight

Answer 46

Sumps located under each wing are used to check for contamination during the preflight

Question 47

What provides power to turn the propeller?

Answer 47

**The engine** provides power to turn the propeller

Question 48

Where is a Reciprocating Engines mounted?

Answer 48

Mounted to firewall, which protects occupants, and turns the propeller

Question 49

What does a Reciprocating Engine power?

Answer 49

Powers Accessories: * alternator, * vacuum pump (for instruments), and * provides heat

Question 50

Where is the power generated in a reciprocating engine?

Answer 50

Cylinders are where the power is generated

Question 51

What makes sure the intake and exhause valves open/close at the correct times?

Answer 51

Intake & exhaust valves must open/close at correct times. **Regulated by a camshaft**

Question 52

Camshaft rotates at ??? the rate of the crankshaft

Answer 52

Camshaft rotates 1/2 the rate of the crankshaft

Question 53

Intake/exhaust valves open/close??? per complete cylinder cycle = once per ?? crankshaft revolutions = ?? per camshaft revolution

Answer 53

Intake/exhaust valves open/close **_1 time_** per complete cylinder cycle = once per **_2_** crankshaft revolutions = **_once_** per camshaft revolution

Question 54

An dual ignition system in a small airplane includes

Answer 54

For small airplanes, this system includes: * Two magnetos which send electric current to the spark plugs. Two spark plugs per cylinder. Each magneto sends current to one spark plug in each cylinder

Question 55

Having a ____ ignition system results in more ___ burning of the fuel/air mixture, and is more \_\_\_\_\_\_\_

Answer 55

Having a **dual** ignition system results in more **even** burning of the fuel/air mixture, and is more **fuel efficient**

Question 56

The starter is powered by the \_\_\_\_\_\_\_

Answer 56

Starter is powered by the battery

Question 57

When starter is engaged, it \_\_\_\_\_\_\_

Answer 57

When starter is engaged, it rotates the crankshaft