Ch. 2 - B - The Powerplant and Related Systems

Question 1

what are the two categories of engines?

Answer 1

Reciprocating and Turbine

Question 2

Describe the basics of reciprocating engine operation

Answer 2

Converts chemical energy into mechanical energy within the cylinders. A fuel-air-mix is compressed within the cylinder by a piston. At moment of compression, the spark plug fires to ignite the mixture. The combustion creates energy which is converted to work and transferred via the crankshaft and connecting rods to drive the propeller.
Moveable pistons attach to the crankshaft by the connecting rods. Together, they change the back and forth motion generated by the pistons into rotary force which drives the prop.

Question 3

The Four-Stroke Cycle

Answer 3

1. Intake: Piston moves away from the cylinder head on intake stroke. Intake valve opens and draws fuel-air-mix into the combustion chamber.
2. Compression: Piston moves back towards the cylinder head, intake valve closes and fuel-air-mix is compressed.
3. Power: The compression nears completion and the spark plug fires to ignite the mixture. The power stroke is caused by the rapidly expanding gasses from the controlled burn and it drives the piston back providing power to rotate the crankshaft.
4. Exhaust: The piston moves back away from the cylinder head and expels the burnt gases through opened exhaust valve.
   This takes place several hundred times per minute. Each cylinder operates on a different stroke. Continuous rotation of crankshaft is provided by the precise timing of the power strokes in each cylinder. Depends on ancillary systems like induction, ignition, fuel, oil, cooling, and exhaust.

Question 4

What is an Induction System?

Answer 4

Bring Outside air into the engine, mix it with fuel to the correct proportion, and deliver it to the cylinders where combustion occurs.

Question 5

With regard to induction, what do the throttle and the mixture controls do?

Answer 5

The throttle controls the amount of the fuel-air-mix being delivered to cylinders.
The mixture control adjusts the ration of the fuel air mix itself.

Question 6

What does the Tachometer display?

Answer 6

Engine speed controlled by the throttle in revolutions per minute.

Question 7

What is the difference between a fixed-pitch propeller and a constant-speed propeller?

Answer 7

Fixed-Pitch: Engine speed controlled by the throttle and displayed on Tachometer.
Constant-Speed: Propeller speed is adjustable through propeller control within the cockpit. Moving the propeller control sets the engine rpm. Throttle controls the engine output as reflected on a manifold pressure gauge (NOT the Tachometer). Propeller control is displayed on tachometer. The gauge displays the pressure of the fuel-air-mix inside the intake manifold in inches of mercury.
Both have mixture controls .

Question 8

Intake Port

Answer 8

A port near the engine compartment though which air flows through a filter. If filter is clogged, alternative air sources are available.

Question 9

Generally describe the function of a carburetor

Answer 9

Air from the induction system arrives at the carb which mixes the air with fuel and delivers it to the combustion chamber.

Question 10

What is the operating principle of float type carburetor ?

Answer 10

The float carb relies on the pressure differential between the air inlet and the venturi throat.

Question 11

Describe the effect of the venturi throat

Answer 11

The shape of the venturi increases the inlet air’s velocity and decreases its pressure, creating an area of low pressure. Meanwhile, the float chamber is vented to the outside so it remains equal to atmospheric pressure. The higher atmospheric pressure in the float chamber forces fuel fuel through the discharge nozzle.

Question 12

List and describe all components of a float style carburetor.

Answer 12

Air inters from outside the plane through the inlet. This air flows into a venturi chamber that increases velocity and decreases density of the air.
The nozzle is being fed fuel from the float chamber where a float gives us a way to gauge our fuel level. The float chamber is vented to the outside so it stays equal to the atmospheric pressure, which is always higher pressure than the low pressure area created by the venturi.
The passage though which fuel flows from the float chamber to the discharge nozzle has a mixture needle capable of restricting the rate of flow into the discharge nozzle. The full rich position leaves the entrance to the passage open, while leaning the mixture causes the needle to descend into the entry hole to limit flow.
The fuel enters the float chamber directly through the fuel inlet.
An air bleed connects the discharge nozzle to back to the float chamber by another route. This allows some air to mix with the fuel being drawn out f the discharge nozzle. This is to decrease fuel density and promotes more complete fuel vaporization.
Just beyond the venturi, the chamber widens to accommodate the throttle valve. The throttle controls the flow of the fuel-air-mix leaving the venturi. After passing by the throttle valve, the fuel-air-mix is routed to the combustion chambers.

Question 13

Describe leaning and enriching the mixture, and why it is necessary.

Answer 13

Carbs are calibrated at sea level such that the proper fuel-air ratio is achieved when it is set to FULL RICH position. As altitude increases the inlet air density starts to decrease. The inlet air is less dense, but the fuel density remains roughly the same. This means that more fuel particles than there are air particles in the same volume of air. If the fuel-air-mix is too rich then it may lead to engine roughness, normally caused by carbon buildup on spark plugs. The excessively rich mix lowers the temp in the cylinders inhibiting complete combustion

Question 14

Why lean the mixture?

Answer 14

To compensate for decreased inlet air density, we need to limit the rate of fuel flow. Decreasing the flow from the float chamber results in decreased fuel density.
For runup at high elevation airports, or for climbing or cruising altitudes.

Question 15

Why enrich the mixture?

Answer 15

If descending from high altitudes, the mixture will have to be enriched. as the air density increases the fuel needs to match. An excessively lean mix will result in high engine temps.

Question 16

If the engine temp gauge is creeping toward the warm side what should be done to the mixture?

Answer 16

Increasing engine temps mean you need to enrich the mix. If the air-fuel ratio is starved of fuel, it will burn hot.

Question 17

If engine temp gauge is falling to the cold side, what should be done to the mix?

Answer 17

The mix needs to be leaned if the engine temp is getting too cold. If there is too high of a fuel to air ratio then the vapor will be too laden with fuel to burn properly. Too much fuel will lead to cold temps in cylinders and fouled spark plugs.

Question 18

What is the main disadvantage of the float style carb?

Answer 18

Carburetor Icing. The process of fuel vaporization and the decreasing air pressure in the venturi causes a sharp temp drop within the carb. If water vapor in the air condenses when carb temp is at or below freezing ice forms on the inside surfaces including the throttle valve.
Carb Ice restricts the flow of the fuel-air-mix out of the carburetor which reduces power and causes engine failure.

Question 19

During what weather conditions is carb icing most likely?

Answer 19

When intake air is below 21 degrees Celsius (70 degrees F), and relative humidity is above 80%
Due to venturi, carb ice may occur at 38 degrees C (100 degrees F) with humidity as low as 50%

Question 20

What are the symptoms of Carb ice?

Answer 20

In fixed propeller planes, the first indication is a drop in RPM, followed by engine roughness and fuel starvation. For constant speed propeller planes these will be accompanied by shifts in manifold pressure.

Question 21

During what circumstances is carb ice most dangerous?

Answer 21

During descents, because reduced power may allow for carb ice to build unnoticed. When one tries to add power back in, power will not be there, causing a hazardous emergency landing.

Question 22

What is the purpose of a carburetor heat system?

Answer 22

It is designed to combat carburetor icing by rerouting the intake air over exhaust cylinders (or other heat source). When ON, a valve cuts off airflow from the normal intake port and draws it from an alternate air intake which passes around the exhaust pipes or other heat source from the engine.

Question 23

How does using carb heat impact engine performance, and why does it have that effect?

Answer 23

With carb heat engaged there will be a slight decrease in engine power. This is because the heated air is less dense than the outside air. With lowered air density, the mixture enrichens because the fuel density remains the same making for a disproportionate amount of fuel in the mix.

Question 24

For fixed-pitch propeller planes, how can one tell if carb ice is present via instruments?

Answer 24

When ice is present and you engage carb heat there should be a drop in RPM followed by a gradual increase in RPM as the ice melts. If there is no ice then there will be a slight decrease in RPM, and it will remain constant.

Question 25

With regard to monitoring carb heat, what is different about Constant-Speed propellers vs. Fixed-Pitch ?

Answer 25

Constant-Speed propellers will display the drop in engine performance due to carb heat via the manifold pressure gauge. For fixed-pitch, the drop in RPM is observed via the tachometer.

Question 26

When should you use full carb heat?

Answer 26

Whenever you reduce the engine RPM below the normal operating range, or when you suspect the presence of carb ice. Always check POH for specific guide.

Question 27

What are the advantages of fuel injection over float carburetor designs?

Answer 27

Lower fuel consumption, increased horsepower, lower operating temperatures, and longer engine life. PREVENTS CARB INDUCTION ICING

Question 28

What are the four basic components of a fuel injection system?

Answer 28

1. Fuel Pump 2. Fuel control unit 3. Fuel manifold valve 4. Fuel discharge nozzles (plural)

Question 29

Regarding Fuel Injection: What are the components of the fuel pump system; what is their function ?

Answer 29

The pump system moves fuel from the tank to the fuel control unit. There is a electric boost pump provides pressure to the fuel control unit for initial engine starting. The engine-driven boost pump has its own route from which to draw fuel from the tank, potentially bypassing the electric boost pump. The engine-driven pump provides fuel under pressure to the fuel control unit after engine start. The output pressure changes as engine speed changes.

Question 30

Regarding Fuel Injection: What is the fuel control unit, what does it do?

Answer 30

The fuel control unit meters fuel going to the engine based on the position of the throttle. If the throttle fully engaged, maximum fuel will be delivered to the fuel manifold valve.

Question 31

Regarding Fuel Injection: what is the manifold valve and what is its function?

Answer 31

The fuel manifold valve receives fuel being sent from the fuel control unit. The manifold valve distributes fuel evenly to all cylinders and provides a fuel shutoff when the mixture is put in the idle-cut off position.

Question 32

What is the fuel discharge nozzle and what is it's function?

Answer 32

The fuel discharge nozzle mixes air with the fuel received from the from the manifold valve and injects the fuel-air mixture into the cylinder intake port. There is one nozzle per cylinder.

Question 33

What are the disadvantages of fuel injection systems?

Answer 33

Increased Sensitivity to fuel contaminants, and more complex starting procedures especially when the engine is hot.

Question 34

What problem do Supercharging and Turbocharging remedy?

Answer 34

Operating a reciprocating engine at high altitudes decreases engine efficiency as a result of lower air density. Any normally aspirated engine will suffer this problem, but if the intake air can be compressed more fuel could be added to mix, increasing engine power output.

Question 35

Describe what a supercharger does for an engine

Answer 35

Sea-level performance may be achieved at higher altitudes if a supercharger is used. A supercharger compresses the intake air using a pump driven by the engine. If air can be compressed, more fuel can be added to the mix leading to increase in overall engine output. However, since engine power is used to drive the pump it decreases the net power increase added by the supercharger.

Question 36

Describe what a turbocharger does for an engine

Answer 36

A turbocharger is a more efficient version of a supercharger. Turbocharging is more efficient because it pressurizes the air using a mechanism driven by engine exhaust gases instead of using engine power and which would otherwise be wasted through vents. Both super and turbochargers are fuel injected.

Question 37

What are the four main parts of an ignition system and what is the system’s function?

Answer 37

The function of the ignition system is to provide the spark that ignites the fuel-air mix in the cylinder. The four main parts of an ignition system: Magnetos, Spark Plugs, Interconnecting wires, and the ignition switch. There are upper and lower magneto wires. The upper wires are black in the textbook, and they connect to the opposite magneto. For instance, the left cylinders would have an upper and lower spark plug. The upper magneto wires connect to the right most magneto, while the lower magneto wires from the same cylinder would run to the left most magneto and vice versa. The lower magneto wires run to the magneto on the same side. Each magneto is connected to one of the two spark plugs in each cylinder.

Question 38

What are magnetos, describe how they function.

Answer 38

They are self, contained, engine-driven units that supply electrical current to the spark plug. It uses a permanent magnet to generate electrical current completely independent of the of the aircrafts electrical system. The system begins when you engage the starter, and the crankshaft starts to turn. Anytime the crankshaft is operating, so are the magnetos.

Question 39

What is a dual ignition system and what does it do?

Answer 39

It means there are two individual magnetos, separate wires, spark plugs and other components. It is to enhance reliability because if one goes out, the engine will still run, albeit with decreased performance. Each magneto fires one of the two spark plugs in each cylinder. The firing of two spark plugs increases engine performance by improving combustion.

Question 40

How are magnetos controlled from the cockpit?

Answer 40

The magnetos are controlled via the ignition switch. The ignition switch has several positions: Off, Right, Left, Both, and Start (moving from left to right in orientation).

Question 41

How do you identify malfunctioning magnetos in the preflight check?

Answer 41

When moving the ignition switch from both to only the right one observes the corresponding drop in RPM. It should drop within a range specified by the manufacturer. Same for only the left magneto. If there is too sharp of a decrease in RPM it is evidence of possible fouled spark plugs, broken or shorted wires from magnetos to plugs, or improperly timed firing of plugs.

Question 42

Why is it so important to have the ignition switch set to “off” position following engine shutdown?

Answer 42

If the ignition switch is not set to the off position, the engine can still fire and turn over, even if the battery and master switches off. The magnetos require no outside source to generate power which would turn the propeller. There is potential for serious injury.

Question 43

What would be the impact of broken or loose wires in the ignition system?

Answer 43

If the ignition switch is properly set to the off position, but the ignition switch’s ground wire is disconnected or broken the magneto will continue to fire, not responding to the ignition switch input. If this occurs you MUST move the mixture to the idle cutoff position to stop the engine, then have it serviced.

Question 44

What is normal combustion and what is detonation?

Answer 44

Normal combustion occurs in a very controlled, predictable manner. The burn starts at the ignition source of the spark plug and burns directionally away from the spark until it is all consumed. This causes a smooth build up of temp and pressure that ensures the expanding gases deliver maximum force to the piston at the exact right time in the power stroke. Detonation is the opposite. It is an uncontrolled burn which puts stress on engine components by increasing the pressure and temperature. If not addressed, it will cause failure of the pistons, cylinder, or valves. Less severe cases include engine overheating, roughness, or loss of power.

Question 45

Describe the parts and functions of a general aviation turbocharging system.

Answer 45

1. Ram air intake 2. Turbocharger uses a turbine (driven by exhaust gases) and a compressor that pressurizes incoming air. 3. The throttle body regulates how much air reaches the intake manifold. 4. Intake manifold supplies the pressurized air to the cylinders. 5. Used gases exit the cylinders and is ducted through the exhaust manifold which runs the turbine which drives the compressor. 6. The exhaust leaving the exhaust manifold reaches a fork in which one pipe leads to the turbine which drives the compressor, while, the other fork leads to the Waste Gate, after that, those two pipes reconnect and exits through the exhaust discharge. The waste gate controls the amount of exhaust passing through the turbine and the waste gate position is controlled by engine pressure. Turbocharging can also supply air for cabin pressurization, but also increases engine power output.

Question 46

In what circumstances is detonation most likely to occur?

Answer 46

Anytime you let the engine overheat, or use a lower than recommended grade of fuel. Specifically: Takeoff where the temperature of the engine is near the max allowable temp. Operation at high rpm and low airspeed. Extended operations above 75% power with an extremely lean mixture

Question 47

If engine detonation is suspected during takeoff, what is the best course of action ?

Answer 47

Cool the engine by retarding the throttle and climbing at a slower rate. Lowering the nose to increase air speed and use airflow to cool engine.

Question 48

What is preignition and how does it differ from detonation?

Answer 48

Preignition occurs when the fuel/air mix is ignited before the normally timed ignition. Preignition and detonation may occur simultaneously. It is difficult to distinguish between detonation and preignition, but it matters not, because both are addressed by retarding throttle, enriching mix, and lowering nose.

Question 49

What are typical causes of preignition?

Answer 49

A residual hot spot in the cylinder, such as a carbon deposit on spark plug, cracked ceramic spark plug insulator, or any other damage around the combustion chamber.

Question 50

What are the two types of fuel systems found in light airplanes?

Answer 50

Those that require a fuel pump and those that are gravity fed. Fuel pump systems are typically found in low wing planes, where fuel tanks are located below the engine.

Question 51

What are the key parts of a fuel pump system that gravity fed systems lack?

Answer 51

Fuel pump systems have an engine driven pump to provide fuel under pressure to the engine. They also have an electric boost pump controlled by a switch in the cockpit to provide fuel under pressure for initial starting of the engine, and as a backup in case of engine-driven pump malfunction. Fuel pump systems also have a fuel pressure gauge to detect fuel pump malfunctions. If fuel pressure falls below normal, turn on the boost pump to insure fuel is reaching the engine.

Question 52

In a fuel pump airplane, what is the main risk of running a fuel tank completely dry?

Answer 52

It may allow air to enter the fuel system and cause Vapor Lock. This condition will make it difficult to impossible to restart the engine.

Question 53

What is a key part of a gravity fed fuel system that a fuel pump system lacks?

Answer 53

Gravity fed systems occur in airplanes with wing height higher than the engine, allowing gravity to send fuel to the engine. However, most gravity fed systems also have a manual pump called a primer which allows one to pump fuel directly into the intake system prior to start. It is used to start a cold engine when the carb is difficult to vaporize.

Question 54

What are the safety components incorporated into most fuel tanks?

Answer 54

Fuel tanks usually have a fuel vent which allows the pressure in the tanks to remain the same as the air pressure. This prevents a vacuum forming, restricting fuel flow to the engine. Fuel tanks also have a fuel overflow drain which prevents a rupture of a fuel tank due to fuel expansion.

Question 55

In what units do fuel quantity gauges typically display?

Answer 55

Fuel quantity gauges measure using gallons or pounds.

Question 56

Is it okay to rely solely on fuel quantity gauges?

Answer 56

No, always visually check fuel level in preflight and compare to gauges.

Question 57

What are the types of fuel selector valves and in what situations are fuel valve positions used ?

Answer 57

There are 4 position valves and 3 position valves. 4 positions valves have: Left, Right, Both and Off. Normal position is Both, but Left or Right is used to balance tanks. The Both position is required for takeoffs, landings or maneuvering. 3 position valves have: Left, Right and Off. This demands that one pay close attention to not run a tank dry or create an unbalanced fuel load.

Question 58

What is a fuel strainer and what is it's function?

Answer 58

A fuel strainer removes moisture and other contaminants like sediment. Since these are heavier than aviation fuel they settle to the bottom of the strainer at the sump. Drain the fuel sump before each flight and check to make sure there is no moisture.

Question 59

What are the dangers of moisture in the fuel tanks?

Answer 59

Moisture in the tanks is hazardous because it can freeze in cold weather and block fuel lines. In warm weather it could flow into the carb and stop the engine.

Question 60

What is the best way to avoid moisture in the fuel tanks?

Answer 60

Refuel the tanks after the last flight of the day to prevent moisture from condensing by eliminating air from the tanks. Always check for moisture in preflight and bring to a mechanic if fuel tanks contain water.

Question 61

What is the main hazard associated with refueling and how is it remedied?

Answer 61

The main hazard associated with refueling is static electricity from the fueling process igniting the fumes. The best way to eliminate the threat is to ground the plane to the fuel truck and the fuel truck to the airport surface.

Question 62

How are fuel grades identified?

Answer 62

Fuel grades are identified by octane, or performance number. They are also color coded.

Question 63

Where is the recommended fuel grade and authorized substitutes found?

Answer 63

In the POH

Question 64

What could happen if you use the wrong fuel grade?

Answer 64

It can cause cylinder heads and engine temperatures to exceed normal operating limits. Engine damage or failure may occur.

Question 65

In an emergency is it okay to use the next highest fuel grade as a substitute?

Answer 65

Yes, as long as that is authorized according to the manufacturer.

Question 66

What are the two types of oil systems?

Answer 66

Dry pump: oil is contained in a separate tank and is circulated by a pump. Wet pump: all the oil is carried by a sump which is a core part of the engine. Suitable for most small reciprocating engines.

Question 67

What does oil do for and engine?

Answer 67

Oil lubricates the internal parts of the engine and cool engine temps.

Question 68

If you check the oil gauge and there is lower than normal pressure, what may be the problem?

Answer 68

Below normal oil pressure may mean that the pump is not putting out enough pressure to circulate oil properly.

Question 69

What might be the cause of an abnormally high oil pressure gauge reading?

Answer 69

A clogged oil line.

Question 70

What should you do if there is an abnormal oil pressure reading?

Answer 70

Consider any abnormal reading to mean that the engine is not receiving proper lubrication. Follow the POH instructions. Shut down the engine if the oil pressure does not begin to rise within 30 secs after engine start in warm weather and 60 secs in cold weather.

Question 71

What units are used for the oil pressure gauge?

Answer 71

Pounds per Square Inch (psi) Green is normal operating range and red lines are min and max measures.

Question 72

Which changes more slowly, oil pressure readings or oil temperature readings?

Answer 72

Oil temperature changes more slowly than oil pressure, which should register in 30 secs to a minute depending on air temp. It may take several minutes for the gauge to show any change in temp.

Question 73

What does the oil temp gauge measure?

Answer 73

The oil temp as it enters the engine. Red line is the max allowable temp.

Question 74

What might a high oil temp indicate?

Answer 74

It is especially important to check oil temp when using high power settings since that increases oil temps. High oil temps may also be caused by a plugged oil line, low oil quantity, or a defective temp gauge.

Question 75

What problems can high engine temps cause?

Answer 75

Loss of power, high oil consumption, and possible engine damage.

Question 76

Is oil sufficient to maintain acceptable engine temps?

Answer 76

No, oil systems are vital for cooling, but additional cooling systems are necessary to maintain normal temps.

Question 77

How do cooling systems work?

Answer 77

Outside air enters through an air inlet behind the prop and baffles direct it to where the engine is hottest, typically cylinders, which have fins to increase surface area to increase cooling effect.

Question 78

When is air cooling less effective?

Answer 78

During take offs, go arounds, or any other low airspeed, high power maneuvers.

Question 79

When can air cooling be excessive?

Answer 79

During high speed descents. Some airplanes use cowl flaps to give the pilot more control over air cooling. Cowl flaps are used to accomplish this. Opening cowl flaps creates a larger path for air to escape from the engine compartment, increasing cooling.

Question 80

What types of planes are most likely to have cowl flaps?

Answer 80

Normally cowl flaps are on the underside of engine cowling and are installed on aircraft with high performance engines generating a lot of heat. Proper cowl flap usage prevents engine temp fluctuation and prolongs engine life.

Question 81

What type of gauge is used to know what position to have cowl flaps in?

Answer 81

The cylinder head temp gauge provides a direct temp reading from one of the cylinder heads. Regulate engine temp with the position of the cowl flaps.

Question 82

Besides use of the cowl flaps, what are other methods to reduce engine temps?

Answer 82

Enriching the mix, reducing rate of climb, increasing air speed, and decreasing power setting.

Question 83

If oil and engine temps are above normal what is the most likely cause?

Answer 83

May be using to much power and too lean of a mix.

Question 84

Besides venting exhaust gasses, what else is the exhaust system used for?

Answer 84

Exhaust systems are used to heat the cabin, defrost the windscreen and can sometimes be used for pressurization of the cabin. Heat is transferred to incoming air from hot exhaust via the muffler and shroud used to collect the heat.

Question 85

If you smell exhaust gasses and suspect Co2 in the cabin, what are appropriate procedures?

Answer 85

Turning off the heater, opening fresh air vents and using supplemental oxygen.

Question 86

What are the basic parts of a propeller and how do they work to achieve thrust?

Answer 86

A central hub and two or more blades attached. Each blade is an airfoil which acts like a rotating wing, producing thrust.

Question 87

Are propeller blades uniform in their angle? Describe the sections of airfoils along the blade.

Answer 87

No, the airfoil sections along the blade change from the tip to the hub. When the prop rotates, the sections nearest to the hub rotate at slower speeds than the tip, so low speed airfoils are used closest to the hub and high speed ones used towards the tips. Each section of the blade is set at a different angle to the plane of rotation. There is a gradual decrease in blade angle giving the blade it's twisted appearance.

Question 88

What is the purpose of the twisted propeller?

Answer 88

To generate nearly uniform thrust throughout the length of the blade.

Question 89

What is the overall blade angle?

Answer 89

The avg. of the different angles of each section of the prop.

Question 90

What do we call a prop with a low blade angle?

Answer 90

Low blade angle is referred to as a climb propeller, it provides best performance in takeoff and climb.

Question 91

What do we call a prop with a high blade angle?

Answer 91

A high blade angle is referred to as a cruise propeller. It is best at high speed cruise and high altitude flight.

Question 92

What defines a fixed pitch propeller?

Answer 92

Fixed pitch propellers have a blade angle that is selected on the basis of what is best for the primary function and cannot be changed by the pilot. The only power control is via the throttle and the indicator is the tachometer.

Question 93

What defines a constant speed propeller?

Answer 93

The blade angle can be adjusted for the most efficient operation. Also referred to as a variable pitch or controllable pitch propeller. It is more efficient than fixed pitch. It is able to convert a high percentage of the engine's power into thrust over a wide range of r.p.m. and airspeed combos.

Question 94

How are the engines of constant speed propellers controlled from the cockpit?

Answer 94

Constant speed propeller engines are controlled directly by the throttle and indirectly by the propeller control.

Question 95

How is the power output of the engine controlled and how is it indicated?

Answer 95

The power output is adjusted using the throttle and is indicated on the manifold pressure gauge.

Question 96

How is the pitch of the propeller blades controlled and how is it indicated ?

Answer 96

The propeller control is used to adjust the pitch of the propeller blades and the resulting engine r.p.m is indicated on the tachometer. A single pitch prop only allows one to adjust power output via the throttle and only displays the r.pm. on tachometer, not the manifold pressure gauge.

Question 97

What propeller pitches are used for take off vs cruising?

Answer 97

A low blade angle combined with high r.p.m. setting will allow for maximum thrust for take off. After reaching cruising conditions use a higher pitch and lower r.p.m.

Question 98

What is important to avoid internal engine stress in constant speed propeller planes?

Answer 98

With constant speed, avoid low r.p.m settings with high manifold pressure. For a given r.p.m there is always a max allowed manifold pressure. Check POH.

Question 99

What kind of mechanism is used to control the propeller pitch in constant speed props?

Answer 99

The propeller control acts by the movement of high pressure oil hydraulics that move the oil within the pitch change assembly.

Question 100

If it is necessary to start a propeller by hand, what is important to remember about a the procedure?

Answer 100

When hand starting the plane a competent pilot must be at the controls, but the person hand propping is in charge of the starting procedure.

Question 101

What is an alternator, how do they work, and what are the advantages of using them compared to generators ?

Answer 101

Alternators are mounted to and driven by the engine. They are used to power a 14-28 volt direct current system. Advantages include light weight, lower maintenance, and uniform output even at low r.p.m. Alternators produce alternating current and convert it to direct current. Direct current is delivered to a bus bar which distributes the current to the various electrical components. The various bus bar accessories are protected by circuit breakers. However, you should make sure that all electrical equipment is turned off before starting the engine to protect sensitive components from damage caused by random voltages generated during the starting process.

Question 102

What is the purpose of the battery ?

Answer 102

It's main purpose is to provide a means of starting the engine. It also permits limited operation of electrical equipment, such as radios, without starting the engine, It is also a source of standby/ emergency power in case of alternator malfunction.

Question 103

What are the two types of ammeters and what are they used for?

Answer 103

Ammeters are used to monitor the electrical current in amperes. One type reflects the current flowing to or from the battery. The other type displays the load placed on the the alternator (often called the load meter). The first type shows the charging rate of the battery. A minus indication shows that more current is being drawn from the battery than is being replaced. The load meter shows the total load placed on the alternator. When all electrical components are turned off it reflects the amount of charging current demanded by the battery.

Question 104

After starting the engine, what should the ammeter show?

Answer 104

It is normal for the ammeter to be on the plus side, showing that there is ample current replacing the lost current caused by engine start. After the battery is charged, the needle with stabilize near zero and the alternator will be able to provide all necessary power.

Question 105

If the ammeter is negative, or discharging, what does that mean? What are possible causes?

Answer 105

The electrical accessories are placing such a load that the alternator is not able to replace the current and the battery has to kick in to help sustain power. There may be a malfunctioning alternator, or the electrical load is excessive.

Question 106

If the ammeter is negative, or discharging, what should you do?

Answer 106

Reduce the electrical load by any means possible and land as soon as practicable.

Question 107

What does the ammeter load meter tell you that the ammeter does not?

Answer 107

The load meter displays the amount of current being drawn by the electrical equipment. The POH/AFM will tell you the normal load to expect. Loss of the alternator will cause a readout of zero.

Question 108

What does the master switch control, does it include the ignition system?

Answer 108

The master controls the entire electric system. The magnetos supply electrical current to the spark plugs. However, the engine starter won't operate without the master being on because power for the engine starter comes from the electrical system, not the magnetos. (magnetos supply current to spark plugs, but not the engine starter).

Question 109

What position should the master be in normal operations? For alternator malfunction? For checking equipment before starting the engine?

Answer 109

For normal operations, the master switch should be full on. In case of alternator malfunction, the alt side of the master can be turned off to isolate it. If you want to check the condition of the electrical equipment before starting the engine, selecting only the battery side can achieve that.

Question 110

What are circuit breakers and fuses used for?

Answer 110

To protect various components from overloads. With circuit breakers resetting the breaker will usually reactivate the circuit, unless an overload or a short exists.

Question 111

What will the circuit breaker do if there is an overload or a short?

Answer 111

When you reset the breaker it will continue to pop, indicating an electrical problem.

Question 112

Do manufacturers provide a holder for spare fuses in the event of a problem ?

Answer 112

Yes, most do include spare fuses, and they can be replaced mid-flight. You should know the location of the circuit protection device for each electrical component. The component name is printed on the circuit breaker panel near the associated fuse.

Question 113

In what conditions are you required to carry extra fuses?

Answer 113

FAR's require you to carry extra fuses when flying at night.