Propellers and Systems

Question 1

Propeller Pitch

Answer 1

• Distance in feet a propeller travels forward in one revolution

Question 2

Theoretical (Geometric Pitch)

Answer 2

The distance the prop would travel if it were 100% effective

Question 3

Practical (Effective) Pitch

Answer 3

The actual distance the prop travels

Question 4

Propeller Slip

Answer 4

Difference between theoretical and practical pitch

Question 5

Coarse Pitch (Low RPM)

Answer 5

• Large angle (more torque), big bite of air
• Travels forward a greater distance and moves at a slower speed
• Used during cruise

Question 6

Fine Pitch (High RPM)

Answer 6

• Small angle (less torque), small bite of air
• Travels forward a smaller distance and moves at a faster speed
• Used during Takeoff and climb

Question 7

Fixed Pitch Propellers

Answer 7

• Common in Most training aircraft
• Pitch optimized for both climb and cruise performance (blade angle constant)
• Less efficiency, more fuel consumption

Question 8

Variable Pitch - Adjustable Pitch

Answer 8

• Blade Angle can be adjusted on the ground
• Good for adapting the aircraft to a specific role
• Prop can’t be adjusted in flight

Question 9

Variable Pitch - Controllable Pitch

Answer 9

• Blade Angle can be adjusted in flight
• Pilot can optimize performance for given phases of flight
• Disadvantage is that blades must constantly be readjusted

Question 10

Variable Pitch - Constant Speed Prop

Answer 10

• Blade Angles adjust automatically to maintain constant RPM
• More complex system, heavier, requires more maintenance
• Uses engine oil and nitrogen pressure to control blade angle
• Prop control in cockpit adjusts set RPM
• Prop goes to full fine if engine fails

Question 11

Prop Governor

Answer 11

• Contains rotating flyweights geared to engine
• Flyweights sense engine speed
• Oil enters or leaves prop hub base on flyweights which changes prop angle

Question 12

Constant Speed Prop Power Increase

Answer 12

1. Mixture
2. Prop
3. Throttle

Question 13

Constant Speed Prop Power Decrease

Answer 13

1. Throttle
2. Prop
3. Mixture

Question 14

Constant Speed Prop Overspeed

Answer 14

• Occurs when conditions try to increase prop RPM by decreasing load
• Prop moves into finer pitch to counter

Question 15

Constant Speed Prop Underspeed

Answer 15

-Occurs when conditions try to decrease prop RPM by increasing load
- Prop moves into coarser pitch to counter

Question 16

Fuel Mixture

Answer 16

• Octane (Fuel Inhibitor)
• Heptane (Fuel Promoter)

Question 17

Octane

Answer 17

Prevents fuel detonation and smooth controlled burning

Question 18

Fuel Grades

Answer 18

• Octane rating usually determined by compression ratio of engine
• Number equivalent to percent octane (74 Octane)
• If over 100, expressed as performance number, the higher the number, the better
• Always use HIGHER grade, lower can cause detonation and engine damage
• Higher only causes lead fouling of spark plugs

Question 19

80/87 Octane

Answer 19

• Red
• 6 lbs/gal
• Gasoline Base

Question 20

100LL

Answer 20

• Blue
• 6 lbs/gal
• Gasoline Base

Question 21

100/130 Octane

Answer 21

• Green
• 6 lbs/gal
• Gasoline Base

Question 22

Jet A1

Answer 22

• Clear or Straw
• 7 lbs/gal
• Kerosene Base

Question 23

Carburetor

Answer 23

• Measures correct quantity of fuel
• Vaporizes Fuel
• Mixes fuel and air in proper proportion
• Delivers mixture to cylinders
• Amount of air regulated by throttle (butterfly valve)

Question 24

Too Rich Mixture

Answer 24

• Unburned Fuel expelled through exhaust
• Fouled plugs, Rough running, loss of power

Question 25

Too Lean Mixture

Answer 25

• Hotter Engine, runs rough
• Causes backfiring and detonation

Question 26

3 Ways to set mixture

Answer 26

• RPM
• Fuel Flow Gauge
• Exhaust Gas Temperature (EGT)

Question 27

Fuel Vaporization Carburetor Ice

Answer 27

• Heat absorbed from surround air to vaporize fuel
• Reduces temp by 30ºC
• Water vapour will freeze if air is moist

Question 28

Throttle Carburetor Ice

Answer 28

• Low pressure in venturi and around butterfly valve reduces air temperature by 30ºC
• Ice can form and block passages or restrict movement of throttle
• Chokes airflow to engine

Question 29

Impact Carburetor Ice

Answer 29

• Can occur if flying in visible moisture in temps below zero
• builds up on intake, filter screen, and butterfly valve
• chokes airflow to engine

Question 30

Carburetor Heat

Answer 30

• Takes unfiltered hot air from muffler
• Hot air is less dense so mixture should be leaned

Question 31

Fuel Injection System

Answer 31

• No carb ice, better fuel flow, faster throttle response
• precise control of mixture, better fuel distribution
• Better in cold weather
• Increased overall engine efficiency
• alternate air source may be used if intake becomes blocked
• much worse on hot days due to vapour lock
• difficult to restart engine due to fuel starvation

Question 32

Turbocharger

Answer 32

• Fools engine into thinking it is working at sea level
• Uses energy of hot exhaust gases to power a compressor
• Boosts intake air pressure

Question 33

Supercharger

Answer 33

• Fools engine into thinking it is working at sea level
• Uses rotational energy of crankshaft to power a compressor
• Boosts fuel/air mixture pressure

Question 34

Short Stack Exhaust System

Answer 34

• Used on non-turbocharged or low power engines
• 1 Exhaust stack on either side of the engine

Question 35

Collector Exhaust System

Answer 35

• Used on all turbocharged engines and larger engines
• All Exhaust gases collected in one common exhaust collector tube

Question 36

Ignition System Components

Answer 36

• 2 Magnetos
• 2 Spark Plugs in each cylinder
• Ignition leads
• Magneto Switch

Question 37

The Magneto

Answer 37

• Not attached to battery or electrical system
• Generates low tension current and transforms it into high tension current
• Distributes current to individual spark plugs at desired time to have them fire
• Mags off = circuit grounded
• Mag on = complete circuit
• Ground wire broken means a live mag

Question 38

Shielding

Answer 38

• Purpose is to prevent ignition current from interfering with other electrical systems
• Accomplished by grounding all other systems to the airframe