Propellers and Systems Flashcards
1
Q
Propeller Pitch
A
- Distance in feet a propeller travels forward in one revolution
2
Q
Theoretical (Geometric Pitch)
A
The distance the prop would travel if it were 100% effective
3
Q
Practical (Effective) Pitch
A
The actual distance the prop travels
4
Q
Propeller Slip
A
Difference between theoretical and practical pitch
5
Q
Coarse Pitch (Low RPM)
A
- Large angle (more torque), big bite of air
- Travels forward a greater distance and moves at a slower speed
- Used during cruise
6
Q
Fine Pitch (High RPM)
A
- Small angle (less torque), small bite of air
- Travels forward a smaller distance and moves at a faster speed
- Used during Takeoff and climb
7
Q
Fixed Pitch Propellers
A
- Common in Most training aircraft
- Pitch optimized for both climb and cruise performance (blade angle constant)
- Less efficiency, more fuel consumption
8
Q
Variable Pitch - Adjustable Pitch
A
- Blade Angle can be adjusted on the ground
- Good for adapting the aircraft to a specific role
- Prop can’t be adjusted in flight
9
Q
Variable Pitch - Controllable Pitch
A
- Blade Angle can be adjusted in flight
- Pilot can optimize performance for given phases of flight
- Disadvantage is that blades must constantly be readjusted
10
Q
Variable Pitch - Constant Speed Prop
A
- 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
11
Q
Prop Governor
A
- Contains rotating flyweights geared to engine
- Flyweights sense engine speed
- Oil enters or leaves prop hub base on flyweights which changes prop angle
12
Q
Constant Speed Prop Power Increase
A
- Mixture
- Prop
- Throttle
13
Q
Constant Speed Prop Power Decrease
A
- Throttle
- Prop
- Mixture
14
Q
Constant Speed Prop Overspeed
A
- Occurs when conditions try to increase prop RPM by decreasing load
- Prop moves into finer pitch to counter
15
Q
Constant Speed Prop Underspeed
A
-Occurs when conditions try to decrease prop RPM by increasing load
- Prop moves into coarser pitch to counter
16
Q
Fuel Mixture
A
- Octane (Fuel Inhibitor)
- Heptane (Fuel Promoter)
17
Q
Octane
A
Prevents fuel detonation and smooth controlled burning
18
Q
Fuel Grades
A
- 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
19
Q
80/87 Octane
A
- Red
- 6 lbs/gal
- Gasoline Base
20
Q
100LL
A
- Blue
- 6 lbs/gal
- Gasoline Base
21
Q
100/130 Octane
A
- Green
- 6 lbs/gal
- Gasoline Base
22
Q
Jet A1
A
- Clear or Straw
- 7 lbs/gal
- Kerosene Base
23
Q
Carburetor
A
- 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)
24
Q
Too Rich Mixture
A
- Unburned Fuel expelled through exhaust
- Fouled plugs, Rough running, loss of power
25
Too Lean Mixture
- Hotter Engine, runs rough
- Causes backfiring and detonation
26
3 Ways to set mixture
- RPM
- Fuel Flow Gauge
- Exhaust Gas Temperature (EGT)
27
Fuel Vaporization Carburetor Ice
- Heat absorbed from surround air to vaporize fuel
- Reduces temp by 30ºC
- Water vapour will freeze if air is moist
28
Throttle Carburetor Ice
- 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
29
Impact Carburetor Ice
- Can occur if flying in visible moisture in temps below zero
- builds up on intake, filter screen, and butterfly valve
- chokes airflow to engine
30
Carburetor Heat
- Takes unfiltered hot air from muffler
- Hot air is less dense so mixture should be leaned
31
Fuel Injection System
- 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
32
Turbocharger
- Fools engine into thinking it is working at sea level
- Uses energy of hot exhaust gases to power a compressor
- Boosts intake air pressure
33
Supercharger
- Fools engine into thinking it is working at sea level
- Uses rotational energy of crankshaft to power a compressor
- Boosts fuel/air mixture pressure
34
Short Stack Exhaust System
- Used on non-turbocharged or low power engines
- 1 Exhaust stack on either side of the engine
35
Collector Exhaust System
- Used on all turbocharged engines and larger engines
- All Exhaust gases collected in one common exhaust collector tube
36
Ignition System Components
- 2 Magnetos
- 2 Spark Plugs in each cylinder
- Ignition leads
- Magneto Switch
37
The Magneto
- 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
38
Shielding
- Purpose is to prevent ignition current from interfering with other electrical systems
- Accomplished by grounding all other systems to the airframe
