04. Piston Engine: Fuel Systems Flashcards
1
Q
3 qualities that piston engine fuel must contain
1. Contain significant quantity of ____
2. Be able to form ____
3. ____ but controllably
A
- Energy
- Vapour
- Burn quickly
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2
Q
At ____℃ AVGAS has a density of ____ kg per litre
A
- 15℃
- 0.72
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3
Q
What is vapour lock
A
Partial or complete interruption of fuel flow due to AVGAS turning into vapour in the fuel feed
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4
Q
What is the term used when the AVGAS turns into a gaseous state preventing fuel flow
A
VAPOUR LOCK
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5
Q
The term used to explain the rapid spontanous combustion of mixture
A
DETONATION
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6
Q
What noise can be heard if detonation is occurring
A
ENGINE KNOCKING
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7
Q
What are 4 consequences of detonation
A
- REDUCED POWER output
- CYLINDER TEMPERATURE rises rapidly
- HOTSPOTS - due to uneven temperature
- PHYSICAL DAMAGE (due to hotspots)
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8
Q
What are 4 causes of detonation
A
- FUEL - Fuel with poor anti knock
- MIXTURE - Incorrect mixture ratio
- PRESSURE - Anything that raises temperature or pressure of mixture
- TEMPERATURE - High engine temperature
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9
Q
What do the following 4 traits cause
1. Fuel with poor anti knock
2. Incorrect mixture ratio
3. Anything that raises temperature or pressure of mixture
4. High engine temperature
A
DETONATION
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10
Q
Whare are the 4 following traits consequences of;
1. Reduced power output
2. Cylinder temperature rises rapidly
3. Hotspots - due to uneven temperature
4. Physical damage (due to hotspots)
A
DETONATION
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11
Q
What is the defintion of pre-ignition
A
Ignition of mixture before spark plug fires
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12
Q
What is a cause of pre-ignition within the cylinder
A
LOCAL HOTPOST
Local hotspots caused by carbon deposits
Likely to happen when cylinder is excessively hot or contaminated with carbon deposits
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13
Q
- Local hotspots in the cylinder are likely to cause what?
- They are typically as a result of what?
A
- Pre-ignition
- Carbon Deposits
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14
Q
The primary cause of pre-ignition
A
WEAK MIXTURE
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15
Q
The 3 key symptoms of pre-ignition
Think PRE-ignition
A
- POWER - Loss of power
- ROUGH RUNNING
- ENGINE - Overheating
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16
Q
Pre-ignition worsens with INCREASED or DECREASED RPM
A
INCREASED
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17
Q
Detonation reduces with INCREASED or DECREASED RPM
A
DECREASED
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18
Q
What is running-on
A
Engine continues to run a short period after shut down
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19
Q
If the engine continues to run after shut down, what is this known as, and what is it a characteristic of
A
- Running-on
- Pre-ignition
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20
Q
What is an octane rating
A
Indicates fuels resistance to detonation
AKA anti-knock value
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21
Q
The HIGHER or LOWER the octane rating, the HIGHER or LOWER the resistance to detonation
A
- HIGHER
- HIGHER
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22
Q
What additive is used to control detonation
A
TETRA-ETHYL LEAD
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23
Q
What colour is 100LL fuel
A
BLUE
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24
Q
What colour is 100 fuel
A
GREEN
25
What are 3 things that can increase the likliehood of detonation
| American C O P's can detonate
1. CARB HEAT - at high power settings
2. OVERHEATED - Overheated cylinders
3. POWER - High power, low RPM
## Footnote
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26
If the fuel with the anti-knock rating you require isnt available, you may temporarily use a fuel with HIGHER or LOWER anti-knock properties
HIGHER
## Footnote
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27
What is the ratio of air to fuel that ensures complete combustion
15:1
## Footnote
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28
The ratio if 15:1 is of what to what
AIR to FUEL
## Footnote
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29
The air to fuel ratio of 15:1 is typically referred to by which 3 names
1. Stoichiometric mixture
2. Chemically correct
3. Ideal ratio
## Footnote
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30
1. A mixture of 8:1 is RICH or LEAN
2. A mixture of 20:1 is RICH or LEAN
1. Rich
2. Lean
## Footnote
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31
1. What is the ratio of a *rich* mixture
2. What is the ratio of a *lean* mixture
1. 8:1
2. 20:1
## Footnote
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32
The risk of *detonation* increases under what power setting conditions
HIGH POWER
## Footnote
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33
High power settings INCREASE or DECREASE the risk of *detonation*
INCREASE
## Footnote
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34
What is the function of having an excessively rich mixture
COOLING
| Extra fuel not burned off, liquid aids cooling
## Footnote
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35
What does excessively rich mixture cause in the exhaust gases
BLACK SMOKE
## Footnote
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36
1. What effect does weaker mixture have on the temperature of burning gas?
2. What effect does this have on the *engine temperature*
1. Cooler burning temperature
2. Higher engine temperature
## Footnote
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37
A weaker burning mixture will increase the temperature of the ____ and reduce the temperature of the ____
1. Cylinder head
2. Exhaust gas
## Footnote
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38
What is the combined advantage and disadvantage of using a weak mixture in terms of efficiency
1. Disadvantage - Reduced power
2. Advantage - Reduced fuel consumption
## Footnote
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39
What is a result of prolonged ground running at idle with a rich mixture
SPARK PLUG FOULING
## Footnote
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40
What is *spark plug fouling* a result of
RICH MIXTURE when RUNNING IDLE
## Footnote
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41
What component is used to measure EGT or cylinder head temperature
## Footnote
EGT - Exhaust Gas Temperature
THERMOCOUPLES
## Footnote
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42
The highest combustion temperature occurs at what mixture ratio
STOICHIOMETRIC
15:1
## Footnote
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43
Peak EGT occurs when the mixture is what ratio
STOICHIOMETRIC
15:1
44
How can you achieve *power cruise* mixture setting
*LEAN MIXTURE* to achieve *peak EGT*
Slowly *ENRICH* until *EGT drops* slightly
## Footnote
Ideal power cruis mixture ratio 12:1
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45
What is the ideal *power cruise* mixture ratio
12:1
## Footnote
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46
How can you achieve *economy cruise* mixture setting
*LEAN MIXTURE* to achieve *peak EGT*
Slowly *LEAN* mixture until *EGT drops* slightly
## Footnote
Ideal economy cruis mixture ratio 17:1
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47
What is the ideal *economy cruise* mixture ratio
17:1
## Footnote
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48
How does the pilot control the amount of air delivered to the engine
THROTTLE
## Footnote
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49
What does the throttle control the delivery of to the engine
AIR
## Footnote
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50
What does EDP stand for
ENGINE DRIVEN PUMP
## Footnote
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51
How is the amount of fuel in a float chamber regulated
By a FLOAT
## Footnote
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52
What is the purpose of the *float*
Regulates amount of fuel in the float chamber
## Footnote
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53
What is the purpose of an EDP
## Footnote
EDP - Engine Driven Pump
Ensures postive supply of fuel under pressure to the carburettor
## Footnote
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54
what causes fuel to be drawn up the U-tube into the throat
VENTURI EFFECT
## Footnote
The throat is a venturi
When engine is running, air is drawn into the throat
As a result of the venturi effect, pressure drops, causing fuel to be drawn into the throat
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55
What is the purpose of the fuel nozzle in a basic float carburettor
ATOMISE FUEL
## Footnote
As fuel is drawn into the throat, the nozzle will finely atomise the fuel
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56
What is the purpose of the *pressure balance* in a basic float carburettor
MAINTAIN CORRECT MIXTURE RATIO
| Across a range of airspeeds and flight conditions
## Footnote
Maintain correct mixture ratio across range of airspeeds and flight conditions
Connects the intake and the float chamber
At high speeds, ram air effect would force air into the throat, increasing the pressure which reduces the fuel flow through the nozzle.
Similarly, higher altitudes have reduced air density, meaning less pressure in the throat, resulting in excessive fuel mixture.
The pressure balance mantains the mixture ratio
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57
What is the name of the component used in a basic float carburettor the help reduce the fuel flow through the nozzle at higher speeds which results in excessive air mass flow through the throat of the chamber. This component also aids in the mixture by adding air into the fuel before it is atomised by the nozzle
DIFFUSER
## Footnote
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58
What is the purpose of a *diffuser*
REDUCES FUEL FLOW
## Footnote
Helps reduce the amount of fuel flow through the nozzle when the pressure drops excessively in the throat, which would result in excessive fuel
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59
What is the purpose of a *mixture control valve* in a basic float carburettor
COMPENSATES for effect of CHANGING AIR DENSITY
## Footnote
As the altitude increases, the air density decreases, which would result in less air passing through the throat
The mixture control valve helps to compensate for the change in air density pressure
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60
What colour are *manual mixture controls*
RED
## Footnote
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61
What is the name of the component in a basic carburettor float to provide rich mixture when the engine is idle i.e. when the butterfly is closed
SLOW RUNNING JET
## Footnote
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62
What is the purpose of a *slow running jet*
Provides rich mixture when engine idle / butterfly closed
## Footnote
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63
How does a pilot operate the *shut-off* valve
PULL MIXTURE REWARDS
## Footnote
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64
A *power enrichment system* is required at HIGH or LOW power settings
HIGH POWER
## Footnote
Provides addition rich micture to cool the cylinders
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65
What is the name of the system that provides additional rich mixture in a basic float carburettor to cool the cylinders
POWER ENRICHMENT SYSTEM
## Footnote
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66
What is the purpose of the *accelerator pump*
Injects a quantity of fuel directly into the venturi
## Footnote
This is done when the throttle is rapidly moved forward.
When this happens, air flow to engine increases instantanously, but there is a slight delay before reduced pressure in throat causes additional fuel to be injected
This can cause the engine to hestitate or stop
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67
# Basic float carburettor
When a pilot rapidly moves the throttle forward, what happens to the air flow and pressure in the float.
What component is fitted to help counteract the effects
1. Air flow rapidly increases
2. Pressure drop lags
3. Accelerator pump
## Footnote
This is done when the throttle is rapidly moved forward.
When this happens, air flow to engine increases instantanously, but there is a slight delay before reduced pressure in throat causes additional fuel to be injected
This can cause the engine to hestitate or stop
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68
A drop in ____ and ____ are the 2 main contributors to carburettor icing
1. Pressure
2. Temperature
## Footnote
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69
What is the most relevent factor to carburettor icing
HUMIDTY
## Footnote
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70
When RH is more than ____%, carburettor icing may be expected in all flight conditions
## Footnote
RH = Relative Humidity
60%
## Footnote
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71
Serious carburettor icing is likely in ambient temepratures between ____℃ and ____℃ with a RH of ____%
## Footnote
RH = Relative Humidity
1. 18℃
2. 25℃
3. 30%
## Footnote
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72
What is the most dangerous condition likely to cause carburettor icing
CRUISE or DESCENT POWER
WARM day with MODERATE or HIGH HUMIDITY
## Footnote
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73
What is the risk associated with a warm day with relatively high humidity, and the pilot just started a descent
CARBURETTOR ICING
## Footnote
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74
What are the 6 symptoms of carburettor icing
| The **M**an **R**oughly **J**ammed the **E**xhaust in a **R**esolute **P**erformance
1. **M**anifold Pressure
2. **R**ough Running
3. **J**ammed Throttle
4. **E**xhaust temperature drop
5. **R**PM
6. **P**erformance (Reduced)
## Footnote
Loss of RPM
Reduced Performance
Reduced inlet manifold pressure
Decreased exhaust gas temperature
Rough running
Jammed throttle
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75
What is the likely first sign of carb icing on a *fixed pitch propeller* engine
REDUCED RPM
## Footnote
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76
What is the likely first sign of carb icing on a *variable pitch propeller* engine
REDUCED MANIFOLD PRESSURE
RPM initially remains the same
## Footnote
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77
How does carb heating work
Pilot manually selects carb heating
Hot air drawn from heat exchanger
## Footnote
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78
What are the 2 benefits of selecting carb heating
1. Alternative source of air
2. Prevents/removes icing
## Footnote
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79
What are 5 key disadvantages of using carb heating
| P bR I D E - Be proud to use carb heat
**REMEMBER:** Carb **P**ower **bR**eaks **I**ce, **D**etonators **E**xplode
1. **P**OWER (Reduced)
2. **B**REAKING ICE (Reduces power)
3. **I**NDUCED ICING (Temperature increase to a point ideal for icing to occur)
4. **D**ETONATION
5. **E**NRICHED MIXTURE
## Footnote
Reduces engine power
Induced icing. Cold ambient temperature, adding hot air may raise the air to the ideal temperature for icing to occur
Drop in power where ice breaks off and is ingested into the engine
Heated air at high power can cause detonation
Hot air is less dense, which enriches the mixture for the same power setting
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80
What is the purpose of an *air induction system*
Introduce mixture into each cylinder
## Footnote
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81
On a *fuel injected engine* when the alternative air source is selected, the RPM WILL or WILL NOT show a drop
WILL NOT DROP
| Alternative air supply is *NOT* heated
## Footnote
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82
What is *induction icing*
ICING on AIR INTAKES
## Footnote
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83
What are 3 key advantages of a *fuel injection system*
| Think **F**uel **I**njection **S**ystem
1. **F**UEL - Reliable fuel delivery
2. **I**CING - Better icing protection
3. **S**PEED - Quicker throttle response
## Footnote
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84
How does a *fuel injection* system differ significantly to a *carburettor* system
NO VENTURI
| Fuel delivered to engine under pressure
## Footnote
As fuel is delivered to the engine under pressure, there is no need for a venturi, which is how a carubruettor engine achieves fuel distribution into the throat
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85
What are 5 core components of a *continuous-flow injection* system
| Fuel injection
## FOOTNOTE
**REMEMBER:** The **M**an has _2_ **P**umps to **I**nject **F**uel
1. **M**ANIFOLD valve
2. **P**UMP - EDP - Engine Driven Pump
3. **P**UMP - Electric Pump
4. **I**NJECTOR assembly
5. **F**UEL nozzles
## Footnote
EDP - Engine Driven Pump - Supplies fuel under pressure
Electric pump - Supplies fuel to injector assembly
Injector Assembly - Adjust fuel flow according to throttle and mixture positions
Manifold valve - distributes fuel from injector assembly to fuel nozzles
Fuel Nozzles - spray atomised fuel into inlets of cylinders
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86
In a *continuous-flow injection* system, what are the 2 functions of the electric pump
## Footnote
THINK...
*continuous-flow* - keep going if something fails
*injection* - What component is like a syringe
1. Provide pressure if EDP fails
2. Prime engine before start
## Footnote
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87
In a *continuous-flow injection* system, what is the *metering valve* connected to
## Footnote
THINK what are the pronounced syllables in each word..
*me**T**ering* - think.. T...ta..ta
*v**A**lve* - think A..ah..ah
T A
THROTTLE ASSEMBLY
## Footnote
When the throttle lever is moved towards full power, the throttle butterfly opens, so does the metering valve
This allows more fuel flow
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88
In a *continuous-flow injection* system, what are the 2 core functions of the manifold valve
1. Divide fuel between all cylinders
2. Provide means of stopping fuel flow
## Footnote
When the mixture control is set to idle cut off, manifold valve provides a means to stopping fuel flow
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89
Large engine and diesel engines use ____ to deliver fuel to the cylinders
DIRECT FUEL INJECTION
## Footnote
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90
What does FADEC stand for
FULL AUTHORITY DIGITAL ENGINE CONTROL
| FADEC
## Footnote
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91
How is a *carburettor* engine primed on start up
PLUNGER
## Footnote
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92
How is an *injector system* primed on start up
BOOSTER PUMP SWITCHED ON
## Footnote
Fuel automatically supplied when the booster pump is switched on
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93
*Detonation* is controlled by adding ____ to fuel
LEAD
## Footnote
Summary
94
The *pressure balance duct* prevents ____ mixture
EXCESSIVELY WEAK
## Footnote
Summary
95
The *diffuser* prevents ____ mixture
EXCESSIVELY RICH
## Footnote
Summary
96
Petrol engines produced more CARBON MONOXIDE or SOOT than diesel engines
CARBON MONOXIDE
| Produce less soot than diesel engines
## Footnote
Summary
97
What 2 weather conditions are likely to cause *induction icing*
1. SNOW
2. HAIL
## Footnote
Summary
98
Name each of the parts in the *Basic Float Carburettor* engine
[LINK HERE](https://drive.google.com/file/d/1P5HG_l71SaehyipNPOrRnrBaWcwZYo_k/view?usp=share_link)
1. EDP (Fuel delivered by EDP)
2. Fuel Inlet Filter
3. Needle Valve
4. Float
5. Accelerator Pump
6. Pressure Balance Duct
7. Throttle Butterfly
8. Venturi (Throat)
9. Jet/Nozzle
10. Diffuser
11. Slow Running Jet
12. Economiser Control
13. Mixture Control Valve
## Footnote
[LINK HERE](https://drive.google.com/file/d/1P5OmFamJ2j-tHvcDap3bFTnTsNEDY51V/view?usp=share_link)
