04. Piston Engine: Fuel Systems Flashcards
3 qualities that piston engine fuel must contain
1. Contain significant quantity of ____
2. Be able to form ____
3. ____ but controllably
- Energy
- Vapour
- Burn quickly
Pg 81
At ____℃ AVGAS has a density of ____ kg per litre
- 15℃
- 0.72
Pg 81
What is vapour lock
Partial or complete interruption of fuel flow due to AVGAS turning into vapour in the fuel feed
Pg 81
What is the term used when the AVGAS turns into a gaseous state preventing fuel flow
VAPOUR LOCK
Pg 81
The term used to explain the rapid spontanous combustion of mixture
DETONATION
Pg 82
What noise can be heard if detonation is occurring
ENGINE KNOCKING
Pg 82
What are 4 consequences of detonation
- REDUCED POWER output
- CYLINDER TEMPERATURE rises rapidly
- HOTSPOTS - due to uneven temperature
- PHYSICAL DAMAGE (due to hotspots)
Pg 82
What are 4 causes of detonation
- FUEL - Fuel with poor anti knock
- MIXTURE - Incorrect mixture ratio
- PRESSURE - Anything that raises temperature or pressure of mixture
- TEMPERATURE - High engine temperature
Pg 83
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
DETONATION
Pg 83
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)
DETONATION
Pg 82
What is the defintion of pre-ignition
Ignition of mixture before spark plug fires
Pg 83
What is a cause of pre-ignition within the cylinder
LOCAL HOTPOST
Local hotspots caused by carbon deposits
Likely to happen when cylinder is excessively hot or contaminated with carbon deposits
Pg 83
- Local hotspots in the cylinder are likely to cause what?
- They are typically as a result of what?
- Pre-ignition
- Carbon Deposits
Pg 83
The primary cause of pre-ignition
WEAK MIXTURE
Pg 83
The 3 key symptoms of pre-ignition
Think PRE-ignition
- POWER - Loss of power
- ROUGH RUNNING
- ENGINE - Overheating
Pg 83
Pre-ignition worsens with INCREASED or DECREASED RPM
INCREASED
Pg 83
Detonation reduces with INCREASED or DECREASED RPM
DECREASED
Pg 83
What is running-on
Engine continues to run a short period after shut down
Pg 83
If the engine continues to run after shut down, what is this known as, and what is it a characteristic of
- Running-on
- Pre-ignition
Pg 83
What is an octane rating
Indicates fuels resistance to detonation
AKA anti-knock value
Pg 85
The HIGHER or LOWER the octane rating, the HIGHER or LOWER the resistance to detonation
- HIGHER
- HIGHER
Pg 85
What additive is used to control detonation
TETRA-ETHYL LEAD
Pg 85
What colour is 100LL fuel
BLUE
Pg 85
What colour is 100 fuel
GREEN
What are 3 things that can increase the likliehood of detonation
American C O P’s can detonate
- CARB HEAT - at high power settings
- OVERHEATED - Overheated cylinders
- POWER - High power, low RPM
Pg 86
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
Pg 86
What is the ratio of air to fuel that ensures complete combustion
15:1
Pg 86
The ratio if 15:1 is of what to what
AIR to FUEL
Pg 86
The air to fuel ratio of 15:1 is typically referred to by which 3 names
- Stoichiometric mixture
- Chemically correct
- Ideal ratio
Pg 86
- A mixture of 8:1 is RICH or LEAN
- A mixture of 20:1 is RICH or LEAN
- Rich
- Lean
Pg 86
- What is the ratio of a rich mixture
- What is the ratio of a lean mixture
- 8:1
- 20:1
Pg 86
The risk of detonation increases under what power setting conditions
HIGH POWER
Pg 87
High power settings INCREASE or DECREASE the risk of detonation
INCREASE
Pg 87
What is the function of having an excessively rich mixture
COOLING
Extra fuel not burned off, liquid aids cooling
Pg 87
What does excessively rich mixture cause in the exhaust gases
BLACK SMOKE
Pg 87
- What effect does weaker mixture have on the temperature of burning gas?
- What effect does this have on the engine temperature
- Cooler burning temperature
- Higher engine temperature
Pg 87
A weaker burning mixture will increase the temperature of the ____ and reduce the temperature of the ____
- Cylinder head
- Exhaust gas
Pg 88
What is the combined advantage and disadvantage of using a weak mixture in terms of efficiency
- Disadvantage - Reduced power
- Advantage - Reduced fuel consumption
Pg 88
What is a result of prolonged ground running at idle with a rich mixture
SPARK PLUG FOULING
Pg 88
What is spark plug fouling a result of
RICH MIXTURE when RUNNING IDLE
Pg 88
What component is used to measure EGT or cylinder head temperature
EGT - Exhaust Gas Temperature
THERMOCOUPLES
Pg 89
The highest combustion temperature occurs at what mixture ratio
STOICHIOMETRIC
15:1
Pg 89
Peak EGT occurs when the mixture is what ratio
STOICHIOMETRIC
15:1
How can you achieve power cruise mixture setting
LEAN MIXTURE to achieve peak EGT
Slowly ENRICH until EGT drops slightly
Ideal power cruis mixture ratio 12:1
Pg 89
What is the ideal power cruise mixture ratio
12:1
Pg 89
How can you achieve economy cruise mixture setting
LEAN MIXTURE to achieve peak EGT
Slowly LEAN mixture until EGT drops slightly
Ideal economy cruis mixture ratio 17:1
Pg 90
What is the ideal economy cruise mixture ratio
17:1
Pg 90
How does the pilot control the amount of air delivered to the engine
THROTTLE
Pg 91
What does the throttle control the delivery of to the engine
AIR
Pg 91
What does EDP stand for
ENGINE DRIVEN PUMP
Pg 92
How is the amount of fuel in a float chamber regulated
By a FLOAT
Pg 92
What is the purpose of the float
Regulates amount of fuel in the float chamber
Pg 92
What is the purpose of an EDP
EDP - Engine Driven Pump
Ensures postive supply of fuel under pressure to the carburettor
Pg 92
what causes fuel to be drawn up the U-tube into the throat
VENTURI EFFECT
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
Pg 93
What is the purpose of the fuel nozzle in a basic float carburettor
ATOMISE FUEL
As fuel is drawn into the throat, the nozzle will finely atomise the fuel
Pg 93
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
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
Pg 95
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
Pg 96
What is the purpose of a diffuser
REDUCES FUEL FLOW
Helps reduce the amount of fuel flow through the nozzle when the pressure drops excessively in the throat, which would result in excessive fuel
Pg 96
What is the purpose of a mixture control valve in a basic float carburettor
COMPENSATES for effect of CHANGING AIR DENSITY
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
Pg 97
What colour are manual mixture controls
RED
Pg 98
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
Pg 99
What is the purpose of a slow running jet
Provides rich mixture when engine idle / butterfly closed
Pg 99
How does a pilot operate the shut-off valve
PULL MIXTURE REWARDS
Pg 99
A power enrichment system is required at HIGH or LOW power settings
HIGH POWER
Provides addition rich micture to cool the cylinders
Pg 100
What is the name of the system that provides additional rich mixture in a basic float carburettor to cool the cylinders
POWER ENRICHMENT SYSTEM
Pg 100
What is the purpose of the accelerator pump
Injects a quantity of fuel directly into the venturi
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
Pg 101
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
- Air flow rapidly increases
- Pressure drop lags
- Accelerator pump
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
Pg 101
A drop in ____ and ____ are the 2 main contributors to carburettor icing
- Pressure
- Temperature
Pg 102
What is the most relevent factor to carburettor icing
HUMIDTY
Pg 102
When RH is more than ____%, carburettor icing may be expected in all flight conditions
RH = Relative Humidity
60%
Pg 103
Serious carburettor icing is likely in ambient temepratures between ____℃ and ____℃ with a RH of ____%
RH = Relative Humidity
- 18℃
- 25℃
- 30%
Pg 104
What is the most dangerous condition likely to cause carburettor icing
CRUISE or DESCENT POWER
WARM day with MODERATE or HIGH HUMIDITY
Pg 104
What is the risk associated with a warm day with relatively high humidity, and the pilot just started a descent
CARBURETTOR ICING
Pg 104
What are the 6 symptoms of carburettor icing
The Man Roughly Jammed the Exhaust in a Resolute Performance
- Manifold Pressure
- Rough Running
- Jammed Throttle
- Exhaust temperature drop
- RPM
- Performance (Reduced)
Loss of RPM
Reduced Performance
Reduced inlet manifold pressure
Decreased exhaust gas temperature
Rough running
Jammed throttle
Pg 105
What is the likely first sign of carb icing on a fixed pitch propeller engine
REDUCED RPM
Pg 105
What is the likely first sign of carb icing on a variable pitch propeller engine
REDUCED MANIFOLD PRESSURE
RPM initially remains the same
Pg 105
How does carb heating work
Pilot manually selects carb heating
Hot air drawn from heat exchanger
Pg 106
What are the 2 benefits of selecting carb heating
- Alternative source of air
- Prevents/removes icing
Pg 106
What are 5 key disadvantages of using carb heating
REMEMBER: Carb Power bReaks Ice, Detonators Explode
P bR I D E - Be proud to use carb heat
- POWER (Reduced)
- BREAKING ICE (Reduces power)
- INDUCED ICING (Temperature increase to a point ideal for icing to occur)
- DETONATION
- ENRICHED MIXTURE
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
Pg 107
What is the purpose of an air induction system
Introduce mixture into each cylinder
Pg 108
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
Pg 110
What is induction icing
ICING on AIR INTAKES
Pg 111
What are 3 key advantages of a fuel injection system
Think Fuel Injection System
- FUEL - Reliable fuel delivery
- ICING - Better icing protection
- SPEED - Quicker throttle response
Pg 113
How does a fuel injection system differ significantly to a carburettor system
NO VENTURI
Fuel delivered to engine under pressure
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
Pg 113
What are 5 core components of a continuous-flow injection system
Fuel injection
REMEMBER: The Man has 2 Pumps to Inject Fuel
- MANIFOLD valve
- PUMP - EDP - Engine Driven Pump
- PUMP - Electric Pump
- INJECTOR assembly
- FUEL nozzles
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
Pg 114
In a continuous-flow injection system, what are the 2 functions of the electric pump
THINK…
continuous-flow - keep going if something fails
injection - What component is like a syringe
- Provide pressure if EDP fails
- Prime engine before start
Pg 114
In a continuous-flow injection system, what is the metering valve connected to
THINK what are the pronounced syllables in each word..
meTering - think.. T…ta..ta
vAlve - think A..ah..ah
T A
THROTTLE ASSEMBLY
When the throttle lever is moved towards full power, the throttle butterfly opens, so does the metering valve
This allows more fuel flow
Pg 116
In a continuous-flow injection system, what are the 2 core functions of the manifold valve
- Divide fuel between all cylinders
- Provide means of stopping fuel flow
When the mixture control is set to idle cut off, manifold valve provides a means to stopping fuel flow
Pg 116
Large engine and diesel engines use ____ to deliver fuel to the cylinders
DIRECT FUEL INJECTION
Pg 117
What does FADEC stand for
FULL AUTHORITY DIGITAL ENGINE CONTROL
FADEC
Pg 118
How is a carburettor engine primed on start up
PLUNGER
Pg 118
How is an injector system primed on start up
BOOSTER PUMP SWITCHED ON
Fuel automatically supplied when the booster pump is switched on
Pg 118
Detonation is controlled by adding ____ to fuel
LEAD
Summary
The pressure balance duct prevents ____ mixture
EXCESSIVELY WEAK
Summary
The diffuser prevents ____ mixture
EXCESSIVELY RICH
Summary
Petrol engines produced more CARBON MONOXIDE or SOOT than diesel engines
CARBON MONOXIDE
Produce less soot than diesel engines
Summary
What 2 weather conditions are likely to cause induction icing
- SNOW
- HAIL
Summary
Name each of the parts in the Basic Float Carburettor engine
LINK HERE
- EDP (Fuel delivered by EDP)
- Fuel Inlet Filter
- Needle Valve
- Float
- Accelerator Pump
- Pressure Balance Duct
- Throttle Butterfly
- Venturi (Throat)
- Jet/Nozzle
- Diffuser
- Slow Running Jet
- Economiser Control
- Mixture Control Valve
