RPL Engines and Systems Flashcards
What is a cylinder?
A chamber in which fuel and air is burned
What is a piston?
Helps to burn fuel and the motion of the piston drives the plane
What is the purpose of piston rings?
Seals combustion chamber
Supporting heat transfer from piston to cylinder wall
Regulating engine oil consumption
What do spark plugs do?
Ignites fuel air mixture in the cylinders
What are the inlet/exhaust valves?
Inlet valves allow fuel and air into the cylinders and exhaust valves open to release burnt gases after combustion
What is the purpose of mixture?
To mix fuel and air to a correct ratio in order for optimal efficiency of engine
What is the result of perfectly mixed fuel?
No remaining fuel after burning
What is the perfect fuel:air ratio?
15 air : 1 fuel
What is the normal cruise mixture?
13 air : 1 fuel
Whats the difference between richer mixture and leaner mixture?
Richer - more fuel/less air
Leaner - less fuel/more air
At which air : fuel ratio will fuel not burn and what are other effects?
8 air : 1 fuel will not burn fuel and can also cause flooding and engine problems
What happens during flight when the mixture is too lean?
EGT temperature will rise
What are possible effects if mixture too rich?
Engine down on power
Carbon build up
Spark plug fouling
What are the possible effects if the mixture is too lean?
Engine down on power (not enough fuel in cylinders_
Engine easily overheats
Detonation can occur
What are the 4 engine strokes?
Intake (down)
Compression (up)
Power (down)
Exhaust (up)
What happens on the intake stroke?
Inlet valve is open and exhaust valve is closed
Piston moves down barrel
Fuel and Air is drawn into combustion chamber
What happens on the compression stroke?
Both valves are closed
Piston moves down
Fuel/Air is compressed
Temperature is increased
What happens on the power stroke?
Both valves are open
Spark plug ignites the fuel/air mixture
Pressure of combustion forces piston down the barrel
What happens on the exhaust stroke?
Final stroke
Piston is forced up the barrel
Gases produced are exited into the exhaust system
What is the modified otto cycle?
Ignition and valve timing are adjusted to extract maximum output of the engine
How are valve timings adjusted?
Camshafts
What are the factors effecting engine output?
Quantity of gas in cylinders Temperature reached during combustion Position of throttle control Engine RPM Mixture condition Supercharging/Turbocharging
What are the 2 types of abnormal combustion?
Detonation and pre-ignition
What is detonation?
Occurs when fuel is too hot then ignited by spark plugs in which causes an explosion rather than a controlled burn
What are the primary causes of detonation?
Excessive air temperature
Over-lean mixture at high settings
Excessive manifold pressure
Overheated engine
What to do if detonation is suspected?
Richen mixture
Throttle back to reduce pressure in cylinders
Increase airspeed to reduce cylinder head temerpatures
What is pre ignition?
Ignition that commences before the spark from the plug in which is caused by a hot spot in cylinder
Primary causes of pre ignition?
Lead deposit
High power when mixture is too lean
Overheated spark plugs
What are the results from pre-ignition?
Rough running
Possible back fire
Rise in cylinder head temperature
Possible engine damage
What is the purpose of an ignition system?
To provide a correctly timed spark to the combustion chamber to ignite fuel/air mixture
How doe the ignition system work?
A high tension is generated and is made to jump the gap a the tip of a spark plug in which a low tension current cannot
What are the components of the ignition system?
Battery
Starter motor
Impulse Coupling
Magnetoss
What is the magneto ignition?
Magneto uses a permanent magnet to generate an electrical current in which is sufficient enough to jump across the spark plug gap
What is a magneto?
An electrical generator mounted on the rear of the engine
What are the advantages of a magneto ignition?
Spark cannot be produced where the crankshaft is not turning
Magneto is independant of the remainder of the aircraft electrical system
What are the disadvantages of a magneto ignition?
Expensive
Currents produced are weaker at low RPM such as engine start
How does dual ignition systems work?
Magneto of each ignition system supplies one of the two spark plugs per cylinder
What are the advantages of dual ignition systems?
Offer safety in the event of failure of one ignition system
They result in more efficient fuel combustion when both are active
What is the ignition switch?
Allows ignition system to be turned off and the selection of either left or right magnetos only or both simultaneously
What is the impulse coupling?
The generation of high voltage at low rpm via a rapid turn of the magneto via tension enough to release a spring
What problem does impulse coupling solve?
Producing a strong enough spark to start up the engine whilst the magneto magnet is on idle or weak
What are spark plugs?
A conductor of electricity that accepts the high voltage from the magneto in which is utilised for the ignition of fuel/air mixture within the cylinder
What are some precautions of the magneto system?
Prolonged use of starter motor will drain battery and overheat the starter
Severely discharged battery can explode
Prolonged use of the starter motor could also cause it to overheat and possibly ignite
What should be done if the starter has been used for over 30 cumulative seconds?
Allow system to cool for several minutes
What happens if only a single magneto is selected?
Combustion efficiency is reduced in which will result in less power on regular throttle settings due to more time taken for a full combustion to occur
The opposite magneto is grounded
What happens if there is not a drop in RPM when a single magneto is selected?
Opposite magneto still supplies a spark or the opposite magneto was not working when both was selected
How can the ignition system be checked before take off?
Switch from both magnetos to L then return to both, note the rpm drop and regain, apply to R too
What are the typical figures for the magneto system?
Check both at 2000rpm
Max drop on a single magneto is 125rpm
Difference between L and R drop should not exceed 50rpm in difference
How could the ignition system still be live if the off position is selected?
Loose or broken wires or by swinging the propellor manually
What is a dead-cut?
Temporarily turning the magneto off to note a sudden loss in power then returning to both
What happens if the ignition is off but the engine continues to run?
The magneto system is not grounded and therefore still live
What is carburetor icing?
The build up of ice within the carburetor
What are the symptoms of carburetor icing?
Rough Running
Power loss resulting in RPM drop
What is the solution to carburetor icing?
Activate carburetor heat
What happens when carburetor heat is activiated?
The hot air released creates a richer mixture due to the low air density and therefore result in less power and rpm
When should carburetor heat be used?
Unexplained drops in RPM
Unexplained rough running
What would happen when the carburetor heat is activated whilst ice is present?
RPM would initially drop then would increase after the icing has melted
What is the components electrical system?
Lights
Avionics (Radio)
Some instruments
Flaps
What is the bus bar?
The main conductor and distribution centre of the electrical system in which the alternator and battery supply power into the bus bar
What does the battery do within the electrical system?
Provides initial electrical power to rotate engine
Back up or emergency electrical power
What does the alternator do?
Powers the aircraft systems and recharges the battery after the engine has started in which its output is between 14-28 volts
What does the ammeter do?
An instrument that measures the amount of current flowing through the load
Monitor the performance of the aircraft electrical system
Shows if alternator/generator is producing adequate electricity
What does the centre zero ammeter indicate if the reading is in the negative and if it is in the positive?
Negative - Current is being drawn from the battery more than its being charged
Positive - The rate of charge of the battery
What does a full scale negative and positive indicate on the centre zero ammeter reveal?
Full scale negative - malfunction of alternator/generator
Full scale positive - malfunction of regulator
What is the left zero ammeter?
Indicates only when the alternator is delivering a load
When will the ammeter read zero?
Battery on and engine off
Engine on and alternator off
What should the left zero ammeter indicate when the battery is charged and the alternator is operating?
Slightly above zero reading
What would the left zero ammeter read if the electrical systems are turned on?
Ammeter reading would increase
What does it mean if the left zero ammeter drops to zero mid-flight?
Alternator failed
What is the purpose of the exhaust system?
Expel burnt hot gases from the cylinders into the atmosphere
Cabin heating
Carburetor heat for carburetor engines
What is the plenum chamber?
Where cold and hot air is mixed for cabin distribution
What are the disadvantages of the heating system?
A leak in the heat exhaust manifold can allow carbon monoxide to enter the cabin when heat is on
What are the colours of the carbon monoxide detector and what do they indicate?
Orange - normal conditions
Black - carbon monoxide leakage
What should be done in a case of suspected carbon monoxide leak?
Cabin heat turned off
All possible sources of fresh air opened and oxygen to be used if possible
Land ASAP
What are some carbon monoxide poisoning symptoms?
Headache
Dizziness
Nausea
What is the purpose of the lubrication system?
Supply oil to the engine for the lubrication and cooling of all parts of the engine prone to heating via surface friction
What happens if oil is too cool or hot?
Cool - Thick and sticky in which may not flow through small engine clearances and therefore oil pressure rises
Hot - Thin and running in which oil pressure will drop
What is the oil sump?
Gathering of oil in a reservoir attached to the lower part of the engine after going through the engine
Identify and describe the 2 different oil sumps?
Wet Sump - engine where sump is attached to it in which most light aircraft use
Dry Sump - Has scavenge pumps that extracts oil from the sump and places it back to the external oil tank (utilised by aerobatic aircraft)
What are the components of the lubrication system?
Oil Pump Oil filter Bypass valve Pressure relief valve Oil cooler Temperature gauge Pressure gauge Filler Cap
Why do aircrafts require the right additives?
To prevent foaming, undesirable carbon/sludge deposits and corrosion
What compound oil do aircraft engines use?
Asheless dispersant
What is oil viscosity?
Measures an oil’s flow properties
High viscosity - Slow flow
Low viscosity - Faster flow
What do high and low oil levels indicate during pre-flight inspection?
Low - Inadequate lubrication that can lead into engine overheating
High - Excess oil to pass through piston rings into the combustion chamber in which means oil is burnt in the cylinders
Burnt oil is indicated by blue smoke out of the exhuast
Why is excessive heat in an aircraft engine undesirable?
Affects the way fuel/air burns
Weakens and reduces life of the engine parts
Impairs adequate lubrication
How much percent of heat energy released during combustion is actually useful?
25%
How is the engine temperature kept within acceptable limits?
Oil circulates within the engine
Expulsion of heat energy via exhaust
Air cooling circulates cool air
How are most modern aircraft engines cooled?
Cooled by the openings at the front of the engine cowling in which the air flows into the cylinders and around the engine via baffles
What is the purpose of engine baffles?
Reduces uneven cooling and prevents hot spots
When is air cooling least effective?
High power and low airspeed such as take off and go around
When should cowl flaps be open?
When taxiing
Take off
Climb
Cruise
What are the effects of high engine temperature?
Loss of power Reduction of lubrication efficiency Excessive oil consumption Negatively affects fuel/air mixture Causes detonation Weaken engine components
How can high engine temperatures be avoided?
Open cowl flaps
Richen mixture
Reduce engine power
Increase airspeed
What is the purpose of the fuel system?
Provide fuel storage and the supply an adequate flow to the carburetor and fuel injection unit for operating conditions
What is the fuel system required to do?
Continuously provide fuel and positive fuel pressure during changes of altitude, attitude and sudden power changes
What are the components of the fuel system?
Fuel tanks Fuel tank vents Sumps/drains Filters/strainers Fuel pumps Selector valve Priming system Gauges
What is the difference in fuel tanks in high and low wing aircraft?
Low wing - Fuel delivered to engine via fuel pump
High wing - Fuel is gravity fed to the engine
When should the electric fuel pump be switched on?
Critical maneuvers such as take off, landing and low flying as will prevent fuel starvation if the mechanical fuel pump fails
How is priming achieved?
Manual priming pump
Electric boost pump and the accelerator pump
How does priming work?
Sending fuel directly to the inlet manifold just before the cylinders
Bypassing the carburetor
What does the selector valve do?
Selects which tank the fuel is sourced from
Which fuel does a piston engine aircraft utilise?
AVGAS
What are the 2 grades of fuel used in Australia?
100/130 Green
Low lead fuel 110LL Blue
Which fuel does jet engines use?
AVTUR (kerosine)
What are the most common causes of malfunction?
Fuel pump failure Vapour locks Blocked fuel tank vents Incorrect grade fuel Fuel contamination
How is the failure of an engine driven fuel pump indicated?
Zero fuel pressure on gauge
What should be done to restore fuel pressure?
Activate electric fuel pump and land as soon as practicable
What is the result of fuel vaporising in the wrong place?
Fuel starvation
How is fuel grade measured?
Combustion stability (anti-knock/anti-detonation) in which is indicated by octane rating
What does higher octane rating indicate?
Greater fuel stability and detonation resistance
What are possible effects of lower grade fuel?
Increased risk of detonation
Spark plug fouling
Corrosion of exhaust valve
What are the 3 primary contaminants of fuel in order of importance?
1) Water
2) Other petroleum products
3) Solid matter
How can fuel be checked for contamination?
By checking the fuel sump/drain with a tube before every flight
What is the purpose of the unusable fuel line?
For contaminants to sink down the bottom to be prevented from flowing into the engine and to be drained
What can be done to reduce contamination?
Fill tanks overnight to prevent condensation and water in the tanks
Make sure correct fuel is being used
Checking visually for water and particles
What are the refueling distance limits?
15m of exposed public building
9m of unsealed building
6m of stationary aircraft
5m of sealed building
What should be done if the fuelling equipment is immobile?
Aircraft to be placed where it can be rapidly be moved to a place of safety
What should a pilot in command do after fuelling is complete?
Fuel and oil tanks are securely refitted and a fuel drain is carried out
What happens if there is a fuel spill within 15m an aircraft?
Do not turn on or operate nearby aircraft
What should be done if a tachometer fails?
Use known power settings (half throttle = 2000rpm)
Land as soon as practicable
What does the cylinder heat temperature indicate?
That the temperature of the hottest cylinder is within limits
What are the reasons for the CHT reading being too high?
Fuel/Air mixture too lean Detonation/Pre-ignition Too low airspeed at high power settings Cowl flaps malfunctioning Blocked cylinder cooling fins
What are the actions to be taken if the CHT reading is excessive?
Richen the mixture Open cowl flaps Reduce power Increase airspeed Land as soon as possible if CHT remains excessively high
What does the Exhaust Gas Temperature (EGT) indicate?
To source temperature readings for the best economy mixture
When does the oil temperature gauge measure oil temperature?
After oil passes through the oil cooler
What can abnormally high oil temperature be attributed to?
Low oil quality
Oil cooler blockage
Faulty temperature gauge
Incorrect oil type
What can be done when there is a high oil temperature reading?
Reduce power or increase airspeed (or both)
Richen mixture
Open cowl flaps
Land as soon as practible
When does the oil pressure gauge measure oil pressure?
After the oil comes out of the cooler and feeds into the engine parts
What does low oil pressure mean?
Insufficient oil pressure in the engine to maintain adequate lubrication
What are the factors/malfunctions that may lead to a lack of oil pressure?
Oil pump failure
Failed bearings
Leaking oil lines
Insufficient oil supply
What should be done if a faulty oil pressure gauge is suspected?
Check for oil temperature gauge, a normal reading usually means a faulty oil pressure gauge
Land as soon as practicable
What can be suspected from a sudden loss of oil pressure and a rise in oil temperature and what actions should be taken?
Engine failure
Reduce power
Land as soon as practicable
What does a complete loss of fuel pressure indicate and what actions should be taken?
Engine driven pump is inoperative
Switch on the boost pump
Land as soon as practicable
What does a gradual loss of fuel pressure indicate?
Blocked fuel vent
