AGK - Engines Flashcards
What comes after ‘suck’ in the Otto Cycle
Squeeze (Compression)
What’s after ‘blow’ in the Otto cycle
Sleeps
What are the main reasons that the ‘4 stroke cycle’ can only be considered hypothetical?
Ineffective crank angle
Finite combustion time
the volume within cylinder between TDC and top of cylinder is called?
Clearance Volume
Total amount of fuel and air mixture drawn into cylinder is called?
Charge
What is the charge inside the cylinder ignited by?
Spark Plugs
What is the principle of energy transfer of a piston engine?
Chemical > Heat > Pressure > Mechanical
Name the 4x strokes in the theoretical 4 stroke cycle
Induction > Compression > Power > Exhaust
How many full rotation will the crank shaft traveled within a 4 stroke cycle ?
2
Stroke definition
distance the piston travels between its lowest and highest points
Ignition occurs…….
Between the compression and power stroke
Top most limit of the piston
Top Dead Centre (TDC)
The average pressure exerted on the piston during power stroke is called ?
Mean Effective Pressure (MEP)
Most of the work on the power stroke is done ______ the piston reaches BDC
Before (therefore the exhaust valve opens before the end of power stroke)
The exhaust valve remains open until slightly after TDC (exhaust valve lag), why is that needed?
Longer time available to clear the cylinder of exhaust gas via residual pressure and momentum
At high RPM, piston is travelling so fast that ignition is further ______ in order for the power stroke to receive peak pressure
Advanced
The crankshaft can be directly connected to?
The Propeller
The crankshaft can also be indirectly connected to the propeller via?
A Gearbox
The ‘up down’ motion of the piston is called?
Reciprocal movement
Definition of ineffective crank angle
Close to TDC and BDC, there is very little linear displacement of the piston despite the angular rotation speed remains unchanged
What does the practical 4 stroke cycle exploites? And how?
The ineffective crank angle and finite combustion time
Altering the valve timing in relation to stokes and altering the ignition timing
Inlet valve _____ and ______ maximise the amount of charge that enters the cylinder
Lead , lag
The mixture inside the cylinder is only compressed when both inlet and outlet valves are ______
Closed
1 Pascal or pressure is______
Small in the grand scheme of things as it is only 1N per square metre
Humidity is
A measure of the amount of Water Vapour within a volume of gas
For any gas, at a given temp and pressure, the number of molecules present must be _______ for a particular volume
Constant (therefore as humidity increase, H2O replaces more N2 and O2 within a given volume of air, and as H2O has less mass vs N2 and O2, the volume of air will decrease in mass)
Boyle’s Law
P1 V1 = P2 V2
Absolute temperature of a gas is ________ in Boyle’s law
Constant
Charles Law
For a specific mass of gas, at constant pressure
V is proportional to T
Combines Gas Law
PV / T = Constant
Mechanism of heat transfer (not met version)
Convection
Conduction
Radiation
Newton’s Laws of motions are:
It’s okay I trust you got this right. If not please refer to POF, I can’t be bothered typing them all.
Thrust produced by a prop or jet engine depends on Two things :
The ‘amount’ of air and how much is that amount of air being accelerated
Formulas for Thrust
F = M x (V [jet] - V [flight])
1 horse power is approximate equal to _____ watts
740 watts
What is Torque?
A twisting force
Amount of Torque depends on?
Force applied
The length of the arm which force is applied and the angle between the two.
SI unit for Torque
Newton Metre - NM
Mechanical efficiency of an engine is expressed as a ratio between ?
The useful power produced to the theoretical power produced
Modern piston engines are about _____% efficient
80
The more work that an engine has to do to power it’s own components the ______ efficient it will be.
Less
Engine power is determined by the _____ of mixture ignited in the cylinder
Mass
More mass more power
Multiple cylinders produce ______ power delivery
Smoother
______ and ______ of cylinders can be increased to increase power
Number and size
Firing interval of an engine is determined by?
Diving 720 degrees by the number or cylinders
Engines can be classified by:
Number of cylinders Cylinder arrangement Method of cooling Type of fuel and induction system Type of fuel used Prop drive arrangement
Rotary engines have _____ crankshaft and ______ rotating cylinders
Fixed, rotating
Radial engines have ______ cylinders and ______ crankshaft
Fixed, rotating
Radial engines have the advantage of being ______ and ______ and have a ______ surface area for cylinder cooling.
Small, light, large
What’s the major disadvantage of radial cylinder configuration
Imposes significant constraints of aircraft design resulting in high drag
Another major draw back of radial engines is that ______ can pool in the cylinders that are inverted.
Oil
In-line engines have ______ ______ frontal area but ____ difficult to cool. Hence usually limited to _____ cylinders.
Relatively small, more, 6
In-line engines are often ______
Inverted
What is the most common engine cylinder arrangement?
Horizontally opposed engine (box or flat)
What are the benefits of having horizontally opposed engine cylinder arrangement ?
Short, rigid that sits easily within a streamlined nacelle, which reduces drag.
Horizontally opposed engines typically have _ , _ or _ cylinders.
4,6,8
Horizontally arranged engines are usually ______ cooled
Air
Cylinder comprises of 2 main components
Head and Barrel
Barrel in the cylinder of aero engine is typically made from?
Steel
Aero engines always have at least _____ spark plugs as an in built redundancy for safety
2
2 sets of spark plugs in aero engine is connected to ______ ______ magnetos
Two separate
As well as safety, using 2 spark plugs per cylinder ensures ______ and ______ ______ fuel burn, improving combustion efficiency.
Quicker and more even
Top of the piston is called the ______
Crown
The lower part of the piston is called the ______
Skirt
_______ rings are fitted around the top of the piston to prevent gases from escaping
Compression
What connects the piston to the crankshaft?
Connecting rod
The connecting rod is connected to the ______ ______ of the crankshaft at the ______ ______
Crank pin, big end
To save weight, aero engines tend to have ______ strokes
Short
Cylinder firing sequence
1342
What’s the benefit of alternating the firing order of cylinders
To reduce stresses on the crankshaft
The crank shaft, connecting rod and pistons are collectively known as?
The crank assembly
The camshaft operates the valves via?
Push rods
Camshaft always rotate at what speed?
Half the speed of crankshaft
Inlet and exhaust valves are ______ valves
Poppet
Inlet and exhaust valves are opened by ? And closed by?
Opened by camshaft and closed under spring pressure
How many springs are located around the valve stem for redundancy. The are also wound in what manner?
2.
Wound in opposite directions.
Inlet valve is normally ______ than exhaust valve
Larger
The moving parts of an engine must be lubricated to reduce ______ and ______
Friction, wear
Engine oil has which secondary functions?
Cooling,
Cleaning carbon deposits and metal flakes
Protecting against corrosion
Hydraulic operations
What are important indicators of engine health?
Oil temperature and pressure
Aero engine oil is typically…… . And its viscosity reduces with ______ temperature
A Mineral oil.
Increased
Aero engine oil must be able to maintain……
Suitable viscosity over a wide range of temperatures.
Apart from maintaining viscosity in wide range of temperatures, what other properties must engine oils have?
Have low evaporation rate
Inhibit corrosion
Inert
Discourage the formation of sludge
To meet engine oil requirements, additives are used to form compound oils. What are identification prefixes?
W80, AD100
Engines have ______ ______ or ______ ______ lubrication systems
Dry sump, wet sump
In the dry sump system, the oil is held in a ______ mounted ______ from the engine, but in the wet sump the oil is held in the ______ of the crankcase
Tank, remotely, bottom
Oil pressure in a dry sump typically reaches _______ to ______ psi.
60 - 70
Spent oil in a the dry sump is pumped back to the tank via a _______ pump
Scavenge
Oil returns from the engine via the scavenge pump and ______ line and spills onto a ______ plate
Return (scavenge), deaerator
The de-aerated oil recycled into the hot well of the tank to allow good circulation to establish _______. The hot well then gradually heats the cooler oil in the tank which eventually be able to flow ______ through the hot well.
Quicker.
Through
Magnetic plugs are?
Also known as chip detectors that are fitting in the oil return line. Ferrous particles from the engine are caught by the magnets and these particles can be examined to give an indication of wear and failure of components
Oil pump in a dry sump is ______ driven
Engine
The wet sump system uses the same components as the dry sump except?
No return (scavenge) line or scavenge pump. And no oil tank reservoir
The crankshaft splashing through the oil helps to lubricate the working surfaces. This is known as ?
Splash lubrication
Dry sump system oil check after flight
Immediate
Wet sump system oil check after flight
About 20 mins after shut down
Excessive cooling of the oil can cause the oil to ……..
Congeal in the matrix and block it
In the dry sump system the oil cooler is fitted in the _________ ______. In the wet sump system the cooler is normally fitted in the ______ ______ to the engine.
Return line.
Pressure supply.
Oil pressure should typically indicate within ______ seconds of engine start.
30
Hydraulicing occurs when oil ______ into the cylinders when they are ______. To avoid damage to cylinders, manually turn the prop to work the valves to allow oil to ______ from the cylinder.
Leaks, inverted, escape
Liquid cooling system extract heat from the engine by running a mixture of ______ and ______ through galleries built into the crank case.
Water and glycol
Hot fluid in the cooling system is piped into the radiator and cooled by ______ ______.
Ram air
Aero engines can be air cooled instead of liquid cooled to save ______ and ______ working components.
Weight., reduce
Temperature on the cylinder is measure at the ______ ______. And sensors are fitted on ______ cylinders, where the ______ temperature is displayed
Cylinder head. All. Highest
Cylinder head temperature is controlled by:
Amount of power produced
Aircraft speed
Temperature of cooling air
Mixture ratio
Engine is more likely to overheat when…….
Using high power during a climb
During start of the engine, the starter motor drives the engine via a ______ or ______ ______ on the engine flywheel
Gearbox, Tooth gear
As soon as engine starts, an ______ clutch disengages the Drive from the motor.
Overrun
If starter warning lamp remains on for more than _____ seconds after engine start, the starter motor have failed to ________. The engine must ______ ______.
30, disengage, shut down
Magnetos generate ______ tension electricity to power the spark plugs.
High
The purpose of the ignition system is to provide ______ of sufficient strength and duration at precisely the right moment in the cycle to ensure efficient ________
Sparks, combustion
The critical components of the ignition system are ________ to ensure that any single failure doesn’t result in total loss of engine ______.
Duplicated, power
Magnetos are ______ ______
Engine driven
The generator section of the magneto comprises a ______ pole rotating permanent magnet.
4
Primary winding, also called the ______ ______ circuit is wound around the soft iron stator. It comprises of a few turns of ______ wire.
Low tension, thick
The secondary circuit, also called the ______ ______ circuit, is wound over the primary circuit. The secondary winding contains many more turns of ______ wire and so it acts as a step-up transformer
High tension, thin (fine)
The primary circuit is continuously ______ and ______ by a contact breaker. This has two effects:
1) it converts continuous flow of AC current into a series of ______
2) The collapse of the magnetic field around the primary winding produces a surge of energy in the secondary winding, resulting in a series of ______ voltage, ______ current pulses of electricity that are distributed to the distributor.
Broken, reform
1) pulses
2) high, low
What’s the purpose of the distributor in the ignition system?
Alternately distribute the high voltage pulses of electricity to spark plugs
The collapse of the magnetic field caused by the opening of contact breaker points can induce a current in the primary winding, it can be sufficiently strong to produce ______ at the contact breaker points, which can cause damage to the breakers.
Arching
A ________ is fitted in parallel with the contact breaker to prevent arching.
Capacitor
The high tension voltage delivered to the spark plugs need to be in the region of ______ volts
30000
As well as the magneto, the engine also drives the contact breaker rotor and distributor rotor via a spindle, therefore their operating speed _____ directly with engine ______
Vary, RPM
Each magneto is controlled by its own ______ switch
Ignition
The ignition switch lead is called the ______ lead
P
When the ignition switch is open, the ignition circuit is ______. The provides a _____ ______ protection in flight.
Live, fail safe
On the ground, a disconnected wire results in a _________ live circuit
Permanently
Advantage of 2 spark plugs per cyclinder?
Quicker rise to peak cylinder pressure by providing more even burn of the fuel gas mixture.
The magneto is ________ to reduce the possibility of internal arching at altitude.
Pressurised.
Magneto’s output voltage is directly proportional to ______ ______
Engine RPM
An impulse coupling comprises a ______ loaded clutch mounted between the drive spindle from the engine and the magneto shaft. The drive spindle winds up the spring in the clutch, and as its released, the spring ______ and spins the ______
Spring, unwinds, magneto
What is the common ‘extra’ component between the LT and HT booster.
Using the aircraft battery
In the LT booster, a second set of ______ ______ points in the LT booster coil circuit ensures a sufficiently retarded spark. The circuit is switch ______ once engine has started.
Contact breaker, off
in the HT booster, a current is fed from the ________ to power the primary winding. A ______ ______ in the coil interrupts the primary winding circuit produce a continuous stream of high-voltage impulses, in the secondary HT circuit.
Battery, trembler interrupter
On a spark plug, a small ______ is set to separate the two electrodes. When HT voltage is applied, a strong ______ is created as the current arch the gap, this ignites the fuel air mixture.
Gap, spark
If the gap in the spark plug is too small the spark may be too ______. If the gap to too big there may…………..
Weak,
Maybe no spark at all
When oil , carbon and lead deposits from the fuel blocks the gap in the spark plug and causing the failure to spark, this is known as?
Fouling
Mag drop check is carried out ______
Twice
First mag drop check is done ______ ______ at about ______ to ______ RPM.
Second mag drop check is done during ______ ______ at about ______% of max engine RPM
After startup, 1000 to 1200
Power checks, 75%
No drop in RPM during mag drop check indicates one half of the ignition system is ______ ______ .
Not earthed
Excessive RPM drop and rough running indicates _________ ________
Ignition problem
if the amber starter warning lamp remains on for more than ______ after engine start the motor may have _____ to disengage. The engine must be _____ _____
30 seconds
Failed
Shut Down
The magneto is an….
AC generator, transformer and distribution system providing high voltage current to the spark plugs. It is independent of the aircraft battery and electrical system.
Engine rotation drives _____ which deliver high tension _____ to the spark plugs.
Magnetos
Electricity
The Ignition system must…
Provide sparks at precisely the right moment in the cycle to ignite the mixture.
Most light aircraft aero engines have __ magnetos
and each magneto powers a _____ _____ in each cylinder.
2
Spark plug
When the ‘P’ switch is closed the magneto is _____ and when it is open the magneto is _____
Off
On
The switch must be closed to _____ the circuit. This provides a fail safe _____, but is unsafe _____
Earth
In flight
On the ground
2 advantages of spark plugs:
Helps accelerate the combustion process
Is fail safe
Magneto’s output voltage is _____ _____ to
engine RPM.
Directly proportional
Magnetos are pressurised to reduce the possibility of
_____ _____ at altitude.
Internal Arcing
A mag drop (Magneto check) is carried out _____
Twice
The First mag drop is just after start at about _____ - _____ RPM. Each magneto is switched off in turn. The RPM should _____ but the engine should continue to ______ ______.
1000-1200 RPM
Drop
Run smoothly
The second mag drop is at about _____ of max RPM. Each magneto is _____ _____ in turn. RPM drop must be ______ _____.
75%
Switched off
Within limits
Spark pulgs can have a build up of _____ _____ which can lead to the plug _____
Dirt and oil
Fouling
The low tension booster is only live when _____ the _____.
Cranking
Engine
Impulse coupling is creating _____ _____ and _____ _____
High tension
Retarded Sparks
In a mag drop what indicates a failure of one half of the ignition circuit?
A complete dead cut
What indicates one half of the ignition system is not being earthed.
No drop in RPM
