Engine Flashcards
5 Engine Configurations
Radial In-line Upright In-line Inverted Horizontally Opposed Vee
Parts of the Piston?
The crown Compression Rings Oil Scraper Ring Gudgeon Pin Connecting Rod "Con-Rod" Big-end Bearings (Connects to crank shaft)
How does the piston work?
Pistons move back and fourth in the cylinder where a mixture is burned .A crank shaft turns the linear motion to rotating motion to the propeller
The four-stroke engine cycle
Intake (Suck) - Fuel/air mixture sucked into cylinder
Compression (Squeeze) - Inlet valve + compression occurs
Power (Bang) - Spark plug ignites forcing piston back
Exhaust (Blow) - Remaining gasses forced out
What is the equation for compression ratio?
Total volume
——————
Clearance volume
Explain the ignition system?
A magneto (separate from normal electrical engine) is a high powered magnet that produces a high current to start a spark
Magneto failsafe
The right and left magneto connect to either side meaning that if one fails all the pistons will continue to ignite (loss of 100RPM = failed magneto)
Same side Down
Opposite Top
Impulse coupling
Slows down spark plug during low cranking RPM (When starting engine)
Accelerates the magnet momentarily to generate a high voltage
Exhaust system
Burned gases leave engine and are carried out to the atmosphere. Exhaust fumes leaking into the cabin can lead to carbon monoxide poising
The Carburettor
combines petrol wth oxygen. (1 part fuel/ 12 parts air by weight)
Rich = excess fuel Lean = Shortage of fuel
Higher you climb = less oxygen to less fuel needed
The venturi controls throttle valve (butterfly valve)
Acceleration through venturi = decreased static pressure (Bernoulli’s principle)
Accelerator Pump
Will attempt to push more fuel into engine so it starts if throttle opened quickly - creates rich engine mixture
Idling System
Close throttle when plane is idle. small idling jet with inlet near butterfly valve to keep engine at low RPM
Fuel/Air Mixture control
To maintain correct mixture pilot must reduce the amount of fuel entering.
Excess fuel = Rich
Too little air = Lean
Detonation
Fuel nd air mixture prematurely ignited during compression stroke causing engine damage
What causes detonation
Low grade fuel
Heat
Incorrect mixture setting
Carbon particles in the combustion chamber
Carburettor icing
Usually formed at temps 10 to -20 degrees Celsius when relative humidity is high
High altitude - cold air, cold fuel = intake valve/throttle icing over
lead to rough running/Power loss
Apply carburettor heat before it happens
Fuel Injection System
No Carburettor. Fuel directly mixed into the induction manifold into cylinders
Venturi system still used for pressure differential coupled to a fuel control unit
separate fuel line carries fuel to the discharge nozzle in each cylinder head
Components of the Cylinder
Inlet/Outlet
Piston
Spark Plugs
Combustion Chamber
What is the Camshaft?
Opens + Closes inlet and exhaust valve
Connected to crankshaft so in relation moves at half speed
Basic description of the fuel tank
Fuel in tanks usually installed in wings
(Reduces stress on wings e.g. bending due to weight)
A sump and drain allows for heavy impurities to gather and be drained off
(E.g. water)
Tanks often contain baffles preventing fuel surging in flight
Top of fuel tank vented allow atmospheric pressure to be retained in tank as altitude changes/fuel used up
Fuel vents should checked in pre-flight
Overflow drain prevents excessive pressure build up if fuel volume increases due to pressure - (Expands with heat + vapour)
High-wing aircraft = gravity fed
Low-wing aircraft = pump fed
(By law tank should be left 2% empty to account for fuel expansion at high temps)
What is a baffle?
Helps hold the tank in place stopping the fuel from surging/sloshing around
Important for air-cooled aircraft engine - help direct air over cylinders - top to bottom.
Fuel Selection (What pilot do, What if bad thing)
Pilot selects which tank to pull fuel from/shut fuel off
Loss of power, should suspect
Lack of fuel to engine
Carburettor icing
Fuel Gauges
ALWAYS DO VISUAL CHECK
DO NOT RELY ON GAUGE
Fuel Labelling + Colour coding
Dictates what kind of fuel it is. Each colour represents a different type and indicates what the fuel should look like
Blue/Red - AVGAS 100LL
Blue/Grey/Red - AVGAS 100LL
Yellow/Red - MOGAS
Yellow/Grey/Red - MOGAS
Black/White/Black/White/Black - JET A1
Transparent
Black/White/Black/Grey/Black - JET A1
Fuel/Oil Checks
Should be down first to see if any contaminates
(water denser than fuel so rests at bottom of tank)
Check oil cooler is free from insects, bird nests any oil leakage/fatigue cracks
(Pilots operating handbook usually shows oil grade as SAE rating)
Typical Lubrication system
> It reduces friction
Cools hot section of the engine
Carries away contaminants (Cleans)
Provides a seal - (OIl makes it tighter)
(Oil must have correct properties)
Oil properties
Must be sufficiently viscous over operating temp range of engine
Have high flash point = will not vaporise excessively or catch fire
Must be chemically stable/not change state or characteristics
Oil properties
Sump, pump and filters
Wet sump engine has sump to store oil (Own oil) - most light aircraft
Dry-sump engine has SCAVENGE pumps - scavenge oil from somewhere else (Where ever it can find it)
Oil filters/screens placed in the system to remove foreign material (dust, carbon particles)
Malfunctions in the Oil/Lubrication System
Oil type - incorrect oil = poor lubrication, poor cooling + engine damage
Oil temp + Pressure may be abnormal
Oil Quantity - Should be checked prior to flight, as it gradually decreses due to = burning mixture in cylinders, loss as mist through air breather, leaks
Faulty Oil Pressure Gauge
(Gauges can develop faults and give false readings)
High Oil pressure - Pressure relief valve in system should stop oil from reaching high pressure
Low/Fluctuating pressure - Associated with a rise in oil temp while in flight - land as soon as possible
Gradual Loss of oil - Oil temp rises as less oil does same amount of work
The cooling system
Risk of not having one/the standard
High enginge temps should be avoided they:
Reduce efficiency of lubrication system
Adversely affect combustion - “detonation”
Weaken engine components + shorten engines life
Most modern = Engines cooled by exposing cylinders to air - cooling fins increase surface area
Burning fuel = heat (Around 750 degrees)
2 types of cooling systems
Air cooling + liquid cooling (Most use air)
Pilot must check fins in pre-flight for debris
Fixed Cowl Outlet +Variable Cowl Flaps
lets air out during circulation
Fixed - More air can escape
Variable - controlled by pilot
The electrical system
Require system for:
Cabin lights, landing lights, inst lights, starter motors, electric flaps, radar, radio, pilot heaters, fuel gauges, fuel boost pumps, retractable
undercarriage etc
Modern us DC
Bus Bar
Distribution centre of electrical system. It is a metal bar allowing electrical current to be supplied to various circuits/units
The Battery
Light aircraft = lead acid battery creates current via chemical reaction. Classified according to voltage
Series + Parallel Battery Connections
Series = increases volts amp hours remain the same
Parallel = volt remains the same increase amp hours
Alternator + Generator
Most craft run by Alternator have to be converted from AC to DC via rectifier
Adv
Lighter than generator
Produces relatively constant voltage
Easier to maintain
Dis
Requires intial current from battery to work. Needs to “excite” alternator
Typical Charging System
Ammeter tells Pilot if electricty is flowing from or to charging unit
If current flowing from the battery the ammeter shows a discharge
Current flowing to battery ammeter shows charge
Master Switch
Must be on for any other electrical system to receive power. Recharged when engine runs
Split into two in craft with alternator
(No alternator = 30 mins for power)
Landing gear
Allows for movement on ground
Connected via either:
String spring leaf of steel/fibre glass
Struts + braces
Oleo-pneumatic unit
The Oleo Unit
Act as suspension system. Filled with nitrogen gas (Shock absorber) and hydraulic oil (stops excessive rebound)
Torque Link
Align nose wheel to airframe
Shimmy Damper
Prevents Oscillation of wheel on ground
shimmy shimmy yah
Creep Marks + Tyre Pressure
Tyre pressure wrong = tyre creep
Normal operation stresses can lead tyre creep - inner tube may suffer - valve may be unusable + break
Typical Hydraulic Braking System
Fluid goes down break line pushing pads slowing down disc break
Parking Brake
Holds pressure on wheel brakes and can be used when plane is parked
Pre-flight checks: No leaks in hydraulic system brake disc are not corroded Pads not worn Brake assembly firmly attached
Instruments - Airspeed indicator
Colour codes relate to specific speed mins/limits
Vs0 - stalling speed flaps/gears down
Vs1 - Stalling speed flaps/gears up
Vfe - Max speed permitted flaps down
Va - Design manoeuvring speed
Vno - Normal operating speed
Vne - NEVER EXCEED SPEED
Instrument Altimeter + static vent
Altimeter - measures pressure outside to get height.
Can tell height via amount of pressure (less = higher)
Static vent - Measures static pressure
Vertical speed indicator
VSI - Converts rate of change of altitude and expresses it in ft per minute
(Using the fact pressure decreases with altitude)
Turn co-ordinator, Turn indicator, Balance indicators
Instruments indicate aircrafts rate of turn
Attitude Indicator
Shows pitch + bank angle
Nothing on performance of craft
Direction indicator
DI - Gyroscopic instrument aligned with magnetic compass periodically in flight
Can be known as Heading indicator (HI) or Directional Gyro (DG)
Magnetic compass
Primary source of direction
indicates magnetic heading
T.V.M.D.C. W.E.
True Virgins Make Dull Company
+Whiskey, -Ethics
True / Variation / Magnetic heading / Deviation Compass
