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)
