The Aeroplane Engine Flashcards
What are the two main types of engine?
Piston/reciprocating Gas turbine (jet)
Name the 5 main types of piston engine cylinder configuration
Radial In-line upright In-line inverted Horizontally opposed Vee
Picture the location and purposes of the following:
Inlet valve
Combustion chamber
Outlet valve
Spark plug
Cylinder
Piston
Connecting rod
Crankshaft
What piston configuration is most common in light aircraft?
Horizontally opposed
Name each stage of the four-stroke engine cycle
Intake
Compression
Power
Exhaust
What is the compression ratio?
The total difference between the cylinder volume at BDC and the clearance volume when at TDC
At what stage does the spark ignition take place?
Shortly before TDC
How is valve timing controlled?
By a camshaft rotating at half speed, gear-driven by the crankshaft
What is meant by valve lead and valve lag?
The premature and delayed opening and closing of valves during intake stroke in order to allow for maximum fuel amount prior to combustion
What is ‘valve overlap’?
The brief period during which the inlet valve and the exhaust valve are open at the same time
Describe generally, the ignition system in a single piston aircraft
Most usually have dual, independent ignition systems supplying each spark plug
What supplied the high tension current for each spark plug?
Magnetos
What drives the magnetos?
The magnetos are mechanically driven by the engine
Describe the structure and operation of a magneto
- A magnet rotated near a conductor
- Coil of wire wound around the conductor
- Rotation of magnetic field causes a current through the coil
- Transformer (coil with many more turns) is wound around the primary coil
- Transformer creates higher voltage, which is fed to spark plugs
- Spark jumps across electrodes
How is the charge in a magneto timed?
- Specifically placed breaker points in the primary coil are forced open and shut by a small cam
- The sudden collapse of the current in the primary coil creates a large current in the secondary coil
What regulates the timing of the distribution of electricity to each spark plug?
The distributor
How many times must a cylinder fire (per revolutions)?
Once in every two revolutions
How is the timing of the distrubutor regulated?
It has a rotor which is geared to the crankshaft in such a way that it turns once for every two turns of the crankshaft
What is an ignition harness and what is its purpose?
The name for ignition leads being bound together
Leakage of current from the ignition harness will lead to…
Rough running
What effect may altitude have upon ignition harnesses?
It may create rough running without current leakage
How must the ignition harness be included in a pre-flight inspection?
It must be checked for chafing and heat-cracking
How is the electric starter motor powered?
By the battery
Describe the current between the battery and the starter motor
It is very high and requires heavy duty wiring
What would be the impact of the ignition switch being directly connected to the starter circuit?
The required high voltage would result in very heavy cabling, heavy weight, significant loss of charge over a small distance and high energy currents in the cockpit environment
How are the dangers of connecting the ignition to the starter circuit avoided?
The connection from the battery to the starter motor is remotely controlled by a solenoid-activated switch
