Engine Operation Basics

Ignition of fuel/air mixture in a four-stroke piston engine occurs during the compression stroke.
The timing of the ignition is between 20° and 25° before TDC during the compression stroke.
The RPM of the engine does not affect ignition timing.
The piston is moving towards TDC during the compression and exhaust strokes.
The correct sequence of the four strokes is: Induction, compression, power, exhaust.
Valve overlap occurs between the exhaust and induction strokes.
The term "valve overlap" refers to the period when both inlet and exhaust valves are open around TDC.
"Valve lag" indicates that the inlet valve closes after the piston has passed BDC.
"Valve lead" refers to the inlet valve opening prior to the piston reaching TDC.
Alternate air in a fuel injection system feeds air from within the engine cowling to the induction system.
The primary purpose of a cowl flap is to control air flow over engine cylinders for optimal temperature.
Cylinder head temperature gauges typically read from the hottest cylinder.
Fins on engine cylinders and barrels improve cooling.
Baffles in engine compartments direct airflow for better cooling.
Engine crankshaft balancing is achieved by counterweights attached to the crank cheeks.
Counterweights prevent damage from vibrations.
Open and close the throttle smoothly to avoid stressing the crankshaft.

An accelerator pump in a carburetor provides extra fuel when the throttle is opened rapidly.
When the throttle is opened quickly, the accelerator pump discharges additional fuel into the venturi.
The accelerator pump compensates for increased air volume when the throttle is opened rapidly.
A primer pump should be used for cold engine starts, as it pumps fuel directly into the induction system.
The primer pump is more effective than the throttle accelerator pump in delivering fuel.
When starting an over-primed or flooded engine, the mixture should be leaned until the engine starts, then gradually richened to keep it running.

Engine main bearings and crankshaft are lubricated by both high-pressure oil and splash lubrication.
The lubrication system uses a gear type pump coupled with splash lubrication.
The pressure relief valve maintains constant oil pressure across engine power changes.
Low oil pressure and high oil temperature indicate low oil supply.
A dry sump system uses a scavenge pump to return oil from the sump to the oil tank.
In a wet sump system, oil is stored in the engine sump and distributed by a pressure pump.
Wet sump oil is cooled primarily by ram air through an oil cooler.
Wet sump oil temperature is measured after leaving the oil cooler.
Normal engine operation is indicated by a light grey coating on the firing end of a spark plug.
Black oily deposits on the firing end indicate oil slipping past piston rings and burning in the combustion chamber.
Dry, black, powdery carbon on the firing end indicates oil slipping past piston rings and burning in the combustion chamber.
The oil in a wet sump system passes through the oil cooler before being fed to the engine components.
An oil pressure gauge is located between the pressure relief valve and the sump.
The engine breather pipe relieves excess sump pressure.

A hydraulic system operates on the principle of pressure transmission through a fluid.
The accumulator stores hydraulic fluid under pressure.
An accumulator stores unpressurized fluid for emergency use.
A low-pressure filter is located between the reservoir and the pump.
A non-pressurized hydraulic fluid reservoir has an air vent to allow fluid level expansion and contraction.
The vent prevents a vacuum by allowing air into the reservoir.
Vegetable and mineral hydraulic fluids cannot be mixed.
Mineral-based hydraulic fluid is typically red.

During a right turn while taxiing, the turn coordinator ball moves left and the needle shows a right turn.
When taxiing, a left turn causes the turn coordinator ball to move right and the needle to move left.
During a right turn, the direction indicator heading should increase.

During a level, coordinated turn, wing load is a function of the bank angle.
A semi-monocoque fuselage design provides shape and rigidity through formers and stringers, with the stressed skin carrying some load.
A monocoque fuselage design relies on the outer skin to carry all flight loads.
A semi-cantilever monoplane uses bracing struts at the base of the fuselage to support the wings.
A servo tab is connected directly to the pilot controls.
The main spar is the most important structural component of a wing.
The main spar is the primary load-carrying component in an aluminum stressed skin wing.
Ribs provide both strength and shape in a stressed skin wing.
The main longitudinal member in a Truss type fuselage is the longeron.
Ailerons and flaps are typically attached to the rear or auxiliary spar.
Torsion refers to the twisting load on an airframe.
A torque link on a nose wheel shock strut assembly keeps the nose wheel aligned with the airframe.
Torque links prevent the piston and wheel from rotating within the cylinder.

A coarse pitch propeller provides better cruise performance than a fine pitch propeller.
To increase power on an airplane with a constant speed unit (CSU), richen the mixture, increase RPM, then increase the manifold pressure setting.
With a constant speed unit, increasing power while maintaining RPM will keep the RPM constant.
For an airplane with a fixed pitch propeller, decreasing speed with a constant throttle setting will decrease RPM.
During a shallow dive with a fixed pitch propeller, increasing speed with no change in power setting will increase RPM.

The mandatory periodic inspection (MPI) should be carried out annually or every 100 hours of flight time, whichever comes first.
A Certificate of Release to Service is issued after an MPI and is valid for 12 months or 100 hours of flight time, whichever comes first.
The Supplements section of the Aircraft Flight Manual contains information about optional equipment not installed in a standard aircraft.
For domestic flights in South Africa, the aircraft must carry certificates of registration, airworthiness, and release to service, along with a list of visual signals and intercepting aircraft procedures.
Maintenance carried out on an aircraft while away from base must be transferred to the appropriate logbook within 48 hours after the aircraft's return to its base.
Records of maintenance carried out at an aircraft's base of operation must be entered in the logbook within 48 hours of completion.

Newton's first law refers to equilibrium.
Newton's second law refers to acceleration and deceleration.
Newton's third law refers to action and reaction.
During level flight, reducing power causes the nose to drop because the center of gravity is located forward of the center of pressure.
As the angle of attack increases, the center of pressure moves forward.