12.10.4(d) . connecting rods; 

12.10.4(c) . pistons; 

12.10.4(b) . cylinder heads; 

12.10.4(a) . cylinders; 

(Pictures)

12.10.4. Explain the function of the main components of a four-stroke cycle piston engine including: 

Cylinders – provide the enclosed space for combustion to take place
Pistons –    moves back and forth within the cylinder and provide a gas-tight seal
Connecting Rods – connect the piston to the crankshaft
Crankshaft – converts the reciprocating movement of the piston to a turning motion and transmits the power developed in the cylinders to the propeller
Crankcase –
Camshaft – is gear-driven by the crankshaft of the engine and rotates at half crankshaft speed
Valves – the Intake Valve admits the fuel/air mixture to the cylinder and the Exhaust Valve allows the burnt gasses to be expelled
Spark Plugs – ignite the compressed fuel/air mixture in the cylinder
Injectors –

12.10.2. Identify typical cylinder configurations used for aircraft piston engines.

Radial – have their cylinders arranged in a circle around the crankshaft
In-line – cylinders are arranged in one or more lines

Inverted in-line – the crankshaft / propellor shaft is at the top of the engine

Horizontally exposed – the “standard” is the air-cooled piston engine with horizontally exposed or flat configuration and four, six or eight cylinders arranged horizontally in two lines on opposite sides of the crankshaft
(Pictures)

12.6.46. Identify the approximate angle for best L/D ratio.

 The best L/D ratio is at about 4deg angle of attack on most general purpose wings.
Because most light aircraft don’t have angle of attack indicators the only way of knowing that you are operating at the best L/D ratio is to use the airspeeds recommended by the manufacturer.

12.6.44. Describe a typical curve of lift/drag (L/D) ratio versus angle of attack for an asymmetrical aerofoil. 

The Lift to Drag Ratio is the ratio of lift produced to drag created at any given angle of attack.
The maximum lift to drag ratio occurs at the most efficient angle of attack.
The lift to drag ratio increases up to approx 4 deg angle of attack and then decreases as the angle of attack is increased further. (graph)

12.6.42. Identify curves of parasite, profile, induced and total drag versus aerofoil airspeed.

++Diagram++
Parasite drag increases with indicated airspeed – it is proportional to the square of the indicated airspeed
Induced drag decreases with increasing airspeed – it is proportional to 1/IAS squared.

12.6.40(b) . aspect ratio. 

Induced drag decreases as aspect ratio increases.