Powerplant

Thrust

The force that propels an aircraft forward and overcomes drag.

Lift

The force that allows an aircraft to stay airborne and counteracts the weight of the aircraft.

Aircraft Engine

The power component of an aircraft propulsion system.

Piston Engines

Internal combustion engines that use reciprocating pistons to convert pressure into rotational motion.

Gas Turbine Engines

Continuous and internal combustion engines that use the pressure from exploding fuel to turn a turbine and produce thrust.

Aircraft Piston Engine

Also known as a reciprocating engine, it is an internal combustion engine that uses reciprocating pistons to convert pressure into rotational motion.

Gas Turbine

A type of combustion turbine that consists of a gas compressor, a combustor, and a turbine on the same shaft.

Difference between Piston and Gas Turbine Engine

Piston engines use pistons to convert pressure into rotational motion, while gas turbine engines use the pressure from exploding fuel to turn a turbine and produce thrust.

Wright Brothers

Orville and Wilbur Wright, known for inventing, building, and flying the world's first successful motor-operated airplane.

In-Line Engine

An engine with an even number of cylinders aligned in a single row parallel to the crankshaft.

V-Type Engine

An engine with cylinders arranged around a single crankshaft in two in-line banks that are 45, 60, or 90 degrees apart.

Radial Engine

An engine consisting of cylinders arranged radially about a central crankcase.

Opposed Engine

An engine with an even number of cylinders, with each cylinder on one side of the crankcase "opposing" a cylinder on the other side.

Crankcase

The foundation of a reciprocating engine that contains the engine's internal parts and provides a mounting surface for the engine cylinders and external accessories.

Crankshaft

The component that transforms the reciprocating motion of the pistons and connecting rods into rotary motion to turn a propeller.

Bearings

Surfaces that support and reduce friction between two moving parts.

Connecting Rod

The link that transmits the force exerted on a piston to a crankshaft.

Pistons

Movable plugs inside the cylinders of a reciprocating engine that move up and down.

Cam Ground Piston

An aircraft engine piston ground in such a way that its diameter parallel to the wrist pin boss is less than its diameter perpendicular to the boss.

Crown

The top surface of the piston that is subjected to forces and heat during engine operation.

Ring lands

Reliefs cut into the side profile of the piston where the piston rings sit.

Ring groove

A recessed area on the perimeter of the piston used to retain a piston ring.

Skirt

The portion of the piston closest to the crankshaft that helps align the piston in the cylinder bore.

Wrist pin boss

A bore that connects the small end of the connecting rod to the piston by a wrist pin.

Piston head design

Different designs of the piston head, including flat head, recessed head, concave head, and dome head.

Piston rings

Metal rings that fit into grooves around the outside of a piston to prevent gas leakage, transfer heat, and reduce oil seepage.

Piston ring gap

The point where a piston ring is split.

Piston ring gap measuring

The process of measuring the gap between piston rings.

Blow-by

The loss of pressure in the engine cylinder caused by leakage past the piston ring.

Compression rings

The top rings used to seal the piston in the cylinder and prevent gas from escaping during engine operation.

Oil rings

Rings that control the amount of oil applied to the cylinder walls and prevent oil from entering the combustion chamber.

Cylinders

Provide the combustion chamber where gases expand to produce power.

Cylinder barrel

The high strength steel tube in which the piston moves up and down.

Cylinder skirt

The portion of the cylinder that protrudes into the crankcase.

Cylinder mounting flange

Used to attach the cylinder to the crankcase.

Cooling fins

Thin ribs that carry heat from the surface of the cylinder into the air.

Cylinder bore

The inside diameter of the cylinder barrel.

Choke bore cylinder

A cylinder with a slightly smaller diameter at the top portion than at the skirt.

Cylinder wall

The shiny, well-polished inside surface of the cylinder barrel.

Nitriding

A form of case hardening that changes the surface strength of the cylinder walls.

Cylinder honing

The process of roughening the cylinder surface in a specified crosshatch pattern.

Chrome plating

A method of hardening a cylinder by applying a thin coating of chromium to the inside of the cylinder barrel.

Electroplating

The process used to chrome plate a cylinder bore.

Cylinder head

Acts as a lid on the cylinder barrel and provides an enclosed chamber for combustion.

Spark plug inserts

Threaded bushings that are screwed and shrunk into the cylinder head for spark plug installation.

Intake port

Passage for fuel/air mixture to enter the cylinder during the intake stroke.

Exhaust port

Passage for exhaust gases to exit the cylinder during the exhaust stroke.

Valve guide

Prevents the poppet valve from getting off axis during operation.

Rocker arm

Absorbs the lifting force of the push rod to open and close the poppet valve.

Rocker arm bosses

Support and give strength to the rocker shaft.

Rocker arm pin

Acts as a pivot for the rocking arm action of a rocker arm.

Valve seat insert ring

Ensures no leakage of compressed air during power and compression strokes.

Priming line

Passage for injected raw fuel directed into the cylinder for an easy engine start.

Intake valve

Controls the amount of fuel/air mixture entering the cylinder.

Exhaust valve

Allows exhaust gases to exit the cylinder.

Poppet valve

A T-shaped valve with a circular head.

Flat head valve

A poppet valve with a flat head, typically used on intake valves.

Semi-tulip valve

A poppet valve with a slightly concave area on its head.

Tulip valve

A poppet valve with a deep wide indented area on its head.

Mushroom valve

A poppet valve with a convex head.

Valve face

The portion of the poppet valve that forms a seal with the valve seat.

Valve stem

The portion of a poppet valve that rides in the valve guide.

Valve neck

Joins the valve stem to the valve head.

Valve head

The part of a vertically opening valve that opens and closes the valve.

Valve springs

Helically wound steel wire springs used to close the poppet valves.

Valve spring retainer

Installed on top of the valve springs to hold them in place.

Split valve key

Used to lock the valve spring retainer to the valve stem.

Valve float

Occurs when the frequency of a valve spring causes vibration at its resonance frequency.

Camshaft

A gear-driven shaft with lobes used to operate the intake and exhaust valves.

Cam ring

A ring or plate with lobes ground around its periphery.

Cam lobe

An eccentric used to change rotary motion into linear motion.

Valve lifter

Component that rides on the camshaft or cam ring and pushes against the push rod.

Solid lifter

A solid metal cylinder that transmits the lifting force from the camshaft to the pushrod.

Hydraulic lifter

Uses oil pressure to cushion the impact of the cam lobe striking the lifter.

Push rod

Transmits the movement of the cam to the rocker arm to open the valves.

Valve clearance

The space between the tip of the valve stem and the rocker arm face.

Propeller shafts

Shaft used to transmit power from the engine to the propeller.

Tapered propeller shafts

Shaft that tapers in diameter towards the end.

Splined propeller shafts

Shaft with rectangular grooves for attaching the propeller.

Flanged propeller shafts

Shaft with a flat flange at the end for bolting the propeller.

Engine identification

Code consisting of letters and numbers to identify the engine type and features.

Crankcase

Part of the engine that houses the crankshaft and other internal components.

Plain bearings

Bearings made of nonferrous metals used in aircraft engines.

Safety circlets

Rings installed on valve stems to prevent valves from falling into the combustion chamber.

Multiple valve springs

Used to dampen vibrations at different engine speeds.

Hardened cylinder walls

Achieved through processes like nitriding and chrome plating.

Valve stem groove

Allows for the installation of safety circlets or spring rings.

Nonferrous bearing materials

Materials such as silver, bronze, aluminum, and various alloys used in plain bearings.

Abnormal wear indication

Presence of nonferrous bearing materials in the oil sump and on the surface of the oil filter.