Basic Aircraft Systems


The basic information on principles, fundamentals, and technical procedures in the subject matter areas relating to the powerplant rating and contains an explanation of the units that make up each of the systems that bring fuel, air, and ignition together in an aircraft engine for combustion. It also contains information on engine construction features, lubrication systems, exhaust systems, cooling systems, cylinder removal and replacement, compression checks, and valve adjustments. Because there are so many different types of aircraft in use today, it is reasonable to expect that differences exist in airframe components and systems.

An aircraft engine, or powerplant, produces thrust to propel an aircraft. Reciprocating engines and turboprop engines work in combination with a propeller to produce thrust. Turbojet and turbofan engines produce thrust by increasing the velocity of air flowing through the engine. All of these powerplants also drive the various systems that support the operation of an aircraft.

Aircraft Engines

Most small aircraft are designed with reciprocating engines. The name is derived from the back-and-forth, or reciprocating, movement of the pistons that produces the mechanical energy necessary to accomplish work. An aircraft turbine engine consists of an air inlet, compressor, combustion chambers, a turbine section, and exhaust. Thrust is produced by increasing the velocity of the air flowing through the engine. Turbine engines are highly desirable aircraft powerplants. 

Engine Fuel and Fuel Metering Systems

The engine fuel system supply fuel to the engine’s fuel metering device under all conditions of ground and air operation. The engine fuel system usually includes the engine-driven pumps and the fuel metering systems.

Induction and Exhaust Systems

The induction system brings in air from the outside, mixes it with fuel, and delivers the fuel-air mixture to the cylinder where combustion occurs.

Ignition and Electrical Systems

In a spark ignition engine, the ignition system provides a spark that ignites the fuel-air mixture in the cylinders and is made up of magnetos, spark plugs, high-tension leads, and an ignition switch.

Engine Starting Systems

Most aircraft engines, reciprocating or turbine, require help during the starting process. Hence, this device is termed the starter.

Lubrication and Cooling Systems

The purpose of a lubricant is to reduce friction between moving parts. Because liquid lubricants or oils can be circulated readily, they are used universally in aircraft engines.


The propeller is a rotating airfoil, subject to induced drag, stalls, and other aerodynamic principles that apply to any airfoil. It provides the necessary thrust to pull, or in some cases push, the aircraft through the air.

Engine Removal and Replacement

Procedures for removing or installing an aircraft engine usually vary widely with the type of aircraft and the type of engine. 

Engine Fire Protection Systems

Because fire is one of the most dangerous threats to an aircraft, the potential fire zones of all multiengine aircraft currently produced are protected by a fixed fire protection system.

Engine Maintenance and Operation

Both maintenance and complete engine overhauls are performed normally at specified intervals. This interval is usually governed by the number of hours the powerplant has been in operation.


The basic information on principles, fundamentals, and technical procedures in the subject matter areas relating to the airframe rating and contains information on airframe construction features, assembly and rigging, fabric covering, structural repairs, and aircraft welding. This section also contains an explanation of the units that make up the various airframe systems. Because there are so many different types of aircraft in use today,

Aircraft Structures

The history of aircraft structures underlies the history of aviation in general. Advances in materials and processes used to construct aircraft have led to their evolution from simple wood truss structures to the sleek aerodynamic flying machines of today. 

Aerodynamics, Aircraft Assembly, and Rigging

Three topics that are directly related to the manufacture, operation, and repair of aircraft are: aerodynamics, aircraft assembly, and rigging. 

Aircraft Fabric Covering

Fabric-covered aircraft play an important role in the history of aviation. The use of fabric covering on an aircraft offers one primary advantage: light weight. In contrast, fabric coverings have two disadvantages: flammability and lack of durability.

Aircraft Metal Structural Repair

It is important that metal structural repairs be made according to the best available techniques because improper repair techniques can pose an immediate or potential danger.

Aircraft Electrical System

The satisfactory performance of any modern aircraft depends to a very great degree on the continuing reliability of electrical systems and subsystems.

Aircraft Instrument Systems

Since the beginning of manned flight, it has been recognized that supplying the pilot with information about the aircraft and its operation could be useful and lead to safer flight.

Communication and Navigation

Avionics is a conjunction of the words aviation and electronics. It is used to describe the electronic equipment found in modern aircraft.

Hydraulic and Pneumatic Power Systems

The word “hydraulics” is based on the Greek word for water and originally meant the study of the physical behavior of water at rest and in motion. Hydraulic systems in aircraft provide a means for the operation of aircraft components.

Landing Gear Systems

Aircraft landing gear supports the entire weight of an aircraft during landing and ground operations. They are attached to primary structural members of the aircraft. 

Aircraft Fuel System

All powered aircraft require fuel on board to operate the engine(s). A fuel system consisting of storage tanks, pumps, filters, valves, fuel lines, metering devices, and monitoring devices. 

Ice and Rain Protection

Rain, snow, and ice are transportation’s longtime enemies. Flying has added a new dimension, particularly with respect to ice. 

Cabin Environmental Control Systems

Crew and passengers use oxygen systems, in conjunction with pressurization systems, to prevent hypoxia. Pressurized aircraft that use air cycle air conditioning systems mix bleed air with cold air produced by the air cycle machine expansion turbine to obtain warm air for the cabin. 

Fire Protection Systems

A fire zone is an area, or region, of an aircraft designed by the manufacturer to require fire detection and/or fire extinguishing equipment and a high degree of inherent fire resistance.
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