| Home | Privacy | Contact |

Pilot's Handbook of Aeronautical Knowledge
Aircraft Structure

Types of Aircraft Construction

| First | Previous | Next | Last |

Pilot's Handbook of Aeronautical Knowledge



Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making




Engine compartment
Figure 2-13. Engine compartment.

is to streamline the flow of air around the engine and to help
cool the engine by ducting air around the cylinders.

The propeller, mounted on the front of the engine, translates
the rotating force of the engine into thrust, a forward acting
force that helps move the airplane through the air. The
propeller may also be mounted on the rear of the engine as
in a pusher-type aircraft. A propeller is a rotating airfoil that
produces thrust through aerodynamic action. A low pressure
area is formed at the back of the propeller's airfoil, and high
pressure is produced at the face of the propeller, similar to the
way lift is generated by an airfoil used as a lifting surface or
wing. This pressure differential pulls air through the propeller,
which in turn pulls the airplane forward.

There are two significant factors involved in the design of
a propeller which impact its effectiveness. The angle of a
propeller blade, as measured against the hub of the propeller,
keeps the angle of attack relatively constant along the span
of the propeller blade, reducing or eliminating the possibility
of a stall. The pitch is defined as the distance a propeller
would travel in one revolution if it were turning in a solid.
These two factors combine to allow a measurement of the
propeller's efficiency. Propellers are usually matched to a
specific aircraft/powerplant combination to achieve the best
efficiency at a particular power setting, and they pull or push
depending on how the engine is mounted.


The subcomponents of an airplane include the airframe,
electrical system, flight controls, and brakes.

The airframe is the basic structure of an aircraft and is designed
to withstand all aerodynamic forces, as well as the stresses
imposed by the weight of the fuel, crew, and payload.

The primary function of an aircraft electrical system is to
generate, regulate, and distribute electrical power throughout
the aircraft. There are several different power sources on
aircraft to power the aircraft electrical systems. These power
sources include: engine-driven alternating current (AC)
generators, auxiliary power units (APUs), and external power.
The aircraft's electrical power system is used to operate the
flight instruments, essential systems such as anti-icing, etc.,
and passenger services, such as cabin lighting.

The flight controls are the devices and systems which govern
the attitude of an aircraft and, as a result, the flightpath
followed by the aircraft. In the case of many conventional
airplanes, the primary flight controls utilize hinged, trailingedge
surfaces called elevators for pitch, ailerons for roll, and
the rudder for yaw. These surfaces are operated by the pilot
in the flight deck or by an automatic pilot.

Airplane brakes consist of multiple pads (called caliper pads)
that are hydraulically squeezed toward each other with a
rotating disk (called a rotor) between them. The pads place
pressure on the rotor which is turning with the wheels. As
a result of the increased friction on the rotor, the wheels
inherently slow down and stop turning. The disks and brake
pads are made either from steel, like those in a car, or from a
carbon material that weighs less and can absorb more energy.
Because airplane brakes are used principally during landings
and must absorb enormous amounts of energy, their life is
measured in landings rather than miles.

Types of Aircraft Construction

The construction of aircraft fuselages evolved from the early
wood truss structural arrangements to monocoque shell
structures to the current semimonocoque shell structures.

Truss Structure

The main drawback of truss structure is its lack of a
streamlined shape. In this construction method, lengths of
tubing, called longerons, are welded in place to form a wellbraced
framework. Vertical and horizontal struts are welded
to the longerons and give the structure a square or rectangular
shape when viewed from the end. Additional struts are needed
to resist stress that can come from any direction. Stringers
and bulkheads, or formers, are added to shape the fuselage
and support the covering.