| 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




As technology progressed, aircraft designers began to enclose
the truss members to streamline the airplane and improve
performance. This was originally accomplished with cloth
fabric, which eventually gave way to lightweight metals such
as aluminum. In some cases, the outside skin can support all
or a major portion of the flight loads. Most modern aircraft
use a form of this stressed skin structure known as monocoque
or semimonocoque construction. [Figure 2-14]

Semimonocoque and monocoque fuselage design
Figure 2-14. Semimonocoque and monocoque fuselage design.


Monocoque construction uses stressed skin to support almost
all loads much like an aluminum beverage can. Although
very strong, monocoque construction is not highly tolerant
to deformation of the surface. For example, an aluminum
beverage can supports considerable forces at the ends of
the can, but if the side of the can is deformed slightly while
supporting a load, it collapses easily

Because most twisting and bending stresses are carried by
the external skin rather than by an open framework, the need
for internal bracing was eliminated or reduced, saving weight
and maximizing space. One of the notable and innovative
methods for using monocoque construction was employed by
Jack Northrop. In 1918, he devised a new way to construct
a monocoque fuselage used for the Lockheed S-1 Racer.
The technique utilized two molded plywood half-shells that
were glued together around wooden hoops or stringers. To

construct the half shells, rather than gluing many strips of
plywood over a form, three large sets of spruce strips were
soaked with glue and laid in a semi-circular concrete mold
that looked like a bathtub. Then, under a tightly clamped lid, a
rubber balloon was inflated in the cavity to press the plywood
against the mold. Twenty-four hours later, the smooth half shell
was ready to be joined to another to create the fuselage.
The two halves were each less than a quarter inch thick.
Although employed in the early aviation period, monocoque
construction would not reemerge for several decades due to
the complexities involved. Every day examples of monocoque
construction can be found in automobile manufacturing where
the anybody is considered standard in manufacturing.


Semimonocoque construction, partial or one-half, uses a
substructure to which the airplane's skin is attached. The
substructure, which consists of bulkheads and/or formers
of various sizes and stringers, reinforces the stressed skin
by taking some of the bending stress from the fuselage. The
main section of the fuselage also includes wing attachment
points and a firewall On single-engine airplanes, the engine is
usually attached to the front of the fuselage. There is a .reproof
partition between the rear of the engine and the flight deck or
cabin to protect the pilot and passengers from accidental engine
.res. This partition is called a firewall and is usually made
of heat-resistant material such as stainless steel. However,
a new emerging process of construction is the integration of
composites or aircraft made entirely of composites.

Composite Construction


The use of composites in aircraft construction can be dated
to World War II aircraft when soft fiberglass insulation was
used in B-29 fuselages. By the late 1950s, European high
performance sailplane manufacturers were using fiberglass
as primary structures. In 1965, the FAA type ceritfied the
first all-figerglass aircraft in the normal category, a Swiss
sailplane called a Diamanté HBV. Four years later, the FAA
ceritfied a four-seat single-engine Win decker Eagle in the
normal category. By 2005, over 35 percent of new aircraft
were constructed of composite materials.

Composite is a broad term and can mean materials such as
fiberglass, carbon fiber cloth, Kevlar© cloth, and mixtures
of all of the above. Composite construction offers two
advantages: extremely smooth skins and the ability to
easily form complex curved or streamlined structures.
[Figure 2-15]