Wing construction is basically the same in all
types of aircraft. Most modern aircraft have all metal wings, but many older
aircraft had wood and fabric wings. Ailerons and flaps will be studied later in
fig 1 - 5 wood and fabric wing structure
To maintain its all-important aerodynamic shape, a wing must
be designed and built to hold its shape even under extreme stress. Basically,
the wing is a framework composed chiefly of spars, ribs, and (possibly)
stringers (see figure 1-5). Spars are the main members of the wing. They
extend lengthwise of the wing (crosswise of the fuselage). All the load carried
by the wing is ultimately taken by the spars. In flight, the force of the air
acts against the skin. From the skin, this force is transmitted to the ribs and
then to the spars.
Most wing structures have two
spars, the front spar and the rear spar. The front spar is found near the
leading edge while the rear spar is about two-thirds the distance to the
trailing edge. Depending on the design of the flight loads, some of the
all-metal wings have as many as five spars. In addition to the main spars, there
is a short structural member which is called an aileron spar.
The ribs are the parts of a wing which
support the covering and provide the airfoil shape. These ribs are called
forming ribs. and their primary purpose is to provide shape. Some may have an
additional purpose of bearing flight stress, and these are called compression
The most simple wing structures
will be found on light civilian aircraft. High-stress types of military aircraft
will have the most complex and strongest wing structure.
fig 1 - 6 wing and fuselage attachments
Three systems are used to determine how wings
are attached to the aircraft fuselage depending on the strength of a wing's
internal structure. The strongest wing structure is the full cantilever which is
attached directly to the fuselage and does not have any type of external,
stress-bearing structures. The semi-cantilever usually has one, or perhaps two,
supporting wires or struts attached to each wing and the fuselage. The
externally braced wing is typical of the biplane (two wings placed one above the
other) with its struts and flying and landing wires (see figure 1-6).
In order to confer lateral
stability to an aircraft, the wings may be angled upwards from the fuselage
towards the wingtips. This is known as a dihedral. Some wings may be inclined
the opposite way and this is called anhedral and allows aircraft to be very
manoeuvrable, as is needed for military or aerobatic aircraft.