the heavy-duty fasteners. Otherwise, their
construction features are about the same.
Figure 2-12 shows the parts of a light-duty Dzus
fastener. Notice that they include a spring and a stud.
The spring is made of cadmium-plated steel music
wire, and is usually riveted to an aircraft structural
member. The stud comes in a number of designs (as
shown in views A, B, and C) and mounts in a dimpled
hole in the cover assembly.
When the panel is being positioned on an aircraft,
the spring riveted to the structural member enters the
hollow center of the stud. Then, when the stud is
turned about one-fourth turn, the curved jaws of the
stud slip over the spring and compress it. The
resulting tension locks the stud in place and secures
Some fasteners cannot be classified as rivets,
turnlocks, or threaded fasteners. Included in this
category are connectors, couplings, clamps, taper and
flat-head pins, snap rings, studs, and heli-coil inserts.
FLEXIBLE CONNECTORS AND COUPL-
INGS.A variety of clamping devices are used in
connecting ducting sections to each other or to
various components. Whenever lines, components, or
ducting are disconnected or removed for any reason,
you should install suitable plugs, caps, or coverings
on the openings to prevent the entry of foreign
materials. You should also tag the various parts to
ensure correct reinstallation.
You should exercise
care during handling and installation to ensure that
flanges are not scratched, distorted, or deformed.
Flange surfaces should be free of dirt, grease, and
corrosion. The protective flange caps should be left
on the ends of the ducting until the installation
progresses to the point where removal is necessary.
In most cases it is mandatory to discard and
replace seals and gaskets. You should ensure that
seals and gaskets are properly seated and that mating
and alignment of flanges are fitted. This will prevent
the excessive torque required to close the joint, which
imposes structural loads on the clamping devices.
Adjacent support clamps and brackets should remain
loose until installation of the coupling has been
Figure 2-12.Dzus fastener.