manipulating and adjusting the spray gun. Spray guns
are usually classed as either suction feed or pressure
feed. The types are divided by two methods--the type
of container used to hold the paint material and the
method in which the paint is drawn through the air cap
assembly.
SUCTION FEED.--The suction-feed spray gun is
designed for small jobs. The container for the paint is
connected to the spray gun by a quick-disconnect
fitting, as shown in figure 5-33. The capacity of this
container is approximately 1 quart. The fluid tip of this
type of spray gun protrudes through the air cap, as
shown in figure 5-34. The air pressure rushing past the
fluid tip causes a low-pressure area in front of the tip.
This causes paint to be drawn up through the fluid tip,
where it is atomized outside the cap by the air pressure.
PRESSURE FEED.--The pressure-feed spray
gun is designed for use on large jobs where a large
amount of spray material is to be used. The spray
material is supplied to the gun through a hose from a
Figure 5-33.--Suction-feed spray gun.
pressurized tank. This spray gun is designed to operate
on high-volume, low-pressure air. This type of
nonreflective material and meet the gloss requirements
equipment eliminates the evaporation of the volatile
of the coating system. Decals should not be used to
substances of the mixture before striking the surface
apply large markings, such as the national insignia. The
because the paint and air are mixed in the tanks. In other
use of MIL-C-83286 is not required to apply aircraft
words, a wetter coating is applied.
unit markings.
Spray Gun Maintenance
PAINTING EQUIPMENT AND
MAINTENANCE PROCEDURES
Fluid leakage at the front of the gun is an indication
that the fluid needle is not seating properly. This may be
The equipment and techniques used to paint
caused by a fleck of dried material in the nozzle, or the
aircraft are covered here. You will frequently use and
fluid needle packing may be too tight. It may also be
maintain spray guns, air compressors, and regulators.
caused by a bent fluid needle, a broken fluid needle
spring, or the wrong size fluid needle for the fluid tip.
Spray Guns
Air leakage results from an improperly set air
valve. This may be caused by a bent valve stem, broken
The spray gun atomizes the material to be sprayed.
spring, or damaged valve or valve seat.
You direct and control the spray pattern by
Figure 5-34.--Suction and pressure fluid tips and air caps.
5-33
