NAVAIR 01-1A-509-3
01 March 2005
TM 1-1500-344-23-3
TO 1-1-689-3
CHAPTER 3
INSPECTION AND CORROSION PRONE AREAS
bundle can carry moisture into the avionic equipment
3-1. CORROSION PRONE AREAS.
housing via an electrical connector backshell. Military
3-1.1. GENERAL. There are certain corrosion-prone
aircraft are generally susceptible to moisture and other
areas common to all aircraft. For example, the bilge
fluid intrusion originating from the following sources:
area of an airframe is particularly susceptible to
moisture intrusion. This area is where cable runs, wire
a. Rainstorms
bundles, coaxial cables, lights, and antenna are
installed. It is almost impossible to seal the equipment
b. Water washdown systems
and components in this area against moisture and fluid
intrusion. Even though the bilge is a rather obvious
c. Hand washing cycles
problem area, there are other areas of concern, such
as structural, electromechanical, and electronic
d. Sea water spray
components.
e. Environmental control systems
3-1.1.1. Frequent inspections and spot checks are
fundamental to the preventive maintenance aspects of
f. Hydraulic, fuel, and engine oil, anti-icing and
an avionic corrosion control program. . This should be
coolant line leaks
done by personnel familiar with the detection, analysis,
and treatment of corrosion and microbial attack.
g. Condensation from cyclic temperature and
pressure variation
3-1.1.2. The most useful tool for detection of corrosion
is the human eye. Visual inspection can usually reveal
h. Emergency firefighting materials
the existence of corrosion and microbial attack in their
initial stages. This is usually when corrosion treatment
i. Solvents, detergents, strippers, and other
is relatively easy. When corrosion or microbial attack
cleaning materials
is apparent, a specific and immediate program for
corrective treatment involves paint and/or surface
3-1.3. STRUCTURAL. Parts including housings,
coating removal and cleaning. In addition, removal of
covers, supports, brackets, cabinets, and chassis are
corrosion/fungus, restoration of surfaces, and prompt
required for structural support. Corrosion on these
application of protective coatings/paint finishes are
parts should be treated to eliminate long term
also required. Each type of corrosion has its own
deterioration. Severe corrosion usually results from
peculiarities and requires special treatment.
coatings failure and subsequent attack on exposed
metal. The corrosion is caused by handling or
3-1.2. MOISTURE AND OTHER FLUID INTRUSION
environmental attack such as moisture and/or microbial
SOURCES. The flexible airframe of modern military
contamination. Major repairs should be performed at
aircraft prevents effective sealing. Equipment bay
Depot level. Preventive maintenance, corrosion control,
doors, access panels, ducts, static pressure sensors,
and touchup procedures may be accomplished at the
and other fuselage openings allow moisture intrusion.
Intermediate maintenance level. Organizational/Unit
As a result, moisture and other fluids pool in water-
maintenance level can provide minor assistance with
traps or bilge areas not designed for their presence. In
these procedures.
addition, the mission profile, mode of operation, and
field climatic exposure extremes compound any
3-1.4. ELECTROMECHANICAL. Motion is an integral
p r o b l e m s associated with the inadequate
function of electromechanical switches, relays,
environmental integrity of the airframe. When water
potentiometers, motors, generators, and synchro parts.
penetrates the airframe, these lines and cables help
Failure of these parts normally does not occur during
direct moisture and fluid contaminants to avionic
operation. The friction tends to keep the critical surfaces
equipment and components. A simple hydraulic line
clean enough to permit operation. Storage or nonuse
can direct water many feet through the airframe and
in certain environments tends to promote corrosion of
deposit it on equipment. This often occurs in areas of
these parts. The principle causes of malfunction are
the airframe that are assumed to be protected. A wire
dust, condensates, resultant corrosion products