FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 6. Corrosion, Inspection, and Protection | 13. Corrosion Proofing of Land Planes Converted to Sea Planes | 6-208. Recommended Precautions
9/8/98
AC 43.13-1B
SECTION 13. CORROSION PROOFING OF LAND PLANES
CONVERTED TO SEA PLANES
6-206. GENERAL. A special problem is
encountered in the conversion of land planes to
seaplanes. In general, land planes do not re
ceive corrosion proofing to the same extent as
do seaplanes. Corrosion-proofing standards
for land planes converted to seaplanes are di
vided into two classes, necessary minimum
precautions and recommended precautions.
Regardless of such precautions, it is imperative
that the exterior surfaces of seaplanes be
washed with clear fresh water immediately
following extended water operation, or at least
once a day when operated in salty or brackish
water. Wash interior surfaces of seaplanes ex
posed to spray, taking care to prevent damage
to electrical circuits or other items subject to
injury.
6-207. NECESSARY MINIMUM PRE-
CAUTIONS. The following procedures are
considered the minimum to safeguard the air
worthiness of converted aircraft and are not in
themselves intended to maintain airworthiness
for an indefinite period.
a. Unless already protected, treat ex
posed fittings or fittings that can be reached
through inspection openings with two coats of
zinc chromate primer, paralketone, nonwater
soluble heavy grease, or comparable materials.
This applies to items such as wing-root fit
tings, wing-strut fittings, control-surface
hinges, horns, mating edges of fittings, and at
tached bolts.
b. Coat non-stainless control cables with
grease or paralketone or other comparable
protective coating, if not replaced with corro
sion-resistant cables.
corrosion and refinish if corrosion attack is su
perficial. If a part is severely corroded, replace
with an adequately corrosion-proofed part.
6-208. RECOMMENDED PRECAUTIONS.
Recommended precautions are those which are
suggested as a means of maintaining such air
craft in condition for safe operation over ex
tended periods.
a. Provide additional inspection openings
to assist in detecting corrosion. Experience
has shown openings to allow inspection of the
lower and rearward portion of the fuselage to
be particularly desirable.
b. Incorporate additional provisions for
free drainage and ventilation of all interiors to
prevent collection of moisture (scoop-type ma
rine drain grommets).
c. Protect the interior of structural steel
tubing. This may be done by air and watertight
sealing or by flushing with hot linseed oil and
plugging the openings. Inspect tubing for
missing sealing screws, presence of entrapped
water, local corrosion around sealing screws,
welded clusters, and bolted fittings, which may
be indicative of entrapped moisture.
d. Slit the fabric of fabric-covered aircraft
longitudinally on the bottom of the fuselage
and tail structure for access to these sections.
Coat the lower structural members with zinc
chromate primer (two coats); follow by a coat
of dope-proof paint or wrap with cellophane
tape and rejoin the fabric. This precaution is
advisable within a few months after start of
operation as a seaplane.
c. Inspect all accessible sections of air
craft structure. Clean structural parts showing
e. Spray the interior of metal-covered
wings and fuselages with an adherent corro
sion inhibitor.
Par 6-206
Page 6-41