Technical data

or hook and loop mounted surface conditioning disc, or a disc
fabricated from an abrasive cloth sheet. Use sanders and
grinders attached to high efficiency vacuum systems for dust
recovery. Keep sander heads approximately flush against the
surfaces being sanded and apply the least amount of pressure
necessary to accomplish feathering of the paint.
NOTE
It is essential that a formal maintenance/repair
schedule be instituted for the high efficiency
vacuum units. Replace bags in vacuum units after
each aircraft or large part has been sanded. Do
not use vacuums when the hoses have holes or
tears. Use the minimum length of hose attached
to vacuum units to ensure the highest airflow
rates through the vacuum. Use the vacuum at the
manufacture’s recalls compressed air pressure.
3.1.2.3 Scuff-sand the surface of other area(s) adjacent to
the damaged coatings that are to be coated using abrasive
paper no coarser than 120 grit, 3M Corp medium grade
aluminum oxide surface conditioning disc, or A-A-58054,
Type I, Class 1, Grade C abrasive mat. Use of a random
orbital sander or a pneumatic drill motor fitted with the
surface conditioning disc is preferred.
3.1.2.4 After the finish system has been sanded, use HEPA
vacuums with appropriate attachments to vacuum dust from
aircraft and facility floors. Do not use compressed air unless
absolutely necessary to remove dust from very narrow cracks
and crevices.
3.1.3 Scuff Sanding For Overspraying Existing Coat-
ing Systems On Aircraft. It is always better to start a paint
system from bare metal, however, when authorized in Chap-
ter 8, it is feasible to overspray existing paint systems.
NOTE
Adhesion failure between coatings will require
complete removal of the non-adhering coating.
When intercoat adhesion failure occurs over large
areas, overcoating shall not be accomplished and
complete strip/repaint is required.
3.1.3.1 Aircraft exterior painted surfaces shall initially be
cleaned in accordance with TO 1-1-691 and thoroughly
inspected to determine the soundness the paint film. Areas of
severely deteriorated paint as indicated by loose or peeling
paint, contamination from hydraulic oil, engine oil, fuel or
other fluids, or where bare metal is showing, shall be stripped
per Chapter 2 of this manual.
3.1.3.2 Mask all areas which may be damaged by entry of
fluids or paint dust generated during the cleaning and scuff
sanding operations per Chapter 2 of this manual.
3.1.3.3 Prepare the surface for overcoating by scuff
sanding as follows:
• Sanding of finish systems using motor-driven
abrasives can generate airborne particles and
toxic dust that can injure personnel and create
a possible dust explosion from paint and
abrasive material dust. Work pieces and mo-
torized equipment shall be properly electri-
cally grounded. When using motor driven
abrasives the minimum required personnel
protective equipment shall be dust/particulate
respirator, goggles/face shield, disposable ni-
trile rubber gloves, and cloth coveralls with
paint sock or hooded Tyvek coveralls and
non-slip rubberized foot coverings. Do not
stand above, below or directly next to other
workers. Avoid being “downwind” from oth-
ers using mechanical sanders. Consult Bioen-
vironmental Engineering Services for respira-
tory and ventilation requirements.
• Do not mount an abrasive on a motor driven
tool having an operational speed higher than
the maximum RPM rating of the abrasive.
This can result in disintegration of the abrasive
and can cause injury to personnel
NOTE
Requirements for vacuuming of sanding dusts
may be waived by local Bioenvironmental Engi-
neering, Industrial Hygienists, or the OPR for
corporate safety/health only after approval of
alternative measures for personnel protection.
3.1.3.3.1 Completely scuff-sand the entire exterior surface
of the aircraft, excluding bare metal areas, using abrasive
paper no coarser than 120 grit, 3M Corp medium grade
aluminum oxide surface conditioning disc, or A-A-58054,
Type I, Class 1, Grade C abrasive mat. Scuff sanding shall
include roughing up 100% of the painted surface, removal of
oxidized paint, and feather-edging of all flaked paint. It is not
intended to remove a sound paint system. Light scuffing is
sufficient for adhesion of the primer tie-coat to a sound
topcoat. Do not sand through to bare metal as damage to the
aircraft may occur. All areas where the paint system is nicked,
scratched, or chipped and any edges of the paint system
around areas where paint removal was done are to be
feathered-out (blended smooth) during the sanding operation
per Paragraph 3.1.2. All sanding operations should be accom-
plished using either a random orbital tool or pneumatic drill
motor (12,000 RPM max) fitted with a roloc or hook and loop
mounted surface conditioning disc, or a disc fabricated from
an abrasive cloth sheet. Use sanders and grinders attached to
high efficiency vacuum systems for dust recovery. Keep
sander heads approximately flush against the surfaces being
sanded and apply the least amount of pressure necessary to
accomplish feathering of the paint.
TO 1-1-8
3-2