(7) Polyurethane Tape Preparation. Apply alignment marks to outside of tape at the center as
shown in figure 3-1, sheet 2. Peel back one of the center (1-inch wide) backing strips from the 8" wide
tape approximately 3 inches. Make sure tape does not come in contact with promoter until tape is
(8) Tape Alignment. Align the tape in the position shown in figure 3-26 before pressing to blade.
(9) Polyurethane Tape Application, 8 in. Remove leading edge backing strips as shown in figure
3. Apply first piece
to area shown
in figure 3-25. When the tape
is in proper position,
press the exposed portion on the blade as close to the leading edge as possible. Press down on the
tape, working toward the trailing edge to prevent trapping air bubbles. See figure 3-1, sheet 4. Peel
backing strip back while keeping tape signed and pressing down toward the trailing edge. Remove the
backing strips one at a time, working toward the trailing edge. See figure 3-1, sheet 5. Thoroughly
press down tape. Any bubbles encountered during the application process may be removed by
continuous squeegee stroking towards the edge of tape or by puncturing the bubbles with a needle and
applying pressure to the wet adhesive.
Do not puncture bubbles after the adhesive has dried.
(10) Remove masking tape.
(11) Polyurethane Tape Application, 2 in. Scuff the 8 inch wide tape surface with 120 grit
sandpaper in area to be covered by 2 inch wide tape as shown in figure 3-27. Clean tape surface with
MEK. Apply No. 86 promoter as in Step (6). When dry, apply tape as before.
Repeat Steps (6) through (11) for each blade.
The structure to which the polyurethane protective tape, 3M 8663,
is to be applied should be in recent overhaul or new condition. This
means that repairs have been made and the part has been primed
and painted in accordance with the appropriate technical directive
for that part.
The rotor blade must be smooth. Any dirt inclusions or paint rough-
ness must be sanded off the surface using 400 grit sandpaper. Simply,
the surface should be at least as smooth as you can get it by sanding
with 400 grit sandpaper.
(12) Clean the surface by rinsing with isopropyl alcohol and wiping dry with clean untreated paper towels
(13) Using a small clean rag, apply a thin coat of #86A adhesion promoter to the entire area of the rotor
blade that is to be covered with 3M 8663 PPT film. Let the 86A dry 15 minutes, prior to application of 3M
8663 PPT film.