(9) Tape Application. 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
aligned 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. Apply the remaining
pieces of tape shown in figure 3-22 in the same manner. 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.
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 roughness
must be sanded off the surface using 400 grit sandpaper. Simply, the sur-
face should be at least as smooth as you can get it by sanding with 400
(11) Clean the surface by rinsing with isopropyl alcohol and wiping dry with clean untreated paper towels
(12) 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.
(13) Cut a sheet of 8663 polyurethane protective tape (PPT) to the size of the area to be covered
leaving a margin of 1/8 inch around the perimeter. This margin will later be used for application of the edge
sealant around the perimeter of the PPT sheet.
(14) Prepare a "wetting" solution as follows: To a pint sized spray bottle, add 2 drops of liquid
dishwashing detergent and 1/2 cup of isopropyl alcohol and fill the bottle with clean water. (The actual
mixture is: 75% water, 25% isopropyl alcohol and 2 drops of liquid dishwashing detergent per one liter of
(15) Remove the liner from the sheet of PPT. Liberally spray the adhesive side with "wetting
solution" that was prepared in step #4 above. Also spray the surface of the part to which the PPT is to
(16) Carefully position the PPT on the part. Use a plastic squeegee, starting at the middle of the
sheet, and remove the wetting solution from beneath the PPT sheet, by using long overlapping strokes.
If you should trap an air bubble, lift an edge to allow the bubble to be removed. When the edge is lifted,
respray with more "wetting solution" to insure that no air is trapped under the PPT. Use a clean rag to
mop up the excess water solution at the edges to prevent the water solution from "wicking" back under