The rotor blade must be smooth. Any dirt inclusions or paint
roughness must be sanded off the surface using 400 grit sand-
paper. Simply, the surface should be at least as smooth as you
can get it by sanding with 400 grit sandpaper.
(1) Clean the surface by rinsing with isopropyl alcohol and wiping dry with clean untreated paper
towels or rags.
(2) 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.
(3) 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.
(4) 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
(5) 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
(6) 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
(7) Inspect the installation for lack or air or water bubbles. It is permissible to remove a few small
"blisters" by piercing them with a hypodermic needle, and pressing on the bubble to exclude the
g. Coating Repair. Local damage to the polyurethane coating can be touched up by brushing
additional coating to the damaged area. Carefully remove the disbonded material. Scuff the damaged
area with 120 grit sandpaper. Wipe clean with MEK. Prime the area with AGC 1201-7 primer if the
blade surface is exposed. Coat the damaged area with sufficient coats of polyurethane coating to
match the thickness of adjacent areas. Application of TASK L-100 polyurethane paint to repair minor
damage on agcoat material is authorized for this procedure.
h. Polyurethane Coating Removal. Saturate coating surface with MEK and scrape coating off with a
plastic scraper while soft. Make a final surface wipe with cloth dampened with MEK.
i. Polyurethane Tape Removal. Slowly peel back over itself. Scrape tape with plastic scraper if
necessary. Remove adhesion promoter with cloth dampened with toluene.
j. Track and Balance Check. Check track and balance of main rotor blade per -23 TM.
k. Inspection of Main Rotor Polyurethane Tape.