(17) 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
For a neat job, use masking tape to mask the topside of the PPT sheet
1/32 inch inside the perimeter of the edge.
The application of edge sealant is particularly important in maintaining
3M 8663 polyurethane protective tape integrity when applied at butt joints
of adjacent PPT.
(18) Assemble a nozzle and a cartridge on the 3M EPX applicator. Squirt out a small quantity to
insure that a uniform mix is attained. Using the nozzle, apply a 1/8 inch bead around the perimeter of
the 3M 8663 polyurethane protective tape panel. Allow this to set up for about 10 minutes, before
removing the tape. The sealant should still be liquid.
For best results: To allow the edge of the sealant bead to blend with
the 3M 8663 polyurethane protective tape and paint. Higher tempera-
tures will require less time for the sealant to gel. Lower temperatures
will require more time for the sealant to gel, so some adjustment in
the 10 minutes may be necessary. The objective is to get the masking
tape off while the bead of sealant is still flowable, to let it blend
without a sharp edge.
(19) Inspect the edge seal application for any small air bubbles and if any are found, they can be
relieved by pricking with a hypodermic needle.
(20) The rotor blade is ready to return to service after the sealant is well cured, and the 3M 8663
polyurethane protective tape has had time to reach a acceptable level of adhesion. This is achieved
after 24 hours at 72 degrees.
d. Blade Installation. If necessary, install main rotor blades per -23 TM.
e. Polyurethane Curing. After polyurethane application, allow 24 hours curing time.
f. Tape Repair. Replace the entire damaged piece of tape. Remove with a plastic scraper. Replace
per the installation instructions.
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.