(11) 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.
(12) 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 temperatures 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.
(13) 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.
(14) 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.
k. Inspection of Main Rotor Polyurethane Tape.
(1) Inspect 2-inch tape for wear. No holes allowed.
(2) Inspect 8-inch tape for wear. No more than 1.0 inch-width hole in any spanwise or chordwise
direction allowed on upper or lower side of blade.
(3) Inspect upper and lower trailing edge of tape for disbonding. No more than 0.25 inch
chordwise width for any spanwise length of tape or 0.5 inch chordwise width for 6 inches spanwise
length along a single piece of tape is allowed.
(4) Inspect for inboard and outboard ends of tape segments for disbonding. No more than 0.5 inch
spanwise or chordwise is allowed.
(5) Inspect for internal disbonding of tape segments. No more than a single disbonding larger than
3.0 inches spanwise and/or 2.0 inches chordwise is allowed. In addition, no more than a total of 6
square inches is allowed for multiple disbonds on a single tape segment. There is no limit to the number
of disbonds per tape segment providing material is not torn.