S 397-019
(4) Apply PR 1422, class B sealant over class A sealant:
(a) Follow the sealant manufacturer's instructions to mix the sealant. Ratios to mix the sealant by volume are as follows:
PR 1422, Class A - 1 part A (accelerator) to 10 parts B (base)
PR 1422, Class B - 1 part A (accelerator) to 7-1/2 parts B (base)
NOTE: You can get PR1422 class A and B with a working lifeof
____ 1/2 or 2 hours. Mix the quantity that you can use in the working life of the sealant.
(b) Apply PR 1422, class B sealant on class A sealant with an extrusion gun or a spatula. Fair out the sealant with a fairing tool, plastic scraper or a duckbill nozzle. Make sure the surface of the sealant is below the surface of the adjacent wing skin. Use a spatula or a fairing tool to move air out of the sealant.
NOTE: If it is necessary, you can apply a heavy layer of
____ PR 1422 class B sealant above the level of the wing surface. Let the sealant cure. Cut the cured sealant to a height that is level with the wing surface. Use a knife made from 2024 aluminum sheet.
(c) Let the sealant cure as follows:
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A
747-400 MAINTENANCE MANUAL
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(d) To smooth and fair out the cured sealant, rub the surface with a fine abrasive paper, cloth (aluminum oxide grit), or with a gum rubber buffing wheel.
NOTE: Repair all alodine finish that is damaged by the above
____
procedure.
S 397-020
(5) Apply the PR 1432GP sealant:
NOTE: Use PR 1432GP sealant for locations that must have a large
____
repair.
(a)
Apply the PR 1432GP sealant to the fastener rows in the wing and horizontal stabilizer at the inspar skin and,
-
at the front and rear spar chords
-
at the spanwise skin splices.
(b)
Use the manufacturer's instructions to mix the sealant. The ratio by volume for the mixture is 1 part A (accelerator) to 15 parts B (base).
NOTE:____PR 1432GP has a working life of 1 hour. Mix the quantity that you can use in the working life of the sealant.
(c)
To apply a large amount of PR 1432GP, spray the sealant until the rework area is fully filled. The sealant must extend over the edge of the repair and blend into the not damaged area.
NOTE: You can apply PR 1432GP sealant with a spray gun and
____ pressure spray equipment. Use an external mix spray gun with an orifice diameter of a minimum of 0.085 inches. An atomizing pressure of approximately 35 psi is necessary. If it is necessary, you can make the PR 1432GP sealant thin. Add 10 percent toluene, by volume, to the base material. Mix the solution and then add the accelerator. Keep the mixture shaken.
(d) Let the sealant to cure as follows:
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747-400 MAINTENANCE MANUAL
~.......................................................... | Temperature | Relative Humidity | Time | ............................................................ | 75°F | 50% | 72 Hours | ............................................................ | 120°F | 50% | 18 Hours | 2..............…............................…..............1
(e) Smooth and fair out the cured sealant by rubbing with a fine abrasive paper, cloth (aluminum oxide grit) or with a gum rubber buffing wheel.
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