(d)
You can install a Click Patch only after you make sure there are no structural cracks in the applicable area of the fuel leak.
(e)
The maximum size of a Click Patch is 1.25 inches (31.75 mm) in diameter.
(f)
A Click Patch is a temporary repair and you must make a permanent repair when possible.
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(5)
To apply a fillet seal to a sealed fastener, do these steps:
(a)
Apply a precoat of correctly accelerated BMS 5-26 Type II Class A-2 sealant to the fastener and the area 1/2 inch in width in all directions from the fastener.
NOTE: Precoat is optional when you use Pro-Seal 860, B 1/6
____
sealant.
1) Use a stiff, bristled brush to apply the precoat on the surfaces and into crevices. 2) Let the precoat dry until it is not tacky.
(b)
Use a sealing gun or spatula and apply a layer of BMS 5-45 Class B sealant (or equivalent) sealant around and on the fastener.
(c)
Move the sealant with a sealant fairing tool until you get the dimensions shown in (Fig. 811) for the fillet seal.
(d)
Examine the sealant for holes, bubbles, or spaces.
(e)
If there are holes, bubbles or spaces, do the procedure again.
(f)
If it is necessary, do this task: Apply the Corrosion Resistant Finish (Topcoat) (AMM 28-11-00/701).
S 398-256
(6)
Repair fasteners with metal seal covers.
(a)
Use a sealant cutting tool (Fig. 801) to cut around and below the metal seal cover and to move apart the sealant from the structure.
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A 747-400 MAINTENANCE MANUAL
(b) Hold the metal seal cover with pliers and pull away from the fastener.
NOTE:____ This will remove most of the sealant.
(c) Cut and remove the remaining sealant.
NOTE:____ You do not have to removal small quantities of the sealant that bond tightly to the fastener.
(d) (e) Clean the metal seal covers, fastener ends, and structure with cleaning solvent.Apply precoat to the area with BMS 5-26 Type II Class A-2 sealant.
NOTE:____ Precoat is optional when you use Pro-Seal 860, B 1/6 sealant.
1) Apply the precoat smoothly and equally into all the crevices.
(f) (g) (h) (i) Select a metal cover which has the correct size and shape for the repair.Fill the metal seal cover two-thirds full of BMS 5-45 Class B sealant (or equivalent) with a sealing gun or a clean spatula (Fig. 812).Make sure there is sufficient sealant to be extruded around the base and through the hole in the top of the metal seal cover.Push the sealant in the metal seal cover to make sure there are no holes.
(j) (k) Push the metal seal cover on the fastener until the metal seal cover touches the structure (Fig. 812).Move the extruded sealant around the top of the metal seal cover and remove the unwanted sealant.
NOTE:____ Use clean cheesecloth to rub the sealant fairing tool.
(l) Hold the metal seal cover in its position and move the extruded sealant around the base.
(m) 1) Keep the metal seal cover on the center of the bolt. 2) Do not let the metal seal cover move.If there is not sufficient clearance with adjacent metal seal covers, structures, or fillet seal, you can remove 25% or less of the area of the metal seal cover.
(n) (o) Make sure the metal seal cover has the dimensions shown in (Fig. 813).If it is necessary, do this task: Apply the Corrosion Resistant Finish (Topcoat) (AMM 28-11-00/701).
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
28-11-00
ALL ú ú 01 Page 835 ú Oct 18/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
S 398-257
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