Figure 809
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(9) Apply a faying surface seal, if it is necessary. NOTE: As an alternative procedure, you can lift (move) the seal
____
plane to isolate the bad seal from the fuel.
(a) Apply a layer of BMS 5-26, Type II, Class B sealant to one mating surface with a sealing gun or spatula (Fig. 811).
WING SPAR
WING RIB
CAP SEALED FASTENER
FILLET SEALS ARE ALONG STRUCTURAL JOINTS
THE FITTING MUST BE TEMPORARILY REMOVED AND CLEANED OF USED SEALANT BEFORE YOU APPLY A NEW PREPACK SEAL
Example of a Combination of Prepack Seal and Fillet Seals
Figure 810
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(b)
Move the sealant on all of the surface to get a smooth layer approximately 0.03 inch thick (Fig. 811).
(c)
Assemble the parts in the sealant usable time (Fig. 801).
NOTE: The squeeze-out life (Fig. 801) is the maximum time
____ you can use the sealant to assembly the structure when you apply the mating surface sealant. If the sealant was frozen, it is the maximum time between when you start to thaw the sealant and when you attach of the mating surfaces. If the sealant was not frozen, it is the time between when the you mix the sealant and when you attach the mating surfaces.
(d) Make the sealant that comes out of the joint smooth.
NOTE: You must apply a sufficient quantity of sealant to
____ make sure a continuous bead of the sealant comes out of the two sides of the joint.
(e) If it is necessary, do this Task: Application of Corrosion Resistant Finish (Topcoat) (AMM 28-11-00/701).
NOTE: A layer of corrosion resistant finish is necessary
____ only to protect bare (anodized) metal. It is not necessary to apply a layer of corrosion resistant finish on sealant. Corrosion resistant finish can be applied on sealant, but it is not necessary. Usually topcoat is applied to sealant only when it must be applied to protect adjacent bare metal.
L. Lift the Seal Plane (Fig. 812)
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(1) This procedure is an alternative procedure to repair leaks in these types of seals:
NOTE: It is a better procedure to replace the seal that has the
____ leak because you add a large quantity of sealant when you lift the seal plane.
(a) An injection seal
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(b)
A mating surface seal
(c)
A prepack seal.
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(2) Examine the structure around the bad seal to find where to lift the seal plane.
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CAUTION: DO NOT APPLY SEALANT ON A LAYER OF FINISH THAT IS NOT HEAT
_______ CURED (BAKED ON) BMS 10-20, TYPE II. SEALANT WILL NOT STAY IN PLACE IF IT THE PRIMER IS NOT HEAT CURED. THIS CAN CAUSE FUEL LEAKAGE.
(3) Apply a new fillet seal around the structure with the applicable seals and fasteners to lift the seal plane (Fig. 812).
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