SEALING REPAIRS - DESCRIPTION AND OPERATION

** ON A/C NOT FOR ALL

1. General
Sealants are used on the aircraft structure to stop pressurization and fuel leaks. You must repair the sealant when it has been damaged during maintenance or found damaged on an inspection/check.
For the repair of general sealants Ref. AMM 51-76-11 08.
For the repair of fuel tank sealing Ref. AMM 51-76-12 08.
For more data Ref. ASRM 51-24-00 and ASRM 51-76-00.

** ON A/C NOT FOR ALL

2. Description

A. Terms and Definitions
The table below shows some of the terms used in sealant procedures and their definitions.

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! TERM ! DEFINITION !

!------------------------!----------------------------------------------------!

! Application Life or ! This is the period of time that a sealant remains !

! Pot Life ! suitable for application after it has been mixed. !

!------------------------!----------------------------------------------------!

! Barrier Coating ! A layer of quick-drying sealant that is applied !

! ! over a layer of slow-drying sealant before it has !

! ! fully cured. This term also applies when a layer !

! ! of special material is put over the original !

! ! sealant to protect it. !

!------------------------!----------------------------------------------------!

! Breakable Joint ! A joint that can be easily disassembled. !

!------------------------!----------------------------------------------------!

! Cure ! This refers to the change of a sealant from its !

! ! original mixed condition to its final condition. !

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! TERM ! DEFINITION !

!------------------------!----------------------------------------------------!

! Fillet ! This is formed when sealant is applied into gaps !

! or ! or corners in the structure. The fillet or bead !

! Bead ! can be formed from sealant that is applied for !

! ! this purpose, or from the interfay sealant that !

! ! is squeezed out when a joint is assembled. !

!------------------------!----------------------------------------------------!

! Initial Cure Time ! This is the minimum period of time required before !

! ! a sealant is cured enough to permit a sealed !

! ! joint to be pressure tested. !

!------------------------!----------------------------------------------------!

! Interfay Sealant ! A layer of sealant applied to the contacting !

! ! (faying) surfaces of repair parts before they are !

! ! assembled. !

!------------------------!----------------------------------------------------!

! Leak Path ! This is the path along which a fluid can get !

! ! out of, or into a sealed area. !

!------------------------!----------------------------------------------------!

! Overcoating ! This term refers to the application of a brushing !

! ! thickness sealant over a joint. !

!------------------------!----------------------------------------------------!

! Tack Free Time ! This is the period of time measured from when the !

! ! sealant is mixed until its surface should be !

! ! 'touch dry'. !

!------------------------!----------------------------------------------------!

! Work Life ! This is the period of time within which a joint !

! ! that must be sealed, must be riveted, bolted or !

! ! temporarily fastened, after the sealant has been !

! ! applied to the contacting surfaces of the joint. !

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** ON A/C NOT FOR ALL

3. Sealant Preparation

A. Mixing the Sealant

(1) Refer to the manufacturers instructions for :

mixing ratios,
application life,
tack free time,
cure time,
work life.

(2) Mix the base compound and sealant accelerator slowly until you get an even consistency and color. If you mix quickly you will cause heat and air bubbles and shorten the application life of the sealant.

(3) You must mix the sealant as close to the time of application as possible.

[Rev.10 from 2021] 2026.04.01 01:34:43 UTC