(4)  
If fuel cell is to be removed from cavity, refer to Chapter 28-14-21, Auxiliary Tank Fuel Cells - R/I.

B.  Install Auxiliary Fuel Tank
(1)  
Align auxiliary tank module with aft cargo door opening and slide tank onto ball roller mats in cargo compartment.

(2)  
Move tank into position and secure as outlined in procedure 4.B.(1) thru 4.B.(7).

(3)  
Remove plug from drain hose and connect hose to drain fitting under equipment bay.

(4)  
Plug drain hose in equipment bay and test hose connection for leakage per step (3).

(5)  
Disconnect test air pressure source from cavity drain line and reconnect cavity drain line to drain manifold.

(6)  
Clean inside of cavity.

(7)  
Seal inside of cavity as required (Ref Chapter 51, 46 Section Sealing Index and Requirements).

(8)  
Check cavity for leakage (Ref Auxiliary Fuel Tank Cavities - I/C.

(9)  
Install fuel cells, plumbing and equipment (Ref Chapter 28, Fuel).

(10)
Install electrical connections in fuel system equipment bay and connect ground wires and bonding jumpers to tank.

(11)
Seal exterior of cavity at fuel and vent fittings as required (Ref Chapter 51, 46 Section Sealing Index and Requirements).

(12)
Replace passenger floor panels, carpets and seats removed for tank access (Ref Chapter 25, Interiors).

(13)
Check operation of auxiliary tank electrical equipment (Ref Chapter 28, Fuel).

(14)
Install fuel system equipment access panel and aft cargo compartment partition.

(15)
Install aft cargo door (Ref 52-31-0, Removal/Installation).

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6.  Inspection/Check Aft Auxiliary Fuel Tank
A.  Equipment and Materials
(1)  
Plugs and coverplates as required to isolate tank cavity

(2)  
Vacuum source capable of reducing air pressure in tank cavity to negative 25 inches of water

(3)  
Pressure relief type water manometer

(4)  
Clean water source. Tap water is acceptable

(5)  
Bubble Solution - BMS 10-34, System 3

(6) 
 Brushes

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B.  Check Auxiliary Fuel Tank Cavity for Leakage
(1)  
Install plugs and coverplates at all cavity boundary openings and plug all drain openings inside the cavity.

(2)  
Add water into cavity to make 6-inch level which is area of absolute fuel seal for cavity.

(3)  
With a man inside cavity install coverplate over cavity access opening.

(4)  
Lower pressure in cavity to negative 25-inches of water manometer reading.

(5)  
Check entire lower surface and sidewalls below water level and mark location of any source of bubbling.

(6)  
Check all sealant application above water level (intermediate seal area) for air leak using bubble solution. There shall be no audible leakage around fasteners.

(7)  
Return pressure in cavity to normal.

(8)  
Remove plugs from cavity drains and drain water through drain lines to make sure there is no drain obstruction.

(9)  
Repair any leak found during the test.

(10)
Recheck leak repairs using vacuum, negative 25 inches of water manometer reading in cavity, and applying bubble solution to repair areas.

(11)
When leak repairs have been verified, return cavity pressure to normal.

(12)
Remove all plugs and caps from cavity boundary openings.

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SKIN - DESCRIPTION AND OPERATION
1. General
A.  The fuselage skin varies in thickness according to the loads it must bear in any given area, and it is designed with fail-safe features to ensure alternate load paths in the event of a local failure. Refer to Chapter 53 of the Structural Repair Manual for skin identification.
B.  The thickest skin panels are those over the area where the lower fuselage is cut away to accommodate the wing and the main landing gear wheel well. In this area the skin panels are machined from thick sheets.
C.  Many of the skin panels are attached to each other by bonded longitudinal lap joints, which provide pressure seals in addition to being structural joints. Circumferential skin splices exist aft of the control cabin, at the front spar bulkhead, at the bulkhead aft of the wheel well and at the aft pressure bulkhead.
　
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