DME ANTENNA (REMOVED)
DME Antenna Installation Figure 401
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MAINTENANCE MANUAL

 (b)  Clean the faying surfaces of the DME antenna and the surface of the airplane (AMM 20-11-14/701).
 S 374-076
 (2)  If the airplane surface has corrosion or other damage, do these steps to prepare the airplane surface:
 (a)  Do this task to apply a layer of alodine to the airplane mating surface: Apply Alodine 1000 Solution (AMM 51-21-04/701).
 NOTE: This task removes corrosion, cleans the surface, and
____
 applies the alodine.

 (b)  Apply two layers of BMS 10-79 Type III primer to the airplane mating surface. 1) Let each layer dry for the correct cure time.
 S 394-078
 (3)  
Put a very thin layer of BMS 3-27 on the antenna base.

 S 394-079

 (4)  
Put a layer of BMS 3-27 in the nutplate and the open area where the antenna cable connects to the antenna.

 S 394-077

 (5)  
Prepare the o-ring:

 (a)  
Examine the rubber o-ring, and use a new o-ring if necessary.

 (b)  
Install the o-ring on the new antenna.

 (c)  
Put an extra bead of BMS 3-27 on the pressurized and unpressurized side of the o-ring which surrounds the antenna connector. 1) Make sure you do not get BMS 3-27 on the o-ring or in the

 o-ring groove.

 (d)  
Put a layer of BMS 3-24 on the o-ring and in the o-ring groove.

 S 424-024
 (6)  Install the DME antenna:
 (a)  
Connect the coaxial connector to the antenna.

 (b)  
Put Dow Corning Compound No. 4 on the coaxial connector.

 (c)  
Put the new antenna into position on the airplane surface.

 (d)  
Cover these areas with the corrosion preventive compound, BMS 3-27: 1) Brass stud on the antenna (if installed), 2) Lower area of the moisture guard. 3) Threads and shank of each of the cad plated stainless steel

 screws.

 (e)  
Lightly tighten the cad plated stainless steel screws in a diagonal pattern to hold the antenna in the correct position.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
 G.
H.
I.
A
747-400
MAINTENANCE MANUAL

 CAUTION: TIGHTEN THE SCREWS MANUALLY TO THE CORRECT TORQUE VALUE.
_______ USE OF POWER OR AIR TOOLS TO TIGHTEN THE SCREWS CAN CAUSE DAMAGE TO THE ANTENNA SURFACE.
 (f)  
Manually tighten the screws to 20-25 pound-inches of tourque.

 (g)  
Clean the excess BMS 3-27 with solvent, Series 98 (AMM 20-30-98).

 NOTE: This is important because the aerodynamic sealand, BMS
____ 5-95, will not stick to the BMS 3-27.
Resistance Measurement
 S 764-028
 (1)  Do a check of the continuity between the antenna and the airplane skin:
 (a)  Connect the bonding meter between the head of each screw and the airplane skin: 1) Make sure each measurement of continuity is less than 25
 milliohms.
 S 394-081
 (2)  
Apply the weather aerodynamic sealant, BMS 5-95, to the head of each screw (AMM 51-31-01/201).

 S 864-029

 (3)  
Remove the DO-NOT-CLOSE tags and close these circuit breakers:

 (a)  P7 Overhead Circuit Breaker Panel
 1) 7B8 NAV RADIO DME L
 2) 7B19 NAV RADIO DME R

DME Antenna Test
 S 864-030
 (1)  
Supply electrical power (AMM 24-22-00/201).

 S 734-017

 (2)  
Do a DME System Test for the applicable DME antenna

 (AMM 34-55-00/501).DME Antenna Sealing
 S 864-018
 (1)  Open these circuit breakers and attach DO-NOT-CLOSE tags:
　
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