DUCT ASSEMBLY
CLAMP
A

Conditioned Air Check Valve - Maintenance Practices
Figure 201 (Sheet 1)

K81191
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A

747-400 MAINTENANCE MANUAL
WING GEAR WHEEL WELL FORWARD BULKHEAD
SEAL  SUPPORT ROD
CHECK
VALVE

DUCT BONDING CLAMP
SUPPORT ROD
AIRFLOW JUMPER
BONDING SENSOR
ELECTRICAL CONNECTOR
B

Conditioned Air Check Valve - Maintenance Practices
Figure 201 (Sheet 2)

K81193
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A
747-400 MAINTENANCE MANUAL
 S 022-013
 (4)  Remove the duct from the bottom of the check valve:
 (a)  Remove the electrical connector from the airflow sensor: pack 1 - DT423 pack 2 - DT424 pack 3 - DT425
 NOTE: The airflow sensor is installed in the conditioned air
____ duct that goes through the wing gear wheel well.
 (b)  
Remove the clamp from the bottom end of the duct
 (View A, Fig. 201).

 (c)  
Remove the bonding jumper from the duct bonding clamp.

 (d)  
Remove the support rods from the duct section and remove the duct from the airplane.

 S 212-031
 (5)  Visually inspect the check valve for damage, failure or irregularity
 (a)  
Inspect the check valve flappers for damage, wear and freedom of movement. 1) Check for missing or broken flappers and attaching parts. 2) Check for cracks, nicks, dents, and flatness. 3) Check sealing surfaces for cracks, nicks, and dents.

 (b)  
Inspect the check valve body for damage and wear.
 1) Check for cracks, nicks, and corrosion.

 S 982-032
 (6)  
Replace the check valve if it has damage (AMM 21-21-01/401).

 S 422-030

 (7)  
Reconnect the duct to the check valve.

 (a)  
Rub the mating surfaces of the duct and the valve with a clean lint-free cloth that is moist with isopropyl alcohol.

 (b)  
Install the new seal in the end of the duct.

 (c)  
Install the end of the duct that contains the seal on the check valve.

 NOTE:____It is not necessary to lubricate the seal. The seal is lubricated by the manufacturer.

 (d)  
Attach the support rods to the duct assembly.

 (e)  
Install the bonding jumper on the duct bonding clamp.

 (f)  
Install the clamp assembly. Tighten the clamp to 70 (| 5) inch pounds (7.91 newton meters).

 (g)  
Install the electrical connector on the airflow sensor: pack 1 - DT423 pack 2 - DT424 pack 3 - DT425

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A
747-400 MAINTENANCE MANUAL
 (8)  S 862-016Supply conditioned air to the airplane (AMM 21-00-00/201).
 (9)  S 792-017Do a check for leaks at the duct joints that were disassembled. (a) Light leakage is permitted. (b) If the leakage is strong, align the joints and tighten the clamps.
 S 862-028

 (10) Remove conditioned air to the airplane, if it is not necessary (AMM 21-00-00/201).
 S 092-027 WARNING: REFER TO THE SPECIFIED PROCEDURE WHEN YOU REMOVE THE DOOR LOCKS
　
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