B.
Ground Conditioned Air Connector

________________________________
 (1)  
The ground-conditioned-air connector allows conditioned air to be supplied directly into the mix manifold from a ground air cart. The connector consists of an eight-inch-diameter receptacle, a cover, and a swing check valve. The connector is on the underside of the fuselage, just forward of the left-air-conditioning pack.

 (2)  
ON GUN 001-004 WITH SB 21-51, AND GUN 005-999; the ground-conditioned-air connector also has a butterfly check valve.

 (a)  
Conditioned air from the ground cart forces the swing check valve to open. The check valve automatically closes, but does not seat, whenever pressurized ground air is not available. The check valve is spring loaded so it only seats when the air conditioning packs operate (i.e. a pressurized system).

 (b)  
The butterfly check valve allows air to enter the mix manifold when the ground air cart is used. When the air conditioning packs are used, the check valve does not allow air to enter the ground-conditioned-air connector and flow into the flight-deck-distribution duct.

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 21-21-00
 ALL  ú ú 12 Page 4 ú Mar 20/89
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757 MAINTENANCE MANUAL
 CONDITIONED AIR CHECK VALVE - REMOVAL/INSTALLATION
__________________________________________________
 1.  General_______
 A.  GUN 001-004 WITHOUT SB 21-51; This procedure has instructions to remove and install the check valve for the conditioned air. The check valve is installed in the ground connector duct, which is immediately below the mix manifold. To remove the check valve, the ground connector duct, with the check valve in it, must also be removed.
 B.  GUN 001-004 WITH SB 21-51 AND GUN 005-999; Two check valves are installed below the mix manifold and above the ground connector for the conditioned air.
 (1)  
The swing check valve is installed in the ground connector duct.

 (2)  
The butterfly check valve is on the top flange of the ground connector duct, immediately below the mix manifold. No fasteners are used to hold the butterfly check valve into its position.

 (3)  
This procedure has instructions to remove and install the ground connector duct, the swing check valve, and the butterfly check valve. You must remove the ground connector duct, with the swing check valve in it, before you can remove the butterfly check valve.

 TASK 21-21-01-004-001
 2.  Remove the Check Valve For The Conditioned Air (Fig. 401)______________________________________________
 A.  References
 (1)  
AMM 06-46-00/201, Entry, Service and Cargo Doors (Major Zone 800) Access Doors and Panels

 (2)  
AMM 24-22-00/201, Electric Power Control

 (3)  
AMM 25-50-03/401, Cargo Compartment Bulkhead Lining

 B.  
Access

 (1)  
Location Zones 125/126 Area aft of the forward cargo compartment

 C.  
Prepare for the Removal

 (1)  
Supply electrical power (AMM 24-22-00/201).

 S 864-002

 (2)  
Turn the L and R PACK selectors, on the pilots overhead panel P5, to the OFF position.

 (a)  
Make sure the PACK OFF lights go off.

 S 864-056
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 21-21-01
 ALL  ú ú 13 Page 401 ú Jan 20/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757
MAINTENANCE MANUAL

SEE  A 
BUTTERFLY CHECK VALVE 
MIX MANIFOLD 
BYPASS DUCT 
CLAMP 
GASKET 
WASHER 
BOLT 
(EXAMPLE) 
SWING 
CHECK VALVE  RUBBER SLEEVE 
BOLT  GROUND 
WASHER  CONNECTOR DUCT 
(EXAMPLE) 
GASKET 
AIRPLANE 
SKIN 
GROUND 
CONNECTOR 
SPACER 
FAIRING 
A 
Conditioned Air Check Valve Installation 
　
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