29-22-00
ú ú 01 Page 3 ú Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
B69351
A 737-300/400/500MAINTENANCE MANUAL
TO SYSTEM A RETURN
LEGEND
PRESSURE
SUPPLY RETURN
Power Transfer Unit (PTU) Schematic
Figure 2 (Sheet 2)
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29-22-00
VALVE BEFORE FILTER ú ú 02 Page 4 ú Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
B70067
A
737-300/400/500
MAINTENANCE MANUAL
TO SYSTEM A RETURN
LEGEND
PRESSURE
FLOW LIMITER FILTER
SUPPLY RETURN CHECK VALVE HYDRAULIC FUSE
Power Transfer Unit (PTU) Schematic
Figure 2 (Sheet 3)
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29-22-00
ú ú 02 Page 5 ú Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
B69397
A 737-300/400/500MAINTENANCE MANUAL
TO SYSTEM A RETURN
LEGEND
PRESSURE
FLOW LIMITER FILTER
SUPPLY RETURN CHECK VALVE
HYDRAULIC FUSE
Power Transfer Unit (PTU) Schematic
Figure 2 (Sheet 4)
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29-22-00
ú ú 01 Page 6 ú Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
B69412
A 737-300/400/500MAINTENANCE MANUAL
4. PTU Control Valve (Fig. 3)
_________________
A. The control valve is an electric motor operated shutoff valve in the PTU motor pressure line from the A system. The valve is on the lower forward wall of the left wheel well. The two-position normally closed valve is electrically operated to direct system A hydraulic pressure to the PTU. A flow limiter is installed upstream of the control valve to limit flow to the PTU.
5. EDP Pressure Switch (Fig. 3)
___________________
A. The pressure switch senses the loss of system B EDP pressure and provides one of the electrical signals necessary to open the control valve. The pressure switch is located on the right side of the wheel well forward bulkhead.
6. Operation (Fig. 2)
_________
A. The PTU is an integral motor/pump unit using system A pressure to operate wing leading edge devices upon loss of system B EDP pressure. The PTU control valve circuit reacts to air/ground, flap and system B EDP conditions to automatically provide system A pressure to the PTU. The circuit requires the following sensings to provide 28v dc current to operate the control valve motor:
(1)
An air sensing at the NOSE GEAR AIR/GROUND sensing relay.
(2)
A trailing edge flap position indication greater than zero and less than fifteen.
(3)
A system B EDP low pressure sensing below 2350 psi minimum for at least 0.5 seconds.
B. A reversal of any sensing , except system B EDP low pressure, will cause the PTU control valve to close, shutting off system A pressure to the PTU motor.
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29-22-00
ALL ú ú 02 Page 7 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
HYD SYS B EDP RLY HYD B SYS EDPPRESS SW
Power Transfer Unit (PTU) Control
Figure 3
A 737-300/400/500MAINTENANCE MANUAL
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