C. Press the ACTUATED botton to reset the ball to black. The TEST 2 button tests the back-up solenoid in the same way.
NOTE: Hydraulic system A must be pressurized before you press the
____
ACTUATED button to reset the transfer valve.
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737-300/400/500MAINTENANCE MANUAL
D. Any time the following conditions are met, the solenoids will activate in the transfer valve and the white ball will appear:
(1)
Hydraulic pressure is initially available in system B.
(2)
Landing gear lever is in other than DN position.
(3)
Either main gear is in other than an up and locked position.
(4)
Left engine speed drops below approximately 56 percent N2 (8050 |5 rpm).
(5)
Landing gear logic is in the air mode.
E.
The solenoids in conjunction with system B hydraulic pressure cause a slide in the valve to move to transfer the hydraulic source for landing gear retraction from system A to system B. The ACTUATED indicator on the E-11 cannot be reset until system A hydraulic pressure has been restored as hydraulic pressure is required to reposition the valve. After the valve has been repositioned the indicator on the E11 will remain in the actuated position until it has been manually reset.
7. Air-Ground Sensing Test Switches (Fig. 1)________________________________
A. Three air-ground sensing test buttons are located in the lower left corner of the front panel of the shelf. Above each button is an LED. To the right of the test buttons are two rows of relays identified by equipment number and labled GROUND SENSING, AIR SENSING, or NOSE SENS.
B. When the GROUND SENSING button is depressed, the signal from the ground sensor to M990 ground sensing solid state switch in the E-11 box is interrupted. This causes the relays labled GROUND SENSING to relax. When R279 is relaxed, the LED above the GROUND SENSING switch comes on, indicating the relays have switched to the air mode.
C. When the AIR SENSING button is depressed, a signal is sent to the M991 air sensing solid state switch in the E-11 shelf. This excites the relays labled AIR SENSING and switches them to the air mode. When R276 switches, the LED above the AIR SENSING switch comes on to indicate that the relays are in the air mode.
D. When the NOSE SENSE button is depressed, a signal is sent to the M1110 nose gear air sensing solid state switch in the E-11 shelf. This relaxes the relays labled NOSE SENS switching them to the air mode. When R321 relaxes, the LED above the NOSE SENSING button comes on indicating that the relays have switched to the air mode.
E. When the buttons are released, the relays they control are automatically returned to the ground mode.
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737-300/400/500MAINTENANCE MANUAL
LANDING GEAR LOGIC SHELF - TROUBLE SHOOTING
___________________________________________
1. General_______
A. A number of airplane system receive air/ground signals from relays on the front of the E-11 Shelf. This procedure may be used after isolating a fault in any of those systems to a specific relay in the E-11 Shelf. This procedure is intended to further isolate the fault to a failed relay, a failed solid state card or a failed proximity sensor.
B. The E-11 Shelf is located on the right side of the radar bay just forward of the nose wheel well.
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