(2)
Ground Locks - Landing Gear
B. Prepare for Parking Brake System Test
(1)
Provide external electrical power (Ref. 24-22-0/201).
(2)
Make sure that you install the ground locks of the main and nose gear (Ref. 32-00-01/201).
C. Brake System Accumulator Precharge Check
(1)
Remove the pressure from hydraulic systems A and B (Ref. 29-11-0/201 and 29-12-0/201).
(2)
Place chocks under wheels.
(3)
Fully apply the brakes approximately 10 times to remove the brake pressure from the brake accumulators.
(4)
Remove the bleed screws and install the pressure gages at the bleed ports of the brakes.
(5)
Make sure that the precharge pressures of the brake accumulator agree with the placards on the aft wall of the wheel well.
D. Parking Brake System Test
(1)
Pressurize hydraulic systems A and B (Ref. 29-11-0/201 and 29-12-0/201).
(2)
Push the brake pedals and set the parking brake.
(3)
Make sure that the parking brake light stays on.
(4)
Make sure that the pressure at each brake is 3000 ± 100 psi.
(5)
Fully push the brake pedals.
(6)
Make sure that the parking brake lever goes back to the parking brake released position and the parking brake light goes off.
E. Accumulator Bleed Down Test - Parking Brake Set
(1)
Pressurize hydraulic systems A and B (Ref. 29-11-0/201 and 29-12-0/201).
(2)
Set the parking brake.
(3)
Remove the pressure from hydraulic systems A and B after 10 minutes.
(4)
Do a check at the end of any time periods that follow. If the necessary pressure drop for one time period is not within the limits, you can use the next time period.
NOTE: It is necessary to operate the pumps at least 10 minutes to let the accumulator temperatures stabilize.
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May 01/98 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 32-44-0 Page 503
NOTE: It is permitted to read the brake pressures from the brake pressure gage in the flight compartment, the brake accumulator gages, or the brake pressure gages installed on the brakes.
(a)
After 10 minutes, the pressure drop should be less than 250 psi
(b)
After 30 minutes, the pressure drop should be less than 500 psi
(c)
After 1 hour, the pressure drop should be less than 700 psi
(d)
After 8 hours, the brake pressures should be greater than 1000 psi.
(5)
If the brake accumulator pressures bleed down faster than it is allowed, do the parking brake trouble shooting procedure (Ref 32-44-0/101).
(6)
The trouble shooting of the parking brake system can be delayed until the next convenient maintenance period if the conditions that follow are met:
(a)
With the parking brake set, the brake accumulator pressure drop must be less than 1000 psi in the first 1/2 hour
(b)
With the parking brake released, the brake accumulator pressure drop must be less than 350 psi in the first 1/2 hour.
(c)
The system passes the "Accumulator Bleed Down Test - Parking Brake Released".
F. Accumulator Bleed Down Test - Parking Brake Released
(1)
Pressurize hydraulic systems A and B (Ref 29-11-0/201 and 29-12-0/201).
(2)
Record A and B brake pressures.
NOTE: It is permitted to read brake pressures from the brake pressure gage in the flight compartment, the brake accumulator gages, or the brake pressure gages installed on the brakes.
(3)
Shut off source of hydraulic power for systems A and B after 10 minutes. Record the time of shutoff as the test start time.
NOTE: It is necessary to supply hydraulic power for at least 10 minutes before test start to let the accumulator temperatures stabilize.
(4)
Do a check on the pressure at 30 minutes after test start. The pressure drop should be smaller than 450 psi for each system A and B.
(5)
If the brake accumulator pressures bleed down faster than is allowed, do the Brake Accumulator System - Parking Brake Released trouble shooting procedure.
G. Return the Airplane to Normal
(1)
Remove the pressure gages in the brakes and install the bleeder plugs.
(2)
Pressurize the hydraulic systems A and B (Ref 29-11-0/201 and 29-12-0/201).
(3)
Push the brake pedals slowly and fully six times to bleed the brakes.
(4)
Remove chocks from wheels if not needed.
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