Loss of Normal Braking without Warning Indication

TASK 32-42-00-810-919-A
Loss of Normal Braking without Warning Indication

1. Possible Causes

SEL VALVE-BRK [23GG]
wiring from the BSCU (10GG) pin AA/10E to the pressure switch (86GG) pin A/B
PRESS SW-PARK BRK [86GG]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 31-32-00-869-002	Procedure for the Class 3 Fault Reading
AMM 32-41-11-400-006	Installation of the MLG Wheel
AMM 32-42-11-000-001	Removal of the Brake Selector Valve
AMM 32-42-11-400-001	Installation of the Brake Selector Valve
AMM 32-45-17-000-001	Removal of the Park Brake - Pressure Switch
AMM 32-45-17-400-001	Installation of the Park Brake - Pressure Switch
AMM 32-46-00-740-005	BITE Test of BSCU - Normal Braking TEST

3. Fault Confirmation
Subtask 32-42-00-710-075-A

A. Test
Read the CLASS 3 FAULTS report of the two BSCU Systems AMM 31-32-00-869-002.

4. Fault Isolation
Subtask 32-42-00-810-174-B

A. If the CLASS 3 FAULTS report gives two BRK NORM SERVOVALVE maintenance messages on one side at the same time or four BRK NORM SERVOVALVE maintenance messages on the two sides at the same time:

replace the SEL VALVE-BRK [23GG] AMM 32-42-11-000-001 AMM 32-42-11-400-001.

(1) If the fault continues or if the CLASS 3 FAULTS report gives no maintenance messages:
(a) On the MCDU, do a BSCU 1(2) NORMAL BRAKING TEST AMM 32-46-00-740-005 and make sure that there is no fault detected.
(2) If the test is not OK and gives: TEST NOT PERFORMED with the message:
PARK BRAKE : ON
(3) Do a check for a ground signal at pin AA/10E of the BSCU (10GG)
(a) If there is a ground signal:
1 Disconnect the wire at pin A/B of the pressure switch (86GG)
2 Do a check for a ground signal at pin A/B of the pressure switch (86GG)
(4) If there is no ground signal:
(a) Repair or replace the wiring from the BSCU (10GG) pin AA/10E to the pressure switch (86GG) pin A/B.
(5) If there is a ground signal:
(a) Replace the PRESS SW-PARK BRK [86GG] AMM 32-45-17-000-001 AMM 32-45-17-400-001.
(6) On the MCDU, do a BSCU 1(2) NORMAL BRAKING TEST again.
(a) If the test is OK but the fault continues:
Do an inspection of the four tachometer driving mechanisms and make sure that:

The tachometer drive shaft moves freely.
There is no deformation (twisting) and/or sign of friction on the drive shaft.
The splines of the tachometer drive shaft are in the correct condition.
The splines of the tachometer hubcap or the splines of the debris guard (if brake fans are installed) are in the correct condition.

(b) Replace the damaged parts as necessary and make sure that the splines of the tachometer are coated with grease before final assembly AMM 32-41-11-400-006.

Subtask 32-42-00-710-106-A

B. After the subsequent flight, make sure that the fault does not continue.

[Rev.8 from Aug 2018] 2026.04.04 04:31:37 UTC