Slat Speed Commanded but Slat Half Speed Detected

TASK 27-81-00-810-824-A
Slat Speed Commanded but Slat Half Speed Detected

1. Possible Causes

25CV
26CV
aircraft wiring
POB SOLENOID
POB Solenoid Valve
Hydraulic Motor of the Slat PCU
Filters

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	MEGOHMMETER 100 MOHMS - MEASURING VOLTAGE 45 VDC
No specific	1	MULTIMETER - STANDARD

B. Referenced Information

REFERENCE	DESIGNATION
ASM 278102
ASM 278103
AMM 27-84-00-710-001	Operational Test of the Slat System
AMM 27-84-52-000-001	Removal of the Pressure-Off Brake of the Slat Power Control Unit
AMM 27-84-52-400-001	Installation of the Pressure-Off Brake of the Slat Power Control Unit
AMM 27-84-53-000-001	Removal of the Valve Blocks of the Power Control Unit (Slat)
AMM 27-84-53-000-002	Removal of the Solenoid Valves of the Power Control Unit (Slat)
AMM 27-84-53-000-003	Removal of the Filters of the Valve Blocks
AMM 27-84-53-400-001	Installation of the Valve Blocks of the Power Control Unit (Slat)
AMM 27-84-53-400-002	Installation of the Solenoid Valves of the Power Control Unit (Slat)
AMM 27-84-53-400-003	Installation of the Filters of the Valve Blocks
AMM 27-84-54-000-001	Removal of the Hydraulic Motor of the Slat Power Control Unit with the Pressure-Off Brake and the Valve Block Assembly
AMM 27-84-54-400-001	Installation of the Hydraulic Motor of the Slat Power Control Unit with the Pressure-Off Brake and the Valve Block Assembly

3. Fault Confirmation
Subtask 27-81-00-865-058-A

A. Table of the circuit breakers used in this procedure:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	FLIGHT CONTROLS/SLT/CTL AND MONG/SYS1	5CV	B06
121VU	FLIGHT CONTROLS/SLT/CTL/SYS2	7CV	R21

Subtask 27-81-00-710-058-A

B. SFCC Reset and Initialization.
(1) At the circuit breakers.
(a) Open the circuit breakers.
(b) Wait for 3 seconds and close the circuit breakers.
(c) Wait for 60 seconds.
(d) Check the UPPER ECAM and the SD FLT/CTL page for the fault warnings.
(e) Access the SLT ON GROUND FAULTS page and do a check of the ground log.
(f) If the ECAM warning and the ground log is clear:

no further maintenance steps are necessary.

(g) If the ECAM warning and the ground log fault message stays displayed, do the fault isolation.

4. Fault Isolation
Subtask 27-81-00-810-073-A

A. Procedure
(1) Do the operational test of the slats system AMM 27-84-00-710-001

NOTE: For this operational test, it is necessary that the Power Transfer Unit (PTU) is in operation.

(2) During the test procedure in Para 4.A.(1), monitor the ECAM display for the fault indications.
(3) If the fault indication gives a slow extension or slow retraction without a hydraulic fault, isolate the defective PCU and compare the two motor speeds:
(a) Stop the SFCC 1 and move the slats. Measure the extension time.
(b) Energize the SFCC 1 and stop the SFCC 2.
(c) Move the slats and measure the extension time.

NOTE: The time difference shows the slowest system. The slowest system is the PCU with possible internal friction.

(d) During the steps above, if one SFCC is energized and a slat extension starts but the slats do not move freely:

Do a check of the POB solenoid circuit (refer to Para 4.A.(4)).

(e) If the slats move freely, go to Para 4.A.(12).
(4) Do a check of the POB electrical circuit:
(a) Refer to AMM 27-84-52-000-001 Figure 401/Task 27-84-52-991-001.
(b) Find the electrical connector for the valve-block 25CV or 26CV POB solenoids and release it.
(c) Do a check of the aircraft wiring from the SFCC ARINC tray interface to the POB solenoid electrical connectors 25CV-A/26CV-A ASM 278102 and ASM 278103.
(d) If there is a wiring/interface fault, do the repair.
(5) If the A/C wiring is satisfactory, do a check of the circuit resistance and isolate the circuit of the fault related solenoid valve.
(a) On the valve-block use a MULTIMETER - STANDARD and do a check of the resistance between:

For SFCC1 -25CV = POB pins L and K

ASM/278102S01

For SFCC2 -26CV = POB pins L and K

ASM/278103S01

(b) The resistance for the POB solenoid:

P/N 667C0000-02 must be between 71 Ohms and 84 Ohms.
P/Ns 903A0000-01, 1106A0000-01 and 1111A0000-01 must be between 53 Ohms and 60 Ohms.
P/N 5751A0000-01 must be between 53 Ohms and 60 Ohms.

(6) On the valve-block, do a check for circuit isolation:
(a) For the POB solenoid, connect the pins L & K together.
(b) Connect one test lead of the MEGOHMMETER 100 MOHMS - MEASURING VOLTAGE 45 VDC or a 50VDC +5VDC/-5VDC Isolation Tester to the pins LK and the other test lead to pin G.
(c) Supply a test signal for 5 seconds and read the shown resistance value.
(d) The resistance value must be more than 100 Megohms.
(7) If the results of one of the two POB SOLENOID tests in Paras 4.A.(5) and (6) are unsatisfactory, replace the POB solenoid AMM 27-84-53-000-002 and AMM 27-84-53-400-002.
(8) If the results of one of the two POB Solenoid Valve tests in Paras 4.A.(5) and (6) are satisfactory, replace the POB related to the defective channel AMM 27-84-52-400-001 and AMM 27-84-52-000-001.
(9) Do the test in Para 4.A.(3) and if the slats do not move freely, replace the Hydraulic Motor of the Slat PCU AMM 27-84-54-000-001 and AMM 27-84-54-400-001.
(10) If the tests in Paras 4.A.(2) and (3) are satisfactory, do the test given in Para 4.A.(1).
(11) Set the MCDU to MENU MODE and get access to the SLT ON GROUND FAULTS page and make sure that the ground log is clear.
(12) If the CFDS shows the same fault message, then the fault is with the PCU valve-block.
(a) Examine the valve-block Filters AMM 27-84-53-000-003 and AMM 27-84-53-400-003 and clean/replace the examined item.
(b) If the fault continues, do the test in Para 4.A.(1) and do a check of the SLT ON GROUND FAULTS page.
(c) Examine the valve-block 25CV and 26CV and replace the defective item AMM 27-84-53-000-001 and AMM 27-84-53-400-001.
(d) Do the test in Para 4.A.(1) and make sure that the ground log is clear.
(e) Do the SFCC 1 (2) reset (refer to Para 3.B.). Do a check of the EXT/RET electrical circuit.

[Rev.8 from Aug 2018] 2026.04.04 04:27:48 UTC