-
the aircraft is on the ground with CAS below 60 knots.
When the function is active, the ECAM shows the message A-Lock (cyan, pulsing) below the slat position indication (Ref. 27-85-00).
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**ON A/C 303-399,
B. Slat Alpha Lock/Speed Baulk
The Air Data/Inertial Reference Units (ADIRU) supply corrected angle-of-attack (alpha) and computed air speed (CAS) data to the SFCC. The SFCC use the data to prevent slat retraction at high alpha and/or low CAS. Slat retraction is not possible if:
-
the alpha is more than 8.0 deg.
-
the CAS is less than 165 knots.
The function resets if alpha decreases below 7.1 deg. or CAS increases over 171 knots.
Alpha lock/speed baulk is not possible if:
-
the slat retraction is set before alpha is more than 8.0 deg. or CAS less than 165 knots
-
the aircraft is on the ground with CAS below 60 knots.
When the function is active, the ECAM shows the message A LOCK (green, flashing) above the slat position indication (Ref. 27-85-00).
**ON A/C ALL
C. Operation of the Wing Tip Brake
(Ref. Fig. 017)
The WTBs lock the transmission system if some given types of failure occur that requires it to lock the WTBs.
(1)
If one or the other lane of the slat channel finds a failure:
-
the lane arms its own WTB circuits
-
the other channel receives a WTB-arm discrete signal.
(2)
If one or the other lane in the second slat channel also finds the failure:
-
the lane arms its own WTB circuits
-
the first channel receives a WTB-arm discrete signal.
When the SFCCs receive a WTB-arm signal they energize the related WTB solenoid valves. The WTBs lock the transmission system. If one SFCC does not operate, the other SFCC receives a WTB-arm signal automatically. If the other SFCC finds some given types of failure, one solenoid valve on each WTB gets electrical power.
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Wing Tip Brake Logic Figure 017
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(3) Reset
The WTB can only be reset on the ground through the CFDS.
D. Monitoring for Failure Conditions
(1) Monitoring of the Power Transmission System
The SFCCs monitor:
-
the slat position data from the APPUs and the FPPU
-
the rate of change of the slat position data
-
the selected position from the CSU.
The SFCCs use this data to find:
-an asymmetry
-a runaway
-
an uncommanded movement
-
an overspeed.
When the SFCCs find any one of these failures:
-
the valve block solenoids on the PCU are de-energized
-
the POBs are applied and stop their related hydraulic motors
-each channel arms its own WTB circuits and sends a WTB-arm signal to the other channel
-
the WTBs lock the transmission system
-
the SFCCs give a class 1 level 2 caution and the ECAM display unit shows a failure message.
When the WTBs have locked the system, reset is only possible on the ground.
(2) System Jam
The SFCC will find a system jam if the system speed is below 2% nominal for more than 4 seconds.
When the SFCCs find a system jam:
-
the valve block solenoids on the PCU are de-energized
-
the POBs are applied and stop their related hydraulic motors
-
the SFCCs give a class 1 level 2 caution and the ECAM display unit shows a failure message.
If the SFCCs receive a new correct CSU signal, the SFCCs go back to
their normal operation.
If there is low hydraulic pressure, the SFCCs stop system jam
monitoring.
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(3) LRU Monitoring
(a) SFCC1 and SFCC2
Each lane of each slat channel receives output signals from the other lane in the same channel. Each lane compares these signals with its own output signals. If there is a difference for more than 320 milliseconds and minor failure steps are taken:
-
the solenoids on the related valve block are de-energized
-
the POBs lock their related hydraulic motor
-
the other channel receives a WTB-arm signal
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