B. Hydraulic Actuation and Power Transmission (Ref. 27-84-00)
A hydro-mechanical PCU supplies mechanical power to the power transmission system. The PCU has two separate hydraulic motors and two Pressure-Off Brakes (POB). Each hydraulic motor has an electrically controlled valve block, which receives signals from a SFCC.
Torque shafts and gearboxes in the fuselage and the wings transmit the mechanical power from the slat PCU to the rotary actuators which move the slats. Each slat has two rotary actuators, which are installed on the tracks. Torque limiters in the transmission system and the rotary actuators prevent the mechanical overload of the structure.
4. Power Supply____________
(Ref. Fig. 003)
5. Interface_________
Not Applicable
6. Component Description
_____________________
Not Applicable
Hydraulic System - Schematic
Figure 003
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7. Operation/Control and Indicating________________________________
(Ref. Fig. 002, 003)
A. Extension and Retraction of the Slats
The operation of the slats is hydro-mechanical. The PCU moves the mechanical transmission system which operates the slats.
The CSU changes the mechanical signals from the slat and flap control lever into electrical signals. These are sent to the SFCC1 and the SFCC2. They compare the position signal with that from the FPPU. When there is a difference between the signals, the SFCC sends a discrete signal to its related valve block of the slat PCU.
Each valve block lets hydraulic fluid flow to and from its hydraulic motor, in relation to the signal from the SFCC. It thus controls the direction in which the hydraulic motor turns (for extension and retraction of the slats) and its speed (low or high speed).
The torque from the hydraulic motors is transmitted to the differential gearbox, which connects the two motors. The mechanical transmission system then transmits the torque to the rotary actuators which moves the slats.
B. Hydraulic Actuation and Power Transmission
The two hydraulic motors in the PCU give hydraulic actuation. Each hydraulic motor gets power from a different system, green or blue.
Each hydraulic motor has its own valve block and POB. The valve blocks control the direction of rotation and the speed of the output shaft of the PCU. The POB holds the output shaft of the hydraulic motor:
-against torque from the airloads
-when there is a failure in its related hydraulic system
-to lock the transmission at the same time as the WTB.
The two hydraulic motors move the transmission system through a differential gearbox. This causes the slat control surfaces to move to the set position.
It is possible to operate the slat system, at half speed, if the failure conditions listed below occur:
-
loss of one electrical supply
-
loss of one hydraulic system
-
failure of one SFCC, or failure of one of two electrical components
-
failure of one engine.
C. Asymmetry and Power Transmission Monitoring
The SFCC1 and the SFCC2 continuously compare position data from the APPUs and the FPPU to monitor the system. They use this data to find asymmetry, runaway and speed failure conditions.
The proximity switches of the slat disconnect detection system send signals to the Landing-Gear Control Interface-Units (LGCIU). The LGCIUs send signals to the SFCC1 and the SFCC2. If the slat movement is not in the specified limits then the conditions listed below occur:
-the slat PCU is switched off
-a warning is sent to the flight crew.
D. Position Indicating
The upper display unit of the ECAM system shows the position of the slats. Installed on the PCU is an IPPU which supplies flap position data. The IPPU also gives data to the flight data recorder and the Flight Warning System (FWC) (Ref. 27-85-00).
A visual check of the position of the slats can be done through the windows in the fuselage that are adjacent to the slats. The windows to be used are identified by a brown triangle on the sidewall panel above them.
8. BITE Test_________ (Ref. Fig. 004, 005)
The slat system has a Built-In Test Equipment (BITE). You can do tests of the system through the Multipurpose Control and Display Unit (MCDU) in the aircraft cockpit. The MCDU also indicates any failures in the system and gives trouble shooting data for the system.
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