DOC AIRBUS | AMM A320FTHRUST REVERSER CONTROL AND INDICATING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
1. General
The thrust reverser is controlled from the cockpit by means of the throttle control lever.
A thrust reverser latching lever, when actuated, allows the throttle control lever to be moved rearward in the reverse thrust selection area and the thrust reverser to be controlled by the Engine Electronic Control (EEC).
The EEC incorporates a thrust reverser feedback position and ground/flight configuration which generates a command signal to the isolation valve and the directional control valve.
The signal from the EEC to the directional valve is fed to the avionics compartment where it passes through an inhibition relay (also called permission switch) controlled by the Engine Interface Unit (EIU) and the spoiler/elevator computer (SEC) according to the throttle control lever position.
Each channel of the EEC can control and monitor the thrust reverser.
The hydraulic energy required for actuation is supplied from the normal hydraulic system.
The thrust reverser operating sequences are displayed in the cockpit on the lower ECAM display unit. In deployment, an amber REV indication will come into view at the middle of the EPR dial when at least one of the translating sleeves is unstowed (between 10% and 95%).
If this occurs in flight, REV will flash first for 9 sec then it will remain steady. This indication will change to green color when the translating sleeves are fully deployed and the reverse thrust can be applied.
In stowage, the indication changes to amber when one sleeve at least is less than 95 % deployed and disappears when both sleeves are stowed.
** ON A/C NOT FOR ALL The thrust reverser is controlled from the cockpit by means of the throttle control lever.
Thrust Reverser SystemA thrust reverser latching lever, when actuated, allows the throttle control lever to be moved rearward in the reverse thrust selection area and the thrust reverser to be controlled by the Engine Electronic Control (EEC).
The EEC incorporates a thrust reverser feedback position and ground/flight configuration which generates a command signal to the isolation valve and the directional control valve.
The signal from the EEC to the directional valve is fed to the avionics compartment where it passes through an inhibition relay (also called permission switch) controlled by the Engine Interface Unit (EIU) and the spoiler/elevator computer (SEC) according to the throttle control lever position.
Each channel of the EEC can control and monitor the thrust reverser.
The hydraulic energy required for actuation is supplied from the normal hydraulic system.
The thrust reverser operating sequences are displayed in the cockpit on the lower ECAM display unit. In deployment, an amber REV indication will come into view at the middle of the EPR dial when at least one of the translating sleeves is unstowed (between 10% and 95%).
If this occurs in flight, REV will flash first for 9 sec then it will remain steady. This indication will change to green color when the translating sleeves are fully deployed and the reverse thrust can be applied.
In stowage, the indication changes to amber when one sleeve at least is less than 95 % deployed and disappears when both sleeves are stowed.
2. Component location
** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C NOT FOR ALL | |||||
| 3011KM1 | MANUAL CTL VALVE-THRUST REV HYD SYS, ENG 1 | 413 | 78-31-41 | ||
| 3011KM2 | MANUAL CTL VALVE-THRUST REV HYD SYS, ENG 2 | 423 | 78-31-41 | ||
| 4007KS | LOCK IND/PROX SENSOR-THRUST REV LOWER L ACTUATOR | 410 | 78-31-15 | ||
| 4101KS1 | HCU-THRUST REV, 1 | 410 | 71-13-00 | ||
| 4101KS2 | HCU-THRUST REV, 2 | 420 | 71-13-00 | ||
3. Component Description
A. Proximity switch
(1) General
There are four hydraulic actuators, mounted on the forward frame of the thrust reverser. They are supplied with hydraulic fluid by the HCU.
These hydaulic actuators have the following functions:
There are four hydraulic actuators, mounted on the forward frame of the thrust reverser. They are supplied with hydraulic fluid by the HCU.
These hydaulic actuators have the following functions:
- to deploy the translating sleeves
- to stow the translating sleeves
- to lock in the stowed position (two lower actuators).
(2) Description/Operation
(a) The lower actuators incorporate an integral lock mechanism to hold the piston rod when the actuator is in the fully stowed position.
(b) The actuator base is attached to a torque ring and the end of the piston is attached to the translating sleeve. As hydraulic pressure builds up in the actuator, the piston extends. This moves the translating sleeve aft to the deploy position. In the retract mode, the piston retracts which moves the translating back to the stow position.
C. Flexible Shafts
Three flexible shafts connect the four actuators together to synchronize the speed with which the actuators operate. This synchronization keeps the top and bottom of the sleeve traveling at the same rate so the sleeve will not tilt and jam. The synchronization also keeps the two translating sleeves moving together so reverse pressure in the secondary air flow is equal on both sides of the engine.
The flexible shafts are installed inside the extend (deploy) hydraulic hoses. The shaft engages a worm gear at the base of the actuator that translates the turning action of the actuator piston as it moves out or in. A cross-over shaft connects the two upper actuators. Another shaft connects the upper and lower actuators on each side.
Three flexible shafts connect the four actuators together to synchronize the speed with which the actuators operate. This synchronization keeps the top and bottom of the sleeve traveling at the same rate so the sleeve will not tilt and jam. The synchronization also keeps the two translating sleeves moving together so reverse pressure in the secondary air flow is equal on both sides of the engine.
The flexible shafts are installed inside the extend (deploy) hydraulic hoses. The shaft engages a worm gear at the base of the actuator that translates the turning action of the actuator piston as it moves out or in. A cross-over shaft connects the two upper actuators. Another shaft connects the upper and lower actuators on each side.
D. Hydraulic Control Unit (HCU)
(1) General
The hydraulic control unit controls hydraulic fluid flow to the thrust reverser actuators. Control and feedback signals are exchanged with the EEC.
The HCU is mounted on the pylon over the engine centerline, just forward of the C-duct and is accessible from the left side. The hydraulic control unit is a solid state component and includes the following items:
The hydraulic control unit controls hydraulic fluid flow to the thrust reverser actuators. Control and feedback signals are exchanged with the EEC.
The HCU is mounted on the pylon over the engine centerline, just forward of the C-duct and is accessible from the left side. The hydraulic control unit is a solid state component and includes the following items:
- isolation valve solenoid,
- isolation valve,
- directional control valve solenoid,
- directional control valve,
- pressure switch,
- filter and clogging indicator (pop out).
(2) Description
(a) Isolation valve solenoid and isolation valve. The isolation valve solenoid and isolation valve provide the means of isolating the thrust reverser actuation systems from the remaining hydraulic network on the engine. The isolation valve solenoid is a dual coil valve solenoid connected to both channels of the EEC. The isolation valve is in the closed position while the thrust reverser is in the stowed position. Upon actuation of the thrust reverser system, the isolation valve solenoid is energized and the isolation valve is opened.
(b) Directional control valve solenoid and directional control valve:
The directional control valve solenoid and directional control valve directs high pressure hydraulic fluid to the correct end(s) of the actuators to either stow or deploy the translating sleeve. The directional control valve solenoid is a dual wound solenoid connected to both channels of the EEC. The directional control valve solenoid is energized when the deploy command is given and provides hydraulic fluid at hydraulic pump supply pressure to both ends of the actuators through the directional control valve to initiate deployment of translating sleeve.
The directional control valve solenoid and directional control valve directs high pressure hydraulic fluid to the correct end(s) of the actuators to either stow or deploy the translating sleeve. The directional control valve solenoid is a dual wound solenoid connected to both channels of the EEC. The directional control valve solenoid is energized when the deploy command is given and provides hydraulic fluid at hydraulic pump supply pressure to both ends of the actuators through the directional control valve to initiate deployment of translating sleeve.
(c) Pressure switch
The pressure switch is an oval contact switch which provides signals to the EEC to indicate when there is hydraulic pressure downstream of the isolation valve. The pressure switch is closed at pressure between 798 and 1450 psi and is opened at a minimum pressure of 798 psi.
The pressure switch is an oval contact switch which provides signals to the EEC to indicate when there is hydraulic pressure downstream of the isolation valve. The pressure switch is closed at pressure between 798 and 1450 psi and is opened at a minimum pressure of 798 psi.
(d) Filter and clogging indicator
The hydraulic control unit filter is used to filter the fluid supply from the aircraft hydraulic system. The filter is a flow through cartridge type filter. The clogging indicator monitors pressure loss through the filter cartridge and features a pop-out indicator to signal when it is necessary to replace the filter element. The clogging indicator includes two spring loaded magnetic pistons whose magnetic attraction keep the pop-out indicator in the retracted position. The lower magnetic piston monitors the differential pressure between the filtered elements. As the differential pressure increases the piston compresses its spring and moves away from the upper magnetic piston at a preset displacement of approximately 2 mm, the upper magnetic position spring overcomes the magnetic force and drives the pop-out indicator from its retracted position.
The hydraulic control unit filter is used to filter the fluid supply from the aircraft hydraulic system. The filter is a flow through cartridge type filter. The clogging indicator monitors pressure loss through the filter cartridge and features a pop-out indicator to signal when it is necessary to replace the filter element. The clogging indicator includes two spring loaded magnetic pistons whose magnetic attraction keep the pop-out indicator in the retracted position. The lower magnetic piston monitors the differential pressure between the filtered elements. As the differential pressure increases the piston compresses its spring and moves away from the upper magnetic piston at a preset displacement of approximately 2 mm, the upper magnetic position spring overcomes the magnetic force and drives the pop-out indicator from its retracted position.
(3) Operation
Selection of either stow or deploy from the cockpit sends a signal to the engine EEC which, in turn, supplies two independent signals to the thrust reverser HCU isolation valve and directional control valve.
These signals to the HCU are only provided if the EEC has correct signals e.g. reverser position and engine power setting.
Solenoid conditions are as follows:
Selection of either stow or deploy from the cockpit sends a signal to the engine EEC which, in turn, supplies two independent signals to the thrust reverser HCU isolation valve and directional control valve.
These signals to the HCU are only provided if the EEC has correct signals e.g. reverser position and engine power setting.
Solenoid conditions are as follows:
| ------------------------------------------------------------------------------- |
| Conditions Isolation Valve Solenoid Directional Valve Solenoid |
| ------------------------------------------------------------------------------- |
| Forward thrust 0 0 |
| Deploying 1 1 |
| Reverse thrust 1 1 |
| Stowing 1 0 |
| ------------------------------------------------------------------------------- |
NOTE: 1 = solenoid energized
0 = solenoid de-energized
0 = solenoid de-energized
(a) Initial stowed position
In the initial stowed position with the reverser stow control selected in the cockpit, the hydraulic pressure is applied to the input of the HCU. All reverser hydraulic systems are pressurized at the return pressure as long as the aircraft is in flight and no signal is sent to open the isolation valve solenoid.
In the initial stowed position with the reverser stow control selected in the cockpit, the hydraulic pressure is applied to the input of the HCU. All reverser hydraulic systems are pressurized at the return pressure as long as the aircraft is in flight and no signal is sent to open the isolation valve solenoid.
1 When reverse thrust is selected in the cockpit, the EEC ensures that deployment is permitted:
- The right and left main landing gear compressed information from LGCIU via the EIU is available.
- The TLA reverse signal from at least one SEC is available (permission switch in the deployed position).
In that case, the electrical power (28VDC) is sent to the isolation valve solenoid and to the directional valve solenoid.
2 When the isolation valve is opened and the directional control valve solenoid is energized, hydraulic pressure (3000 psi) moves the directional control valve to supply hydraulic pressure to the head end of the actuator to unlock the actuators, and then extending the actuators.
3 As soon as at least one lock sensor indicates unlocked, an "unlocked sleeve" signal is sent by these sensors to the EEC. In the cockpit an amber REV indication is displayed in the middle of the EPR dial or the ECAM display unit.
4 Each translating sleeve arriving at 95 percent of its travel is slowed down until completely deployed through hydraulic actuator inner restriction. This event is indicated to EEC when both Linear variable Differential Transformers (LVDT) [4003KS] and [4004KS] detect this position. REV indication changes to green.
NOTE: When the thrust reverser is in the deployed position, the isolation valve remains energized to maintain the hydraulic pressure in the actuators to prevent vibration. If an uncommanded stow movement is detected, the EEC will de-energize the isolation valve. This will lead to a thrust reverser redeploy due to aerodynamical forces on the blocker doors.
(c) Stow sequence
1 When translating sleeves stowing is selected, the EEC ensures that stowing is permitted. In that case the EEC de-energizes the directional valve solenoid. When one translating sleeve is less than 95 % deployed, REV indication changes to amber.
2 Hydraulic pressure is supplied to the rod end of the actuator, the head is connected to return. A flow limiter controls hydraulic actuator piston retraction speed.
3 When both translating sleeves are fully stowed, they set the proximity switches (lock sensor) which send the "stowed sleeves" information to the EEC. The REV indication disappears.
4 The actuators move until stowing is complete and the lower actuator locks are engaged after which the isolation valve solenoid is de-energized and the reverser is locked in the forward thrust mode position.