DOC AIRBUS | AMM A320FTHRUST REVERSER (T/R) CONTROL AND INDICATING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. System Description
The thrust reverser system comprises two independent translating cowls, forming the fan exhaust duct. These cowls are actuated by four hydraulic actuators (two per cowl). Each of these actuators incorporates a primary lock mounted with two proximity switches reporting to both channels of the EEC about the lock/unlock status. One of the two actuators of each cowl, called locking feedback actuator also incorporates a duplex Linear Variable Differential Transducer (LVDT) connected to each channel of the EEC, providing the cowl position. In the stowed position, each sleeve is retained closed first by the actuator primary locks and secured by a hydraulic Tertiary Lock (TL) which constitutes the third line of defence. Refer to 78-37-00 for the description and operation of the thrust reverser tertiary locking system. As the cowls translate, they expose fixed cascades which, when the blocker doors are deployed, block the normal fan exhaust annulus and direct the fan air through the cascades to provide reverse thrust.
** ON A/C NOT FOR ALL The thrust reverser system comprises two independent translating cowls, forming the fan exhaust duct. These cowls are actuated by four hydraulic actuators (two per cowl). Each of these actuators incorporates a primary lock mounted with two proximity switches reporting to both channels of the EEC about the lock/unlock status. One of the two actuators of each cowl, called locking feedback actuator also incorporates a duplex Linear Variable Differential Transducer (LVDT) connected to each channel of the EEC, providing the cowl position. In the stowed position, each sleeve is retained closed first by the actuator primary locks and secured by a hydraulic Tertiary Lock (TL) which constitutes the third line of defence. Refer to 78-37-00 for the description and operation of the thrust reverser tertiary locking system. As the cowls translate, they expose fixed cascades which, when the blocker doors are deployed, block the normal fan exhaust annulus and direct the fan air through the cascades to provide reverse thrust.
** ON A/C NOT FOR ALL
Functional Interface3. Component Description
A. Hydraulic Actuator
There are four locking actuators on each thrust reverser. There is an upper locking feedback actuator and a lower locking actuator on each thrust reverser half. They attach to the torque box and the translating sleeve. They each have an internal worm wheel that moves a rotating screw and nut which cause the actuator to move in a line. Each actuator also has internal mechanical locks which are the primary locks for the system. Two proximity sensors on the actuator send a signal to the aircraft to indicate whether the actuator is locked or unlocked. A manual lock release on the actuators can be pinned in the unlocked position if there is no aircraft power. The lower actuators have a Manual Drive Unit (MDU) to manually deploy and stow the thrust reverser during maintenance. The upper feedback actuators have a LVDT. During the stow-deploy-stow cycle, the LVDT determines the position of the thrust reverser and sends a signal to the EEC.
There are four locking actuators on each thrust reverser. There is an upper locking feedback actuator and a lower locking actuator on each thrust reverser half. They attach to the torque box and the translating sleeve. They each have an internal worm wheel that moves a rotating screw and nut which cause the actuator to move in a line. Each actuator also has internal mechanical locks which are the primary locks for the system. Two proximity sensors on the actuator send a signal to the aircraft to indicate whether the actuator is locked or unlocked. A manual lock release on the actuators can be pinned in the unlocked position if there is no aircraft power. The lower actuators have a Manual Drive Unit (MDU) to manually deploy and stow the thrust reverser during maintenance. The upper feedback actuators have a LVDT. During the stow-deploy-stow cycle, the LVDT determines the position of the thrust reverser and sends a signal to the EEC.
B. Flexible Shafts
The flexible synchronizing shafts make sure the actuators move in unison to deploy and stow the translating sleeve. The flexible shafts are contained in hydraulic deploy tubes connected between the upper and lower actuators. The flexible shaft has a square drive that engages with the worm and wheel gearbox in the actuator jack head.
The flexible synchronizing shafts make sure the actuators move in unison to deploy and stow the translating sleeve. The flexible shafts are contained in hydraulic deploy tubes connected between the upper and lower actuators. The flexible shaft has a square drive that engages with the worm and wheel gearbox in the actuator jack head.
C. Hydraulic Control Unit (HCU)
The HCU connects the thrust reverser actuation system with the hydraulic distribution system of the aircraft. The HCU controls the flow of hydraulic fluid to the four hydraulic actuators on the thrust reverser. It does this with supply and return connections. The HCU has an Isolation Control Unit (ICU) and a Directional Control Unit (DCU). The ICU has an isolation valve that controls aircraft hydraulic power for the thrust reverser. The DCU has a directional control valve that controls hydraulic pressure to deploy or stow the thrust reverser actuators. There is a cable and lever to manually inhibit the HCU. Two proximity sensors on the ICU send a signal to the aircraft to indicate whether the HCU is active or inhibited.
The HCU connects the thrust reverser actuation system with the hydraulic distribution system of the aircraft. The HCU controls the flow of hydraulic fluid to the four hydraulic actuators on the thrust reverser. It does this with supply and return connections. The HCU has an Isolation Control Unit (ICU) and a Directional Control Unit (DCU). The ICU has an isolation valve that controls aircraft hydraulic power for the thrust reverser. The DCU has a directional control valve that controls hydraulic pressure to deploy or stow the thrust reverser actuators. There is a cable and lever to manually inhibit the HCU. Two proximity sensors on the ICU send a signal to the aircraft to indicate whether the HCU is active or inhibited.
D. Hydraulic T-Piece
The hydraulic T-piece manifold is attached to the pylon at the 12:00 o'clock position (when you look forward). It supplies hydraulic pressure from the HCU to the upper hydraulic actuators. It also supplies the return pressure from the hydraulic actuators to the HCU. It does this with deploy, stow, and return hoses.
The hydraulic T-piece manifold is attached to the pylon at the 12:00 o'clock position (when you look forward). It supplies hydraulic pressure from the HCU to the upper hydraulic actuators. It also supplies the return pressure from the hydraulic actuators to the HCU. It does this with deploy, stow, and return hoses.
E. Filter and Clogging Indicator
A 15-micron filter module on the pylon protects TRAS components from debris that may be in the hydraulic system. The filter module has a red button that is out when the filter is clogged. The thrust reverser will still operate with a clogged filter but the speed will decrease. There is an automatic shut-off valve so you can remove and install the filter without losing a lot of hydraulic fluid.
A 15-micron filter module on the pylon protects TRAS components from debris that may be in the hydraulic system. The filter module has a red button that is out when the filter is clogged. The thrust reverser will still operate with a clogged filter but the speed will decrease. There is an automatic shut-off valve so you can remove and install the filter without losing a lot of hydraulic fluid.
4. Operation/Control and Indicating
A. Indication
The thrust reverser system indications are sent from the EEC to the Display Management Computer (DMC) and the Flight Warning Computer (FWC). The DMC displays the parameters and the warning messages from the FWC on the Engine/Warning Display (E/WD) unit of the Electronic Centralized Aircraft Monitoring (ECAM).
The thrust reverser system indications are sent from the EEC to the Display Management Computer (DMC) and the Flight Warning Computer (FWC). The DMC displays the parameters and the warning messages from the FWC on the Engine/Warning Display (E/WD) unit of the Electronic Centralized Aircraft Monitoring (ECAM).
(1) Normal condition
Aircraft on ground, reverse mode selected from the EEC:
Aircraft on ground, reverse mode selected from the EEC:
(a) For each engine, an amber REV indication in a grey box (outline) appears in the middle of the N1 dial when at least one thrust reverser door is unlocked. This indication changes to green over brightness when both thrust reverser doors are deployed.
(2) Abnormal condition
(a) Aircraft on ground
An amber REV indication in a grey box can appear in two cases:
An amber REV indication in a grey box can appear in two cases:
- Reverse mode not selected and both thrust reverser doors deployed
- At least one thrust reverser door is unlocked.
(b) Aircraft in flight
An amber REV indication in a grey box first flashes then remains steady when at least one thrust reverser door is unlocked, or both thrust reverser doors are fully deployed.
An amber REV indication in a grey box first flashes then remains steady when at least one thrust reverser door is unlocked, or both thrust reverser doors are fully deployed.
B. System Operation
(1) The thrust reverser system has a two-position operation:
- Fully stowed and locked (forward thrust position)
- Fully deployed (reverse thrust position).
(2) The thrust reverser levers in the flight compartment send electrical stow and deploy signals to the TRAS. The TRAS controls thrust reverser operation in the sequence that follows:
- Unlock
- Deployment
- Deployment retention
- Stow
- Lock.
(3) When the thrust-reverser lever is put into the deploy position, the ICU solenoid valve energizes. The ICU supplies high pressure hydraulic fluid to the DCU. The DCU pressure switch sends a pressurized signal to the EEC, and the DCU solenoid valve energizes.
(4) High pressure hydraulic fluid is supplied from the HCU and T-piece connector to the four hydraulic actuators on each thrust reverser. Internal locks on the actuators are released by the hydraulic pressure. The locking actuators and the feedback actuators operate in unison to move the translating sleeves aft to the deployed position.
(5) The translating sleeves move aft and extend the blocker doors into the fan exhaust air path. The cascades come into view as the sleeves move aft to the deploy position.
(6) The thrust reverser is held in the fully-deployed position by hydraulic pressure supplied through the deploy tubes. This pressure is continuously applied to the jack head and rod end of the actuators as long as the DCU solenoid valve is energized.
(7) When the thrust-reverser lever is put into the stow position, the ICU solenoid valve stays energized and the DCU solenoid valve de-energizes. Hydraulic pressure from the actuator jack head is directed into the return tubes and then to the return system. At the same time, hydraulic pressure on the rod end retracts the actuator.
(8) The translating sleeves move forward and retract the blocker doors. The cascades go out of view as the sleeves move forward to the stow position.
(9) When the translating sleeves move to the fully stowed position, internal locks on the actuators are reset. The ICU solenoid valve de-energizes. The DCU pressure switch sends a not-pressurized signal to the EEC. Hydraulic pressure from the rod ends keeps the actuators in the stowed and locked position.