DOC AIRBUS | AMM A320FTHRUST REVERSER (T/R) CONTROL AND INDICATING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
1. System Description
The engine thrust reverser changes the flow of the fan bypass airflow from forward thrust to reverse thrust. The thrust reverser changes configuration when a command signal is sent from the flight deck.
The thrust reverser has a translating cowl (transcowl) that moves forward and aft to facilitate forward and reverse thrust. For reverse thrust, the transcowl opens to the aft position, which is known as the deployed position. For forward thrust, the transcowl closes to the forward position, which is known as the stowed position.
The hydraulic Thrust Reverser Actuation System (TRAS) uses hydraulic fluid supplied by the aircraft systems to move the transcowl. The TRAS includes Linear Variable Differential Transducers (LVDTs) and proximity sensors. These components are used to monitor the TRAS operation and to report status (such as normal and abnormal conditions) during aircraft flight, landing, and reverser thrust.
The TRAS moves the transcowl when the flight crew moves the reverse throttle lever which sends a command signal to the TRAS.
The TRAS has eleven major components which are:
** ON A/C NOT FOR ALL The engine thrust reverser changes the flow of the fan bypass airflow from forward thrust to reverse thrust. The thrust reverser changes configuration when a command signal is sent from the flight deck.
Thrust Reverser Actuation SystemThe thrust reverser has a translating cowl (transcowl) that moves forward and aft to facilitate forward and reverse thrust. For reverse thrust, the transcowl opens to the aft position, which is known as the deployed position. For forward thrust, the transcowl closes to the forward position, which is known as the stowed position.
The hydraulic Thrust Reverser Actuation System (TRAS) uses hydraulic fluid supplied by the aircraft systems to move the transcowl. The TRAS includes Linear Variable Differential Transducers (LVDTs) and proximity sensors. These components are used to monitor the TRAS operation and to report status (such as normal and abnormal conditions) during aircraft flight, landing, and reverser thrust.
The TRAS moves the transcowl when the flight crew moves the reverse throttle lever which sends a command signal to the TRAS.
The TRAS has eleven major components which are:
- Synchronized locking feedback actuators
- Synchronized non-locking actuator
- Synchronized manual locking actuator
- Proximity Sensors
- Manual Drive Units (MDU)
- Isolation Control Unit (ICU)
- Directional Control Unit (DCU)
- Sync shaft and sync tube assemblies
- Over-the-top flex shaft and flex sync tube assembly
- Electrical tertiary lock system
- Electrical Harnesses.
2. Component Description
A. Synchronized Locking Feedback Actuator with Primary Locking System
The synchronized locking feedback actuators are the two upper actuators, which have locks to lock the transcowl in the stowed position. Each synchronized locking feedback actuators has a single channel LVDT, with AC voltage output that is in proportion to the actuator position. The LVDTs give position feedback to Electronic Engine Control (EEC) channels A and B. The LVDTs are part of the synchronized locking feedback actuators and are not Line Replaceable Units (LRUs). There is one right hand side synchronized locking feedback actuator and one left hand side synchronized locking feedback actuator.
Proximity sensors in the synchronized locking feedback actuators send a signal to the EECs when the actuators are in the fully stowed position.
The actuators are synchronized by the flex shaft that connects the two upper actuators. All four actuators stow and deploy at the same rate. Each synchronized locking feedback actuator has a fire seal at the location where the actuator body goes through the thrust reverser forward frame. The fire seals are part of the fire barrier between the transcowl cavity and the fan compartment.
The synchronized locking feedback actuators are the two upper actuators, which have locks to lock the transcowl in the stowed position. Each synchronized locking feedback actuators has a single channel LVDT, with AC voltage output that is in proportion to the actuator position. The LVDTs give position feedback to Electronic Engine Control (EEC) channels A and B. The LVDTs are part of the synchronized locking feedback actuators and are not Line Replaceable Units (LRUs). There is one right hand side synchronized locking feedback actuator and one left hand side synchronized locking feedback actuator.
Proximity sensors in the synchronized locking feedback actuators send a signal to the EECs when the actuators are in the fully stowed position.
The actuators are synchronized by the flex shaft that connects the two upper actuators. All four actuators stow and deploy at the same rate. Each synchronized locking feedback actuator has a fire seal at the location where the actuator body goes through the thrust reverser forward frame. The fire seals are part of the fire barrier between the transcowl cavity and the fan compartment.
B. Synchronized Non-Locking Actuator and Synchronized Manual Locking Actuator
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The synchronized manual locking actuator is the right lower actuator and the synchronized non-locking actuator is the left lower actuator. These actuators are connected by the sync shafts to the upper actuators. The status of the synchronized manual locking actuator and synchronized non-locking actuator is not monitored. All four actuators stow and deploy at the same rate. The synchronized manual locking actuator has a manual locking lever (known as a bumper lever) that is used for personnel safety during maintenance. The bumper lever is used to lock the transcowl in position during ground maintenance.
The synchronized non-locking actuator and synchronized manual locking actuator each have a fire seal at the location where the actuator body goes through the thrust reverser forward frame. The fire seals are part of the fire barrier between the transcowl cavity and the fan compartment.
and
The synchronized manual locking actuator is the right lower actuator and the synchronized non-locking actuator is the left lower actuator. These actuators are connected by the sync shafts to the upper actuators. The status of the synchronized manual locking actuator and synchronized non-locking actuator is not monitored. All four actuators stow and deploy at the same rate. The synchronized manual locking actuator has a manual locking lever (known as a bumper lever) that is used for personnel safety during maintenance. The bumper lever is used to lock the transcowl in position during ground maintenance.
The synchronized non-locking actuator and synchronized manual locking actuator each have a fire seal at the location where the actuator body goes through the thrust reverser forward frame. The fire seals are part of the fire barrier between the transcowl cavity and the fan compartment.
C. Proximity Sensors
Each synchronized locking feedback actuator has a primary lock that prevents accidental transcowl deployment and is operated when it receives hydraulic pressure from the DCU and ICU. The primary lock stays locked without hydraulic power when the TRAS is in the stowed position. The primary lock unlocks when hydraulic pressure is applied, which permits the actuators to move in the deploy direction. The primary locks are continuously monitored by the EEC by two single-channel (channel A and B) proximity sensors on each synchronized locking feedback actuator.
The two single-channel proximity sensors used on each synchronized locking feedback actuator transmit signals on one channel of the EEC. The proximity sensor target transmits lock indication to the proximity sensors. The proximity sensors receive the target indication and then transmit a signal through channels A and B to EEC A and EEC B. The proximity sensors are LRUs. There are no adjustment procedures for the proximity sensors or the targets.
Each synchronized locking feedback actuator has a primary lock that prevents accidental transcowl deployment and is operated when it receives hydraulic pressure from the DCU and ICU. The primary lock stays locked without hydraulic power when the TRAS is in the stowed position. The primary lock unlocks when hydraulic pressure is applied, which permits the actuators to move in the deploy direction. The primary locks are continuously monitored by the EEC by two single-channel (channel A and B) proximity sensors on each synchronized locking feedback actuator.
The two single-channel proximity sensors used on each synchronized locking feedback actuator transmit signals on one channel of the EEC. The proximity sensor target transmits lock indication to the proximity sensors. The proximity sensors receive the target indication and then transmit a signal through channels A and B to EEC A and EEC B. The proximity sensors are LRUs. There are no adjustment procedures for the proximity sensors or the targets.
D. ICU
The ICU controls the hydraulic pressure supplied to the TRAS. The ICU solenoid is operated by the aircraft systems to move the isolation control valve and send hydraulic pressure to the DCU. The isolation control valve is usually held in the closed position by a mechanical spring. When is operates, the isolation control valve energizes the closed solenoid valve. This sends pressure to the pilot area of the spool which moves the valve to the deploy position. This condition permits the supply of hydraulic fluid to go to the other components of the TRAS.
The pressure switch senses the hydraulic pressure and transmits the output pressure status through EEC channels A and B. The limit switch transmits the ICU activated/deactivated status through EEC channels A and B. The pressure and limit switches each have two channels, with each channel has a sensor which is constantly monitored.
The ICU supplies the EEC channels A and B with the data that follows:
The ICU controls the hydraulic pressure supplied to the TRAS. The ICU solenoid is operated by the aircraft systems to move the isolation control valve and send hydraulic pressure to the DCU. The isolation control valve is usually held in the closed position by a mechanical spring. When is operates, the isolation control valve energizes the closed solenoid valve. This sends pressure to the pilot area of the spool which moves the valve to the deploy position. This condition permits the supply of hydraulic fluid to go to the other components of the TRAS.
The pressure switch senses the hydraulic pressure and transmits the output pressure status through EEC channels A and B. The limit switch transmits the ICU activated/deactivated status through EEC channels A and B. The pressure and limit switches each have two channels, with each channel has a sensor which is constantly monitored.
The ICU supplies the EEC channels A and B with the data that follows:
- Output pressure: pressurized/not pressurized
- Inhibition status: inhibited/active (a signal sent by the limit switch and controlled by the inhibition lever).
E. DCU
The DCU controls the hydraulic flow to the actuators. The DCU has a directional valve which has two positions, stow and deploy. The valve is usually held in the stow position by a mechanical spring. When the solenoid is energized, the hydraulic fluid opens the directional spool valve and sends the fluid to the deploy side of the synchronized locking feedback actuators, synchronized non-locking actuator and the synchronized manual locking actuator. The hydraulic flow is supplied by the aircraft systems through the ICU. When solenoid power is removed, the DCU is set back to the off position. This removes high pressure hydraulic fluid from the deploy side of the actuators.
In the off condition, the DCU supplies pressure to the stow port of the actuators which causes the transcowl to overstow. The DCU solenoid is energized by the aircraft system to change positions.
The DCU controls the hydraulic flow to the actuators. The DCU has a directional valve which has two positions, stow and deploy. The valve is usually held in the stow position by a mechanical spring. When the solenoid is energized, the hydraulic fluid opens the directional spool valve and sends the fluid to the deploy side of the synchronized locking feedback actuators, synchronized non-locking actuator and the synchronized manual locking actuator. The hydraulic flow is supplied by the aircraft systems through the ICU. When solenoid power is removed, the DCU is set back to the off position. This removes high pressure hydraulic fluid from the deploy side of the actuators.
In the off condition, the DCU supplies pressure to the stow port of the actuators which causes the transcowl to overstow. The DCU solenoid is energized by the aircraft system to change positions.
F. Sync Shaft, Flex Shaft, and Tube Assemblies
The TRAS has three synchronizing shafts installed in tube assemblies. The shafts make sure that all four actuators move at the same time and at the same rate. The shafts are flexible cores made of wound wire. The three shafts are mechanically synchronized by gears in the actuators. The two right actuators are connected by the right sync shaft. The two left actuators are connected by the left sync shaft. The two upper actuators are connected by the over-the-top flex shaft. The sync shafts are installed in rigid tubes. The over-the-top flex tube is like a hose that can bend as the thrust reverser halves open and close for maintenance and power plant access.
The TRAS has three synchronizing shafts installed in tube assemblies. The shafts make sure that all four actuators move at the same time and at the same rate. The shafts are flexible cores made of wound wire. The three shafts are mechanically synchronized by gears in the actuators. The two right actuators are connected by the right sync shaft. The two left actuators are connected by the left sync shaft. The two upper actuators are connected by the over-the-top flex shaft. The sync shafts are installed in rigid tubes. The over-the-top flex tube is like a hose that can bend as the thrust reverser halves open and close for maintenance and power plant access.
G. MDU for Maintenance
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An MDU is installed on each of the two lower actuators. The MDUs are used only for ground maintenance. One MDU is sufficient to deploy and stow the cowl without a hydraulic or an electric power source. The ICU must be in the deactivated position and the synchronized locking feedback actuators and the tertiary lock system must be unlocked before the MDU is used. Maintenance personnel apply torque to the MDU with a wrench to manually move the transcowl.
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An MDU is installed on each of the two lower actuators. The MDUs are used only for ground maintenance. One MDU is sufficient to deploy and stow the cowl without a hydraulic or an electric power source. The ICU must be in the deactivated position and the synchronized locking feedback actuators and the tertiary lock system must be unlocked before the MDU is used. Maintenance personnel apply torque to the MDU with a wrench to manually move the transcowl.
H. Electrical Harnesses
The electrical harnesses connect each of the TRAS components to the EECs installed on the fan case of the engine. The electrical harnesses connect the ICU, DCU, tertiary lock system, and the proximity sensors on the synchronized locking feedback actuators to the aircraft systems and to the two EECs.
For more information, refer to the inspection of the thrust reverser electrical harnesses (Ref. AMM TASK 71-51-43-210-801-A).
The electrical harnesses connect each of the TRAS components to the EECs installed on the fan case of the engine. The electrical harnesses connect the ICU, DCU, tertiary lock system, and the proximity sensors on the synchronized locking feedback actuators to the aircraft systems and to the two EECs.
For more information, refer to the inspection of the thrust reverser electrical harnesses (Ref. AMM TASK 71-51-43-210-801-A).
I. Tertiary Lock System
Refer to the description and operation of the thrust reverser electrical tertiary lock system (Ref. AMM D/O 78-37-00-00).
Refer to the description and operation of the thrust reverser electrical tertiary lock system (Ref. AMM D/O 78-37-00-00).