DOC AIRBUS | AMM A320FTHRUST REVERSER SYSTEM - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The Thrust Reverser (T/R) system for the V2500 engine is designed for use on the ground to reduce the aircraft landing roll. The T/R is designed to be used at two extreme positions, stowed and deployed. In the stowed position, the T/R provides an aerodynamic fairing between the fan cowl and the core nozzle.
When the T/R is in the deployed position:
The T/R Shut-Off Valve (SOV) is designed to isolate the T/R from the aircraft hydraulic system.
** ON A/C NOT FOR ALL The Thrust Reverser (T/R) system for the V2500 engine is designed for use on the ground to reduce the aircraft landing roll. The T/R is designed to be used at two extreme positions, stowed and deployed. In the stowed position, the T/R provides an aerodynamic fairing between the fan cowl and the core nozzle.
Thrust Reverser SystemWhen the T/R is in the deployed position:
- The translating sleeves are hydraulically moved rearward exposing the cascades.
- The blocker doors are positioned to close the fan duct downstream.
- The fan air exhaust flow is diverted forward through the cascades providing a braking effort for the aircraft.
The T/R Shut-Off Valve (SOV) is designed to isolate the T/R from the aircraft hydraulic system.
2. Description
The thrust reverser system comprises:
** ON A/C NOT FOR ALL The thrust reverser system comprises:
- a hydraulic control unit (HCU) including:
an isolation valve
an isolation valve solenoid
a directional control valve
a directional control valve solenoid
a pressure switch
a filter and clogging indicator
a lockout lever - four actuators with internal lock for lower actuators
- three flexible shafts
- two linear variable differential transformers located on each upper actuator
- two proximity switches located on each lower actuator
- two thrust reverser cowls comprising a fixed structure and 2 translating sleeves latched together.
one thrust reverser shutoff valve.
3. Operation
A. General
The thrust reverser is actuated in response to signals from the Engine Electronic Control (EEC). Selection of either stow or deploy from the cockpit generates a signal to the engine EEC which in turn, supplies signals to the thrust reverser hydraulic control unit.
The thrust reverser is actuated in response to signals from the Engine Electronic Control (EEC). Selection of either stow or deploy from the cockpit generates a signal to the engine EEC which in turn, supplies signals to the thrust reverser hydraulic control unit.
B. Thrust Reverser Deployment
Thrust reverser deployment is initiated by rearward movement of the reverser lever which inputs a signal, via a dual resolver, to the EEC.
The EEC supplies a 28 volt signal to the isolation valve and directional control valve solenoids mounted in the HCU. The transmision of these signals from the EEC is dependent upon the 28 V supply and the weight on wheels switch within the EEC. The supply of the signal to the directional control valve solenoid is also dependent upon the closure of the aircraft permission switch in that line. This switch is closed by the Throttle Lever Angle signal via the spoiler/elevator computer and the Engine Interface Unit energization of the isolation valve solenoid and the directional control valve solenoid allows hydraulic pressure into the system - this event being relayed to the EEC by the pressure switch mounted in the HCU. Pressure in the lower actuators releases the locks and these events are signalled to the EEC by the Proximity Switches (lock sensors). As the pistons move rearward to deploy the reverser, the Linear Variable Differential Transformer (LVDT) on the upper actuators monitors the movement and informs the EEC when the translating sleeve is fully deployed, the Proximity Switches and LVDTs remain active and the isolation valve remains energized.
Thrust reverser deployment is initiated by rearward movement of the reverser lever which inputs a signal, via a dual resolver, to the EEC.
The EEC supplies a 28 volt signal to the isolation valve and directional control valve solenoids mounted in the HCU. The transmision of these signals from the EEC is dependent upon the 28 V supply and the weight on wheels switch within the EEC. The supply of the signal to the directional control valve solenoid is also dependent upon the closure of the aircraft permission switch in that line. This switch is closed by the Throttle Lever Angle signal via the spoiler/elevator computer and the Engine Interface Unit energization of the isolation valve solenoid and the directional control valve solenoid allows hydraulic pressure into the system - this event being relayed to the EEC by the pressure switch mounted in the HCU. Pressure in the lower actuators releases the locks and these events are signalled to the EEC by the Proximity Switches (lock sensors). As the pistons move rearward to deploy the reverser, the Linear Variable Differential Transformer (LVDT) on the upper actuators monitors the movement and informs the EEC when the translating sleeve is fully deployed, the Proximity Switches and LVDTs remain active and the isolation valve remains energized.
C. Thrust Reverser Stowage
Stowage of reverser is initiated by forward movement of the piggyback levers which signal this intent to the EEC. The signal to the directional control valve solenoid is then cancelled by the EEC and permission switch, allowing pressure to remain only in the stow side of the actuators. The pistons then move forward 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.
Stowage of reverser is initiated by forward movement of the piggyback levers which signal this intent to the EEC. The signal to the directional control valve solenoid is then cancelled by the EEC and permission switch, allowing pressure to remain only in the stow side of the actuators. The pistons then move forward 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.
NOTE: During normal reverser operation the isolation valve remains energized for a period of five seconds after the LVDTs have registered fully stowed to ensure full lock engagement and completion of the stow cycle.
D. Inadvertent Stowage/Deployment
If the LVDTs sense a displacement of more than 10% of the thrust reverser actuator travel, the EEC commands an automatic stowage or deployment of the thrust reversers.
If the LVDTs sense a displacement of more than 10% of the thrust reverser actuator travel, the EEC commands an automatic stowage or deployment of the thrust reversers.
(1) Auto-restow
- The EEC signals the isolation valve to open, and as the directional control valve is in the stow configuration the hydraulic pressure stows the thrust reversers.
- The isolation valve remains energized for the rest of the flight.
- If the deployment of the thrust reversers is greater than 15% of their full travel, the EEC commands idle.
(2) Auto-redeploy
- The EEC commands the isolation valve to close and keeps it closed until idle is selected.
- Thus the hydraulic pressure is cut off from the system.
- The aerodynamic load on the thrust reversers is sufficient to deploy again the thrust reversers.
- If the thrust reversers stow by more than 22% of the actuator travel, the EEC sets the engine to idle.
4. System Lockouts
A. Flight Dispatch
There are two locations when the thrust reverser system must be locked out for safety: The HCU which hydraulically locks the system and the translating sleeve which mechanically locks the system.
There are two locations when the thrust reverser system must be locked out for safety: The HCU which hydraulically locks the system and the translating sleeve which mechanically locks the system.
(1) The HCU has a manual lockout lever that moves the isolation valve in the HCU which blocks hydraulic pressure to the translating sleeve actuators. The lever is moved manually and held in place by a lockout pin which is stowed in the HCU.
(2) The left and right translating sleeves have a mechanism to lock the translating sleeve so that it cannot deploy. When the lockout pin is put in the lockout assembly, it engages the fixed structure of the C-duct and prevents movement of the translating sleeve. Two fittings are located on the side of the translating sleeve near the middle, the upper fitting is the lockout assembly, the lower fitting is the lockout pin stowage bracket assembly. When the T/R is used, the upper fitting has a plug in it. To lockout the translating sleeve, the position of the lockout pin and the plug are reversed. The outer end of the lockpin extends out from the surface of the sleeve when the pin is put in the lockout assembly.
B. Ground Maintenance
(1) The HCU has a manual lockout levers that moves the isolation valve in the HCU which blocks hydraulic pressure to the translating sleeve actuators. The lever is moved manually and held in place by a lockout pin.
The lockout pin used to lockout the HCU for ground maintenance has a red flag and is not the lockout pin stowed in the HCU.
The lockout pin used to lockout the HCU for ground maintenance has a red flag and is not the lockout pin stowed in the HCU.
(2) The lower actuators on each side of the T/R can be held in the unlocked position. This is achieved by manually moving the levers on each actuators and inserting lockout pins with a red flag. The actuators are manually unlocked to manually operate the translating sleeves.
The lower actuators on each side of the thrust reversers have a manual drive mechanism mounted in the actuator base.
In normal operation the lock levers are hydraulically unlocked and locked.
The lower actuators on each side of the thrust reversers have a manual drive mechanism mounted in the actuator base.
In normal operation the lock levers are hydraulically unlocked and locked.
5. Thrust Reverser Manual Opening/Closing
A. General
Thrust reverser system can be operated manually on the ground for maintenance purposes using a manually operated drive shaft.
A manually bypassable non return valve is used to allow movement of the translating sleeves without any hydraulic blockage.
Thrust reverser system can be operated manually on the ground for maintenance purposes using a manually operated drive shaft.
A manually bypassable non return valve is used to allow movement of the translating sleeves without any hydraulic blockage.
NOTE: To get access to this valve, the corresponding pylon access panel must be removed.
B. Operation
(1) Initial conditions
- the HCU isolation and directional control valve solenoids are not energized
- lower actuators are locked in the stowed position.
(2) Manual deploying
(a) Move the lockout lever of the HCU to the locked position and hold it in place by the ground lockout pin
(b) Move the lower actuator lock lever to the unlocked position and insert the lockpin to hold it as shown in figure
(c) Move the non return valve to the by-pass position.
(d) Using the manual drive shaft move the translating sleeves towards the deploy position.
Fluid necessary to prevent hydraulic blockage is sucked from the hydraulic reservoir through the return line and the non return valve.
Fluid necessary to prevent hydraulic blockage is sucked from the hydraulic reservoir through the return line and the non return valve.
(3) Manual stowing
(a) Move the translating sleeves towards the stowed position using the manual drive shaft. Excess fluid is returned back to the hydraulic reservoir through the return line and the non return valve.
NOTE: This operation does not need to bypass the non return valve : fluid flows in its normal flow way.
(b) When the translating sleeves reach their fully stowed position, release the lower actuator lock lever to its locked position.
(c) Move the non return valve lever to its normal position and release the HCU lockout lever by removing the lockout pin.
(d) Move the non return valve lever back to "normal" (a mechanical feature, integrated with the pylon access panel, would however prevent leaving the lever in the "wrong" bypassed position for flight).