A320, CFM56-5B, Session 4, Thrust Reverser system , for training purposes only.

A320 CFM56-5B thrust reverser system:
The thrust reverser system is of the aerodynamic blockage type. It consists of 4 pivoting blocker doors which stop and redirect fan discharge airflow.
Two doors are installed on each "C" duct.
Thrust reverser operation is possible on ground only.
The thrust reverser system is hydraulically supplied by the corresponding hydraulic pump on the engine.
The thrust reverser is isolated from the hydraulic supply by a Shut Off Valve.
Each door is operated by a hydraulic actuator.
The actuators receive fluid from the Hydraulic Control Unit (HCU) which is controlled by the Electronic Control Unit (ECU).
Two independent latch mechanisms maintain each pivoting blocker door in the stowed position, one inside the actuator and the second with the door latch.
The door latches are hydraulically released in series at the beginning of the deploy sequence.
Basically the thrust reverser system is controlled through the ECU from the two reverser latching levers located on the throttle control levers.
The HCU has a pressurizing valve and a directional valve to select deploy or stow mode.
The directional valve is operated to deploy only.
For third defense line purposes, the Spoiler Elevator Computers (SECs) have previously opened the Shut Off Valve and the hydraulic pressure is supplied to the HCU.
Then, the Engine Interface Unit (EIU) permits reverser deployment by energization of the inhibition relay, so the directional valve can be opened by the ECU.
To command the thrust reverser, the ECU needs an "A/C on ground" signal supplied by the Landing Gear Control and Interface Units (LGCIUs).
The actual state of the thrust reverser is shown on the ECAM warning display (REVerser indication in the middle of N1 dial).
The signals come from the stow and deploy position switches.
Reverse thrust is allowed when reversers are deployed.
To help trouble shooting, a reverser test can be performed through the MCDU.
For maintenance purposes or to increase A/C dispatch, the HCU is fitted with a deactivation lever to deactivate the thrust reverser system.
For the lock-out procedure, four lock-out bolts should also be installed.
WARNING: The thrust reverser system should be deactivated using the HCU lever, before working on the system or on the engine.
If not, the thrust reverser can accidentally operate and cause serious injuries to personnel and/or damage to the reverser.