DOC AIRBUS | AMM A320FTHRUST REVERSER - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The fan thrust reverser is located immediatly downstream of the fan frame.
An adaptor ring attached to the rear engine fan frame interfaces between the engine and the reverser itself.
In direct thrust configuration, the cowling masks the blocker doors, thus providing fan flow ducting with minimized thrust loss.
In reverse thrust configuration, the blocker doors are deployed in order to obstruct the fan duct; the fan flow is ejected laterally through the reverser with a forward velocity component which provides the reverse thrust. To give access to the engine, the reverser consists of two half-fan ducts (D - ducts) hinged at pylon and latched at the bottom.
The left and right thrust reverser systems are interchangeable except the cascades that control the efflux pattern.
The thrust reverser includes acoustic linings, a pressure relief system, LP turbine case and core compartment cooling systems and fire walls.
The doors are hydraulically actuated. Supply is directly made from the engine driving pump and the return is made to a servo control return circuit.
The thrust reverser hydraulic control unit (HCU) controls through the ECU signals, the sequence and functions of:
** ON A/C NOT FOR ALL The fan thrust reverser is located immediatly downstream of the fan frame.
Thrust Reverser SystemAn adaptor ring attached to the rear engine fan frame interfaces between the engine and the reverser itself.
In direct thrust configuration, the cowling masks the blocker doors, thus providing fan flow ducting with minimized thrust loss.
In reverse thrust configuration, the blocker doors are deployed in order to obstruct the fan duct; the fan flow is ejected laterally through the reverser with a forward velocity component which provides the reverse thrust. To give access to the engine, the reverser consists of two half-fan ducts (D - ducts) hinged at pylon and latched at the bottom.
The left and right thrust reverser systems are interchangeable except the cascades that control the efflux pattern.
The thrust reverser includes acoustic linings, a pressure relief system, LP turbine case and core compartment cooling systems and fire walls.
The doors are hydraulically actuated. Supply is directly made from the engine driving pump and the return is made to a servo control return circuit.
The thrust reverser hydraulic control unit (HCU) controls through the ECU signals, the sequence and functions of:
- unlocking,
- deploying,
- stowing and,
- locking of the blocker door latches and actuators.
Movement of each blocker door is independent of the other doors. Actuation time for the total system is less than two seconds, therefore, the blocker doors are not synchronized. Appropriate interlocks and position microswitches are incorporated in the system ; upper ECAM display indication in the cockpit provides thrust reverser position and status.
The fan reverser system on one engine is completely independent of the other engine system.
The FADEC incorporates two identical channels (A and B) which receive signals. Only the channel "in control" transmits control signals.
2. Description
The thrust reverser system includes:
** ON A/C NOT FOR ALL The thrust reverser system includes:
- a Hydraulic Control Unit (HCU) including:
a pressurizing valve,
a directional valve,
a pressure switch,
a flow limiter,
a filter. - Four actuators with inner latch,
- Four door latches,
- Four door position switches for the stow position, two double switches for the deploy position,
- hoses,
- one electrical junction box.
3. Operation
A. General
The thrust reverser is actuated in response to signals from the ECU. Selection of either stow or deploy from the cockpit generates a signal to the engine ECU. The ECU, in turn, supplies two independent signals to the thrust reverser HCU pressurizing and directional control solenoid valves. Opening of the HCU pressurizing valve actuates a pressure switch: this provides a signal which indicates that the thrust reverser is pressurized.
The thrust reverser is actuated in response to signals from the ECU. Selection of either stow or deploy from the cockpit generates a signal to the engine ECU. The ECU, in turn, supplies two independent signals to the thrust reverser HCU pressurizing and directional control solenoid valves. Opening of the HCU pressurizing valve actuates a pressure switch: this provides a signal which indicates that the thrust reverser is pressurized.
B. Thrust Reverser Deployment
Upon receipt of the deploy signal from the ECU, the thrust reverser HCU initially provides:
Upon receipt of the deploy signal from the ECU, the thrust reverser HCU initially provides:
- hydraulic pressure to the stow side of the blocker door actuators and
- unlock pressure to the blocker door latches.
These latches are hydraulically unlocked in series; each latch must thus be unlocked before hydraulic pressure is provided to the next one. When the thrust reverser HCU receives a hydraulic signal indicating that all the latches are unlocked, the hydraulic pressure is provided to the deploy side of the blocker door actuators. When deploy pressure is supplied to the actuators, the secondary locks within each actuator release, resulting in deployment of the actuators. As the blocker doors move away from the stow position, the "unstow" switches on each door are activated. Activation of the switches generates an indication of an unstowed reverser for the cockpit. At 95 percent of the fully deployed position, switches are activated providing cockpit indication of reverser deployed. Hydraulic pressure is then removed from the system.
C. Thrust Reverser Stowage
When reverser stow is selected, the thrust reverser HCU ports hydraulic pressure only to the retract side of the actuators pistons and stows the blocker doors. When the blocker doors reach the stowed position, the door latches are engaged and locked. Switches are also activated to send reverser STOWED signals to the cockpit. The hydraulic pressurizing valve is then closed and pressure is removed from the system. All the switches are dual sensing for redundancy.
In normal operation, the ECU sets the engine at idle when the doors are in transit.
When reverser stow is selected, the thrust reverser HCU ports hydraulic pressure only to the retract side of the actuators pistons and stows the blocker doors. When the blocker doors reach the stowed position, the door latches are engaged and locked. Switches are also activated to send reverser STOWED signals to the cockpit. The hydraulic pressurizing valve is then closed and pressure is removed from the system. All the switches are dual sensing for redundancy.
In normal operation, the ECU sets the engine at idle when the doors are in transit.
D. Inadvertent Deployment
In case of an inadvertent deployment of the thrust reverser, the ECU commands the restow and sets the engine at idle in some specific deployment configurations.
These configuration are as follows:
In case of an inadvertent deployment of the thrust reverser, the ECU commands the restow and sets the engine at idle in some specific deployment configurations.
These configuration are as follows:
| ------------------------------------------------------------------------------- |
| ! DOOR POSITION STATUS ! FUNCTIONS ACCOMPLISHED BY THE ECU ! |
| !----------------------------------------!------------------------------------! |
| !at least 1 door >2 % ! 4 doors >2 % ! Restow ! Idle ! |
| !---------------------!------------------!-------------------!----------------! |
| ! Yes ! No ! Yes ! No ! |
| !---------------------!------------------!-------------------!----------------! |
| ! Yes ! Yes ! Yes ! Yes ! |
| ------------------------------------------------------------------------------- |
E. Autorestow Operation
In autorestow operation, the ECU shall stow the thrust reverser when all of the following are true:
In autorestow operation, the ECU shall stow the thrust reverser when all of the following are true:
- Engine running
- Aircraft on ground
- Throttle lever angle (TLA) greather than -4.3 degrees
- Detected reverser position is one of the following
- At least one door unstowed
- Reverser system is inadvertently pressurized) - Fan speed is below 71%, the actuation system's restow capability.
The autorestow function shall be deactivated if the thrust reverser doors cyclefrom unstowed to stowed at least twice.
4. Maintenance
Thrust reverser actuation system can be made inoperative (as a safety procedure when personnel are working around the blocker doors or in order to dispatch an aircraft with inoperative thrust reverser) by using the "inhibition" feature incorporated into the thrust reverser HCU.
Installation of an inhibition pin to lock the HCU lever in the "inhibited" position will prevent hydraulic pressure from being delivered to the thrust reverser latches and actuators; therefore making the reverser inoperative (the fan cowl dorrs must be open). When an aircraft is dispatches with an inoperative thrust reverser, blocker door lockout pins are provided to secure the door in the stowed position. These fins are an additional lockout feature.
A readable warning on the middle of each door informs maintenance people of the potential hazard created by an inadvertent deployment of the doors.
** ON A/C NOT FOR ALL Thrust reverser actuation system can be made inoperative (as a safety procedure when personnel are working around the blocker doors or in order to dispatch an aircraft with inoperative thrust reverser) by using the "inhibition" feature incorporated into the thrust reverser HCU.
Installation of an inhibition pin to lock the HCU lever in the "inhibited" position will prevent hydraulic pressure from being delivered to the thrust reverser latches and actuators; therefore making the reverser inoperative (the fan cowl dorrs must be open). When an aircraft is dispatches with an inoperative thrust reverser, blocker door lockout pins are provided to secure the door in the stowed position. These fins are an additional lockout feature.
A readable warning on the middle of each door informs maintenance people of the potential hazard created by an inadvertent deployment of the doors.
5. Electrical Supply
All electrical circuits are designed to operate with 28 VDC nominal voltage.
All electrical circuits are designed to operate with 28 VDC nominal voltage.