EXHAUST SYSTEM 78.

EXHAUST - GENERAL - DESCRIPTION AND OPERATION1 . General Part of the air absorbed by the fan is directly evacuated to the outside;the remaining part is directed to the engine combustion chamber and burnt gases are ejected through an exhaust nozzle.The engine exhaust section directs fan discharge air for either normal or reverse thrust operation.In forward thrust mode, fan air flow and burnt gases are evacuated directlyat the back.Each engine is equipped with a reverser system which reverses cold fan air by means of blocker doors, integrated in the short nacelle body. The blocker doors turn the engine airflow forward and provide a braking effect for the aircraft on the ground.Thrust reverser can be operated only on the ground.

3 . DescriptionThe exhaust system consists of a primary nozzle for hot exhaust and a fannozzle which incorporates the thrust reverser system.A. Hot ExhaustThe primary exhaust forms the rear part of the engine.It consists of a center body and a rear conical nozzle.B. Fan NozzleThe fan nozzle forms a part of the nacelle and provides an annulus forexit of the fan flow.It consists of fixed cowls, with pivoting doors which form :- a continuation of the nacelle aerodynamic line- the outer wall of the exhaust nozzle.This outer wall contains an inner cowl forming the inner wall of the exhaust nozzle.The fan nozzle/thrust reverser assembly is hinged to the pylon andclamped to the engine fan frame.C. Thrust Reverser System The thrust reverser system uses part of engine exhaust power to provide additional aerodynamic braking during aircraft landing.The thrust reverser system is hydraulically actuated by the hydraulicpump mounted on the engine.

EXHAUST SYSTEM 78.

It is controlled through the FADEC (Full Authority Digital EngineControl) from the cockpit by a lever hinged to the corresponding throttle

control lever.

EXHAUST SYSTEM 78.

EXHAUST SYSTEM 78.

HOT EXHAUST - DESCRIPTION AND OPERATION1 . GeneralThe hot exhaust consists of a center body and a conical primary nozzle.The nozzle directs the primary exhaust gas aft and regulates the gas stream flow.A. Core Nozzle (or Primary Nozzle)(1) Description The primary nozzle is composed of:- a forward flange for attachement to the engine outer primary exhaust frame (A6 flange) with 16 bolts,- a conventional stiffened sheet metal inner and outer skin,- and a forward bulkhead. A spring seal is attached to the outer barrel which interfaces with the pylon. The outer barrels are of skin and frame construction.The primary nozzle structural assembly is a riveted conventional sheet metal structure.

EXHAUST SYSTEM 78.

B. Centerbody(1) Description---The centerbody is composed of:- a forward flange for attachment to the engine inner primary exhaustframe (A7 flange) with 16 bolts and,- a stiffened sheet metal formed section with an open aft end for theengine center vent system.

THRUST REVERSER - DESCRIPTION AND OPERATION1 . 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 returncircuit.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. Actuationtime for the total system is less than two seconds, therefore, the blocker

EXHAUST SYSTEM 78.

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 . DescriptionThe 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

EXHAUST SYSTEM 78.

the deploy position,- hoses,- one electrical junction box.

3 . OperationThe thrust reverser is actuated in response to signals from the ECU.Selection of either stow or deploy from the cockpit generates a signal tothe engine ECU. The ECU, in turn, supplies two independent signals to thethrust reverser HCU pressurizing and directional control solenoid valves.Opening of the HCU pressurizing valve actuates a pressure switch: thisprovides a signal which indicates that the thrust reverser is pressurized.B. Thrust Reverser DeploymentUpon receipt of the deploy signal from the ECU, the thrust reverser HCUinitially 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 ofreverser deployed. Hydraulic pressure is then removed from the system.C. Thrust Reverser StowageWhen 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 DeploymentIn case of an inadvertent deployment of the thrust reverser, the ECUcommands the restow and sets the engine at idle in some specificdeployment configurations.

E. Autorestow OperationIn autorestow operation, the ECU shall stow the thrust reverser when allof the following are true:- Engine running

EXHAUST SYSTEM 78.

- 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 . MaintenanceThrust reverser actuation system can be made inoperative (as a safety procedure when personnel are working around the blocker doors or in order todispatch 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 ofthe potential hazard created by an inadvertent deployment of the doors.5 . Electrical SupplyAll electrical circuits are designed to operate with 28 VDC nominal voltage.

EXHAUST SYSTEM 78.