ATA 26 - FIRE PROTECTION

• The engines and the APU have individual fire detection systems.

Each system consists of two identical detection loops (A and B) mounted in parallel.

• FDU (Fire Detection Unit), 2 units, one for each Engine, Each FDU has 2 independent channels (A and B) and each channel is associated with a fire detection loop.

FDU Channel A → Loop A

FDU Channel B → Loop B

• FDU (APU Fire Detection Unit), just one computer dedicated to APU

• We have just 1 cargo firex bottle for both cargo compartments, bottle is located in the FWD cargo.

In cockpit we have 2 pushbuttons, one for FWD cargo and another one for AFT cargo. Once smoke is detected a red smoke indication appears to the cargo compartment associated pushbutton. Press to discharge.

• The FDU sends FIRE and FAULT signals to the Flight Warning Computer for display on the ECAM.

Each engine is equipped with 2 fire bottles located in the pylon. For the APU, there is just one fire extinguisher bottle located in the aft fuselage forward of the APU firewall.

• Avionics SMOKE detector is fitted in the extraction duct and will detect smoke coming from the computers and control boxes controlled by AEVC.

• In the enhanced cabin the SDCU is replaced by the Smoke Detection Function (SDF), which is integrated in the Cabin Intercommunication Data System (CIDS). The standard system includes one extinguishing bottle located into the FWD cargo compartment (for A318 and A319 relocated to the AFT bulk cargo compartment RH side).

An optional system includes two bottles.

• The engine Fire Detection Unit (FDU) has two channels capable of detecting any case of engine fire and loop failure.

Each channel does the same detection logic depending on the loop A and loop B status.

• Fire extinguishing for 10 seconds: this is required to reduce engine windmilling.

• ENG FIRE pushbutton pushed out → wait 10 seconds, if fire is still present → discharge 1st bottle → wait 30 seconds, if fire is still present → discharge 2nd bottle.

• A shunt plug (or shorting clip) will prevent bottle discharge which could cause injury to maintenance personnel. The cartridge installed must be supplied by fire bottle vendor and agreed with the specification indicated in the AMM.

• When an APU fire is detected on ground, the APU shuts down automatically and the fire extinguishing system is automatically triggered.

• Avionics System Ventilation Controller (AEVC) is connected to a detector located in the vicinity of the air extractor. It detects smoke in the avionics ventilation air.

• (CLASSIC) SDCU (Smoke Detector Control Unit) detects smoke in the cargo compartment areas and lavatories.

• (ENHANCED) SDCU is integrated in the CIDS system.

• APU firex bottle is located in the aft THS compartment.

• In case of failure of one channel, the smoke detection is still done by the remaining channel.

In case of failure of both channels, the fault is displayed on the ECAM, the SC is triggered and MASTER CAUT light comes on. The failure is also indicated to the CFDIU.

• When cargo smoke is detected (BULK smoke is shown as an example), the Continuous Repetitive Chime (CRC) sounds, the MASTER WARNing flashes and the SMOKE light on the CARGO SMOKE panel comes on.

The isolation valves of the cargo compartment are automatically closed and the ISOLation VALVE FAULT light on the CARGO HEAT panel comes on.

• In case of lavatory smoke detected: the amber lavatory indicator light, installed outside on the lavatory wall, flashes.

• Fire and Smoke detection recap:

- SDCU (Smoke detection Control Unit) → Smoke detection of Cargo areas and lavatories

- AEVC (Avionics Equipment Ventilation Computer → Smoke detection of A/A Bay

- FDU (Fire Detection Unit) → Fire detection of ENG 1, ENG 2 and APU (APU FDU)

ENGINE FIRE PROTECTION

• Each engine fire detection system consists of two independent loops A and B connected in parallel to the Fire Detection Unit (FDU), on pylon, fan and core.

• In case of a loop failure the Fire Detection Unit provides a loop fault warning signal to the ECAM and Centralized Fault Interface Unit (CFDIU).

• Never check the continuity of the squib using a conventional ohmmeter.

• MAX EGT Temp during start-up is 725°C.

• ENG fire detection loops:

- LOOP A → FDU 1

- LOOP B → FDU 2

• FIRE AND SMOKE detection systems:

- FIRE DETECTION on ENGs (2 firex each) and APU (1 firex)

- SMOKE DETECTION on Lavatories (1 firex), Cargo areas (1 firex) and E/E bays