Fire Protection - Cargo Compartment

Cargo Compartment Fire Protection

Cargo Compartment Fire Protection consists of these systems:

• Cargo Compartment smoke detection.
• Cargo Compartment Fire Warning.
• Cargo Compartment Fire Extinguishing.

Cargo Compartment Smoke Detection

The forward and aft cargo compartments each have dual smoke detectors installed.

Each cargo compartment has two fans that can draw air through the smoke detectors. Only one fan operates at a time. The second or standby fan starts automatically on sensing a failure of the operating fan.

During normal operations, both detectors in each compartment must sense smoke to activate fire warnings. When smoke is detected the associated Cargo Fire Warning Light illuminates and the EICAS warning FWD/AFT CARGO FIRE displays.

The SYSTEM FAIL light illuminates and the EICAS advisory message FIRE/OVHT SYS displays to indicate failure of the Cargo Compartment smoke detection system. An EICAS status message indicates the inoperative loop. The SYSTEM FAIL light and advisory message can be reset to allow monitoring of the remaining systems.

Fault monitoring of the cargo smoke detectors only occurs when the Fire Protection system is tested. When a fault is detected, the systems reconfigures itself for single detector operation. The operating smoke detector is still capable of activating the cargo warnings.

Cargo Compartment Fire Warning

The indications of a cargo compartment fire are:

• The fire bell sounds.
• The master WARNING lights illuminate.
• The FWD or AFT cargo fire warning light illuminates.
• The discrete FIRE warning light illuminates.
• The EICAS warning message FWD or AFT CARGO FIRE displays.

The fire warning lights remain illuminated as long as the fire signal exists. The fire bell may be silenced by any of the following actions:

• Extinguishing the fire and clearing the smoke.
• Pushing either Master WARNING/CAUTION Reset Switch.
• Pushing the illuminated cargo compartment ARMED switch.

The fire warning bell rings intermittently for 2 seconds on, then 3 seconds off.

Cargo Compartment Fire Extinguishing

Three fire Extinguisher bottles are installed for cargo compartment fire extinguishing. Pushing the FWD or AFT cargo compartment ARMED switch:

• arms the extinguishers for that compartment
• Turns off both left and right air conditioning recirculation fans
• Silences fire warning bell
• Closes the respective cargo heat valves
• Removes power to the galleys

Pushing the cargo fire bottle discharge switch initiates discharge of all three fire bottles. The first bottle discharges immediately into the selected compartment. The remaining bottles automatically discharge either 30 minutes later or when the aircraft has landed at a reduced flow rate into the selected compartment. Total protection provided is 195 minutes.

The CARGO BTL 1 advisory message usually displays on EICAS within a few seconds of pressing the cargo fire bottle DISCH switch. The CARGO BTL 2 EICAS advisory message will display when the remaining bottles discharge. The DISCH light illuminates when either bottle discharges.

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