Text-only reference. Published from the recorded official FAA Chapter 9 PDF. Diagrams, photographs, and figure artwork are not reproduced here; use the official FAA PDF for those materials.
9-15 L E F T 1 2 DISCH R I G H T 1 2 DISCH ENG BTL 1 DISCH ENG BTL 2 DISCH ENGINE FIRE PANEL (P8) Discharge nozzles Engine bottle discharge lights Engine fire switches Front spar (ref) Engine fire extinguishing bottles Discharge manifold Discharge nozzles CAUTION WARNING Loop 1 Master warning/ caution light (2) Left engine fire switch Right engine fire switch APU fire switch Unlocking SolendidP310 standby power mgmt panel P105 left integration panel L R WEU (2) 28V DC BAT. BUS FIRE HANDLE UNLOCK ASG card (2) AIMS cabinet (2) Systems arine 629 buses Left engine fire detection card Left fuel control switch Speaker (2) Loop 2 • Fire alarm • OVHT alarm • Temp data • Fault data } Fire alarm 1 MD&T Fuel spar ignition relay MD&T Fire alarm 2 Fire warning switch 9-16 Left engine Right engine Bottle 1 Bottle 2 L E F T 1 2 DISCH R I G H T 1 2 DISCH ENG BTL 1 DISCH ENG BTL 2 DISCH ENGINE FIRE PANEL (P8) Discharge assembly To discharge nozzles Check valve Discharge manifold To discharge nozzles Pressure switch Identification plate Pressure switch test button Safety relief and fill port Handle Mounting lug (4) Discharge port (2) Discharge assembly (2) Pressure switch Squib (2) Pressure switch electrical connector Squib The squib is installed in the discharge assembly at the bottom of the fire container. A fire container has two squibs, one for each engine. The squib is an electrically operated explosive device. When the squib is activated, it fires a slug through the breakable disc, and nitrogen pressure inside the bottle pushes the Halon through the discharge port. The squib fires when the fire switch is pulled and turned to the DISCH 1 or DISCH 2 position. [Figure 9-22] Engine Fire Switches The engine fire panel is in the flight deck on the P8 aisle stand.
The engine fire panel has a fire switch for each engine and a discharge light for each fire bottle. [Figure 9-26] The engine fire switch has four functions: • Gives an indication of an engine fire, • Stops the engine, • Isolates the engine from the aircraft systems, and • Controls the engine fire extinguishing system. The fire switch assembly incorporates a solenoid that locks the fire switch so that the flight crew cannot pull it accidently. If an engine has a fire, the fire warning light comes on and the solenoid energizes to release the switch. When the solenoid is energized, the fire switch can be pulled.
When the fire detection system malfunctions or the solenoid is defective, and the flight crew wants to extinguish an engine fire, someone must push the fire override switch. The fire override switch allows the fire switch to be pulled when the solenoid is not energized. When the fire switch is pulled, the push-pull switch contacts operate electrical circuits that stop the engine and isolate it from the aircraft systems. With the switch pulled, it can be rotated to left or right to a mechanical stop at the discharge position. The rotary switch contacts close and operate the fire extinguishing system.
When the fire switch is pulled, the switch isolates the following aircraft systems from the engine: • Closes the fuel spar valve. • Deenergizes the engine fuel metering unit (FMU) cutoff solenoid. • Closes the engine hydraulic pump shutoff valve. • Depressurizes the engine driven hydraulic pump valve. • Closes the pressure regulator and shutoff valve. • Removes power from thrust reverser isolation valve. • Trips the generator field. • Trips the backup generator field. [Figure 9-27] 9-17 Electrical connector Diaphragm Gland nut Bottle (REF) Discharge port Ground lugSquib Discharge assembly LEFT Disch 1 2 LEFT Disch 1 2 ENG BTL1 DISCH ENG BTL2 DISCH Engine fire warning light Quick release fastener (4) Engine fire switchEngine fire override switch Electrical connector Engine bottle discharge lights Engine Fire Operation If an engine has a fire, the engine fire detection system gives a fire warning in the flight deck. The engine fire warning lights come on to identify which fire switch to use to extinguish the fire. The solenoid in the fire switch energizes and releases the switch so that the fire switch can be pulled. If the solenoid does not energize, push the fire override switch to release the fire switch manually. When the fire switch is pulled, it stops the engine, and the fire switch isolates the engine from the aircraft systems.
If the fire warnings do not go away when the switch is pulled, position the switch to the DISCH 1 or DISCH 2 position, and hold the switch against the stop for one second. This fires the squib in the fire extinguisher container and releases the fire extinguishing agent into the engine nacelle. Ensure that the engine bottle discharge light comes on. If the first bottle does not extinguish the fire, the switch must be placed to the other DISCH position. This fires the squib for the other bottle. APU Fire Detection & Extinguishing System The APU fire protection system is similar in design to engine fire protection systems, but there are some differences.
The APU is often operated with no personnel in the flight 9-18 P310 standby power management panel ENG fuel spar/ ignition relay Solenoid Engine fire switch 28V DC BAT. BUS RUN CUTOFF FIRE HANDLE UNLOCK } AIMS Fuel spar valve circuit Engine FMU cutoff solenoid EDP shutoff valve circuit EDP depressurization circuit Pressure regulator and shutoff valve circuit Thrust reverser isolation valve circuit Generator field circuit Backup generator field circuit Engine fire extinguishing circuit Engine fire detection circuit deck and; the APU fire protection system can operate in an unattended mode on the ground with the engines not running. If there is an APU fire in the unattended mode, the fire extinguisher discharges automatically. The APU operates in the attended mode when at least one engine is running. If there is an APU fire in this mode, the crew discharges the bottle manually. Fire switches are located on the cargo fire/ engine control panel and the service and APU shutdown panel located outside the aircraft on the nose landing gear.
[Figure 9-28] APU Fire Warning If there is an APU fire, the APU fire detection system gives fire warnings and automatically stops the APU. The APU fire warning light comes on to identify the correct fire switch to use to extinguish the fire. The fire switch solenoid releases the switch so that it can be pulled up. If the APU is running, it stops when the fire switch is pulled. The fire switch isolates the APU from the aircraft systems. Fire Bottle Discharge If the fire warnings do not go away with the switch out, put the switch to the left or right DISCH position. Hold the switch against the discharge stop for one second. This fires the bottle squib and releases the fire extinguishing agent into the APU compartment. Verify that the APU bottle discharge light comes on. [Figure 9-29] 9-19 Bottle discharged light P40 service and APU shutdown panel Fire bottle armed light APU fire shutdown switch APU bottle discharge switch A A A Pressure switch Test button APU bottle discharge Master Dim & Test APU fire switch disch disch In Out Fire/Overheat test APU fire extinguishing bottle Cargo fire/engine control panel (P5) APU bottle discharge APU fire shutdown Bottle discharged Fire bottle armed AIMS cabinet (2) P40 service and APU shutdown panelP310 standby power management panel 10 seconds delay APU EXT shutdown APU remote warning Fire alarm 1 Unattended fire alarm APU fuel system & ELMS Fire EXT APU 28V DC hot battery bus APU RMT fire indicator/auto discharge arm 28V DC hot battery bus