26-21-00  ENGINE AND NACELLE FIRE EXTINGUISHER SYSTEM Back

A. System Function

The engine and nacelle fire extinguisher system (the system) lets the flight crew extinguish fires which occur in the engine nacelles.

B. System Components

The primary components (also ref. Fig. 1) of the system are:

• Two fire-extinguisher bottles (Ref. Fig. 2)
• Four pyrotechnic cartridges
• Two fire-extinguisher selector switches
• A thermal-relief discharge-indicator (Ref. Fig. 2)
• Two outlet discharge indicators (Ref. Fig. 2)
• Two two-way check tees (Ref. Fig 2 and Fig. 3)
• The pipes and discharge nozzle (Ref. Fig. 4)

C. System Operation

1. The engine extinguishing system has two fire-extinguisher bottles (the bottles), which contain extinguishant. On each bottle there are two discharge outlets. The outlets let the extinguishant go into either the left or right engine. The discharge is controlled by an explosive cartridge. When the explosive cartridge operates, extinguishant flows into the engine nacelle through the system pipe. The cartridge operates when the flight crew operate the FIRE EXT switch in the center pedestal (in the flight compartment).
2. Each bottle can release one supply (shot) only of extinguisher. The extinguishant is released to engine zones 1, 3A and 3B of the applicable nacelle (Ref. 71-00-00) at the same time. The discharge outlet of each bottle is connected to its applicable engine through the two-way check tee. The system has discharge indicators to show if the bottles have operated. A pressure gage, on each of the bottles, show that the contents of the bottles are at the correct pressure.