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Illustrated technical information covering Vol 2 Over 800 multi-choice systems questions Close up photos of internal and external components Illustrated history and description of all variants of 737 Databases and reports of all the major 737 accidents & incidents History and Development of the Boeing 737 - MAX General flightdeck views of each generation of 737's Technical presentations of 737 systems by Chris Brady Detailed tech specs of every series of 737 A collection of my favourite photographs that I have taken of or from the 737 Press reports of orders and deliveries Details about 737 production methods A compilation of links to other sites with useful 737 content Study notes and technical information A compilation of links to major 737 news stories with a downloadable archive A quick concise overview of the pages on this site


These are found on the stbd aft fuselage. The yellow disc indicates that the squib has discharged and the red disc that the bottle has over-pressured. The pressure gauge is optional and may not be fitted on all airframes.

The second photo (bottom right) shows the condition of the discs shortly after the APU fire extinguisher had been discharged. Notice how the squib disc has only moved slightly and the over-pressure disc not at all. This could easily be missed on a walkaround.

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*** Updated 14 Nov 2021 ***

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