BLEED SELECTION, REGULATION AND CROSSBLEED
The pneumatic network supplies more than cabin conditioning. The supplied description lists engine starting, wing anti-ice, hydraulic-reservoir pressurisation and water-system pressurisation among its consumers. Its sources are engine bleed, APU load-compressor air and a suitable high-pressure ground connection. These are distinct from a ground electrical source. When interpreting a failure, identify both the air source and the consumer: an available source does not prove an intact route to every user. [67, PDF p. 2]
Engine bleed regulation selects an appropriate compressor stage and regulates pressure and temperature before air reaches the distribution system. The precooler and its control path are part of that regulation. A bleed valve, a high-pressure selection valve and a temperature-regulation function do different jobs; replacing them with the phrase bleed ON loses diagnostic information. Monitoring computers supervise the system, while duct-overheat detection concerns the area surrounding hot-air pipes rather than merely the temperature of correctly contained air. [67, PDF pp. 3–6]
The crossbleed duct and valve connect the two sides when the required configuration calls for it. APU and ground connections join that network through their respective routes. The BLEED page is useful because it joins selected states, actual valve information and available air into one view. An automatic valve movement can be a protective response to a leak or a normal part of a starting sequence. Interpret its cause before treating a changed indication as an invitation to override the system. [67, PDF pp. 7–8] [68, PDF pp. 3–5]
Starting and pack demand are linked, but the normal sequence depends on the aircraft standard. The V3 presentation and current option register identify different pack-inhibit standards. Record that option before comparing first-engine and second-engine starts. A configuration difference can explain different valve timing without implying a defective pack. After starting, verify the intended engine-supplied air arrangement and restored conditioning. A stable engine, a closed start valve and a correctly configured pneumatic network are related completion checks, not interchangeable observations. [53, FADEC chapter, engine-start pack-inhibit standards] [70, Available Options: fnx_start_pack_inhibit_type] [23, PDF pp. 1048–1050]
Engine bleed, APU BLEED and crossbleed controls. [63, PDF p. 1]