Pneumatic Systems - Quick Reference Notes

Air systems that perform pressurization, cooling/actuation, or sensing; air may be routed from engine bleed, APU, or GPU.
Sources interconnect via cross-bleed duct; monitored by BMCs and ECAM bleed page.
Key components: bleed valves, HP valves, APU bleed valve, cross-bleed selector, Starter, BMC1/BMC2, ECAM bleed page.

Each engine has a bleed system; two identical systems per engine.
Engine bleed valve opens if engine bleed pressure > $8 \text{ psi}$ and APU bleed valve is closed.
When pressure drops (e.g., due to low engine speed), the high-pressure (HP) valve opens to maintain bleed pressure $32 \text{ to } 40 \text{ psi}$ .
A pre-cooler uses engine fan air to cool the bleed air to $200^\circ\mathrm{C}$ ; the pre-cooler inlet/outlet temperatures are monitored.
Normally, the intermediate pressure stage supplies bleed air; HP valve provides fallback if needed.
There are two bleed systems connected via the cross-bleed duct; cross-bleed valve is used to manage interconnection.
Bleed pushbuttons (ENG BLEED) open/close engine bleed valves;AUTO/ON positions manage automatic operation during start.

The APU provides power and pressurized air on the ground and can support systems when engines are off.
APU bleed valve opens when APU speed > $95\%$ and APU bleed push-button is ON (APU master switch ON).
Cross-bleed valve can be opened to interconnect bleed air with engine bleed sides.
ECAM bleed page shows APU bleed valve status; FAULT indicates leak or abnormal condition.

GPU provides external electrical power and pressurized air on the ground, enabling preflight checks and cabin conditioning with engines off.

High-pressure bleed air is used to drive the pneumatic starter, enabling engine start.
On the ground, engines can be started via GPU, APU bleed air, or from a running other engine.
Pneumatic starter drives the engine accessory gearbox, cranking to $15\%-20\%$ of full speed before ignition engages and the engine stabilizes at ground idle.

Pneumatic bleed air pressurizes hydraulic reservoirs used for landing gear, flaps, brakes, etc.
Hydraulic power is supplied by either an ACMP (air-driven) or an electrically driven pump (ELCU-controlled) with an auxiliary ADP option.
ACMP is usually the primary source; ADP provides supplemental power at high demand.
System uses MSOV (modulating shut-off valve) to control ADP drive from pneumatic pressure; temperatures and pressures are monitored and displayed.

Pneumatic high-pressure air powers the air conditioning packs to regulate cabin temperature and humidity.

Functions: air supply, pressure control, temperature regulation, safety.
Air supply sourced from bleed air or external source at proper pressure/temperature.
Pressure control maintains a safe cabin pressure roughly equivalent to an altitude of $6{,}000 \text{ to } 8{,}000 \text{ ft}$ .
Temperature regulation combines incoming air with recirculated cabin air and adjusts distribution.
Safety mechanisms include relief valves and sensors to prevent over/under-pressurization.

Pneumatic air is supplied to wing anti-icing systems to prevent ice buildup on wings, preserving lift and control in icing conditions.

BM C1/BMC2 monitor bleed pressure, temperature, and valve positions; left BMC typically handles left side, right BMC the right.
ECAM bleed page displays valve positions (green = normal open/closed, amber = discrepancy).
If a fault is detected, the bleed page is shown automatically on ECAM.

Bleed valves open when pressure > $8 \text{ psi}$ ; HP valve maintains $32 \text{ to } 40 \text{ psi}$ .
APU bleed valve opens for APU operation when APU speed > $95\%$ , APU bleed switch ON, and no leaks.
Cross-bleed valve operation depends on selector and engine/APU states; normally closed when engines running.
Pre-cooler temperature target is $200^\circ\mathrm{C}$ for bleed air.