ATA 36 - PNEUMATIC

• The control of the pneumatic system is usually automatic. Bleed Air Monitoring Computers (BMCs) control the automatic function. (one per engine).

• The APU can supply bleed air up to an altitude of 20000 ft. (6096 m)

• PRV Regulate the bleed air pressure to 44 PSI, FAN air thermostat regulate temp up to 200°C (+/- 15°C)

• The HP bleed valve operates pneumatically and is connected by a sense line to a pressure regulator valve, spring loaded closed req 8 PSI to open, regulate pressure at 36 PSI.

• The bleed pressure regulator valve (PRV) regulates the downstream pressure to 44 PSI. It is installed in the duct downstream of the IP bleed check valve and the HP bleed valve. The PRV is spring loaded closed and stars to open at 8 PSI upstream pressure.

• The OPV starts to close >75 PSI and is fully closed > 85 PSI and re-opens < 35 PSI.

• The fan air valve (FAV) is spring loaded closed and pneumatically controlled by the temperature control thermostat (CT) via sense line.

• Leak detection: The overheat sensing elements continuously monitor the surrounding areas for overheat conditions. The FAULT light stays on as long as the overheat condition exists.

• HYD RESERVOIRS air pressurization is provided by ENG 1 bleed-air, X-Bleed for ENG 2.

• X-BLEED VALVE position is the same of APU BLEED VALVE positional.

• Bleed-air back stream protection is achieved by BLEED PRV (Bleed Valve).

• HP VALVE starts opening at 8 PSI and regulates pressure up to 36 PSI.

• BLEED PRV regulates pressure up to 44 PSI and it is controlled by the CTS (Control Thermostat sensor), CTS closes BLEED PRV if pre-cooler temp above 245°C.

• CTS (Control Thermostat sensor) has 2 sending elements, one for BMC 1 and the other one for BMC 2.

• CTS controls BLEED PRV directly and HP valve indirectly.

• HP VALVES are monitored by BMCs.

• Both BLEED PRV and BLEED HP VALVE are spring loaded close in absence of bleed-air pressure.

• BLEED PRV has a thermal fuse (that melts in case of ENG fire), thermal fuse closes the PRV valve.

• OPV (Over-pressure Valve) opens at 36 PSI, starts closing at 75 PSI and fully closes at 85 PSI.

• CTS (Control Thermostat sensor) controls also the FAV (Fan Air Valve) in order to keep bleed-air temperature at 200°C.

• BLEED PRV has 2 operation modes:

1) PNEUMATIC MODE → Reverse flow protection and bleed-air temperature

limitation downstream of the pre-cooler (200°C)

2) ELECTRICAL MODE → ENG BLEED P/B “OFF” or ENG FIRE P/B “RELEASED”

ENGINE PNEUMATIC

• APU bleed air supply has priority over engine bleed air supply.

• The Engine Bleed Valve operates pneumatically and regulates the downstream pressure to 44 psi.

• The Fan Air Valve (FAV) allows the bleed air temperature to be maintained at 200°C.

• Wing and packs: Wings have a double loop of sensing elements. APU single loop, pylon single loop.

• The HP valve opens if the bleed pressure is less than 36 psi.

• The pressure regulation system is monitored by two BMCs.

• The HPV is forced closed when the PRV is closed via the PRV/HPV sense line.

• The CTS operates in two modes, pneumatically and electrically, causing a partial or complete closure of the PRV.

• The bleed-air OPV (Over Pressure Valve) starts to close at 75 PSI. It is fully closed at 85 PSI and opens again at 35 PSI.

• The Fan Air Valve (FAV) pneumatically regulates the fan air flow to the pre-cooler for bleed air temperature regulation (200°C).

• PRE-COOLER: Cools hot air coming from engines and routes it to wing anti-ice, packs, hyd reservoirs, potable water pressurization etc, PRE-COOLER is located in the ENG pylon.

• During ENG startup process air conditioning PACK VALVE will close automatically in order to give bleed priority to the engine.

• The ENG BLEED P/B in the cockpit commands related ENG BLEED VALVE, same for APU. APU BLEED P/B → APU BLEED VALVE.

• Bleed is provided by APU only if manually selected “ON” and if BMC 1 (APU related BMC) doesn’t detect any leak, otherwise it is inhibited.

• APU bleed is monitored by BMC 1.

• Bleed leak detection loops:

- LOOP A → BMC 1

- LOOP B → BMC 2

• Wing leak detection loops trigger if TEMP is above 124°C.

• If APU bleed-air is running and CROSS-BLEED VALVE is set closed, ENG 1 won’t provide bleed-air.

• ENG symbols on ECAM SD bleed page (1,2) are amber when ENG are off and become white when engines are running.

• APU, IP, HP white indication on ECAM SD bleed page are always displayed.

• Bleed pressure indication becomes amber when BLEED PRESS < 4 PSI.

• Bleed PRV (Pressure and Regulating Valve) regulates IP VALVE bleed pressure, it doesn’t regulate HP VALVE pressure. PRV regulates IP BLEED air up to 44 PSI.

• HP VALVE OPENS when ENG is low idle, transfer of bleeding between IP and HP is done purely pneumatically. HP VALVE is usually closed in flight since ENG is running at high rpm.

• PRV closes when:

- ENG BLEED P/B is selected “OFF”

- ENG FIRE P/B is selected “ON”

- During leak detection (BMC 1,2)