The indicating system gives pneumatic system indications to the flight crew. The function of the indication system is to give indication on the condition of the pneumatic system and its related components.

The IASC provide pneumatic system status to the DCU and RDC for display. Unusual conditions will be shown on the engine indication and crew alerting system (EICAS).

The distribution system indication is available on the ECS synoptic page. Valve status, line pressure, and temperature are available on the synoptic page. These synoptic pages are selected through the Cursor Control Panel (CCP) and usually displayed on the either MFD.

The BPSs are used to sense the pressure downstream of the Intermediate Pressure Valves.

There are two units, one per each engine bleed, located in the AFT equipment bay and connected by sense lines to the Intermediate Pressure Valve downstream pressure tapping, installed on the high pressure ducting.

The BPS is a gauged pressure transducer allowing pressure measurement.

High Pressure Transducers are plumbed in line to indicate bleed air pressure in the high pressure system plumbing.

The amber L (R) WING A/I PRESS HIGH caution message will show when an over-pressure condition is sensed downstream of the L (R) HPV. The high pressure sensors are found in the aft equipment compartment, downstream of the HPVs. The sensors are gauge pressure transducers that can measure pressure from 0 to 75 psig (0 to 517.11 kPa). It is used to monitor the HPV output pressure.

The High Pressure Shutoff Valve is a 2 inch valve body machined in a stainless steel casting with WJ13 flanges with a sealed butterfly on an inclined axis.

A pneumatic actuator based on a GX design with a piston / diaphragm assembly and a return spring. A micro switch indicates the state FC/NFC.

An ON/OFF solenoid will open when the upstream pressure >10 psig, and the solenoid is energized.

The valve is installed in the aft equipment bay, near the pylon interface. A micro switch indicates the state FC/NFC. A pressure reducer delivers a constant pressure (14 +/- 1 psig) to actuator.

A pressure regulator limits downstream pressure (50 ± 3 psig) for IPV ON/OFF solenoid. With the valve solenoid de-energized the valve will be fully closed.

The Cross-Bleed Valve (CBV) provides interconnection and isolation capability of R/H and L/H sides of the bleed air manifold.

The Cross-Bleed Valve (CBV) is operated from the Push Button Annunciator located on the Air Cond/Bleed panel. With both engines operating, the valve is normally closed. When using the APU for bleed air, the valve is selected open to provide both systems with bleed air. During left or right engine starts, the valve is automatically opened to supply bleed air to the starter system.

The indicating system has interfaces with the systems that follow: