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Pneumatic System

G500 Systems

The pneumatic system takes 4th and 8th stage engine compressor air in the right combinations and modulates that to the right pressure and temperature for the air conditioning, anti-ice, and other systems to use. It is about as automatic as any I've ever seen.

Work in progress



How it Works . . .


Engine and APU Bleed Air Source Control

So how does the airplane turn very hot air into very cold air and make it all comfortable in the end? Easy. First, hot air from the engine 4th and/or 8th compressors, is used. The 4th stage is normally used but in case it can't deliver the needed air, the 8th stage will provide the additional (or all) of the air. The 8th stage air is controlled by the High Stage Valve (HSV). You don't want that higher pressure 8th stage air somehow backflowing into the 4th stage, so you have a Mid Stage Check Valve to prevent that. You also have a Pre-cooler Heat Exchanger. From their it enters the bleed air manifold. This pressure is measured by Bleed Air Manifold Pressure Sensors (Transducers) and checked with a Manifold Pressure Regulating and Shut-off Valve (MPRSOV). The output from each engine is normally kept separate using an Isolation Valve. You can also connect bleed air from the APU or from External Air. All of this is orchestrated by Bleed Air Controllers with input from the pilots via the Bleed Air Control Panel.

Pneumatic Flow Control and Pressure Regulation

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Photo: G500 Bleed air manifold pressure, PAS, p. 13-4

Click photo for a larger image

[PAS, p. 13-3

  • Normal pressure range: 14 to 52 psi

  • Nominal pressure point for upper range → 44 +/- 8 psi

  • Uses 4th stage air augmented by 8th stage as necessary

  • Minimum pressure set points. 8th stage valve modulated to maintain following minimum pressures:

    • 2 Pack operation: 14 psi for normal high stage set point, 24 psi for low power ground ops or descent.

    • Single pack ops: 35 psi up to FL 390, 22 psi when above FL 400. (Use of WAI doesn’t change set points.)

Pneumatic Temperature Regulation

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Photo: G500 Pre-cooler temperatures, PAS, p. 13-4

Click photo for a larger image

[PAS, p. 13-4

  • Maximum temperature set points are modulated by the 8th stage valve to control amount of air leaving engine to maintain a maximum of 700°F at Pre-cooler Inlet when WAI selected ON.

  • Modulates fan air valve to control amount of fan air entering the pre-cooler heat exchanger to maintain maximum of 400°F at Pre-cooler outlet, or 500°F at pre-cooler outlet when hotter air needed for travel through WAI crossover duct.


The Components in Greater Detail . . .


4th and 8th Compressor Bleed Valves

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Photo: G500 Engine bleed valves, PAS, p. 13-6

Click photo for a larger image

[MTM, ATA 36, p. 11]

  • Engine bleed air supplied to the aircraft bleed system is taken from the lower temperature and pressure fourth (4th) stage and/or higher temperature and pressure eighth (8th) stage of the engine compressor.

  • Under most operating conditions, fourth (4th) stage bleed air pressure and temperature is adequate for aircraft systems operation and is more efficient for engine use. At low power settings, eighth (8th) stage air may be required to meet minimum pressure and/or temperature needs (Figure 36-3).

[PAS, p. 13-3]

  • High (8th) Stage Valve. Commanded to modulate as needed by BACs, spring loaded closed, commanded to begin opening when mid (4th) stage air inadequate.

APU Load Control Valve and APU Check Valve

[PAS, p. 13-3

  • Located on APU turbine case

  • Controlled by APU bleed air switch, requires electrical power to operate and pneumatic pressure to open.

  • ON/OFF valve to the pneumatic manifold, connects to right manifold only.

  • When opens → isolation valve opens at same time; one minute delay if EGT < 149° and WOW in ground mode or immediately if WOW in air mode for an engine airstart.

Bleed Air Control Panel

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Photo: G500 Bleed air control panel, PAS, p. 13-9

Click photo for a larger image

[PAS, p. 13-3

  • Controls bleed air from engines or APU

  • White Lines → System design or architecture

  • L ENG and R ENG switches are guarded

  • Normal switch positions

    • L ENG, R ENG → Selected ON (pushed in)

    • APU → Selected ON (pushed in); on ground normally until engine start, then APU selected OFF. Allowed ON until Lineup / Takeoff checklist for better ECS performance. After landing check, APU selected ON unless operational requirements dictate otherwise.

    • Isolation valve → AUTO (Out); OPEN with APU bleed ON, CLOSED with APU bleed OFF.

  • APU bleed air switch. ON opens APU load control valve and isolation valve when APU on speed, connects bleed air to system via right manifold only. (Available to left side via isolation valve open.) One minute delay if EGT < 149° and WOW in Ground Mode or immediately if WOW in air mode for an engine airstart.

  • Engine start switch

  • ON → Opens isolation valve

Bleed Air Controllers

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Photo: G500 Bleed air controllers, PAS, p. 13-3

Click photo for a larger image

[PAS, p. 13-3

  • Receive inputs from many sources including: altitude, Static air temp (SAT), engine LP RPM, and switch positions (bleed air, wing anti-ice, air conditioning packs, engine start switch).

  • Maintains proper bleed air pressure and temp by modulating 8th stage bleed valves, fan air valves, and WAI valves.

  • Outputs to DCN to display fault messages and synoptic page info.

Bleed Air Manifold Pressure Sensors (Transducers)

External Air Connection and External Air Check Valve

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Photo: Bleed air manifold pressure sensors, MTM, fig. 36-9

Click photo for a larger image

[MTM, ATA 36, p. 18]

  • The bleed air manifold pressure sensors are mounted on brackets above their respective left or right bleed air manifold out board of the isolation valve (Figure 36-9). The sensor is powered by conditioned 15 VDC from its onside bleed air controller. It measures the pre-cooler outlet bleed air pressure and generates an electrical current proportional to that pressure and provides it to the onside bleed air controller.

High Stage Valve (HSV)

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Photo: Bleed air manifold pressure sensors, MTM, fig. 36-9

Click photo for a larger image

[MTM, ATA 36, p. 18]

  • The bleed air manifold pressure sensors are mounted on brackets above their respective left or right bleed air manifold out board of the isolation valve (Figure 36-9). The sensor is powered by conditioned 15 VDC from its onside bleed air controller. It measures the pre-cooler outlet bleed air pressure and generates an electrical current proportional to that pressure and provides it to the onside bleed air controller.

Isolation Valve

[PAS, p. 13-3

  • Opens to connect left and right manifolds automatically when ENGINE START switch → ON, L / R Engine CRANK switch → ON (OHPTS → DU/Ctrl/Test), APU bleed air ON and APU stabilized at 100% RPM.

  • Opens manually when directed by checklist, allows APU and external air to feed both manifolds.

Manifold Pressure Regulating and Shut-off Valve (MPRSOV)

[PAS, p. 13-3]

  • High (8th) Stage Valve. Commanded to modulate as needed by BACs, spring loaded closed, commanded to begin opening when mid (4th) stage air inadequate.

  • Manifold Pressure Regulator and Shutoff Valve (MPRSOV), commonly referred to as bleed air shutoff valve. Controlled by L or R bleed air switches on overhead panel, requires electrical power to operate and pneumatic pressure to open. (Will not open without electrical power.) Functions as both an ON/OFF valve to the pneumatic manifold and a pressure regulator by modulating to maintain 14 to 52 psi.

Mid Stage Check Valve

Work in Progresss

Pre-cooler Heat Exchanger

Pre-cooler inlet temperature sensor

Work in Progresss

Pre-cooler heat exchanger

Work in Progresss

Fan air valve

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Photo: G500 Pre-cooler exhaust, PAS, p. 13-7

Click photo for a larger image

[PAS, p. 13-3

  • Located in engine pylon.

  • Controls temperature of engine bleed air using fan discharge air for cooling. BAC monitors pre-cooler outlet and inlet temperatures, modulates opening of fan-air valve as required. Fan-air is directed to flow across pre-cooler heat exchanger and then overboard via pre-cooler exhaust on the bottom of pylon.


Limitations


Limitations . . .

[G500 AFM, §01-36-10] Single Bleed Air System Operating

  1. Takeoff with a single bleed air source requires isolation valve closed until 1500 feet AGL or until clear of takeoff obstacles (whichever is higher).

  2. Wing anti-ice operation with a single bleed air source is restricted to single ECS pack operations.

  3. The maximum altitude for wing anti-ice operations with a single bleed air source is 32,000 feet.

  4. Maximum airspeed for wing anti-ice operations with a single bleed air source is 0.85M.

References

Gulfstream GVII-G500 Airplane Flight Manual, Revision 1, August 31, 2018

Gulfstream GVII-G500 Production Aircraft Systems, Revision 1, Oct 1, 2018

Revision: 20190602
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