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Aviation Systems Design
Frederic ABADIE
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Pneumatics Systems Architecture
Bleed Control SystemBCS architectureInterfacesBCS functionsBCS controller
Bleed Distribution System
OverHeat Detection System
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Pneumatics Systems Architecture
Bleed Control SystemBCS architectureInterfacesBCS functionsBCS controller
Bleed Distribution System
OverHeat Detection System
4 Aviation Systems Design2012-2013
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Bleed Control System (BCS) supplies pressure & temperature regulated air from :Engine HP / LP portsAPU pressure portsHigh Pressure Ground Cart
Bleed Distribution System (BDS) ensures distribution towards users :
Environmental Control System :Cabin Pressure, Air conditioningWing and Engine Anti-IceFuel Tank Inerting SystemWater or Hydraulic tanks
pressurisationFuel heating... water pipes de-icing, rain protection...
Overheat Detection System (OHDS)Ensures that no leakage is present along the bleed ducting
Aviation Systems Design 52012-2013
HPGround Cart
Bleed Control
Air Conditioning Ice Protection
Pressureregulation
Tanks pressurisation
Fuel tank inerting
Engine Start
Bleed Distribution
Overheat Detection
APU
Engine
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Pneumatics Systems Architecture
Bleed Control SystemBCS architectureInterfacesBCS functionsBCS controller
Bleed Distribution System
OverHeat Detection System
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Main functions of the BCS are :Selection ofEngine Bleed Ports
Pressure Control
Temperature Control
Flow Sharing between Engines
~200C~40 psi
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BleedControl & Monitoring
Computer
ENGINES
GROUND
CART
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Bleedstarterpipe
Bleed ports
Engine gearbox
Rolls Royce
Trent family
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BCS main functions (RR Trent)Bleed port selectionThe HP Valve is opened to extract air from High PressurePort when engine is running at low rating ( Ground, Descent )while the IP Valve is closedDuring Take Off, Climb, Cruise the IP Valve is open and bleedair comes from the Intermediate Pressure Port while the HP
Valve is closed
Pressure ControlIf the IP Valve is open , the Pressure Regulating Valve(Bleed Valve) controls the pressure around ~40 psi If the HP Valve is open , both valves adjust the pressureThe pressure is limited to ~80 psi thanks to the OPV
Over Pressure Valve which shut off the bleed supply in caseof pressure excess
Flow Sharing Used in CrossBleed Valves = Open configuration
DP sensors are comparing the flows between both engines.The Pressure Regulating Bleed valves are used to regulate each engine bleed flow
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BCS main functions (RR Trent)Temperature ControlThe Pre-Cooler circuit uses cold air coming from fan (~ -50C in Cruise) to cool down the bleed air comingfrom Engine Bleed Ports
According to temperature measured at pre-cooler,the BCS controls the Fan Air Valve motor to supplythe adequate amount of Fan Air to regulate thetemperature ~200C
The Temperature Control function involves thefollowing components :
Pre-coolerFan Air Valve assemblyTemperature Sensors
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Control & Monitoring ComputerBleed valves are electrically controlled by the BCS controller. Most ofoperations are done in automatic or semi-automatic mode , with possibleoverride by the pilotBCS controller receives inputs from temperature and pressure sensors
located throughout the pneumatic system, valve position indicators ,cockpit command P/B , in addition to general A/C information (air data,ground/flight indication) BCS controller allows to :- Regulate pressures and temperatures to the required targets
(for air conditioning, de- icing, cabin or tanks pressurisation) - Master the valves sequence for engines start
- Report the status and warnings to cockpit crew
Manual valve manifolds directly fitted on engine allow operationon ground without the A/C being electrically powered
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Pneumatics Systems Architecture
Bleed Control SystemBCS architectureInterfacesBCS functionsBCS controller
Bleed Distribution System
OverHeat Detection System
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Bleed Distribution principlesX-Bleed duct interconnect the different Bleed Sources(engines, APU, HP Ground Cart)
X-Bleed valves can isolate or interconnect the variousBleed Air Sources. The Centre X- Bleed Valve isolates the
L/H and the R/H Bleed Air from each other.
APU Isolation Valve isolates the APU Bleed Air Systemfrom the other systems
APU Bleed Air supply is possible on ground and duringclimb or descent.
All the valves of Bleed Distribution System are operatedthrough the Bleed Control & Monitoring Computer
BCS 1
BCS 4
BCS 2
BCS 3
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Pneumatics Systems Architecture
Bleed Control SystemBCS architectureInterfacesBCS functionsBCS controller
Bleed Distribution System
OverHeat Detection System
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PrinciplesIf a pneumatic system duct is damaged, a hot air leak can occur, withpossible impact on structure and components.CS25.1438 imposes that the consequence of a single bleed leak shall not bemore than Hazardous
Overheat Detection System (OHDS)continuously monitors the pneumaticsystem during flight to detect bleed leaks.Advanced versions of the system allowto localise and isolate the leak
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OHDS architectureOverheat Detection System is composed of 2 independant Sub-Systems ,each of them monitoring a set of detector loops.
Overheat alarm is triggered when both loops (A and B), dedicated to a duct,
detect together an overheatingAviation Systems Design 172012-2013
Loop A.1
Loop B.1
Bleed Control SystemFlight Warning
Displays...
Loop B.2
Loop A.2
OverheatcontrollerB
Overheatcontroller
A
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Aviation Systems Design
Frederic ABADIE
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Ice accretion risks
Ice detection
Wing Anti-Ice
Engine Anti-Ice
Probes Anti-Ice
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Ice accretion present important risksLoss of lift on leading edges, engine air inlet, slats...Reduction of manoeuvrability (slats, VTP...)Reduction of engine compressor efficiencyEngine imbalance
Probes freezingWindscreen maskingFuel tank vents clogging...
For certification, icing conditions are defined in
CS
25.1 - Appendix C Part I Atmospheric Icing Conditions 2012-2013 21 Aviation Systems Design
Leading edges
Enginefan blades
Engineinlet
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On groundAn aircraft that is ready for flight must NOT have either ice, or snow, orslush or frost on its critical flight surfacesA/C can be normally powered on down to -15C
Defrost procedures must be applied in case of icing conditions(specific Maintenance Manuel chapters for each System)
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Aviation Systems Design 232012-2013
In flight : icing conditions detectionExternal probes detect icing conditions by optical reflectometryor magnetic resonance
Anti-Ice systems activationActivation of de-icing functions is triggered by
Automatic action of the de-icing control computer
Manual activation requested upon Ice Detector statusAdvisory upon Aircraft Flight Manual (based on Air Temperature / visible accretion...)
Probes de-icing is performed by electrical heating (inhibited on ground)Wing and Engines de-icing use Bleed air or inflatable boots
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Wing leading edge heatingBleed Air is distributed to slats and/or wingLeading Edges on both sides.This function is inhibited on ground.
Inflatable de-icing bootsAn engine-driven pneumatic pump or bleedair is used to inflate the rubber boots.
Upon inflation, ice is cracked and should falloff the leading edge of the wing.De-icing boots can be operated in a singlecycle or allowed to cycle at automatic, attimed intervals.
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Nacelle leading edge Anti-IceBleed Air from one engine is directed from HP / IP com pressor to Nacelleleading edge. This function is inhibited on ground to prevent nacelledamages and ground operators injuries.
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Probes HeatingComputer
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Questions ?
