Aircraft Environmental Control Systems

1 University AERO 4003 Lecture November 9th, 2010 OmerMajeed, Environmental Control SystemsA Presentation of Current Systems and New University AERO 4003 Lecture November 9th, 2010 OutlineToday s lecture is an introduction to Aircraft Environmental Control Systems (ECS). Theobjective is to present a top level view of the Systems , from regulatory requirements to thearchitecture and function of the individual Systems . Some requirements and componentswill be addressed in more detail as examples. Summary of my education and career ECS definition and main applicable regulations Role of safety analysis in system design Bleed Air (Pneumatic) System functions and architecture Bleed Leak Detection System function Air Conditioning System functions and architecture Cabin Pressurization Control System functions and architecture New technology developments in ECS: Boeing 787 Dreamliner Questions?

2 University AERO 4003 Lecture November 9th, 2010 Education & Career SummaryEducation:Bachelor of Aerospace Engineering, Carleton University, 1992. First graduating of Aerospace Engineering, Carleton University, 1995. Thesis topic was numericalmodeling of transverse impact on composite Canada Commercial PilotLicenceand Multi-Engine Rating (2001).Career:IngeniaCommunications (1995-1997).National Research Council s Centre for Surface Transportation Technology (1997-1998).Liebherr-Aerospace (1999-2008) as air Systems engineer in Toronto (GX, Q400), W ichita(CL300) and Toulouse (A380).Founded Specific Range Solutions Ltd. (2008) specializing in flight optimization solutions, aswell as air Systems analysis and design ( ).

3 Professional Affiliations:Member of PEO since November 10th, member of AIAA (W ichita) andRAeS(Toulouse).Current member of executive of CASI Ottawa Definition and RegulationsEnvironmental Control Systems Control the temperature, pressureand air flow into theaircraft pressure vessel which includes the cockpit (flight deck), cabin and interiorcompartments. Safety monitoring is also performed cabin altitude (ZC), cabin transport-category Aircraft , ECS comprises various Systems performing thefollowingfunctions: bleed air supply, bleed leak detection, air conditioning, distribution, avionicscooling, cabin pressurization Control , oxygen supply.

4 The trendtoday is towards increasingintegration of all air Systems , including wing anti-ice/de-ice functions via a commoncontroller architecture. Two system Control modes are typicallyprovided on modern aircraftsystems: automatic (1 active + 1 stand-by) and manual (back-up).Some of the main applicable regulations for ECS are per Transport Canada s AirworthinessManual Chapter 525: Ventilation Cabin Ozone Concentration Pneumatic SystemsAll Aircraft Systems must perform their intended function underany foreseeable operatingcondition and permit safe continuation of the flight after any failure fail-safe concept. Equipment, Systems , and University AERO 4003 Lecture November 9th, 2010 Boeing 737-300/500 ECS Schematic**The Boeing 737 Technical Guide, Chris Brady, Tech Pilot Services 2006L/H WAIR/H University AERO 4003 Lecture November 9th, 2010 System Safety Analysis / Functional Hazard AssessmentHazard (Risk) = Severity * ProbabilitySeverity(Failure Condition)DefinitionFAA ReferenceEASA ReferenceNoneNormal operationN/AAMC (No Safety Effect)MinorFailure conditions which would not significantly reduceairplane safety, and which involve crew actions that are wellwithin their (Minor)Major (i)

5 Failure conditions which would reduce the capability of theairplane or crew to cope with the adverse operatingconditions to the extent that there are significant reductionsin safety margins or functional (Major)Major (ii)Failure conditions which would reduce the capability of theairplane or crew to cope with the adverse operatingconditions to the extent that there are large reductions insafety margins or functional (Hazardous)CatastrophicFailure conditions which would prevent continued safe flightand (Catastrophic)Probability(Failure Rate/Flight Hour)DefinitionFAA ReferenceEASA ReferenceNoneNormal operationN/AAMC (No Safety Effect)ProbableFailure > 10E-5AC (Probable)Improbable (i)10E-5/FH > Failure > 10E-7/FHAC (Remote)Improbable (ii)10E-7/FH > Failure > 10E-9/FHAC (Extremely Remote)Extremely ImprobableFailure < 10E-9AC (Extremely Improbable) University AERO 4003 Lecture November 9th, 2010 Bleed Air System FunctionsThe Bleed Air System also known as the Pneumatic System suppliesthe air required by thedownstream consumers while regulating the pressure and temperature of the air from theengines to values of 45 psig and 200oC, respectively.

6 The system also selects the engineport from which to air is supplied by the engines or the Auxiliary Power Unit(APU). Air is drawn from thecompressor stage, upstream of the combustor. Engine bleed is typically used in flight. At take-off and ISA conditions, representativevalues are 85 psig and 280oC for an engine LP (Low Pressure) port and 200 psigand 420oC for the HP (High Pressure) port. Bleed temperatures can exceed 540oC. APU bleed is typically used on the ground and permitted in flight up to a certainaltitude. On a cold day (-40oC), APU supplies air at 60 psig and 160oC on theground. On a hot day (+40oC), it supplies air at 40 psig and bleed reduces thrust and increased fuel burn (SFC), the impact is a function ofsupply port (LP/IP or HP) and mass flow.

7 Use of LP/IP bleed ispreferred because ofreduced impact on fuel pack pressure is in the range of 15 to 20 psig which requires a minimum portpressure of 23 psig. If LP port pressure is lower than minimumvalue, then HP port isselected via High Pressure Valve (HPV). A check valve preventsreverse flow into LP is extracted evenly from around the compressor to minimizedownstream disturbanceof the core University AERO 4003 Lecture November 9th, 2010 Bleed Air System Functions and ArchitectureBleed pressure is controlled via a Pressure Regulating Valve (PRV) which typically includesreverse flow protection. Older Systems feature pneumatic Control via a downstreampressure tap, while more recent Systems use electro-pneumatic Control with reference to adownstream pressure temperature is controlled via a Fan Air Valve (FAV) whichmodulates the fan (cold) airflow through thePrecooler, an air-to-air heat exchanger.

8 Legacy Systems feature pneumaticcontrol via a thermostat. Current system design uses electro-pneumatic Control withreference to a downstream temperature University AERO 4003 Lecture November 9th, 2010 SOLENOIDACTUATOR S/ATEST PORT INTAKEBUTTERFLYVALVE S/AOPENINGCLOSINGPOSITION INDICATOR To Control pressure delivered to downstreamusers per system requirements. To balance the flow between adjacent EngineBleed Air Systems when Cross Bleed Valves areopen. To ensure shut-off function of the EngineBleed Air System in case of :A380 Pressure Regulating Valve Functions and DesignDESCRIPTION:6 diameter butterfly valve, pneumatically actuated,electrically controlled via solenoid & torque motor,commanded by the COMPONENT OFBLEED VALVE POSITIONC losedOpenClosed position disagreeXXPosition Data not Available1PR VALVE POSITIONC losedOpenClosed position disagreeXXPosition Data not Available25 Pneumatic Air Distribution System ATA36-12XX1103 Temperature data not availableNormalBleed Temperature Low / HighEngine Bleed Temperature303004 Engine Bleed PressureXX110 Pressure data not availableNormalBleed Pressure Low / High40300A380 Bleed Air System Synoptic University AERO 4003 Lecture November 9th.

9 2010 Bleed Leak Detection FunctionA bleed air leak is a fire risk max. allowable surface temperature to avoid fuel auto-ignition is 204oC per FAA AC Bleed leak is also a risk to aluminum andespecially composite primary structure. Leak detection requiredvia thermal switches (zonalsensors) or via continuous elements which are routed along elements are preferred due to coverage, integrity monitoring and they functionafter being cut (post-PBIT). They allow for the location of the event along the circuit. Dualloops are used in critical areas for redundancy and to minimizefalse leak detection loops are 1/8 dia. coaxial wires (inner conductor and outer shell) separatedby a high resistance eutectic salt calibrated to a specific melting temperature.

10 W hen theloop is locally heated, the salt melts and a short results whichchanges the loop voltage change = Leak detectionBleed leaks can also result in overpressure in compartments, soprovision for blowoutpanels may also be University AERO 4003 Lecture November 9th, 2010 Air Conditioning System FunctionsThe Air Conditioning System (ACS) conditions the fresh air fromthe Bleed Air System andsupplies it to the cockpit and cabin zones at the requested massflow rate. Conditioningrefers to the regulation of temperature and the removal of humidity. The system may haveprovision torecirculatea portion of the cabin requirements: Supply adequate fresh air sufficient oxygen and removeodours.