1、Designation: F 2490 05e1Standard Guide forAircraft Electrical Load and Power Source CapacityAnalysis1This standard is issued under the fixed designation F 2490; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTECorrected parentheses in Eq 6 editorially in March 2007.1. Scope1.1 This guide covers how to prepare an electrical loadanalysis (ELA)
3、 to meet FederalAviationAdministration (FAA)requirements.1.2 The values given in SI units are to be regarded as thestandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appr
4、o-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 FAA Aeronautics and Space Airworthiness Standards:214 CFR 23.1309 Normal, Utility, Acrobatic, and CommuterCategory AirplanesEquipment, Systems, and Installa-tions14
5、 CFR 23.1351 Normal, Utility, Acrobatic, and CommuterCategory AirplanesGeneral14 CFR 23.1353 Normal, Utility, Acrobatic, and CommuterCategory AirplanesStorage Battery Design and Instal-lation14 CFR 23.1419 Normal, Utility, Acrobatic, and CommuterCategory AirplanesIce Protection14 CFR 23.1529 Normal,
6、 Utility, Acrobatic, and CommuterCategory AirplanesInstructions for Continued Airwor-thiness14 CFR 91 General Operating and Flight Rules14 CFR 135.163 Operating Requirements: Commuter andOn Demand Operations and Rules Governing Persons onBoard Such AircraftEquipment Requirements: AircraftCarrying Pa
7、ssengers under IFR3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 abnormal electrical power operation (or abnormaloperation), noccurs when a malfunction or failure in theelectric system has taken place and the protective devices ofthe system are operating to remove the malfunc
8、tion or failurefrom the remainder of the system before the limits of abnormaloperation are exceeded.3.1.1.1 DiscussionThe power source may operate in adegraded mode on a continuous basis when the power charac-teristics supplied to the using equipment exceed normal opera-tion limits but remain within
9、 the limits for abnormal operation.3.1.2 alternate source, nsecond power source that may beused instead of the normal source, usually on failure of thenormal source.3.1.2.1 DiscussionThe use of alternate sources creates anew load and power configuration and, therefore, a newelectrical system that ma
10、y require separate source capacityanalysis.3.1.3 cruise, ncondition during which the aircraft is inlevel flight.3.1.4 electrical source, nelectrical equipment that pro-duces, converts, or transforms electrical power.3.1.5 electrical system, nconsists of an electrical powersource, the electrical wiri
11、ng interconnection system, and theelectrical load(s) connected to that system.3.1.6 emergency electrical power operation (or emergencyoperation), ncondition that occurs following a loss of allnormal electrical generating power sources or another malfunc-tion that results in operation on standby powe
12、r (batteries orother emergency generating source such as an auxiliary powerunit (APU) or ram air turbine (RAT) only, or both).3.1.7 ground operation and loading, ntime spent in pre-paring the aircraft before the aircraft engine starts.3.1.7.1 DiscussionDuring this period, the APU, internalbatteries,
13、 or an external power source supplies electrical power.3.1.8 landing, ncondition starting with the operation ofnavigational and indication equipment specific to the landingapproach and following until the completion of the rollout.1This guide is under the jurisdiction of ASTM Committee F39 on Normal
14、 andUtility Category Airplane Electrical Wiring Systems and is the direct responsibilityof Subcommittee F39.01 on Design, Alteration, and Certification.Current edition approved Oct. 1, 2005. Published October 2005.2Available from U.S. Government Printing Office Superintendent of Documents,732 N. Cap
15、itol St., NW, Mail Stop: SDE, Washington, DC 20401.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.9 nominal rating, nthis rating of a unit power sourceis its nameplate rating and is usually a continuous duty ratingfor specified
16、operating conditions.3.1.10 normal ambient conditions, ntypical operatingconditions such as temperature and pressure as defined by themanufacturers technical documentation.3.1.11 normal electrical power operation (or normal opera-tion), nassumes that all the available electrical power systemis funct
17、ioning correctly with no failures or within the MasterMinimum Equipment List (MMEL) limitations, if a MMELhas been approved (for example, direct current (DC) genera-tors, transformer rectifier units, inverters, main batteries, APU,and so forth).3.1.12 normal source, nprovides electrical powerthrough
18、out the routine aircraft operation.3.1.13 takeoff and climb, ncondition starting with thetakeoff run and ending with the aircraft leveled off and set forcruising.3.1.14 taxi, ncondition from the aircrafts first movementunder its own power to the start of the takeoff run and fromcompletion of landing
19、 rollout to engine shutdown.4. Significance and Use4.1 To show compliance with 14 CFR 23.1351, you mustdetermine the electrical system capacity.4.2 14 CFR 23.1351(a)(2) states that:4.2.1 For normal, utility, and acrobatic category airplanes,by an electrical load analysis or by electrical measurement
20、sthat account for the electrical loads applied to the electricalsystem in probable combinations and for probable durations;and4.2.2 For commuter category airplanes, by an electrical loadanalysis that accounts for the electrical loads applied to theelectrical system in probable combinations and for p
21、robabledurations.4.3 The primary purpose of the electrical load analysis(ELA) is to determine electrical system capacity (includinggenerating sources, converters, contactors, bus bars, and soforth) needed to supply the worst-case combinations of elec-trical loads. This is achieved by evaluating the
22、average demandand maximum demands under all applicable flight conditions.A summary can then be used to relate the ELA to the systemcapacity and can establish the adequacy of the power sourcesunder normal, abnormal, and emergency conditions.NOTE 1The ELA should be maintained throughout the life of th
23、eaircraft to record changes to the electrical system, which may add orremove electrical loads to the system.4.4 The ELA that is produced for aircraft-type certificationshould be used as the baseline document for any subsequentchanges. When possible, the basic format of the original ELAshould be foll
24、owed to ensure consistency in the methodologyand approach.4.5 The original ELAmay be lacking in certain information,for instance, time available on emergency battery. It may benecessary to update the ELA using the guidance materialcontained in this guide.5. Basic Principles5.1 Aload analysis is esse
25、ntially a summation of the electricloads applied to the electrical system during specified operatingconditions of the aircraft. The ELA requires the listing of eachitem or circuit of electrically powered equipment and theassociated power requirement. Note that the power require-ment for an item may
26、have several values, depending on theutilization for each phase of aircraft operation.5.2 To arrive at an overall evaluation of electrical powerrequirement, it is necessary to give adequate consideration totransient demand requirements, which are of orders of magni-tude or duration to impair system
27、voltage or frequency stabil-ity, or both, or to exceed short-time ratings of power sources,that is, intermittent/momentary and cyclic loads. This is essen-tial, since the ultimate use of an aircrafts ELAis for the properselection of characteristics and capacity of power-source com-ponents and the re
28、sulting assurance of satisfactory performanceof equipment under normal, abnormal, and emergency operat-ing power conditions.5.3 A large majority of general aviation aircraft uses onlyDC power. If an aircraft also usesAC power, the ELAwill haveto include the AC loads as well.6. Procedure for Preparat
29、ion of Electrical Load Analysis6.1 ContentThe load and power source capacity analysisreport should include the following sections:6.1.1 Introduction,6.1.2 Assumptions and Criteria,6.1.3 Load AnalysisTabulation of Values,6.1.4 Emergency and Standby Power Operation, and6.1.5 Summary and Conclusions.6.
30、2 Introduction:6.2.1 The introduction to the ELA report should includeinformation to assist the reader in understanding the function ofthe electrical system with respect to the operational phases ofthe aircraft.6.2.2 Typically, the introduction to the ELA should containthe following:6.2.2.1 Brief de
31、scription of aircraft type, which may alsoinclude the expected operating role for the aircraft;6.2.2.2 Electrical system operation, which describes normal,abnormal, and emergency operations, bus configuration withcircuit breakers, and connected loads for each bus. A copy ofthe bus wiring diagram or
32、electrical schematic should also beincluded in the report;6.2.2.3 Generator, alternator, and other power source de-scription and related data (including such items as batterydischarge curves, inverter, emergency battery, and so forth).Typical data supplied for power sources would be as shown inTable
33、 1;6.2.2.4 Operating logic of system (for example, automaticswitching, loading shedding, and so forth); and6.2.2.5 List of installed equipment.6.3 Assumptions and CriteriaAll assumptions and designcriteria used for the analysis should be stated in this section ofthe ELA. For example, typical assumpt
34、ions for the analysismay be identified as follows:F249005e126.3.1 Most severe loading conditions and operational envi-ronment in which the airplane will be expected to operate areassumed to be night and in icing conditions;6.3.2 Momentary/intermittent loads, such as electrically op-erated valves, th
35、at open and close in a few seconds are notincluded in the calculations;6.3.3 Motor load demands are shown for steady-state op-eration and do not include starting inrush power. The overloadratings of the power sources should be shown to be adequate toprovide motor starting inrush requirements;6.3.4 I
36、ntermittent loads such as communications equipment(radios, for example, VHF/HF communication systems) thatmay have different current consumption depending on operat-ing mode (that is, transmit or receive);6.3.5 Maximum continuous demand of the electrical powersystem must not exceed 100 % of the load
37、 limits of thealternator(s) or generator(s) that are equipped with currentmonitoring capability;6.3.6 Cyclic loads such as heaters, pumps, and so forth (dutycycle); and6.3.7 Estimation of load current, assuming a voltage dropbetween bus bar and load.6.4 Load AnalysisTabulation of ValuesA typical loa
38、dand power source analysis would identify the following detailsin tabular form:6.4.1 Connected Load TableSee Appendix X1.6.4.1.1 Aircraft BusIdentify the appropriate electrical busbeing evaluated. In a multiple bus configuration, there will bea set of tables for each bus (that is, DC Bus 1, DC Bus 2
39、, ACBus 1, Battery Bus, and so forth).6.4.1.2 Condition of Power SourcesNormal, abnormal(abnormal conditions to be specified, for example, one genera-tor inoperative, two generators inoperative, and so forth), andemergency.6.4.1.3 Aircraft Operating PhasesThe following aircraftoperating phases shoul
40、d be considered for the ELA. Assume“night” conditions as the worst-case scenario.NOTE 2Icing conditions should be considered for worst-case sce-narios if the aircraft is approved for flight into known icing in accordancewith 14 CFR 23.1419. However, in some cases, the icing system isdeactivated or n
41、ot installed, so icing may not always be the worst-case.6.4.1.4 Permissible Nonserviceable ConditionsTheanalysis should also identify permissible nonserviceable con-ditions likely to be authorized in the MMEL, if approved,during the certification of the airplane and should includecalculations approp
42、riate to these cases. All MMEL items mustbe accounted for in the load analysis to ensure that theelectrical system capacity is not exceeded when all items arefunctional.6.4.1.5 Circuit BreakerIdentify each circuit breaker bycircuit name or identification number.6.4.1.6 Load at Circuit BreakerThe amp
43、ere loading foreach circuit.6.4.1.7 Operating Time:(1) The operating time is usually expressed as a period oftime (seconds/minutes) or may be continuous, as appropriate.Equipment operating time is often related to the averageoperating time of the aircraft. If the “on” time of the equipmentis the sam
44、e or close to the average operating time of theaircraft, then it could be considered that the equipment isoperating continuously for all flight phases.(2) In such cases in which suitable provisions have beenmade to ensure that certain loads cannot operate simulta-neously, or there is reason for assu
45、ming certain combinationsof load will not occur, appropriate allowances may be made.Adequate explanation should be given in the summary.(3) In some instances, it may be useful to tabulate the datausing a specified range for equipment operating times, such asfollows:5-s Analysis All loads that last l
46、onger than 0.3 sshould be entered in this column.5-min Analysis All loads that last longer than 5 sshould be entered in this column.Continuous Analysis All loads that last longer than 5min should be entered in this column.(4) Alternatively, the equipment operating times could beexpressed as actual o
47、perating time of equipment in seconds orminutes or as continuous operation. In the example given inAppendix X1, the approach taken is to show either continuousoperation or to identify a specific operating time in seconds/minutes.6.4.1.8 Condition of Aircraft OperationPhase of preflightand flight (su
48、ch as ground operation and loading, taxi, takeoff,cruise, and land). For aircraft, the conditions in Table 2 couldbe considered.6.4.2 Calculations:6.4.2.1 The following equations can be used to estimatetotal current, total current rate, and average demand for each ofthe aircraft operating phases (gr
49、ound operation and loading,engine start, taxi, takeoff and climb, cruise, and landing):Total Current A!5Sum of All Current LoadsOperating at a Given Time (1)Total Current Rate A2min!5Number of Units Operating Simultaneously 3 Current per Unit A!3TABLE 1 Typical Data for Power SourcesIdentification 1 2 3Item DC Generator Inverter BatteryNumber of units 2 1 1Continuous rating 250 A 300 VA (total) 35 Ah(Nameplate) . . . . . . . . .5-s rating 400 A . . . . . .2-min rating 300 A . . . . . .Voltage 30 V 115 VAC 24 VDCFrequency . . . 400 Hz . . .Powe
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