1、Designation: F2490 05 (Reapproved 2013)Standard Guide forAircraft Electrical Load and Power Source CapacityAnalysis1This standard is issued under the fixed designation F2490; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers how to prepare an electrical loadanalysis (ELA) to meet FederalAviationAdministration (FAA)requi
3、rements.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 appro-priate safety and health practices and determin
4、e 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 CFR 23.1351 Normal, Utility, Acrobatic, and Comm
5、uterCategory 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, Utility, Acrobatic, and CommuterCategory Airplan
6、esInstructions 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 Passengers under IFR3. Terminology3.1 Definitions o
7、f 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 malfunction or failurefrom the remainder of the system b
8、efore 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 the limits for abnormal operation.3.1.2 alternat
9、e 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 may require separate source capacityanalysis.3.1.3
10、cruise, ncondition during which the aircraft is inlevel flight.3.1.4 electrical source, nelectrical equipment thatproduces, converts, or transforms electrical power.3.1.5 electrical system, nconsists of an electrical powersource, the electrical wiring interconnection system, and theelectrical load(s
11、) 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 power (batteries orother emergency generating source su
12、ch 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, or an external power source supplies electrical po
13、wer.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 AircraftSystems and is the direct responsibility of Subco
14、mmittee F39.01 on Design,Alteration, and Certification of Electrical Systems.Current edition approved July 1, 2013. Published September 2013. Originallyapproved in 2005. Last previous edition approved in 2005 as F2490 051. DOI:10.1520/F2490-05R13.2Available from U.S. Government Printing Office Super
15、intendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.9 nominal rating, nthis rating of a unit power source isits nameplate rating and is usually a cont
16、inuous duty rating forspecified 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 availabl
17、e electrical power systemis functioning correctly with no failures or within the MasterMinimum Equipment List (MMEL) limitations, if a MMELhas been approved (for example, direct current (DC)generators, transformer rectifier units, inverters, main batteries,APU, and so forth).3.1.12 normal source, np
18、rovides electrical powerthroughout 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 ru
19、n and fromcompletion of landing 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 analys
20、is or by electrical measurementsthat 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
21、probable combinations and for probabledurations.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
22、 is achieved by evaluating the 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 maint
23、ained throughout the life of theaircraft 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
24、 the original ELAshould be followed 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 Princ
25、iples5.1 Aload analysis is essentially 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 powe
26、r require-ment for an item may 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-tud
27、e or duration to impair system voltage or frequencystability, or both, or to exceed short-time ratings of powersources, that is, intermittent/momentary and cyclic loads. Thisis essential, since the ultimate use of an aircrafts ELA is forthe proper selection of characteristics and capacity of power-s
28、ource components and the resulting assurance of satisfactoryperformance of equipment under normal, abnormal, and emer-gency operating 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 wel
29、l.6. Procedure for Preparation 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
30、 Summary and Conclusions.6.2 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
31、 following:6.2.2.1 Brief description 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 o
32、fthe bus wiring diagram or 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 source
33、s would be as shown inTable 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. F
34、or example, typical assumptions for the analysismay be identified as follows:F2490 05 (2013)26.3.1 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
35、electrically op-erated valves, that 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 sta
36、rting inrush requirements;6.3.4 Intermittent 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
37、must not exceed 100 % of the load 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 Analysis
38、Tabulation of ValuesA typical loadand 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
39、 bus (that is, DC Bus 1, DC Bus 2, 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 followi
40、ng aircraftoperating phases should 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, th
41、e icing system isdeactivated or not installed, so icing may not always be the worst-case.6.4.1.4 Permissible Nonserviceable ConditionsThe analy-sis should also identify permissible nonserviceable conditionslikely to be authorized in the MMEL, if approved, during thecertification of the airplane and
42、should include calculationsappropriate to these cases.All MMELitems must be accountedfor in the load analysis to ensure that the electrical systemcapacity is not exceeded when all items are functional.6.4.1.5 Circuit BreakerIdentify each circuit breaker bycircuit name or identification number.6.4.1.
43、6 Load at Circuit BreakerThe ampere 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”
44、 time of the equipmentis the same 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 operatesimultaneousl
45、y, or there is reason for assuming certain combi-nations of load will not occur, appropriate allowances may bemade. 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-
46、s Analysis All loads that last longer 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 tim
47、es could beexpressed as actual operating 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 Operation
48、Phase of preflightand flight (such 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 oft
49、he aircraft operating phases (ground operation and loading,engine start, taxi, takeoff and climb, cruise, and landing):Total Current A! 5 Sum of All Current Loads (1)Operating at a Given TimeTABLE 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 . . .Power factor . . . 0.8 . . .Manufacturer ABC XYZ ABCModel
