ASTM F2490-05e1
(Guide)Standard Guide for Aircraft Electrical Load and Power Source Capacity Analysis
Standard Guide for Aircraft Electrical Load and Power Source Capacity Analysis
SIGNIFICANCE AND USE
To show compliance with 14 CFR 23.1351, you must determine the electrical system capacity.
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 measurements that account for the electrical loads applied to the electrical system in probable combinations and for probable durations; and
4.2.2 For commuter category airplanes, by an electrical load analysis that accounts for the electrical loads applied to the electrical system in probable combinations and for probable durations.
The primary purpose of the electrical load analysis (ELA) is to determine electrical system capacity (including generating sources, converters, contactors, bus bars, and so forth) needed to supply the worst-case combinations of electrical loads. This is achieved by evaluating the average demand and maximum demands under all applicable flight conditions. A summary can then be used to relate the ELA to the system capacity and can establish the adequacy of the power sources under normal, abnormal, and emergency conditions.
Note 1—The ELA should be maintained throughout the life of the aircraft to record changes to the electrical system, which may add or remove electrical loads to the system.
The ELA that is produced for aircraft-type certification should be used as the baseline document for any subsequent changes. When possible, the basic format of the original ELA should be followed to ensure consistency in the methodology and approach.
The original ELA may be lacking in certain information, for instance, time available on emergency battery. It may be necessary to update the ELA using the guidance material contained in this guide.
SCOPE
1.1 This guide covers how to prepare an electrical load analysis (ELA) to meet Federal Aviation Administration (FAA) requirements.
1.2 The values given in SI units are to be regarded as the standard.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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Designation: F2490 − 05
StandardGuide for
Aircraft Electrical Load and Power Source Capacity
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Analysis
This standard is issued under the fixed designation F2490; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
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ε NOTE—Corrected parentheses in Eq 6 editorially in March 2007.
1. Scope 3. Terminology
1.1 This guide covers how to prepare an electrical load 3.1 Definitions of Terms Specific to This Standard:
analysis(ELA)tomeetFederalAviationAdministration(FAA) 3.1.1 abnormal electrical power operation (or abnormal
requirements. operation), n—occurs when a malfunction or failure in the
electric system has taken place and the protective devices of
1.2 The values given in SI units are to be regarded as the
the system are operating to remove the malfunction or failure
standard.
fromtheremainderofthesystembeforethelimitsofabnormal
1.3 This standard does not purport to address all of the
operation are exceeded.
safety concerns, if any, associated with its use. It is the
3.1.1.1 Discussion—The power source may operate in a
responsibility of the user of this standard to establish appro-
degraded mode on a continuous basis when the power charac-
priate safety and health practices and determine the applica-
teristics supplied to the using equipment exceed normal opera-
bility of regulatory limitations prior to use.
tionlimitsbutremainwithinthelimitsforabnormaloperation.
3.1.2 alternate source, n—secondpowersourcethatmaybe
2. Referenced Documents
used instead of the normal source, usually on failure of the
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2.1 FAA Aeronautics and Space Airworthiness Standards:
normal source.
14 CFR 23.1309Normal, Utility, Acrobatic, and Commuter
3.1.2.1 Discussion—The use of alternate sources creates a
Category Airplanes—Equipment, Systems, and Installa-
new load and power configuration and, therefore, a new
tions
electrical system that may require separate source capacity
14 CFR 23.1351Normal, Utility, Acrobatic, and Commuter
analysis.
Category Airplanes—General
3.1.3 cruise, n—condition during which the aircraft is in
14 CFR 23.1353Normal, Utility, Acrobatic, and Commuter
level flight.
Category Airplanes—Storage Battery Design and Instal-
3.1.4 electrical source, n—electrical equipment that
lation
produces, converts, or transforms electrical power.
14 CFR 23.1419Normal, Utility, Acrobatic, and Commuter
3.1.5 electrical system, n—consists of an electrical power
Category Airplanes—Ice Protection
source, the electrical wiring interconnection system, and the
14 CFR 23.1529Normal, Utility, Acrobatic, and Commuter
Category Airplanes—Instructions for Continued Airwor- electrical load(s) connected to that system.
thiness
3.1.6 emergency electrical power operation (or emergency
14 CFR 91General Operating and Flight Rules
operation), n—condition that occurs following a loss of all
14 CFR 135.163Operating Requirements: Commuter and
normalelectricalgeneratingpowersourcesoranothermalfunc-
On Demand Operations and Rules Governing Persons on
tion that results in operation on standby power (batteries or
Board Such Aircraft—Equipment Requirements: Aircraft
other emergency generating source such as an auxiliary power
Carrying Passengers under IFR
unit (APU) or ram air turbine (RAT)) only, or both).
3.1.7 ground operation and loading, n—time spent in pre-
paring the aircraft before the aircraft engine starts.
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This guide is under the jurisdiction of ASTM Committee F39 on Aircraft
3.1.7.1 Discussion—During this period, the APU, internal
Systems and is the direct responsibility of Subcommittee F39.01 on Design,
batteries,oranexternalpowersourcesupplieselectricalpower.
Alteration, and Certification of Electrical Systems.
Current edition approved Oct. 1, 2005. Published October 2005. DOI: 10.1520/
3.1.8 landing, n—condition starting with the operation of
F2490-05E01.
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navigational and indication equipment specific to the landing
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F2490 − 05
3.1.9 nominalrating,n—thisratingofaunitpowersourceis 5. Basic Principles
its nameplate rating and is usually a continuous duty rating for
5.1 Aloadanalysisisessentiallyasummationoftheelectric
specified operating conditions.
loadsappliedtotheelectricalsystemduringspecifiedoperating
3.1.10 normal ambient conditions, n—typical operating
conditions of the air
...
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