Installation Instructions

GTN 6XX/7XX AML STC Installation Manual 190-01007-A3
Page 3-36 Rev. 4
3.7 Electrical Load Analysis
A complete electrical load analysis (ELA) must be completed on each aircraft prior to installation to
verify that the aircraft electrical system is capable of supporting the GTN and optional GMA 35. If it is
determined that the modification results in an increase in electrical load then it must be further verified
that the aircraft electrical system remains in compliance which includes both electrical generation
capacity, and if loads have been increased, that reserve battery capacity remains adequate to support loads
essential to continued safe flight and landing. If the existing battery does not meet the battery capacity
requirements, a battery that has sufficient capacity must be installed. The installation of another battery is
not approved by this manual and is beyond the scope of this manual and STC. Separate airworthiness
approval must be obtained. The Blank Emergency Power Calculation Form, Figure 3-18, may be used for
this reserve battery capacity calculation.
ASTM F2490-05, Standard Guide for Aircraft Electrical Load for Power Source Analysis, provides
acceptable guidance for conducting a complete analysis of increased electrical load.
As part of the installation it must be shown that the maximum electrical system demand does not
normally exceed 80% of the alternator data plate rating. Satisfactory completion of the ELA should be
recorded on FAA Form 337. There are several approaches that could be taken, as described in the
following sections. For each approach, use the values outlined in Table 1-5.
NOTE
Circuits should be protected in accordance with the approved data in this document (see
Appendix E for recommended circuit breaker ratings) and the guidelines in AC 43.13-1B,
Chapter 11, Section 4.
3.7.1 Aircraft with Existing Electrical Load Analysis
If there is an existing ELA for the aircraft, this must be updated to reflect the modification. It must show
that the alternators/generators have adequate capacity to supply power to the modified systems in all
anticipated conditions. Add the applicable typical current draw values from to the existing ELA under
continuous operating conditions. Ensure that the new aircraft electrical load does not exceed the rated
capacity of the installed generator/alternator. After performing the calculations, if the additional load of
the GTN exceeds the rated capacity of the generator/alternator, proceed to the steps in Section 3.7.2. If the
additional GTN load still exceeds the generator rated capacity, alternate FAA approval is required for
installation of the GTN in the aircraft.