Table 3-25 Net Electrical Load Change Calculation Example (14 Vdc Aircraft) - Garmin GI 275 Installation Manual

Net change to the electrical load with the GI 275 installed must be determined. Net decrease in electrical
load requires no further analysis, assuming that the electrical system is within limits. This is likely to occur
when existing equipment is removed or older systems are replaced with newer equipment that requires less
power to operate. The amended electrical load calculation documenting load reduction should be filed with
other aircraft permanent records. A sample net electrical load calculation is shown for a 14V aircraft in
Table 3-25.

Table 3-25 Net Electrical Load Change Calculation Example (14 VDC Aircraft)

Equipment Removed
Item
KI 227 ADF Indicator [1]
KI 525A Pictorial NAV Indicator (HSI)
KA 51B Slaving Accessory [2]
KI 256 Horizon Indicator (ADI)
Mid-Continent MD 200-206 VOR/LOC/GS
Indicator
KG 102A Directional Gyro
Shadin ADC 200
Notes:
[1] Received power from ADF receiver, which was left in the aircraft.
[2] Received power from KG 102A, which was also removed. The load for the KA 51B is
included as part of the KG 102A load.
A complete Electrical Load Analysis must be performed to show adequate capacity of the alternator/
generator if the electrical load is increased with GI 275 installed. ASTM F 2490-05 Standard Guide for
Aircraft Electrical Load and Power Source Capacity Analysis offers guidance on preparing an ELA.
Alternatively, electrical loads under different operating conditions can be measured (refer to Section 3.5.1).
3.5.1 Measurement of Electrical Loads
It must be shown that the maximum electrical demand for each alternator does not exceed 80% of the
alternator data plate rating. Discussed in this section is the ELA for a single alternator/single battery
electrical system determined by load measurement. It must be modified accordingly for aircraft with
multiple batteries or alternators. During measurement, applied electrical system loads must account for
combinations and durations for probable aircraft operations.
NOTE
Class IV aircraft cannot measure the electrical loads and must perform an ELA.
NOTE
Circuits must be protected and LRU circuit breaker ratings must meet specifications in Section 3.2.
Additionally, follow guidelines in AC 43.13-1B, Chapter 11, Section 4.
CAUTION
To avoid damage to equipment, the ammeter must be capable of handling the anticipated load.
190-02246-10
Rev. 11
Load [A]
Garmin GI 275 ADAHRS+AP (PFD),
0.00
GMU 11, GTP 59
0.36 Garmin GI 275 ADAHRS (HSI)
0.00
0.76
0.30
3.00
1.30
SUBTOTAL 5.72
GI 275 Part 23 AML STC Installation Manual
Equipment Added
Item
SUBTOTAL
NET CHANGE
Page 3-30
Load [A]
2.00
2.00
4.00
-1.72