Garmin GI 275 Installation Manual page 94

The current measurement is best accomplished with an in-circuit or clamp-on calibrated ammeter with
0.5 A or better precision. Continuous rate, as indicated on the alternator and the battery data plate/
nameplate, must be noted.
1. The tabulated form provided in Figure 3-11 can be used to compile a list of electrical loads on the
aircraft. Typically, the list is comprised of existing circuit breakers and circuit breaker switches as
shown by the example in Figure 3-12. Continuous (e.g., GPS) or intermittent (e.g., stall warning
horn, landing gear) loads must be identified.
2. Use the worst-case flight condition and identify which phase of flight each particular load is used
in for normal flight operation. Certain loads are mutually exclusive and will not be turned on at the
same time (e.g., pitot heat and air conditioning). Use only the worst-case load conditions for each
phase of flight.
NOTE
Normal operation is when the primary electrical power generating system is operating
normally. Emergency operation is when the primary electrical power generating system is
inoperative.
3. Use the worst-case flight condition and identify which phase of flight each load is used in for
emergency flight operation. At a minimum, the list of equipment must include:
a. GI 275 ADI (includes GMU 44B or GMU 11 Magnetometer)
b. GI 275 HSI (if applicable)
c. GI 275 EIS (if applicable)
d. AHRS #1 (GRS 77/79) (includes GMU 44B Magnetometer)
e. COM radio #1
f. GPS #1
g. Audio panel [1]
h. Stall warning system (if applicable)
i. Pitot heat
j. Landing light (switched on during landing only)
k. Instrument panel lighting
l. Landing gear indication lights
m. Navigation lights
n. Strobe lights
Notes:
[1] If the landing gear warning or stall warning audio requires the audio panel, then the audio
panel must be included; otherwise, the audio panel is not essential for continued safe
flight/landing and may be omitted.
CAUTION
The pitot heat must be switched on long enough to take the current measurement and then
switched off. Since the pitot probe may get hot, ensure the probe cover is removed. Care
must be taken to avoid burns or damage to the unit.
4. The ammeter must be connected in line between the external power source and the master relay
circuit, as shown in Figure 3-10. This will eliminate errors due to the charging current drawn by
the battery.
190-02246-10
Rev. 11
GI 275 Part 23 AML STC Installation Manual
Page 3-31