Figure 3-8 Ammeter Placement For Current Measurements - Garmin GTX 335 w GPS Installation Guidance

4. Identify whether each load is used in phase of flight for emergency operation. As a minimum these
systems include:
• COM radio #1
• NAV radio #1
• Transponder and associated altitude source
• Audio panel
• Stall warning system (if applicable)
• Pitot heat
• Landing light (switched on during landing only)
• Instrument panel dimming
5. Connect the calibrated ammeter in line between the external power source and the master relay
circuit as shown in figure 3-8. This will eliminate errors because of the charging current drawn by
the battery.
EXTERNAL
POWER
BATTERY

Figure 3-8 Ammeter Placement for Current Measurements

6. Make sure all circuit breakers are closed.
7. Apply external power to the aircraft. Power source voltage should be set to nominal alternator
voltage (usually 13.8 VDC or 27.5 VDC).
8. Turn on the battery master switch.
• Intermittent electrical loads are not measured. It is assumed that if more current is required
beyond what the alternator can supply, this short-duration demand is supplied by the
battery.
9. Set the lighting as given below. These settings will be used for every current measurement that
follows:
• All instrument panel and flood lights should be set to maximum brightness.
• Any other displays with a backlight should be set to 50% brightness.
10. Use the tabulation completed above and switch on all continuous electrical loads used in the
taxiing phase. Record ammeter current reading (measurement (a) in figure 3-9). Follow these
precautions for this measurement:
• The autopilot circuit breaker should be closed.
• The autopilot should not be engaged.
190-00734-17
Rev. 1
+
-
MASTER
RELAY
ALTNTR
ELECTRICAL BUS
Ammeter placement – either
location acceptable (does not
include battery charging current)
GTX 335 w/GPS Installation Guidance
Page 3-23