Garmin 400W Series, Instructions Manual

400W Series 

190-01226-14 Rev. 3 

Instructions for Continued Airworthiness Bell 407 

Page 13 of 26 

Item Interval 

Description/Procedure 

GPS Antennas 
(Only if antenna 
is installed by 
this STC) 

Every 2000 
flight hours or 
ten (10) 
years, 
whichever is 
first 

Perform an electrical bonding test on antennas installed by this 
STC: 

1.  Disconnect coaxial cable(s) from the antenna connector(s). 
2.  Measure the resistance between the antenna connector and 

a nearby exposed portion of the antenna foil ground plane. 

3.  Verify the resistance is equal to or less than 10 milliohms. 
4.  Reconnect the coaxial cable(s) to the antenna connector(s) 

and ensure it is secured. 

In the event of bonding test failure, remove antenna, and clean 
and prepare the hardware mating surfaces as follows: 

Clean countersunk areas of the antenna.  Clean countersunk 
areas using an approved solvent per Bell Specification BHT-
ELEC-SPM, CHP 8. 

Reinstall using unit replacement procedures contained in the 
installation drawing listed in paragraph 2.1 of this document. Any 
reworked antenna installation shall have a resistance of less than 
or equal to 2.5 milliohms. 

HTAWS 
Annunciators (if 
installed) 

Every 2000 
flight hours or 
ten (10) 
years, 
whichever is 
first 

Perform an electrical bonding test: 

1.  Measure the resistance between the metallic body of each 

Vivisun annunciator and the console assembly and verify 
that the resistance is less than or equal to 20 milliohms. 
 

In the event of bonding test failure: 

1.  Inspect the grounding strap which is installed between the 

annunciator panel and the instrument panel. Ensure that the 
fastener hardware is secure and that the strap is not 
damaged. If damaged, replace the bonding strap.  For 
annunciator installation with annunciator mounted in 
instrument panel verify mating surfaces are clean and free 
of corrosion. 

2.  If problem persists, remove the bonding strap and clean the 

mating surfaces of the bonding strap and 
annunciator/instrument panel per Bell specification BHT-
ELEC-SPM CHP8.  For installations with the annunciator 
mounted in instrument panel clean the mating surfaces. 

3.  Reinstall the bonding strap (or annunciator when mounted 

in instrument panel) and verify that the resistance between 
the annunciators and the console assembly after prepping 
bonding surface is less than 10 milliohms. 

2.5.1  Cleaning the Front Panel 

The front bezel, keypad, and display can be cleaned with a soft cotton cloth dampened with clean water. 
DO NOT use any chemical-cleaning agents. Care should be taken to avoid scratching the surface of the 
display. 

2.5.2 Display Backlight 

The display backlight lamp is rated by the manufacturer as having a usable life of 20,000 hours. This life 
may be more or less than the rated time depending on the operating conditions of the 400W Series unit. 
Over time, the backlight lamp may dim and the display may not perform as well in direct sunlight