SIL
SIL <3 is a gps error
Good SIL is > or equal 3
To be acceptable in the United States, the following performance has to be demonstrated:
• NACp ≥ 8
• NACv ≥ 1
• NIC ≥ 7
• SIL ≥ 3
• SDA ≥ 2
NIC – Navigation Integrity Category, which specifies an integrity containment radius around an aircraft’s reported position
• SIL – Source Integrity Level indicates the probability of the reported horizontal position exceeding the containment radius defined by the NIC
I’m not a garmin user, so I’m guessing 430W means it is a WAAS gps.
Bet issue is a setup issue. Would think others with same setup (gps source and transponder can help u sort it out.