MGL Avionics User Forum

This post is directed to Rainier. Currently I have a MGL SP12 transmitting the TSO-C199 TABS protocol to a Trig TT21. Our CAA (Civil Aviation Authority) has provided a spreadsheet to me indicating that I am transmitting a SIL=1 which is not compliant. They require a SIL value of 3.

I note on the outside of the SP12 it indicates a SIL value of 3.

When I read the corresponding Trig information regarding the Trig TN72 (SP12 equivalent) it states the following when the TN72 is interfaced to Trig TT21/22

C199 TABSTransponder sends ADS-B data in accordance with TSO C199; SIL = 1, SDA = 1.
Trig TN72 SIL 3Transponder sends ADS-B data in accordance with FAR 91.227; SIL = 3, SDA = 2.

So how do I get my MGL SP12 or Trig TT21 to comply with the FAR 91.227 and provide values of SIL=3 and SDA=2

In reading the Trig Documentation I note;
GPS CertificationLevel
If you are using the TN72 as a simple NMEA GPS source, it should be set to uncertified. When a C199 TABS GPS source is selected the certification level is not used by the Trig transponder; TSO-C199 uses a special encoding of the design assurance flags. When compliance with FAR 91.227 is being configured, the GPS certification level can be set to level C.

From this I take it that I need to set the GPS certification level in my Trig TT21 but then what input do I use for FAR 91.227 compliance.

Appreciate your help so I can comply.

Thanks Peter

If you are transmitting SIL=1 it means you are transmitting the GPS information from the built in GPS of the iEFIS which is qualified to SIL=1.

Have a look at the dedicated diagnostics page provided on the iEFIS for this.

The Trig transponder interface receives both the SP-12 as well as the iEFIS GPS position. if there is no valid position from the SP-12 it will use the position from the iEFIS and SIL/SDA are both set accordingly.

There is more info on how this all fits together in the SP-12 manual.

If you are using an iBOX - make sure your SP-12 and the trig interface are on the same CAN bus. The SP-12 GPS information goes straight to the trig without touching the EFIS in order to maintain SIL/SDA.