WAAS Approach

WAAS Approach DiagramClick to Zoom

The ARINC 429 Multi-Bit Decoder (SR429/4D) is the latest addition to our NEXSYS Component Technology family of ARINC 429 decoder products. This 4D component has a built-in three bit data decode function of the 429 data stream to provide additional operational capability and deciphering.

An increasingly popular application that could utilize this component involves level of service annunciation for LP/LPV/LNAV and VNAV. Display of LP/LPV/LNAV and VNAV indications obtained from WAAS Approach type data to bring Garmin GTN level of service annunciation into compliance with FAA Circular, AC 20-138B. These current aftermarket indications require the ARINC 429 signal to be converted to discrete outputs as well as additional Boolean post processing to decode which bits off the data stream equal which level of service is currently active.

This solution uses our NEXSYS SR429/4D and a NEXSYS Diode Pack component inside a VIVISUN High Capacity annunciator housing, greatly reducing the wiring, install time and BOM to the confines of a single VIVISUN annunciator. Once the ARINC 429 data is received, the annunciator decodes bits 17, 18 and 19 to correspond with the correct level of service. In applications where our SR429/4D component is utilized, any bit on the ARINC 429 label can be received but now you are able to receive up to four total bits and decode those bits a step further based on input signals (Ground = 1) (Open = 0). This NEXSYS product can also fit inside a NEXSYS Module to further minimizing the wiring, weight and installation time for the design should an annunciator not be needed.

Disclaimer: The configurations and diagrams shown above are provided by Applied Avionics, Inc. as a general example only. The recipient is solely responsible for actual design, electrical wiring, validation, testing, applicability and functionality of the product in regards to the customer’s specific application.