The Honeywell MST-70B was originally designed as a fit, form, and function replacement for the legacy Honeywell MST-67A Mode S transponder with the added capability of meeting ADS-B Out requirements when installed correctly.

While the MST-70B is a key component of an ADS-B compliant solution, the transponder alone does not guarantee compliance. Several additional factors must be considered to ensure the installation meets both regulatory and STC requirements.

Key items typically required for ADS-B compliance with the MST-70B include:

1. Approved GPS Position Source
ADS-B Out requires an approved GPS position source that meets the accuracy and integrity standards defined by an ADS-B mandate.

• The MST-70B does not contain an internal GPS so it must receive position data from an external, approved WAAS GPS such as the NXG-900.
• The GPS source must be specifically listed or approved for use with the MST-70B under the applicable STC.

2. Applicable STC or Approved Data

ADS-B compliance with the MST-70B must be accomplished under an approved Supplemental Type Certificate (STC) or other FAA-approved installation data.

• STC coverage varies by aircraft make and model.
• The STC defines approved GPS sources, antenna requirements, wiring configurations, and configuration settings.These are only two considerations among others such as proper antennas & cabling, correct configuration & aircraft data programming, and post-Installation ADS-B performance validation

The MST-70B was designed to simplify upgrades for operators replacing an MST-67A, however ADS-B compliance is a system-level requirement not just a transponder swap. Aircraft-specific approvals, GPS compatibility, installation quality, and configuration all play a critical role.

For this reason, Southeast Aerospace strongly recommends working with an experienced avionics shop familiar with Honeywell transponder installations and the applicable STCs to ensure proper and compliant installation.