EASA SIB 2024-13: GARRECHT AVIONIK GMBH: Loss of Transponder Reply

What to do

Operators and maintenance organizations should monitor communications from Garrecht Avionik GmbH regarding the availability and implementation of updated FPGA microcode and apply these updates following approved maintenance procedures. Flight crews are advised to regularly check the transponder reply indicator and, if radar contact issues are suspected, to contact air traffic control for confirmation. Procedures to identify the FPGA microcode version are provided in the bulletin's appendix and referenced manuals.

Summary

EASA Safety Information Bulletin 2024-13 addresses the loss of transponder reply issue affecting Garrecht Avionik GmbH Mode-S Secondary Surveillance Radar transponders with specific part numbers including VT-0102, VT-0104, and VT-0201 models. The bulletin highlights detection problems reported by radar manufacturers and air navigation service providers due to an erroneous FPGA microcode firmware implementation. This issue impacts aircraft equipped with these transponders by reducing radar detection reliability under certain interrogation patterns.

What changed

This new bulletin informs stakeholders about the identified loss of transponder replies caused by FPGA microcode versions 12 or below in the affected transponders. It introduces awareness of the problem, provides procedures to identify the installed FPGA microcode version, and announces that Garrecht Avionik GmbH plans to release updated firmware to resolve the issue. No mandatory corrective actions or airworthiness directives are issued at this time.

Why it matters

The loss of transponder reply can significantly affect radar acquisition and detection of aircraft, potentially compromising situational awareness for air traffic control and safety systems such as TCAS II and multilateration. Operators and maintenance organizations need to be aware of this issue to monitor transponder functionality and prepare for upcoming firmware updates. Flight crews should also be vigilant in monitoring transponder reply indicators and coordinate with ATC if radar contact is suspected to be lost.