EASA SIB 2013-07: Mode S Transponders — Capability Reporting Anomaly

What to do

EASA recommends that operators upgrade the affected Rockwell Collins Mode S transponders at the earliest opportunity following the instructions in the referenced Service Information Letter 12-1. Alternatively, a wiring interface change may be considered after consultation with Rockwell Collins, noting that this option may cause frequent TCAS Fail reports and is not suitable for aircraft using a single Gilham coded altitude. No mandatory compliance deadline is specified.

Summary

EASA Safety Information Bulletin SIB No: 2013-07 addresses a capability reporting anomaly in certain Rockwell Collins Mode S transponders, specifically the TDR-94 and TDR-94D models identified by part numbers 622-9352-007, 622-9352-008, 622-9352-108, 622-9210-007, 622-9210-008, and 622-9210-108. This issue affects aircraft certified under FAR, JAR, or CS Parts 23, 25, 27, or 29 that do not have ACAS II equipment installed. The bulletin informs aviation professionals about the incorrect setting of the transponder capability field, which impacts ground radar identification and tracking.

What changed

This bulletin highlights that affected Rockwell Collins Mode S transponders incorrectly set the Capability (CA) Field to zero when installed on aircraft without ACAS II, causing ground stations to misinterpret the transponder's Elementary and Enhanced Surveillance capabilities. It introduces awareness of the anomaly and recommends upgrading the transponder software or implementing a wiring interface change as corrective measures.

Why it matters

The anomaly can lead to increased workload for air traffic controllers due to difficulties in aircraft identification and false radar tracks, especially when multiple affected aircraft operate in close proximity. Operators and maintenance organizations must be aware of this issue to ensure accurate surveillance and avoid potential operational disruptions in airspace relying on the CA field for Mode S transponder capability determination.