Inaccurate Airborne Status Transmitted by Transponders and its Effect on Runway Monitoring and Conflict Alert Systems
- Published
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Affected stakeholders, including aircraft owners, operators, air navigation service providers, and original equipment manufacturers, should review their transponder configurations and operational procedures related to take-off and rejected take-off scenarios. Air traffic controllers should be made aware of the limitations of runway incursion monitoring systems with certain aircraft types, as highlighted in the NAV CANADA urgent bulletin. No specific compliance deadlines are stated, but proactive communication and procedural adjustments are recommended to mitigate risks.
Summary
The Transport Canada Civil Aviation Safety Alert CASA 2021-03 addresses safety concerns related to inaccurate airborne status transmissions by integrated avionics system transponders, specifically affecting Embraer 190 and Boeing 777-300 aircraft. The alert highlights an occurrence at Toronto/Lester B. Pearson International Airport where the Honeywell Primus Epic transponder on an Embraer 190 indicated airborne status prematurely during a rejected take-off, impacting runway incursion monitoring and conflict alert systems. This issue may affect other aircraft equipped with similar avionics systems that use low airborne override thresholds.
What changed
CASA 2021-03 raises awareness of the potential safety risks caused by transponders transmitting airborne status at speeds as low as 50 knots, which is below the 100 knots override threshold recommended by RTCA DO-181E standards. It explains how this premature airborne indication can cause runway monitoring systems like RIMCAS to fail in detecting conflicts during take-off rolls or rejected take-offs. The alert also informs air navigation service providers and operators about limitations in current surface movement guidance and control systems when handling certain aircraft types.
Why it matters
This alert is critical for aviation professionals because inaccurate airborne status transmissions can lead to delayed or missed conflict alerts, increasing the risk of runway incursions and potential collisions during critical phases of flight. Operators and air traffic controllers must understand these avionics behaviors to maintain situational awareness and ensure safe ground operations. Compliance teams need to be aware of these system limitations to properly assess risk and implement mitigations.
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