EASA SIB 2011-15R3: ADS-B Out, Mode S and Mode C Transponder Systems: Ground Testing

What to do

Operators should refrain from using any transponder reported defective by ATC, EUROCONTROL, EASA, or other authorities until a comprehensive test per Appendix 2 of the bulletin is performed and defects corrected. Periodic verification of transponders with analogue altitude encoders is recommended at least every 24 months using calibrated ramp test equipment. Design approval holders must ensure maintenance documentation includes tests consistent with the bulletin's guidance. Communication with notifying authorities about rectification actions is strongly advised.

Summary

EASA Safety Information Bulletin 2011-15R3 titled 'ADS-B Out, Mode S and Mode C Transponder Systems: Ground Testing' provides guidance for owners, operators, and design approval holders of aircraft equipped with Secondary Surveillance Radar Mode S, ADS-B Out transmitters, or Mode C transponder systems. It applies to a wide range of aircraft including those certificated under EASA CS 22, 23, 25, 27, 29, 31HB, VLA, VLR, LSA, and equivalent FAA or JAA requirements. The bulletin emphasizes the importance of accurate ground and flight transponder testing to ensure safe air traffic management operations.

What changed

This revision clarifies the ground test requirements for ADS-B Out, Mode S, and Mode C transponders, removes the previous recommendation for a 24-month recurrence of testing except for transponders with analogue altitude encoders, and extends applicability to Light Sport Aircraft. It also incorporates recommendations from previously withdrawn SIBs 2011-13 and 2011-14 and updates references to include ADS-B Out systems.

Why it matters

Accurate and reliable transponder data is critical for safe air traffic control and collision avoidance systems. This bulletin helps operators and maintenance organizations understand the necessary ground testing procedures to detect and correct transponder defects, thereby maintaining system integrity and compliance. It also provides practical guidance to avoid operational disruptions and ensures that altitude reporting and other transponder functions meet safety standards.