EASA SIB AIR-21-15R1
Aeroplanes with Honeywell Primus II Radio System with Radio Management Unit (RMU) 855 - Navigation System
Summary
The FAA Special Airworthiness Information Bulletin SAIB: AIR-21-15 R1 provides information regarding the Honeywell Primus II Radio System with Radio Management Unit (RMU) 855 installed on various aircraft models including 328 Support Services GmbH Model 328-100 and -300, Learjet Model 45, Embraer EMB-135 and EMB-145 series, Textron Aviation models 500, 550, 560, 650, Hawker 800 series, Bombardier CL-600 and BD-700 series, Viking Air CL-215-6B11, and Textron Aviation Model 750. The bulletin addresses the potential for inadvertent disabling of the Automatic Dependent Surveillance–Broadcast (ADS-B) Out function due to certain avionics power-up sequences involving the RMU-855. This is an informational bulletin and does not mandate regulatory action.
What Changed
This revision of SAIB AIR-21-15 removes certain airplanes from the applicability list. It highlights the issue of ADS-B Out transmissions being disabled inadvertently due to RMU-855 power-up sequences and references Honeywell service documents providing procedures and software updates to address the issue. The bulletin clarifies that the condition is not currently considered an unsafe condition warranting an airworthiness directive.
Why It Matters
This information is critical for aviation professionals because inadvertent disabling of ADS-B Out can lead to non-compliance with federal regulations 14 CFR 91.225 and 91.227, potentially affecting aircraft operation in controlled airspace. Operators and maintenance teams need to be aware of this issue to ensure proper avionics power-up procedures and apply software updates to maintain ADS-B Out functionality and regulatory compliance.
What To Do
Owners and operators of the affected aircraft should follow the procedures and software update instructions outlined in Honeywell Service Bulletin 7013270-34-0024 and Service Information Letter D201507000061 Revision 4 at the earliest opportunity. There is no mandatory compliance deadline, but timely action is recommended to prevent ADS-B Out disablement.