EASA SIB SW-11-61
Honeywell International (formerly Bendix King) KRA 405B Radar Altimeter — Erroneous Altitude Information
Summary
The FAA Special Airworthiness Information Bulletin SAIB: SW-11-61 addresses a potential undetected failure condition in the Honeywell International (formerly Bendix King) KRA 405B Radar Altimeter. This condition may cause the radar altimeter to provide erroneous altitude information without warning, affecting aircraft systems that rely on radar altitude data. The bulletin applies to aircraft equipped with the KRA 405B Radar Altimeter system.
What Changed
This bulletin introduces information about a failure mode in the KRA 405B Radar Altimeter where internal component failures may go undetected, causing the altimeter to output erroneous altitude readings that drift between approximately 800 and 1200 feet. It also informs that Honeywell is working on a design improvement to address this issue but no mandatory regulatory action is currently required.
Why It Matters
This information is critical for aviation professionals because undetected erroneous altitude data can adversely affect aircraft systems such as Automated Flight Control Systems that depend on radar altitude inputs. Operators and pilots need to be aware of this failure mode to identify it during flight and to avoid relying solely on radar altitude information, ensuring safe flight operations and proper system integration.
What To Do
Owners and operators should review their aircraft configurations to understand which systems use radar altitude and assess the impact of this failure condition. Pilots should be trained to recognize the failure mode through normal instrument scanning and to use barometric and GPS altitude as primary references. There are no compliance deadlines or mandatory actions specified in this bulletin.