EASA SIB CASA-2026-04 — Erroneous Height Indication from Radio Altimeters

Summary

The Transport Canada Civil Aviation Safety Alert CASA 2026-04 addresses erroneous height indications from radio altimeters on Airbus Canada Limited Partnership (ACLP) aeroplanes models BD-500-1A10 and BD-500-1A11. It raises awareness of operational issues caused by momentary glitches in radio altimeter data output that affect autothrottle modes and aural warning systems. The alert provides recommendations and corrective actions to mitigate these issues.

What Changed

This new safety alert identifies that inadequate thickness of the radio altimeter antenna gel gasket may cause antenna bending and internal cracking, leading to glitches in radio altimeter data. ACLP issued Service Bulletin BD500-344007 to replace the radio altimeter antenna with a modified gasket design on affected aircraft. Transport Canada may mandate further corrective actions as necessary.

Why It Matters

Erroneous radio altimeter readings can cause unexpected autothrottle mode changes, thrust mode variations during climb, and false landing gear warnings, impacting flight safety and operational reliability. Operators, maintainers, and flight crews must be aware of these risks to prevent inadvertent flight control issues and ensure timely maintenance compliance. Reporting of any unexpected autothrottle mode changes is critical for ongoing safety monitoring.

What To Do

Owners, operators, and maintainers of ACLP BD-500-1A10 and BD-500-1A11 aircraft experiencing unexpected autothrottle behavior or aural warning anomalies should incorporate the modifications described in ACLP Service Bulletin BD500-344007 Issue 001 or later revisions. Flight crews must apply operational procedures from ACLP Flight Operations Transmission A220-FOT-22-30-009 Revision A and Operations Engineering Bulletin 002.01. Report all service difficulties, including unexpected autothrottle mode changes, to Transport Canada as per Canadian Aviation Regulations Part V, subpart 21 (521).