What happened
The BEA has released an interim report detailing three separate incidents involving Airbus neo-family aircraft where the Digital Radio and Audio Integrated Management System (DRAIMS) malfunctioned.
In the first serious incident on 2/20/2024, an Airbus A320neo, registration EI-NSF, experienced a total loss of radio communication and transponder functionality while en route from Dublin to Bordeaux. The crew reported audio crackling and erratic display messages on the Radio Management Panels (RMPs). The aircraft disappeared from civil radar, prompting military coordination to track the plane via primary radar and Flightradar24. During the event, the aircraft experienced a loss of separation with another flight, coming within 3.2 NM horizontally and 175 ft vertically of a British Airways Euroflyer flight.
A second serious incident occurred on 1/13/2025, involving an Airbus A321neo, registration PH-YHA. The aircraft experienced erratic transponder behavior, including 85 Mode C losses and 224 unauthorized transponder code changes. The crew was unable to change radio frequencies and had to use the emergency frequency to establish contact with controllers before landing at Bordeaux-Mérignac.
The third incident, involving an Airbus A321neo, registration PH-YHC, occurred on 4/29/2025. The crew experienced RMP desynchronization and loss of radar contact. The aircraft was forced to perform 360-degree turns to avoid entering restricted Maastricht airspace after Brussels ACC refused to accept the flight due to the lack of transponder data. This incident also resulted in a loss of separation with another aircraft.
The investigation
The BEA investigation focused on the DRAIMS architecture, which manages communications (VHF/HF, SATCOM), aural alerts, surveillance (transponders, ACAS), and radio navigation. The investigation established that a lack of robustness in an Audio Management Unit (AMU) component to Ethernet micro-cuts causes the system to enter a degraded mode. This leads to erratic data processing, resulting in the observed failures in radio, transponder, and navigation functions.
Findings
- The primary cause of the failures is an AMU component vulnerability to Ethernet micro-cuts, which triggers erratic processing of data between the RMPs and the AMU.
- The failure is unpredictable and can cause various symptoms, including audio degradation, frequency desynchronization, and the loss of TCAS and transponder functions.
- Existing radio failure procedures for transponder loss may be insufficient when the failure is caused by a DRAIMS malfunction, as switching to a secondary transponder may not be possible.
- Reliance on third-party flight tracking tools like Flightradar24 during such incidents is dangerous, as these tools use extrapolated data that does not reflect the aircraft's actual position during a transponder failure.
Safety action
- A software patch developed by Thales and Airbus has been certified by EASA to prevent this failure.
- EASA Airworthiness Directive 2025-0118 makes the retrofit mandatory, with a completion deadline of December 4, 2026.
- Airbus has issued temporary operational procedures (OEB 63 for A320neo and OEB 58 for A330neo) to assist crews in managing RMP desynchronization and communication loss.