The management of repetitive defects has long been a challenge for aviation maintenance professionals. When the same fault keeps appearing on an aircraft, it signals that somewhere in the troubleshooting or rectification process, the root cause remains unaddressed. EASA's newly published NPA 2025-12 introduces comprehensive guidance material that could fundamentally change how CAMOs and Part-145 organisations approach this critical safety issue.
Understanding the Current M.A.403 Framework
The existing M.A.403 requirements under EU Regulation 1321/2014 establish the foundation for managing aircraft defects. The regulation distinguishes between defects that seriously hazard flight safety—which must be rectified before further flight—and those that can be deferred under specific conditions using the Minimum Equipment List (MEL) or maintenance data.
Currently, M.A.403(c) requires that any defect not seriously hazarding flight safety shall be rectified as soon as practicable after identification, within any limits specified in the maintenance data or MEL. Deferred defects must be recorded in the aircraft's continuing airworthiness record system or technical log.
The supporting AMC M.A.403(b) calls for an assessment of both the cause and potentially hazardous effects of any defect that could affect flight safety, initiating further investigation to identify the root cause. However, the current framework provides limited specific guidance on what happens when a defect recurs—when troubleshooting fails to eliminate the underlying problem.
Why EASA Took Action: Safety Issue SI-9001
The new guidance material emerges directly from EASA's Safety Risk Management process, specifically Safety Issue SI-9001: "Inadequate management of repetitive defects." This safety concern was identified through analysis of recurring incidents where defects continued to manifest because the underlying root cause was never effectively eliminated.
The problem is multifaceted. In some cases, troubleshooting is simply not performed—perhaps because a flight crew system reset temporarily clears the fault indication. In others, troubleshooting is performed inadequately, with maintenance personnel conducting operational checks rather than retrieving fault codes and following proper troubleshooting procedures. Intermittent faults present particular challenges, manifesting only under specific flight conditions such as vibrations, aerodynamic loads, or control surface movements that cannot be replicated on the ground.
The New GM1 M.A.403: A Comprehensive Framework
The proposed GM1 M.A.403 on Management of Repetitive Defects introduces the first detailed EASA guidance specifically addressing how organisations should identify, monitor, coordinate, and rectify repetitive defects. While primarily targeting complex motor-powered aircraft and air carriers, the guidance applies to all aircraft and associated organisations, including CAOs.
Defining Repetitive Defects
The guidance defines a repetitive defect as an aircraft defect or system malfunction that reoccurs on the same aircraft because the underlying root cause has not been effectively eliminated. Recognising that multiple factors contribute to defect recurrence—spurious fault indications, system resets, intermittent faults, incomplete troubleshooting, or insufficient rectification—EASA acknowledges that a single identification criterion may not be suitable. Organisations may establish criteria based on recurrence within a defined number of flight cycles, flight hours, or operating days.
CAMO Responsibilities Under the New GM1 M.A.403 Framework
The guidance significantly expands CAMO expectations. As part of its defect control system, the CAMO must establish procedures enabling timely identification, control, and coordination of repetitive defect rectification. Crucially, the guidance states that reliance on the AMP reliability programme alone is insufficient—CAMOs must ensure repetitive defects are identified and monitored on a regular basis, resolving them without waiting for the next reliability report.
A risk-based approach is endorsed, recognising that impact on flight safety varies by system. Flight controls, landing gear, and propulsion systems demand additional or more stringent troubleshooting and corrective actions. The guidance even suggests removing aircraft from service for in-depth investigations or conducting maintenance check flights to verify rectification effectiveness.
The CAMO's management system must verify procedures through compliance monitoring, including checking how repetitive defects have been handled over previous months. Hazards and risks must be documented within the SMS, including operational pressure and personnel shortages that may delay rectification.
Part-145 Organisation Responsibilities
Maintenance organisations must consider risks associated with operational pressure, personnel shortages, and the normalisation of failure clearance without proper reporting or troubleshooting. This last point addresses a concerning industry tendency where repetitive failure resets become routine rather than triggering escalation.
Coordination Requirements
The guidance identifies three main stakeholders in the repetitive defect management process: the operator (flight/cabin crew), the maintenance organisation, and the CAMO. Effective coordination is essential, with the CAMO holding overall responsibility for managing these interfaces.
For operator coordination, CAMOs must ensure technical log entries include sufficient information to facilitate troubleshooting—fault messages, flight phase, aircraft system configuration, and cockpit effects. Flight crews must understand that deferring defect reporting until returning to home base is unacceptable. Procedures must inform flight crews when latent or intermittent faults are being monitored, particularly for systems affecting automation functions.
For maintenance organisation coordination, CAMOs must ensure all relevant information including aircraft configuration status is available, previous troubleshooting actions are reviewed to avoid duplicating ineffective attempts, and accurate maintenance records enable adequate monitoring.
Troubleshooting Best Practices
The guidance establishes clear expectations for troubleshooting practices. The absence of a fault on the ground does not mean corresponding failure codes cannot be retrieved from onboard maintenance systems—this data must be accessed and reviewed. A fault that cannot be confirmed on the ground does not automatically mean the aircraft is airworthy.
Maintenance records must include precise references to tasks performed, steps accomplished, inspection results, and measured values. System resets must be used with caution and always recorded in the technical log—a reset may temporarily clear an indication while the underlying fault remains latent.
Significantly, performing only operational checks or repeating identical BITE tests without applying full troubleshooting procedures is explicitly deemed insufficient. While a BITE test may confirm a newly reported fault, it is inadequate for investigating a repetitive defect where comprehensive troubleshooting is required until the root cause is identified.
Implications for MCC and MOC Engineers
The new guidance has significant implications for Maintenance Control Centre (MCC) and Maintenance Operations Centre (MOC) Engineers. These professionals sit at the critical intersection between flight operations, continuing airworthiness management, and maintenance execution.
Currently, MCC/MOC Engineers typically focus on dispatch reliability, managing the MEL, coordinating line maintenance, and ensuring aircraft meet scheduled departures. The new guidance elevates their role in repetitive defect management substantially.
Job descriptions and competency requirements for MCC/MOC Engineers will likely need updating to include explicit responsibilities for repetitive defect identification and monitoring across the fleet. This means implementing systematic tracking mechanisms rather than relying on individual memory or informal communication.
MCC/MOC Engineers will need enhanced authority to escalate repetitive defects that are not being effectively resolved, potentially including the authority to ground aircraft when the same defect recurs after multiple rectification attempts. They must develop procedures to ensure flight crews are informed when intermittent faults are being monitored and that defect deferral decisions consider defect history.
Training programmes should incorporate root cause analysis methodologies, fault isolation management systems, and the ability to interpret onboard maintenance system data. Communication protocols between MCC/MOC, CAMO technical services, and Part-145 maintenance planners will require formalisation.
Implementation Path Forward
Organisations should begin preparing now. A gap analysis comparing current procedures against the new guidance is essential, assessing how repetitive defects are identified, what criteria trigger escalation, how information flows between stakeholders, and whether SMS documentation addresses these risks. CAME and MOE amendments will be required, along with enhanced training for relevant personnel and potentially upgraded defect tracking software.
Conclusion
EASA's proposed GM1 M.A.403 represents a significant step forward in addressing a recognised safety gap. For CAMOs and Part-145 organisations, the message is clear: repetitive defects require dedicated procedures, systematic monitoring, and coordinated action between all stakeholders. The guidance provides a framework that, once adopted, will bring greater structure and accountability to an area where industry practice has often been inconsistent. The consultation deadline of 31 March 2026 provides an opportunity for stakeholders to contribute their operational experience to shaping the final material.
