What is the maximum period of proficiency lapse before refresher training is required for NDI technicians?

The correct answer is three years because NDI (Non-Destructive Inspection) technicians are required to undergo refresher training if there is a lapse in their proficiency due to not having performed NDI tasks for a period exceeding three years. This regulation ensures that technicians maintain their skills and knowledge, which is vital for the integrity and safety of aerospace components. Beyond this three-year threshold, the likelihood increases that a technician may not be familiar with the latest techniques, equipment, or standards that have been introduced, which could compromise their effectiveness in performing inspections. Thus, the three-year maximum period before refresher training is a critical benchmark for maintaining operational readiness and expertise within the field.