Final answer:
The minimum enlisted paygrade required to be designated as a Non-Destructive Inspection (NDI) specialist is typically E-4, which is the rank of a Senior Airman in the United States Air Force.
Step-by-step explanation:
To be designated as a Non-Destructive Inspection (NDI) specialist, a minimum enlisted paygrade is required. According to page 3-12, the minimum enlisted paygrade for an NDI specialist is typically E-4, which is the rank of a Senior Airman in the United States Air Force. This means that an individual needs to have the rank of Senior Airman or above to be designated as an NDI specialist.