Which of the following is a common standard governing phased array ultrasonic testing?

The choice of ASNT SNT-TC-1A as a common standard governing phased array ultrasonic testing is appropriate because this document specifically outlines the requirements for personnel certification in non-destructive testing (NDT), including various methods like ultrasonic testing. It provides a framework for training and assessing the competency of individuals performing ultrasonic testing, which includes phased array techniques. This standard is widely recognized in the industry, particularly in relation to qualification and certification of NDT personnel, ensuring that those who perform these tests have the necessary skills and knowledge.

The other options listed do not specifically address phased array ultrasonic testing or NDT personnel certification. ISO 9001 pertains to quality management systems and is not exclusively related to NDT. IEC 61508 focuses on functional safety in electrical and electronic systems, which does not directly pertain to ultrasonic testing methodologies. ANSI Z359 provides standards for fall protection and safety systems and likewise does not relate to phased array ultrasonic testing. Thus, ASNT SNT-TC-1A is indeed the most relevant standard among the options provided for governing phased array ultrasonic testing.