Nigel,
The copy of AWS D1.1:2006 does mention both Phased Array and TOFD techniques in the section 6.36 Advanced Ultrasonic Systems.
These alternative methods can be used in a proposed procedure that the Engineer has to approve. Phased array can show “experimental evidence” that the required...
The last reply from SJones gives some good examples of applications using a Phased Array instrument. You can find a few more following this link: http://www.harfangmicro.com/Apps.html
I know that PA has been successfully used to replace X-Ray inspection following the AWS D1.1 code(Structural...