A computer implemented method of determining the inspectability of a component by ultrasonic testing, characterised in that the method comprises the steps of: defining: a parent polygon (D) having a geometry of the component to be inspected, the parent polygon (D) comprising one or more critical regions such as regions of the component subject to high stress levels in use; an origin (SE) corresponding to a position of a wavesource within the parent polygon (D); a wavefront geometry of the wavesource; and a maximum wavefront extent (R); determining one or more valid polygon sides (E) of the parent polygon depending on the wavefront geometry of the wavesource; for each valid side (E) of the parent polygon (D), defining a plurality of cutting lines (CL) extending from the vertices of the valid sides (E) to the maximum wavefront extent (R); for each valid side (E) of the parent polygon (D), reflecting the parent polygon (D) about the respective side (E) to define a child polygon (D n ); discarding portions of each child polygon (D n ) which lies beyond a cutting line from the respective side (E) of the parent polygon (D); redefining each child polygon (D n ) as a parent polygon (D), and repeating steps to for each parent polygon (D) until the area within the maximum wavefront extent (R) is filled with polygons (D n ); projecting onto the polygons (D, D n ) within the maximum wavefront extent (R), a test wavefront (WF) having the wavefront geometry spaced from the origin (SE) by a specified distance (X); and reflecting the child polygons (D n ) along the respective sides (E) of their respective parent polygons (D) to project the child polygons (D n ) and test wavefront (WF) onto the original parent polygon (D); wherein a respective side (E) of the component is determined to be inspectable using a wavesource originating from the origin (SE) where it is determined that a wavefront originating from the origin (SE) propagates back to the respective side (E) through the one or more critical regions within a predetermined maximum propagation time. defining: a parent polygon (D) having a geometry of the component to be inspected, the parent polygon (D) comprising one or more critical regions such as regions of the component subject to high stress levels in use; an origin (SE) corresponding to a position of a wavesource within the parent polygon (D); a wavefront geometry of the wavesource; and a maximum wavefront extent (R); determining one or more valid polygon sides (E) of the parent polygon depending on the wavefront geometry of the wavesource; for each valid side (E) of the parent polygon (D), defining a plurality of cutting lines (CL) extending from the vertices of the valid sides (E) to the maximum wavefront extent (R); for each valid side (E) of the parent polygon (D), reflecting the parent polygon (D) about the respective side (E) to define a child polygon (D n ); discarding portions of each child polygon (D n ) which lies beyond a cutting line from the respective side (E) of the parent polygon (D); redefining each child polygon (D n ) as a parent polygon (D), and repeating steps to for each parent polygon (D) until the area within the maximum wavefront extent (R) is filled with polygons (D n ); projecting onto the polygons (D, D n ) within the maximum wavefront extent (R), a test wavefront (WF) having the wavefront geometry spaced from the origin (SE) by a specified distance (X); and reflecting the child polygons (D n ) along the respective sides (E) of their respective parent polygons (D) to project the child polygons (D n ) and test wavefront (WF) onto the original parent polygon (D); wherein a respective side (E) of the component is determined to be inspectable using a wavesource originating from the origin (SE) where it is determined that a wavefront originating from the origin (SE) propagates back to the respective side (E) through the one or more critical regions within a predetermined maximum propagation time. <EOS>