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 having a geometry of the component to be inspected, the parent polygon comprising one or more critical regions such as regions of the component subject to high stress levels in use; an origin corresponding to a position of a wavesource within the parent polygon; a wavefront geometry of the wavesource; and a maximum wavefront extent; determining one or more valid polygon sides of the parent polygon depending on the wavefront geometry of the wavesource; for each valid side of the parent polygon, defining a plurality of cutting lines extending from the vertices of the valid sides to the maximum wavefront extent; for each valid side of the parent polygon, reflecting the parent polygon about the respective side 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 of the parent polygon; redefining each child polygon (D n) as a parent polygon, and repeating steps to for each parent polygon until the area within the maximum wavefront extent is filled with polygons (D n); projecting onto the polygons (D, D n) within the maximum wavefront extent, a test wavefront having the wavefront geometry spaced from the origin by a specified distance; and reflecting the child polygons (D n) along the respective sides of their respective parent polygons to project the child polygons (D n) and test wavefront onto the original parent polygon; wherein a respective side of the component is determined to be inspectable using a wavesource originating from the origin where it is determined that a wavefront originating from the origin propagates back to the respective side through the one or more critical regions within a predetermined maximum propagation time. defining: a parent polygon having a geometry of the component to be inspected, the parent polygon comprising one or more critical regions such as regions of the component subject to high stress levels in use; an origin corresponding to a position of a wavesource within the parent polygon; a wavefront geometry of the wavesource; and a maximum wavefront extent; determining one or more valid polygon sides of the parent polygon depending on the wavefront geometry of the wavesource; for each valid side of the parent polygon, defining a plurality of cutting lines extending from the vertices of the valid sides to the maximum wavefront extent; for each valid side of the parent polygon, reflecting the parent polygon about the respective side 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 of the parent polygon; redefining each child polygon (D n) as a parent polygon, and repeating steps to for each parent polygon until the area within the maximum wavefront extent is filled with polygons (D n); projecting onto the polygons (D, D n) within the maximum wavefront extent, a test wavefront having the wavefront geometry spaced from the origin by a specified distance; and reflecting the child polygons (D n) along the respective sides of their respective parent polygons to project the child polygons (D n) and test wavefront onto the original parent polygon; wherein a respective side of the component is determined to be inspectable using a wavesource originating from the origin where it is determined that a wavefront originating from the origin propagates back to the respective side through the one or more critical regions within a predetermined maximum propagation time.