One of the parts of the calibration process, is to fly arcs, through the centreline/ localiser at , at least 2 distances from the " station" . The arcs normally extend to approximately 2-4 nm on either side of the centreline/ localiser, and must also require a turn and reverse coarse arc. I stand under correction, 1 arc is at 13 DME/nm, which is very close to the arc, reportedly been flown, when this tragedy occurred. At my present airport, the above mentioned arcs are flown at 6 nm and 15nm. These arcs are flown for Every runway with an ILS and as far as I know a VOR approaches for which is published, in this case arcs for Rwy11 and 29. It appears they were possibly flying the arc(s) for Rwy 11, thus west of airport. At bigger airports, with parallel rwys , this gets very complicated together with arriving and departing air traffic.
