The wing ariels were for the Rebecca. As Sycamore said you could have a small map with circles on it but nobody bothered at Oakington. They were mounted back to front, ie, the sharp bit was the leading edge. They would pick up ice by the handful and eventually they would start viabrating and shaking so that in some cases thay would break off. It did not happen very often as we could climb and descend through the icing layer fairly rapidly.