Moreover, the new system was dramatically simpler to use. After locating the target in the sighting system, the bombardier simply made fine adjustments using two control wheels throughout the bomb run. There was no need for external calculation, lookup tables or pre-run measurementseverything was carried out automatically through an internal wheel-and-disc calculator. The calculator took a short time to settle on a solution, with setups as short as six seconds, compared to the 50 needed for the Mk. XI to measure its ground speed. In most cases, the bomb run needed to be only 30 seconds long.