a similar vector calculator directly into the bombsight, combining it with a drift measure similar to the one from the earlier Drift Sight. Like the Drift sight, simply taking a measure of the wind using the sight itself provided all of the unknown variables needed to completely calculate the bombing approach. Unlike the Drift Sight, the new design not only calculated the effect on the distance the bombs travelled, but also indicated the proper direction to fly to approach the target so the aircraft reached it with no residual sideways motion – thereby cancelling any drift no matter the approach direction. His new Course Setting Bomb Sight featured a large compass at the rear that could be used for making general calculations of wind speed or solving navigational problems. In most cases these could be ignored; the bomb aimer dialled in the wind direction on the compass, then wind speed, airspeed and altitude on different knobs. Through internal mechanisms, these adjustments carried out all of the calculations needed to set the approach and range angle. Through these calculations the CSBS allowed bombing from any direction, freeing the aircraft from the wind line for the first time. Production and use In testing in December 1917 at the Scilly Isles air station, in eight bomb runs the CSBS scored two direct hits, and near-misses on all six other runs. Production quickly followed, and by 1918 about 720 had been produced. The Royal Flying Corps (RFC) started using the Mark I sight as soon as supplies were available, and by April 1918 were also fully converted to this type. For his work on the CSBS and the Drift Sight Wimperis was awarded £2,100 by the Royal Commission on Awards to Inventors. In the post-war era, work on new bombsights was seriously curtailed, and little new development had taken place by 1930. Several minor variations of the CSBS had been introduced during this period to adapt to higher speeds, higher or lower altitudes, and new types of bombs. These also included a separate adjustment for trail, the deceleration of the bomb due to drag. At low speeds and altitudes the time between drop and impact was too short for the bombs to reach terminal velocity so the trajectory of the bombs was roughly parabolic. At higher altitudes or forward speeds the bombs would reach terminal long before impact, which had the effect of making