of solutions using dual optics or similar systems were suggested in the post-war era, but none of these became widely used. This led to the introduction of the pilot direction indicator, an electrically driven pointer which the bomb aimer used to indicate corrections from a remote location in the aircraft. Vector bombsights remained the standard by most forces well into the Second World War, and was the main sight in British service until 1942. This was in spite of the introduction of newer sighting systems with great advantages over the CSBS, and even newer versions of the CSBS that failed to be used for a variety of reasons. The later versions of the CSBS, eventually reaching the Mark X, included adjustments for different bombs, ways to attack moving targets, systems for more easily measuring winds, and a host of other options. Tachometric bombsights One of the main problems using vector bombsights was the long straight run needed before dropping the bombs. This was needed so the pilot would have enough time to accurately account for the effects of wind, and get the proper flight angle set up with some level of accuracy. If anything changed during the bomb run, especially if the aircraft had to maneuver in order to avoid defences, everything had to be set up again. Additionally, the introduction of monoplane bombers made the adjustment of the angles more difficult, because they were not able to slip-turn as easily as their earlier biplane counterparts. They suffered from an effect known as "Dutch roll" that made them more difficult to turn and tended to oscillate after levelling. This further reduced the time the bomb aimer had to adjust the path. One solution to this later problem had already been used for some time, the use of some sort of gimbal system to keep the bombsight pointed roughly downward during maneuvering or being blown around by wind gusts. Experiments as early as the 1920s had demonstrated that this could roughly double the accuracy of bombing. The US carried out an active program in this area, including Estoppey sights mounted to weighted gimbals and Sperry Gyroscope's experiments with US versions of the CSBS mounted to what would today be called an inertial platform. These same developments led to the introduction of the first useful autopilots, which could be used to directly dial in the required path and have the aircraft fly