Night Level-Bombing Navigation Tactics

X-Gerät (X-Gadget)
After the Knickebein was defeated by British scientists, the Germans developed another device called the X-Gerät. Unlike the Knickebein beams, which could be received by any German bomber using its Blind Landing set, the X-Gerät beams required special equipment and were to be used by a path-finding specialist unit, KGr 100.
The X-Gerät used four main beams. A Directional Beam, or the Pilot's Approach Beam, was laid exactly over the center-line of the target city from the transmitter site near Cherbourg. This beam was code-named "Weser" (a German river). Three other cross-beams, code-named "Rhein," "Oder," and "Elbe," were transmitted to cross the main beam at preset intervals before reaching the target. The path-finders, He 111s of KCr 100, would take off from the airfield at Vannes in Britanny and fly the 150 miles towards Cherbourg. Over Cherbourg the Pilot's Approach beam would be intercepted and received by the aircraft. The beam was very complex, because it was actually two beams overlapping each other -- a course and a fine. The coarse beam was wide and easy to find. Once the pilot was flying along the coarse beam, he would eventually align the plane with the fine beam, which was much narrower, with an equi-signal zone about 20-30 feet wide. These beams were of the same Lorenz characteristics as Knickebein's but were monitored visually instead of aurally. The pilot and the navigator had visual "kicking" meters that showed if the bomber was astray from the center of the Weser fine beam to either left or right. At this point the pilot's only concerns were to keep the aircraft accurately aligned with the beam, adjust for wind drift, and stay in given attidute.
The navigator also used a separate receiver, which was tuned to receive the cross-beams from the Calais area. There were also a visual indicator and a bomb-release calculator, which took the shape of a large clock with three hands: green, black, and red, and was in fact clockwork. The hand were preset with the aid of charts and tables to factor in variables like altitude and wind speed.
The first cross-beam that intersected the Weser beam was intercepted some distance from the target. This was the Rhein coarse warning beam. Afterwards the pilot had to fly very precisely along the exact center of the approach beam. Thirty kilometers from the target the navigator was alerted for the intersecting of the second fine cross-beam, Oder (20-30 yards wide). Upon receiving this beam, he started the clock and the green and black hands began to move together. The third beam, Elbe, was intercepted fifteen kilometers from the bomb release point. The navigator now pressed the control lever on the clock again, stopping the green and black hands (which calculated the ground speed) and starting the red hand moving towards the now stationary black hand. In less than a minute, when the red and black hands overlapped, an electrical circuit was completed and flares and incendiary bombs were released to mark the target for the other bombers. The actual accuracy of the system was roughly 100 yards at 200 miles, which was near enough to hit a large individual factory when the ballistics of individual bombs and the different wind gradients were factored in. It was certainly the most accurate method of night bombing yet devised by any air force up to that time.

Using X-Gerät to locate Coventry

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An X-Gerät kicking meter. It shows the aircraft slightly left of the beam.
An X-Gerät clock from a captured He 111 of KGr 100.

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