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.
Click on one of the thumbnails below to view the full picture.
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.