I love old movies and watched one a couple of weeks ago called “Tonight and Every Night” that incongruously (it would seem at first glance) combined singing and dancing with the London Blitz. Turns out it was based on a true story about a London theater called the Windmill (the “Music Box” in the movie) that stayed open even as German bombs were falling all around it. Performers would be on stage until a warning siren went off and then they and the theater patrons would head for the reinforced lower level until the danger had passed. The mood of the movie swung freely from sprightly singing and dancing to a couple of deaths at the end as a result of the bombings. (Spoiler – Rita Hayworth’s character lives!)
Anyway, that got me to thinking about what inventions the English military might have experimented with to protect citizens from those bombing attacks so I dug in and found one that was pretty cool.
Fairly early in the Blitz, the Germans used a radio signal-based bombing direction system called Knickebein to get its planes from Germany to its English targets. The bombers followed a radio signal sent by a specially designed large antenna system to the point where they were supposed to drop their bombs. A series of “dots” (a short tone) and “dashes” (a longer tone) would help the pilot keep the airplane at the center of the beam. When another radio beam crossed their “highway in the sky,” and they could hear its tones on a second receiver, the bombardier would drop their load. This was a literal case of “X marks the spot.”
The British confirmed that the Germans were using this landing beam system to drop bombs by eavesdropping on captured Luftwaffe pilots. However, many scientists refused to believe this was possible because they felt the curvature of the earth would not allow radio beams to be sent accurately. Winston Churchill finally settled the controversy by sending British pilots up to find out if the beams were really there. A crew found the beam and followed it. They found the crossbeam, marked the coordinates and later found out that the beams crossed directly over the Rolls Royce plant where the Merlin airplane engines (yes, like the one in our P-51C Mustang) were manufactured.
Since the British now knew what radio frequencies the German pilots were trained to listen for and follow, the Brits started their own system to confuse the Germans. On the nights when raids were expected, they sent up Avro Ansons fitted with receivers to find the radio signals (the Germans turned on the signal early in the missions). Once found, a low “dot” pattern was sent out by the British on the Germans’ frequency. Understandably confused, the German navigator had no idea which “dot” pattern the pilot should use to stay centered. Later, the British modified their tone pattern so that it was indistinguishable from the Germans’. That made the bomb line very wide and the navigator had no way to tell how far they were from the center of the bomb beam, which was what they were supposed to be following.
Now that British could “bend” the beam could be away from the target, they could fool the Germans into dropping their bombs where they wanted them to – away from civilization. Since the Germans were so highly trained to follow the radio beam, it was chaos in the skies for the Luftwaffe pilots.
The Germans implemented other electronic beam navigation systems after the Knickebein, but the deviousness of discovering its existence from the captured German pilots, the struggle to get government scientists to accept that radio beams could effectively be sent in the required pattern, and the ingenious countermeasure the British came up with makes the story of the Knickebein a classic wartime tale of “us vs. them.”
The Mustang and the RISE ABOVE Traveling Exhibit are at the Wings Over McConnell Open House and Air Show at McConnell AFB in Wichita, Kans. this weekend. Admission to the show is free, as is admission to the Traveling Exhibit.
The CAF Red Tail Squadron is a volunteer-driven 501c3 non-profit organization that operates under the auspices of the Commemorative Air Force. For more information, please visit redtail.org.