Lotfernrohr 7
German bombsight simpler than the Norden, used in level bombers.
It replaced earlier models like the Lotfernrohr 3 and BZG 2, and the Lotfe 7C introduced gyroscopic stabilization in January 1941.
Quick Facts
- Primary users
- Luftwaffe level bombers
- Replaced
- Lotfernrohr 3 and BZG 2 bombsights
- Manufacturer
- Carl Zeiss
- Post-war destination
- USSR (about a thousand unused units)
Facts from the source article.
Design
The Norden bombsight had been compromised before the war by Herman W. Lang, a member of the Duquesne Spy Ring who worked for the Carl L. Norden Corporation. Lang provided sketches and plans to the Abwehr during a 1938 visit to Germany. The Norden comprised an optical system and a large stabilization platform, both complex to maintain. German instruments were already similar to the Norden before the war. The Lotfe 7 used gyroscopes to create a stabilized platform for the bombardier, but lacked the Norden's complex interaction with the autopilot. It was a single metal box containing most of the mechanism, with a tube extending from the bottom that held a mirror reflecting the target into a small telescope. The mirror was moved to stabilize the image and track the target, combining functions of the Norden's stabilizer and optics. Controls consisted of three large knurled knobs.
Operation
The Lotfe 7 functioned much like the Norden bombsight. A bombardier found the target through the eyepiece and turned the adjustment dials until the image stopped moving. This let the device measure wind speed by canceling out the drift, which then gave an accurate groundspeed reading. A key difference from the Norden was that the Lotfe 7 could look straight ahead, so the bombardier could aim directly at the real target instead of first locking onto a closer test point. The sight worked for targets between 40 and 90 degrees in front of the aircraft, and up to 20 degrees to either side. During the final run, the autopilot took over, and the bombsight made small course corrections based on the bombardier’s last inputs. Bomb release was usually automatic to avoid timing mistakes. The device sat near the aircraft’s nose, with a mirror tube poking through the fuselage. In planes like the Ju 88 and He 111, the tube ended in a bottom fairing with a flat window. On the Arado Ar 234 and Me 262 bomber prototypes, the tube was exposed to the air, its mirror window nearly flush with the skin. Because the Ar 234 had only one seat, the pilot had to remove the control yoke to reach the sight. After the war, around a thousand unused Lotfe 7s were found at Zeiss factories and sent to the USSR. They were tested in B-25 Mitchells to replace the more complex Norden, but the sight did not work well with the Soviet Si-1 autopilot, and the issues were never fixed.
More in German Inventions of the Nazi Period
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced