page_title: V-1 flying bomb
section_title: Guidance system
hierarchical_section_title: V-1 flying bomb / Description / Guidance system
caption_attribution_description: Čeština: Raketa V-1 v Historisch-technisches Informationszentrum Peenemünde, Německo English: V-1 rocket in Historisch-technisches Informationszentrum Peenemünde, Germany Camera location54°&#160;08′&#160;20.64″&#160;N, 13°&#160;46′&#160;07.9″&#160;E&#160;&#160;&#160;View this and other nearby images on: OpenStreetMap - Google Earth
context_page_description: The V-1 flying bomb —also known to the Allies as the buzz bomb, or doodlebug, and in Germany as Kirschkern or Maikäfer, as well as by its official RLM aircraft designation of Fi 103—was an early cruise missile and the only production aircraft to use a pulsejet for power.
  The V-1 was the first of the so-called "Vengeance weapons" series deployed for the terror bombing of London. It was developed at Peenemünde Army Research Center in 1939 by the Nazi German Luftwaffe at the beginning of the Second World War, and during initial development was known by the codename "Cherry Stone". Because of its limited range, the thousands of V-1 missiles launched into England were fired from launch facilities along the French and Dutch coasts. The Wehrmacht first launched the V-1s against London on 13 June 1944, one week after the successful Allied landings in France. At peak, more than one hundred V-1s a day were fired at south-east England, 9,521 in total, decreasing in number as sites were overrun until October 1944, when the last V-1 site in range of Britain was overrun by Allied forces.
context_section_description: The V-1 guidance system used a simple autopilot developed by Askania in Berlin to regulate altitude and airspeed. A pair of gyroscopes controlled yaw and pitch, while azimuth was maintained by a magnetic compass.  Altitude was maintained by a barometric device. Two spherical tanks contained compressed air at 900 pounds per square inch, that drove the gyros, operated the pneumatic servo-motors controlling the rudder and elevator, and pressurized the fuel system.
  The magnetic compass was located near the front of the V1, within a wooden sphere.  Just before launch, the V1 would be suspended inside the Compass Swinging Building (Richthaus).  There the compass was corrected for magnetic variance and magnetic deviation.
  The RLM at first planned to use a radio control system with the V-1 for precision attacks, but the government decided instead to use the missile against London. However, some flying bombs were equipped with a basic radio transmitter operating in the range of 340-450 kHz.  Once over the channel, the radio would be switched on by the vane counter, and a 400-foot aerial deployed.  A coded Morse signal, unique to each V1 site, transmitted the route, and impact zone once the radio stopped transmitting.
  An odometer driven by a vane anemometer on the nose determined when the target area had been reached, accurately enough for area bombing. Before launch, it was set to count backwards from a value that would reach zero upon arrival at the target in the prevailing wind conditions. As the missile flew, the airflow turned the propeller, and every 30 rotations of the propeller counted down one number on the odometer. This odometer triggered the arming of the warhead after about 60 km (37 mi). When the count reached zero, two detonating bolts were fired. Two spoilers on the elevator were released, the linkage between the elevator and servo was jammed, and a guillotine device cut off the control hoses to the rudder servo, setting the rudder in neutral. These actions put the V-1 into a steep dive. While this was originally intended to be a power dive, in practice the dive caused the fuel flow to cease, which stopped the engine. The sudden silence after the buzzing alerted listeners of the impending impact.
  Initially, V-1s landed within a circle 19 miles (31 kilometres) in diameter, but by the end of the war, accuracy had been improved to about 7 miles (11 kilometres), which was comparable to the V-2 rocket.
caption: A reconstructed starting ramp for V-1 flying bombs, Historical Technical Museum, Peenemünde (2009)
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