Oboe (navigation)

Oboe was a British aerial blind bombing targeting system in World War II, based on radio transponder technology. The system consisted of a pair of radio transmitters on the ground, which sent signals which were received and retransmitted by a transponder in the aircraft. By comparing the time each signal took to reach the aircraft, the distance between the aircraft and the station could be determined. The Oboe operators then sent radio signals to the aircraft to bring them onto their target and properly time the release of their bombs.

The system was first used in December 1941 in short range attacks over France where the necessary line of sight could be maintained. To attack the valuable industrial targets in the Ruhr, only the De Havilland Mosquito flew high enough to be visible to the ground stations at that distance. Such operations began in 1942, when Mosquitos used Oboe both to mark targets for heavy bombers, as well as for direct attacks on high value targets. In an attack on 21 December 1942, Oboe guided bombers dropped over 50% of their bombs on the Krupp factories in Essen, an enormous improvement over previous efforts that resulted in less than 10% of bombs landing on their targets. Versions using shorter wavelengths demonstrated accuracy on the order of 15 meters (49 ft).

Oboe was most used during the Battle of the Ruhr in 1943, after which Bomber Command began moving its attention further eastward, out of Oboe range. For these raids new systems were used, notably increasingly accurate versions of H2S. Additionally, Oboe's limitation of guiding a single aircraft at a time led to the Gee-H system that placed the transponder on the ground and the readouts in the aircraft, allowing around 80 aircraft to use the service at once. Neither offered the accuracy of Oboe, however, which demonstrated the highest average bombing accuracy of any system in the war.

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