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Aviation History
1946
1946 - 0866.PDF
FLIGHT MAY 2ND, 1946 \ PATHFINDER STORY (C O N Tj N U E D \ • trolling and timing of largeforces of heavy bombers on night missions. The next great step for-ward came with the intro- duction of radar bombingaids, the first of which was known as "Oboe."(Incidentally, 'the term radar—'' radio detectionand ranging "—is a han- dier American adaptationof the former British term '' radio direction - find-ing.") Oboe was a blind- bombing devicS, quite un-affected by normal visi- bility, cloud, fog or badweather, and in the hands of experienced operatorsand aircraft crews, it would permit extremelyaccurate results. Its first use was against a powerstation at Lutterade, on December 20th, 1942. Oboe opened up many new possibili-ties and was in regular use until the end of the war. Its chief limitation when it was first introduced was its range,which was comparatively short at the operational altitude of contemporary bombers, though it was extended laterwhen used in conjunction with Mosquitoes operating at altitudes up to 30,000 feet. (An illustrative diagram is insetin the double-page coloured drawing.) The Principle of Oboe Two fixed stations were used for Oboe, known as thetracking or '-cat" station and the releasing or "mouse" station. Each had pulse-transmitter, receiver and range-measuring equipment while the aircraft carried only a transmitter-receiver. Pulses from the fixed stations, re-ceived and retransmitted by the aircraft, were picked up again by the ground stations and the total time of travelsince transmission was measured. The distance of the air- craft from each station was therefore known at-anv time, This P.P.I, photograph is of special interest as it reveals the cruiser Koln and other shippinglying off Horten in the Oslo Fiord. A indicates the Koln, and B, other lzrge ships. so the position lines were circles with the station at the centres. The two stations pooled their range readings and transmitted their result to the aircraft in the form of a fix. The Oboe Beam For blind bombing or marking, the aircraft requiredonly to reach a predetermined position; to do so, the pilot flew by normal navigational methods to a point onthe desired position line of the "cat" station, and then switched on his Oboe. The aural signals of the Oboebeam were similar to those for S.B.A. (Standard Beam Approach), namely E's and T's in Morse which produceda Continuous note in the overlapping zone of the beam. Any deviation from the position line of the trackingstation was indicated by the continuous beam note break- ing up into E's or T's. Very accurate flying was requiredto hold the beam, which was only 17 yards wide. As the aircraft continued along the beam, "distancefrom target " signals were received at eight, five and three 'minutes' time to target, and were in theform of four morse Bs, Cs or Ds res- pectively. At five seconds from therelease point, five half-second pips were heard, followed by a 2^-second dash, thefinish of which marked the moment for bomb release. During the run-up to the target, foras much as the final fifteen minutes, a great deal of strain was experienced bythe pilot, who not only had to hold the beam accurately, but also had to fly atconstant height and fixed air speed, regardless of his greatly increased vulner-ability to predicted flak. At base, to enable the bombing or marking run tobe examined, and the accuracy assessed, a graphic record of the course of the air-craft was produced automatically from signals returned to the releasing station.Among the chief advantages of Oboe in addition to its great potential accuracy,was that all calculations could be made in advance, and that the observationswere made in relative peace and comfort it base stations. Another radar blind-bombing andnavigational aid was introduced for the attack, on Hamburg on January 30th,1943. This instrument, known as H2S,The navigator's compartment on a Lancaster, showing the Gee unit let into thetable, and the H2S on a tubular mounting which is hinged in the horizontal plane.
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