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Aviation History
1946
1946 - 0869.PDF
WAY, 2ND. 1946 FLIGHT 44/ PATHFINDER STORY (CONTINUED) was also used on the majority of subsequent attacks, in- cluding the later series directed against, and resulting in, the destruction of Hamburg. Closely related to A.S.V. (Air to Surface Vessel)—which was the first airborne radar device, and which was demon- strated during fleet manoeuvres.in September, 1938—H2S gave bomber crews a new sense in the form of vision at centimetre wavelengths through darkness or cloud for bombing, marking or navigation. The H2S aerial or scanner unit was mounted in a blister below the mid-upper turret of a Lancaster. The aerial and reflector were caused to rotate by an electric motor at approximately 50 r.p.m. and the radial time base of the P.P.I. (Plan Position Indi- cator) went round in synchronism with them. The echoes received, according to intensity, brightened portions of the cathode-ray tube, giving a facsimile reproduction of the landscape features below. Like A.S.V. for submarine detection, it became apparent in 1943 that H2S could act not only as a " magic eye," but as a warning to the enemy of the presence of the bomber carrying it, and that the pulses transmitted by some early marks of equipment could be picked up by enemy night fighters, and used for homing on to the bomber. H2S had the advantage of being self-contained in the aircraft, and therefore independent of range from base and of ground organization, but a high weight penalty of approximately 700 lb had to be paid. Skill and practice in operating the set and in interpreting the representation it gives are essential for good results, and a great respon- sibility rests upon the H2S operator of a P.F.F. crew. Crews of No. 8 Pathfinder Group, in the later stages of the war, were mostly selected as soon as they left their final crew-training unit, and from then onwards their special training in their squadrons and at the P.F.F. Navi- gational Training Unit filled all available time before operating and between operations. In some cases they were attached to a main-force squadron for a few familiar- izing trips. Their aircraft, Lancasters in the main, con- tained all the latest navigational instruments and the most recent marks of H2S or Oboe, which were the basic target- marking instruments. The exact technique changed in detail from day to day, but the fundamental job of pro- viding a marked poiat on which all bomb-aimers could release their loads remained unchanged. Efforts to Improve Every possible effort was made to improve technique and bombing accuracy both in Pathfinder Force and in the Main-force squadrons. For example, all aircraft were fitted with automatic cameras and photo flashes, and a series of photographs were taken of the bombs or pyro- technics as they were released and as they fell. Prints showing ground detail could then be used to plot the point of impact of the bombs. After raids, an assessment or post-mortem conference was held to discuss every aspect of the operation: also, of course, each crew, first thing after landing, was interrogated over a cup of coffee by intelligence officers, and the captain was invited to give his views on the attack as a whole. Between operations, inter-crew, squadron and group competitive training also played a very important part, and athletic events of all kinds were arranged to keep the crews physically fit. Crews were graded according to their prowess, the most skilled being the Primary Blind Markers. During training on operations, crews served as "supporters" who went in with the early waves of markers, and took photographs (later to be checked for accuracy of position) instead of . dropping target indicators. Frequently they also dropped a load of high explosives with long-delay fuses so that they could feel that their trip had not been unproductive. Their main extra duty on the attack, as signified by the name, was to support the Primary Markers by releasing "Window," the silvered strips dropped in small clouds, at a predetermined rate, to jam the enemy radar detecting devices. This meant that instead of receiving the full con- centration of predicted flak at the target, due to their exposed spearhead position, these first important Waves had some protection and company. Other duties of the Pathfinders were blind and visual illumination by the Flare Wave crews, visual marking, and visual backing-up (renewing) of primary target indicators. This included the centring technique whereby specially trained bomb-aimers were able quickly to assess the mathe- matical centre of a number of T.I.s visible on, say, a city, and to aim at this estimated position their T.I.s of a different colour, to provide a central main marking point. As accuracy of bombing and marking improved, and bomb loads for all Main-force aircraft reached the order of five tons or more, it was found that two hundred air- craft could do the damage previously expected of five hundred, and only the very largest enemy cities required the attention of our total strength. It therefore became customary for two or even three smaller forces to operate » separately, and P.F.F. commitments were thus increased. No. 5 Group of Bomber Command, in particular, operated separately on almost every occasion, and one Mosquito and two Lancaster Pathfinder squadrons we're incorporated in the Group to look after its special marking requirements. Methods of Marking Target marking methods for night bombing are of parti- cular interest, and the ultimate aim of Bomber Command was to be able to attack a target regardless of weather conditions. Blind-bombing instruments made it possible to find the target, but marking it was not always a simple matter. In clear weather, marking on the ground was satisfactory, but, with cloud present, parachute flares were required, and these not only descended slowly, but drifted, and so continuous backing-up (re-marking) was needed during an attack if anything like an accurate aiming point was to be provided over the target. A number of code words were used for the various attacks, according to the type of marking in use. "Para- matta " was one method of blind ground marking, with H2S as the blind-marking instrument. '' Newhaven '' was also ground marking, but included illumination by flares, and visual identification of the aiming point. When Oboe was used as the initial blind-marking instrument, the attacks were qualified by the prefix "Musical," e.g., "Musical Paramatta." Lastly, when sky-marking was used, a " Wanganui " attack took place. The concluding instalment of "PathfinderStory," dealing with target indicators, marking of small high-priority targets, the duties of theMaster Bomber, and enemy reaction will appear in next week's issue dated May gth. R.Ae.S. HATFIELD BRANCH RE-FORMEDT HE Hatfield branch of the Royal Aeronautical Society,which was first formed in 1939 and whose activities had to be suspended on the outbreak of war after only two meet-ings, is being re-formed, and a committee has been elected to arrange a full programme of lectures, visits within the indus-try, and informal discussions. Early in 1943 Mr. R. E. Bishop, the de HaviHand chieidesigner, was mainly responsible (or the formation ol the D.H. Engineering Society which, during the past three years,has arranged 47 lectures and 24 visits for technical personnel of de Havilland and othei firms. This Society will now bemerged in the revived R.Ae.S. branch at Hatfield, of which Sir Geoffrey de Havilland is president and Mr. R. M. Clarkson,the de Havilland assistant chief engineer, the new chairman. The name of the D.H. Engineering Society, however, will beretained by the old society's planning section, which is to con- tinue its work for the firm's production side.
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