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Aviation History
1945
1945 - 1768.PDF
SEPTEMBER 6TH, 1945 bombing force enabled no less than 83 per cent, of the-bombs lifted to be registered as on- target strikes. It is of interest to record that the advent ol radar made the magnificent work of the Path- finder Force possible and, consonantly, the wonderful efficiency of our bombing attack When the P.F.F. Mosquitoes ground-marked a target the name given to the operation was Parramatta, and when the uncanny system of skv-marking was used, the operation was railed Wanganui. Both these types of target marking are "blind," that is, they are done on radar, but when the Oboe system was used the word "Musical" was added to the title. "Newhaven " was the name of another system of target .marking which included both visual and blind marking. It is unfortunate that space forbids our dilating upon these intriguing types of operation ; nevertheless, the radar part of the job is in itself of more than passing interest. Oboe makes use of two ground stations, one Jn Norfolk, the other in Kent, the former being stow 11 as the "releasing" station and the latter as the "tracking" station. The track- ing station transmits a component of a signal beam which runs as a segment of a circle through the target, the radius of the circle being the distance of the target from the track- ing station. The remaining component of the signal beam is supplied by the aircraft equip- ment. Signals are purely aural, there being no visual representation whatsoever; the pilot and navigator each receive signals through their earphones, the pilot's being high pitched, the navigator's low. Each has his own set of signals and consequently the bombing or marking operation is a conjoint effort. Very Narrow Beam We will take the pilot's signals first. Initially, the air- craft must be flown to a waiting point at one end of the beam, and this can be done either by orthodox navigation or by flying on a W/T beam from this country. Having arrived at the waiting point Oboe is switched on and the signals heard. These are the morse T (-) and the morse E (•) which, when overlapping, give a continuous note in the earphones. The overlap zone is only 17 yards wide and so it may be appreciated that pretty accurate flying is needed to keep the continuous note from breaking down into dots or dashes, as deviations from the curved path of the beam will bring about. Subsidiary beams, concentric with the main beam, are spaced at 5-, 10- and 15-mile intervals on both sides, and as these give signals of X, Y and Z respectively over andv 253 cathode-ray tube, on the convex silvered end of which the fluorescent trace or image is registered. The two revolutionary valve elements which made all the difference to transmission. The brass valve on the left is the receiver valve and the other is the magnetron, above the dots and dashes making up the main beam, the pilot will know his position with a fair degree of accuracy if he should, by some mishap, be late in getting to the waiting point. As the aircraft flies along the beam it transmits signals which are received at the releasing station and, conse- quently, as its range is steadily increasing from the releas- ing station, it is possible to plot, at the latter, the exact position of the aircraft at any one instant. It is, of course, absolutely essential that, once on the beam, the pilot flies his aircraft at a constant height and fixed air speed. He must on no account vary these factors. i-iaving, for example, switched on the system at the waiting point, we will now follow the aircraft along the curved path of the beam which leads across the target— the pilot keeping the continuous high-pitched note coming through. The navigator is sitting there listening and, at 10-minutes' flying time from the target, he hears four morse As which are followed by a continuous low note until, at 8 minutes from target, he gets four Bs. When 5 minulgs away four Cs come through, again followed by •--Hie oontinubtKj. note which breaks at 3-minutes' distance to four Ds. After this the continuous note comes through until only 5 seconds away from the target, when five pips are heard for 7.\ seconds fol- lowed by a 2|-second dash. The navigator has the bomb-release button in his hand and, as the 2j-second dash ends, he presses it and the bombs have gone. Immediately the set is then switched off and the aircraft heads for home. This, however, is not the end. At the releasing station a graphic record of the run has been made automatic- ally, and when the crew get back it is they who are told how they have per- formed. It is no good them saying they were bang on when they can be confronted in black and white with evidence that they were, in fact, 50 yards oft. The third of the Bomber Command
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