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Aviation History
1925
1925 - 0718.PDF
NOVEMBER 5, 1925 AIR MINISTRY NOTICES Radio-Goniometric (D.F.) Service on Civil Air Routes : Great Britain, Belgium, France and Holland. 1. By agreement between the Governments of Belgium, Fraince, Holland and Great Britain, the radio-goniometric (D.F.) services for aircraft in these countries, will adopt the organisation for co-ordinated working described below. This organisation will be put into force gradually, commencing from September 25, 1925. 2. Stations.—The following are the stations available :— Stationand T ... . T ., , ,^a7,?~ Re- Call Signal. Latitude. Longitude. length s_5 (metres). GREAT '. BRITAIN— Control Croydon 51° 21'10" W. 0°07'40"W. 900 Station. Lympne 51° 05'00" N. r00'50"E. 900 — Pulham 52° 24'15" N. 1°14'25"E. 900 — BELGIUM— Control Brussels.. 50° 52'50" N. 4° 25'05" E. 900 Station. FRANCE— Control LeBourget48r57'45"N, 2C26'26"E. 900 Station. HOLLAND— Rotter- Control dam 51° 52'40" N. 4° 27' 15" E. 900 Station. 3. Sectors.—The air routes are divided up into sectors so that one aerodrome D.F. station in each country controls all the aircraft D.F. routine within that country's area. One or more D.F. stations collaborate with each Control Station for " position " work. The routes are divided up as follows :— (a) LONDON—FRENCH COAST. Control station . . . . Croydon. Collaborating stations . . Lympne, Pulham. (6) FRENCH COAST—BRUSSELS. Control station . . .. Brussels. Collaborating stations . . Rotterdam, Pulham, and if required, Lympne. (c) FRENCH COAST—ROTTERDAM. , Control station . . . . Rotterdam. Collaborating stations . . Brussels, Pulham, and, if required, Lympne. (d) BRUSSELS—COLOGNE. Control station .. .. Brussels (later Cologne). Collaborating station . . Rotterdam. (e) ROTTERDAM (AMSTERDAM)—EAST DUTCH FRONTIER. Control station . . . . Rotterdam. Collaborating station .. Brussels (later Cologne). (/) FRENCH COAST—PARIS. Control station . . Le Bourget. Collaborating stations . . Lympne, Brussels. (g) LONDON—NORTH OF ENGLAND. Control station . . . . Croydon. Collaborating station . . Pulham. (h) ROTTERDAM (AMSTERDAM)—BRUSSELS. Control station . . . . Rotterdam. Collaborating station . . Brussels (later Cologne). (i) BRUSSELS—PARIS. Control station . . . . Brussels. Collaborating station .. Lympne (later Strasburg). (j) BRUSSELS—STRASBURG. Control station . . . . Brussels. Collaborating station . . Cologne, when opened. 4. Routine.—(1) D.F. assistance will be limited to :— (a) " Single Bearings " as determined by a single station. (b) " Positions "as determined by two or more stations. All bearings transmitted, whether for (a) or (b) will be True bearings.* (2)—(a) " Single bearings " may be given by an individual station to aircraft upon request, provided that the station concerned is not already otherwise occupied. Aircraft operators are to ascertain that a station is free before calling it. (b) For " position " work aircraft will call up and com- municate only with the control station of the area in which they are flying. The D.F.' stations working a sector under a control station will transmit to the latter their bearings obtained, the control station will plot the position of the aircraft and the plotting will be communicated to the aircraft by the control station. * An exception to this rule is made in the case of machines belonging to Imperial Airways, Ltd., when flying towards Croydon. See Air Pilot Appendix para. 35A (published in A.P.M.S. 9). In every instance where "Bearings" or "Positions" are rendered, mention will be made, in passing them, of the exact time of readings. (3) Classification of " Bearings " and " Positions." Bearings will be classified as— (a) First Class—one in which a good, sharply defined and steady " minimum " is present. (b) Second Class—one in which there is any doubt as to the quality of the " minimum." Bearings other than First Class must invariably be qualified when they are passed to aircraft. Positions will be classified as— (a) First Class—one which is plotted from First Class bearings from any two of the observing stations. (b) Second Class—one which is plotted in cases where one or more of the bearings is Second Class. Positions other than First Class must invariably be qualified when they are passed to aircraft. In cases where it is necessary to pass Second Class positions, every endeavour is to be made to obtain further bearings of the higher class as soon as possible afterwards. If it is impossible to obtain satisfactory bearings through any cause whatsoever, the fact will be at once reported to the competent aerodrome authority, who is then empowered to refuse D.F. assistance. (4) Procedure : The procedure employed will be that laid down for Croydon and Pulham in paragraphs 34 atid 35 of the Air Pilot Appendix, with the exception relating to machines of Imperial Airways, Ltd., when flying towards Croydon, mentioned in paragraph 35A of the Air Pilot Appendix (pub- lished in A.P.M.S. 9). 5. Check Bearings.—In order to provide against the danger of giving D.F. bearings which may be inaccurate, the follow- ing routines will be carried out by ground stations :— Each operator on commencing watch will, as soon as routine traffic permits, take check bearings upon all other stations with which his own station normally works in con- junction. A variation of more than 2 degrees from the normal bearings should be immediately reported to the competent authority who will investigate the matter forthwith. If the error appears to be one of considerable magnitude, this authority will, at his discretion, notify any aircraft concerned that bearings cannot be supplied until the cause of the error has been eliminated. Special transmissions for checking purposes should never be requested if advantage can be taken of the object station's normal transmissions. An entry in the log book that check bearings have been taken will be made by all operators upon taking over watch. 6. Distress Calls.—Upon receipt of a distress call the control station of the area in which the call is made, and its co-operating station(s) will concentrate upon getting a tiearing of the aircraft concerned and will at once report results to the aerodrome authority who will take all necessary steps to render immediate assistance. During the time that these two stations are taking such bearings all other route stations within range will concentrate upon getting the sense of any message transmitted. Immediately a distress call is made all ground stations and aircraft will cease normal working on 900 metres and will only resume it upon advice from the control station of the area concerned. During such occurrences R/T communication point-to- point will be limited to the absolute minimum, and such transmissions will only be those concerning the rendering of assistance. 7. Remarks.—In order to ensure an accurate D.F. service, the following points will be borne in mind :— (i) Station clocks and the watches on the various aircraft must be synchronised daily from the Eiffel Tower time signal (G.M.T.). (ii) The operation of taking a bearing must be carried out over the full period that speech is being transmitted for that purpose and every possible endeavour must be made to ensure the maximum accuracy. (iii) The operation of taking bearings and plotting positions is to be most carefully carried out and is never to be hurried. If it is discovered that an erroneous bearing or position has been given the call to the aircraft concerned is to be made at once and a correction given. (iv) Operators must be conversant with every form of procedure likely to be used at any time for direction finding work. 8. Air Pilot Appendix : An amendment to the Air Pilot Appendix will be published in due course. (No. 54 of 1925.) 718-
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