FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1955
1955 - 1087.PDF
FLIGHT, 5 August 1955 199 IN MEMORY of MF and MF/DF Looking Back on Earlier Days of Air Radio By P. OOMEN* RECENTLY I found on my desk, among other papers,a Notice to Airmen. It was just a short Notam con-• taining only a few lines, and there was nothing in it of spectacular importance to civil aviation. Nevertheless, reading it brought to the foreground of my mind a host of memories of a time when civil aviation went through one of its greatest throes of expansion; a time which, in my memory, is associated with the requirement for the highest degree of professional skill in the conduct of radio communications. The Notam merely mentioned that the services on mediumfrequencies (MF), and the associated direction-finding service (DF) would be discontinued as from January 1st, 1955, at theaeronautical radio station in Amsterdam and other locations in the Netherlands. As I said above, there is nothing spectacularabout this; we have seen many Notams with similar contents, and we will, no doubt, be seeing many more in the near future. Theold MF radio service is dying and it is only a matter of time before not one station will be left. Still, MF communications and MF/DF should not pass intooblivion unnoticed; it has performed too valuable a service for aviation to deserve such a fate. The elimination of radio com-munications on medium frequencies marks the close of an era in radio communications in civil flying without which aviationin the Eastern Hemisphere could not have developed as it did. Let us for a moment sit back and review what this communica-tion system has done for air transport, how it has worked and how it was organized, finally to be almost perfect.Nowadays it is customary, even among communications ex- perts and at international communications meetings, to sneer atthe old days of radio telegraphy on medium wavelengths; it is considered a cumbersome, slow method of conveying intelligence;at best, a tolerant smile is the only reward for the courageous soul who dares speak up for MF communications and say that theyperformed the best that could be expected with the state of the technique at the time. However, as a last tribute to MF, let us review the developmentof communications for aviation and bring back to our memories the experiences on the frequency 333 kc/s, the QDMs, QTFs,QBIs and QBBs. As early as 1912 tests took place in order to develop a systemof radio correspondence between the ground and the aircraft, and naturally, World War I contributed greatly to the develop-ment of ground-to-air and air-to-ground communications. Simultaneously with the start of civil aviation in 1919, radio com-munications for this new mode of transportation were initiated. During these first years of civil aviation radio telephony wasused, but, as air routes expanded and greater distances had to be covered, radio telegraphy was found to provide more reliablecommunications; also, it seemed less liable to suffer from inter- ference. In those early days the short waves (below 100 metres)were, for all practical purposes, not yet "discovered", and all communications took place on the so-called "medium wave-lengths", notably on and around 900 metres (333 kc/s). In Europe there was another, very important, reason forchanging from telephony to telegraphy. As international aviation increased more and more, the problem of different languages be-came a great obstacle in the use of telephony. In radio telegraphy the use of codes and abbreviations for a multitude of commonlyused expressions not only overcame the language problem, but also ensured faster communications. The use of radio telegraphyspread from Europe over practically the entire Eastern Hemi- sphere. At first communications traffic was of such a nature thatthe pilot, or the co-pilot, could handle the radio installation; but soon it was found that the presence of an experienced radiooperator on board the aircraft greatly improved overall com- munications. Gradually, all civil aircraft equipped with radioapparatus, except those engaged solely in short-distance flying, carried a radio operator as a member of the crew. While at first radio communications in aviation followed thepractices and procedures of die merchant marine, aeronautical communications in time developed their own characteristics.The nature of aviation demanded certain specific requirements which called for fast and reliable communications and the possi-bility of exchanging a variety of information, between the ground and the aircraft, within a very short time. These requirements resulted in an expansion of the Q-codeused by the merchant marine. With the Q-code it became possible to exchange information on practically all subjects that might beneeded in aviation, in a manner which could be communicated with great speed and which overcame the language difficultiesinherent to radio-telephony. Some of these Q-signals have since become widely known not only to radio operators, but also toall who have been actively engaged in aviation. To mention only a few: — QDM The magnetic course to steer with zero wind to reach me is ... degrees. QAH My height is ... metres. QTF The position of your station, according to the bearings taken by the direction-finding stations which I control is ... QFE Present barometric pressure, not reduced to sea level, is ... millibars. QBI Poor visibility rules are in force. QGO Landing is prohibited at ... -; QAA I expect to arrive at ... at ... (time). QBB Base of the low cloud is ... metres.As air traffic increased, improved procedures and techniques were required; and the operating skill of the communicationspersonnel, on the ground as well as in the aircraft, became greater and greater until it reached a perfection never before attained.Here it should be said that I am speaking of the Eastern Hemi- sphere in general and of Europe in particular. On the NorthAmerican continent an entirely different system developed. Early tests and early radio communications in the Americas andthe rest of the world followed the same pattern for a while; but the change from radio telephony to radio telegraphy was nevermade on the North American Continent. Almost simultaneously with the first development in civil aviation, North American com-munications took into use high frequencies (below a wavelength of 100 metres) instead of medium frequencies (above 100 metres).These high frequencies were found to offer certain advantages which, coupled with the absence of language problems, permittedthe continued use of radio telephony. However, they were not suitable for another development which rose to great heights ofperfection in the Eastern Hemisphere, namely, that of the direc- tion finding (DF) service by ground-stations.We cannot here divulge the interesting subject of the differ- ences in aviation practices, procedures and application of technicalfacilities in the Western Hemisphere as compared with those used in the Eastern Hemisphere; differences in philosophy whichcreated problems of which some are unsolved even today. One of these differences in the philosophy of radio communicationswas that, in the Western Hemisphere, each airline (or operating agency) had been allotted frequency channels for its exclusiveuse; in the Eastern Hemisphere the radio frequencies were always considered to be international property, open to users of allnationalities. Forming the Network s - -* Meanwhile, in Europe, C.I.N.A. (Commission Internationalede Navigation Aerienne), a body which had been established pur- suant to the International Air Convention of 1919, developedprocedures and operating practices for civil aviation, such as for communications, meteorology, etc. Although C.I.N.A. was notworld-wide, a substantial number of States were members, and its work formed the basis on which, after World War II, I.C.A.O.was founded. C.I.N.A.'s headquarters were in Paris, at 60bis Avenue d'lena, now one of the I.C.A.O. regional offices. Together with the development of radio-communications inEurope the need was felt for navigational aids to aviation. It would be going too far if, in this article, we tried to follow thisdevelopment and review the various possibilities that might have been pursued. We can, therefore, only mention that in the courseof years an extensive network of ground-operated direction-find- ing stations were organized in Europe and, in fact, over a largepart of the Eastern Hemisphere. The technique made it possible to determine the direction in which an aircraft lay from a groundstation and, if bearings were taken simultaneously by two or more stations, its position could be established as well. The system,however, called for highly experienced and skilled operators at the ground Stations. The availability of such experienced per-sonnel, on the ground as well as in the aircraft, made it possible to develop the operating techniques and procedures to perfection. As in the case of the radio-telegraphy communications, theprocedures to provide radio bearings to aircraft followed at first the practice used by the merchant marine; then new practicesand procedures, more adapted to the needs of aviation, were introduced. In the merchant marine there is usually comfortabletime available in which to take a radio bearing or series of * Technical Officer, International Civil Aviation Organization.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
