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Aviation History
1926
1926 - 0153.PDF
MARCH 4, 1926 THE WIRELESS EQUIPMENT OF THE DORNIER-WAL SEAPLANE "NE PLUS ULTRA" WIRELESS apparatus now forms a very important part of the equipment of aircraft used for combatant services or for commercial purposes, and not the least of the many factors contributing to the successful trans-Atlantic flight of Com- andantc Franco is the use of the wireless apparatus installed on the Dornier-Wal seaplane—the " Ne Plus Ultra." The Dornier-Wal seaplane is mainly constructed of metal, and was equipped with a Marconi standard type A.D.6 telegraph-telephone set and a marconi direction-finding (D.F.) set. The metal construction of this machine, while assisting considerably in the reduction of magneto disturbances, adversely effects the receptive power of Bellini-Tosi, or any other loop aerial. In the usual wood and canvas construc- tion no difficulty is presented in installing efficient loop aerials. In all metal machines it is therefore necessary to arrange the D.I-', loops as far as possible from closed conducting paths. was accomplished by the use of a 12-valve amplifier divided into two units. The first unit contains six stages of high- frequency amplification and a detector valve, and the second unit contains an oscillator valve, two stages of intermediate frequency magnification, a detector valve, and a note- magnifying valve. Ten Marconi standard type D.E.V. valves and two standard type D.E.Q. valves, taking a total filament current of 2-4 amperes at 3 volts are used. The anode voltage for the receiver is supplied by a 96-volt dry cell battery, and the filaments are run off an accumulator battery. The radiogoniometer and high-frequency tuning unit are of the standard type supplied with aircraft equipments, and cover a wave-range of 600-1,000 metres. The equipment was calibrated on wave-lengths of 600 and 900 metres, and the quadrantal error curves were well within the limits required for navigational purposes. WIRELESS AND THE SPANISH TRANSATLANTIC FLIGHT : The above diagram shows the Marconi Wireless Direction Finding aerial arrangement as fitted on Comandante Franco's Dornier-Wal seaplane. The limiting factor for reception of the Bellini-Tosi aerial is controlled by the area turns of the fore and aft loops, which should be as great as possible. The area turns, however, are limited by the fact that the loops and the supports must be able to withstand considerable wind pressures, vibrations and shocks, and the difficulty of designing a multi-turn loop supported clear of all masses of metal increases dispropor- tionately with the number of turns. To meet these con- ditions, therefore, a special type of loop aerial was fitted on the machine, and the Marconi standard aircraft D.F. receiver was altered to increase the working range of the equipment. The fore and aft loops consist of two single-turn loops supported on struts and arranged symmetrically on each side of the hull, great care being taken to avoid any out-of-balance effects due to the presence of large masses of metal. The two loops are connected in series, and the total area turns is approximately 250 sq. ft. In order to obtain equal recep- tion with the wing coil, a single turn loop is mounted in the plane of the wing. The two sketches show the positions of the two fore and aft loops and the wing loop. The terminal ends of the loops are connected by a length of cable leading to the navigator's position near the pilot. To increase the working range of the direction finder and to compensate for the smaller receptive power of the loops, it was found necessary to increase the overall magnifi- cation of the standard aircraft direction finder receiver. This Results with D.F. Apparatus Reports from Captain Ruis de Alda, the navigator who took the D.F. bearings during the flight, show that bearings were obtained at a distance of 700 kms. (434 miles) from Las Palmas, and such was the accuracy of the readings that the course was directed solely by the aid of the direction finder during this stage of the flight. When nearing Las Palmas visibility was very poor, but the signals from the shore stations enabled the navigator to maintain a direct course to his destination. The reader will, no doubt, be interested in the following extracts of a letter sent by the navigator, Captain J. Ruis de Alda, from Las Palmas to the Chief Engineer of La Compania Nacional de Telegrafia sin Hilos, Spain :— January 25, 1926. " At 50 kms. from the Spanish coast began the clouds which were at 200 m. over sea, and extended to Canary Islands. Therefore, in the case of flying below the clouds layer, we would not be able to do astronomies observations, and over the layer we would not see our deviations pro- duced by the wind. " Since the first bearing obtained, which gave Las Palmas at 7° starboard until the end of the flight, its work was mathematic ; it was giving us the difference in angles of Las Palmas and Teneriffe. Briefly, since 11 a.m. we were directed solely by the D.F. I marked on the chart, obtaining them by the intersection of the two 133
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