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Aviation History
1949
1949 - 1625.PDF
FLIGHT, 22 September 1949 muting circuits which keep the loudspeaker or headphones quitesilent until a signal is actually received. The PR51 receiver has been specially made to the specification of InternationalAeradio, Ltd., and not under Bendix licence in this particulai case. The Plessey automatic constant gain amplifier, type PVi,manufactured'under Bendix licence, should also find an in- creased use in all flying control towers. It ensures that theground transmitter always radiates a fully modulated signal to aircraft, whatever the differences in the levels and quality ofvoices. The instrument is particularly compact, occupying only 3Jin panel space on the standard igin rack. The new M.F. beacon transmitter, the G50 300-watt, manu-factured and developed to a design of R.A.E., was to be found on the Redifon stand. It is, of course, made particularly forthe needs of the Royal Air Force and it is robustly constructed and fully tropicalized to the latest specifications. A modifiedversion of the firm's R50 receiver was also on show, known as the R50A. The chief difference in this new receiver is thatit does not cover the very low frequencies, the elimination of which has enabled the power pack to be built into the receiver.On the same stand, a complete dual M.F. beacon installation was exhibited; it has an automatic change-over device so that,should one transmitter become unserviceable, the other is auto- matically brought into operation. This is a valuable featurein unmanned, out-of-the-way stations. ' McMichael Radio were showing a very flexible form of keyingdevice particularly designed for use with M.F. and other coded radio beacons. Standard Telephones and Cables, Ltd., exhi-bited their wide-range radio equipment specially designed for use in aeronautical ground stations; it included the now well-known PVIB cathode-ray V.H.F. direction finder. This firm has also brought out, as a companion to the V.H.F. trans-mitter type DU2, a 100-watt H.F. version known as DU4 ; it should prove very useful for short-haul point-to-point 01ground-to-air services. Whilst not shown in physical form, the new airfield surveillance radar made by A. C. Cossor, Ltd., wasclearly shown in half-a-dozen photographs illustrating different parts and the general layout of the equipment as it will beinstalled at an actual airfield. A " Gee " ground-station instal- lation was shown on the stand, a notable feature being theexcellent rack form of construction, making for easy servicing and maintenance. A constant-output amplifier, Cossor type 10,was also on view, and this has an additional feature of provid- ing several outlets, enabling up to six transmitters to bemodulated simultaneously from one microphone. Two interesting new items were to be found on the Ministryof Supply stand: first, the long-duration monitoring recorder and, secondly, a new Service H.F. 40-watt transmitter, T1522.Th? first item, developed for R.A.E. by Simon Sound Service, has long been awaited for the monitoring of R/T. conversationbetween airport control towers and aircraft. It will run con- tinuously for eight hours and records on standard 35 mmcinema film. Although this equipment may have a high initial cost, it must be remembered that it replaces the service ofmany radio-telephone operators and, furthermore, makes an infallible record of any conversation carried out. The seconditem has, of course, been developed for use with the Royal Air Force and, being housed in several watertight units, isreadily portable and is therefore suitable for use either at fixed stations or in the field. Another type of speech-recorder was shown on the stand ofthe General Electric Co., Ltd. ; this instrument uses a special type of tape and is able to give a very high standard of repro- An installation for large aircraft—the STI8 high - power H.F. transmitter by Standard Telephones and Cables, Ltd. The remote-control box is also shown. Plessey Bendix V.H.F. Receiver Type PR7I for fixed ground- station use. duction. The example shown is intended for domestic use,but it is hoped that a model will be specially developed suit- able for use in airport control service. A subsidiary of G.E.C., Salford Electrical Instruments, Ltd.,exhibited equipment used for the automatic transmission of meteorological data; known as the radio-sonde, it consistsbasically of a balloon, attached to which is a small transmitter which sends out signals giving height, air temperature andhumidity. The small airports have been well catered for by E. K. Cole,in their new V.H.F. 5-watt transmitter, type CE8. This is an inexpensive rack-mounted, mains-operated, ground trans-mitter and forms a unit of the complete ground station, includ- ing V.H.F. D/F. manufactured by the same firm. The Ministry of Civil Aviation had an interesting displayof position-finding equipment, using the now well-proved Decca Navigator system. This equipment, which has provedso useful in marine service, is now finding an increasing appli- cation in the aeronautical field (see Flight, June 2nd, 1949). In any radio-communication or navigational aid, the mostessential requirement is certainty of service, and it is our belief that the present trends in the new equipments show designersand manufacturers to be keeping this fact well in the forefront. This certainty is already nearly 100 per cent obtainable withcommunications on the V.H.F. band, always provided that the aircraft is in actual range of the ground station. This islargely due to the universal use of crystal control in trans- mitters and receivers, permitting '' push-button '' operation asopposed to the skilled setting of control knobs. It is, there- fore, to be hoped that it may also be applied to all multi-channel H.F. transmitters and receivers, both in the air and on the ground, an application which will be particularly neces-sary if pilot-operated radio-telephony is to come into service in the near future. GOBLIN CLEARED FOR 600-HOUR PERIODS DURING the past 12 months, the D.H. Goblin 2 (No. 1,761)has been subjected to a series of 500-hour trials. The suc- cessful emergence of the unit from this formidable programmehas resulted in the Ministry of Supply (D.E.R.D.) approving the extension of the overhaul life of this type of engine to 600hours—the longest yet. The letter giving official intimation of the decision statedthat: "Two 500 cyclic endurance tests carried out between July, 1948, and March, 1949, on Goblin 2 (No. 1,761) whichwere to a very strenuous schedule based on fight aircraft sorties, were satisfactorily completed without any loss of thrust. Thesetests, which were carried out without the addition of lubri- cating oil to the fuel, demonstrated successfully that this typeof Goblin engine is capable of running under adverse condi- tions for prolonged periods without attention. As a result,the M.O.S. are satisfied that the overhaul life of the Goblin Mk. 2 can be extended to 600 hours, subject to inspection ofthe combustion equipment and renewal of the flame tubes, where necessary, at 300 hours, and routine maintenanceinspections in accordance with the current official servicing schedule." Almost exactly seven years passed between the first runof the Goblin prototype and the shutting down of the pro- duction engine No. 1,761 at the end of 1,000 hours "combat"running at Hatfield. In terms of engine development, seven years is not a long time. When, however, the engine is asrevolutionary as an aircraft gas turbine, a device which in 1942 was as new to the world as were the works of Benz andOtto in 1870, it is the more remarkable that in such a short space of time a degree of reliability very nearly equalling thebest of the established forms of power unit should be achieved. P. iq
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