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Aviation History
1946
1946 - 0481.PDF
MARCH 7TH, 1946 FLIGHT 249 Radio and Civil Aviation LECTURE BYSIR ROBERT WATSON - WATT Aids to Schedule-keeping : Safe Reduction of Factors of Safety i Additional Radio Preferable to Additional Fuel •AT the Institute of Civil Engineers, before members of the l\ R.Ae.S. and guests from among the delegatesto the X jL International Conference on Radio and Radar, Sir Robert Watson-Watt, C.B., LL.D., F.R.S., F.R.Ae.S., on February 28th, delivered his lecture on the Application of Radio to Civil Aviation. Sir Robert opened his very interesting address by stressing that his notes were not an official communication, but a strictly personal restatement of views formed in the course of official work, but based on facts and statements available to all. They were directed towards soliciting the views of the aircraft operator on his needs, of the aircraft designer on the aerody- namic and economic obstacles, and of the ground provisioning authority on the administrative, organisational, and economic factors affecting the choice of system. The purpose of radio aids to air transport (the word radio is used to include radar) was to assist in the transport of the maximum payload in the minimum time at the minimum attainable cost by air services operating at the highest attain- able standards of regularity, punctuality, safety and comfort. The pre-war air transport systems assured safety only by serious sacrifices in regularity and punctuality. With the high traffic densities which alone can assure and mark the success of post-war air transport, the whole structure of the traffic pattern at major airports will be dislocated by any failures to fly accurately on pre-arranged schedules no less familiar to the user, and no less reliable than the pre-war rail- way timetable. This accuracy in timing must be assured by the corresponding elimination of the need for diversions. The lecturer said that the development of the argument was based on another postulate which is seldom contradicted but often forgotten. That is, that the ultimate responsibility, and ultimately the whole responsibility, for the same punctual. execution of a scheduled flight rests on the master of the air- craft. A system of radio aids which is not consciously directed to convey to the master all the information and advice which he requires as a basis for his aided but ultimately unfettered judgment is a bad system. It was most important that this fact should not be overlooked. Radio—an Information Service Sir Robert said that his notes could not be accepted with sympathy unless it was agreed that the sole purpose of radio equipment in air transport was to provide an information ser- vice, and he went on to compare the radio facilities available to civil aviation in 1939 with those used by typical night bombers of 1944. A direct comparison was less unfair than might superficially be assumed because the accurate placing of an individual passenger in space and in time was more im- kportant than the accurate placing of an individual bomb in space and time. The U.K. civil aircraft of 1939 carried an M.F. transmitter-receiver with six spot frequencies for com- munication by W.T. and, if better equipped than average, an .M.F. D/F loop. The largest long-distance aircraft carried additionally H.F. equipment for long-range working. Position-fixing service was provided by ground D/F sta- tions which, with the associated communication channels, be- came overloaded at quite low traffic densities. Such radio- telephonic equipment as was appearing gave speech of poor intrinsic intelligibility, and airborne D/F equipment was sub- ject to very grave errors through the reception of ionospheri- tally propagated signals. The application of the Adcock principle to airborne equipment was then, and indeed still remains, an unsolved problem. Equisignal track guides in the medium-distance form (Radio Range) and the shorter- distance form (Lorenz) were in use in the U.S.A. and Europe respectively, but their defects and limitations had prevented theiT operational introduction in this country. The-heavy night bomber of 1944. operating over the Contin- ent from airfields in this country, carried some 1,300 Ib by Oboe etc. for some is given Weight ib 1,056 665 506 205 1,056 973 1.311 , Loran, civil air- for com- of radio Per centof all-up weight0.42 1.48 3.08 2.56 i-5i 1 39 weight of radio equipment, of which the principal items were: — Ib G.P. set T.1134/R.1155 (M/F and 11/F, W/T and D/F) for iong- and medium-distance communications .... 258 V.H.F. T.R. 1143 (or H/F T.R.IIO6=35 lb) for local control and inter-aircraft R/T communications 95 A. 1134A for intercommunication 28 I.F.F. Mk III (T.3090) 35 A.R.I. 5083 (Gee) for navigation 120 S.B.A.—R.1124C/R.1125A for track guide and approach 75 H2S about 700 Supplemented or replaced in some casesRebecca, radio-counter-measure equipment, The planned weight of radio equipment craft now under construction in the U.K. parison: — All-up weight lb Brabazon I 250,000 , II (Ambassador) .. 45,000 VA (Marathon) .. 16,450 VB (Dove) 8,000 Tudor I 70,000 II 70,000 Commenting on the "growing array of black boxes" with which the radio man horrified and annoyed, the lecturer said that the modern transport aircraft does not drink less than one gallon of fuel per engine per minute. Aircraft desiring to land at one of the largest and best organized of the world's existing airports (probably la Guardia) must even, on present limited traffic densities, be prepared to be held-up for 75 or more minutes before being permitted to land. For this alone they must carry 150 to 300 gallons of additional fuel—in fact, a typical and highly efficient operator, acutely sensitive about payload, who uses twin-engine aircraft, provides 330 imperial gallons, carried, irrespective of weather, for this purpose. This was one ton of fuel, twice the weight of the generous radio installation proposed to be carried against one only of the contingencies which radio aids can eliminate. Sir Robert also said that there were many better reasons than economy for staying on the planned track of the flight plan, but from the point of view of load, it would be better for an aircraft to carry additional radio for constant use than additional fuel. "A factor of safety was in essence a coefficient of ignorance; radio, as the enemy of ignorance, provided for the safe reduc- tion of factors of safety." Sir Robert said that it was certain that the weights of radio units could be halved by techniques already in our possession if the development effort was made available and properly applied. Civil aviation had to fight alike nature and man, and there were four outstanding natural obstacles which fell at the pre- sent time into the order: (1) Cumulo-Nimbus cloud; (2) ice formation; (3) poor visibility; (4) winds. The air will not become the normal milieu of the traveller until aircraft can avoid turbulent areas marked by Cu.-Nim. formation which at the best caused acute passenger discomfort and at the worst might completely break up the aircraft—a danger which in- creases rapidly as the linear dimensions of aircraft increase. Regularity of schedule would necessarily be sacrificed to safety unless aircraft could avoid areas of severe ice accretion. Poor range of visibility was an adverse condition more fre- quently experienced than the previous two. It was given a low rating because combined radio and non-radio resources were
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