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Aviation History
1957
1957 - 0145.PDF
BRITANNIA PROGRESS REPORT . . . mutating at Dar-es-Salaam and Nairobi, and to back up Strato- cruiscrs on the West African run. The thrice-weekly Britannia service to Sydney, which is due to start on March 2, will displace the 749As on this route also; and the progressive introduction of Britannias on the Corporation's other Far Eastern services will, by the autumn, have entirely dis- placed the Argonauts and 749As on those routes. The Britannia will start to serve the route to Tokyo on July 16, and it will be operating to Colombo and Singapore by mid-September. The The spacious, well lit Demonstration Hall at Filton is here the scene of an instrumentation instruction class for mechanics of El Al. The intruding nose in the background is that of Britannia G-ALRX, now used as a crew training mock-up. First air-to-air picture of the Britannia 311. After certification tests this aircratt-^G-AOVA— will be delivered to B.O.A.C. as a 312. only non-Britannia B.O.A.C. services to the east will be those terminating at Bahrein and Karachi: these will be flown by 749As. The future of the 21 Argonauts and the 16 749As is thus un- certain; but it seems probab.e that if their disposal is being con- sidered the 749As will be sold first, and that they will be required to be sold—as they were bought—for dollars. Delivery by Bristol of the first of B.O.A.C.'s 18* long-range Britannia 312s is scheduled for May 9, but the date of its intro- duction by B.O.A.C. into Atlantic service is as yet uncertain. The main reason for this is that B.O.A.C. are up against a weighty crew-training problem. Atlantic crews are still being converted to DC-7Cs, and this training programme will continue until the summer. It remains to be seen whether El Al, who are due to receive the first of their three long-range (313) Britannias only a few days after B.O.A.C.—actually on May 14—will introduce the long-range Britannia on to the Atlantic before B.O.A.C. It seems likely that neither B.O.A.C. nor El Al will want to be scooped by the other in offering the world's first turbine services across the Atlantic. Crew-training is, incidentally, likely to remain one of B.O.A.C.'s biggest problems between now and 1960. During that time the Corporation will have introduced five new types of aircraft— Britannia 102, DC-7C, Britannia 312, Comet 4, and Boeing 707. The inaugural Britannia 102 "Springbok" service will operate from London to Johannesburg via Rome, Khartoum, Nairobi (Entebbe in the rainy season), and Salisbury. It will be thrice- weekly, omitting Salisbury on one service a week. Elapsed time on the London to Johannesburg route (overflying Salisbury) is 22 hr 50 min; the comparable elapsed time for the DC-7B operated by S.A.A. in pool with B.O.A.C. is 23 hours. The full Britannia timetable is reproduced on page 142. *A further seven long-range 312s have been ordered to replace thefive 305s sold by Bristol to Northeast, and the two short-range 302s, which are as yet uncommitted. 147 FLIGHT, 1 February 1957 POWER FOR THE BRITANNIA THE powerplant is a key factor in any transport, and it can determinean airliner's success or failure. Bristol's great commercial venture has grown up around the company's own Proteus which, after a lengthybut steady gestatory period, has emerged as the first large turboprop in the world to enter airline service. Flight published a full description ofthe Proteus 705, powerplant of the Britannia 102, on July 6, 1952; further notes on the 705 and the 755 (the engine of the later Britannias)were contained in our issue of August 12, 1955. In this issue it is desirable to bring the engine picture up-to-date. Overshadowing all other factors in recent Proteus history is the prob-lem which has been posed by engine icing of an unusual form. By the end of 1955 both the Britannia 102 and the Proteus 705 had beengiven a clean bill of health by the A.R.B. and production aeroplanes had flown many hundreds of hours on crew-training and route-proving.The powerplant, in particular, had been most thoroughly proved. Its excellent protection against icing had been exhaustively investigated—and not found wanting—in an arduous programme of trials. Proteus engines mounted in an Ambassador had been subjected to every typeof icing hitherto known, while TV cameras recorded the conditions inside the powerplant (as described in our issue of September 9, 1955).The Proteus was in fact the only turbine engine cleared for unlimited operation in icing conditions. In his own masterly manner Capt. Houston relates on p. 136 exactlywhat form the new trouble took. It comprised sudden extinction of the flame in one or more combustion chambers, and on certain occasionsresulted in complete loss of power in two of the four engines simul- taneously. At no time, however, did the phenomenon cause loss ofaltitude. The incidents were reported in conditions in which no air- frame icing was present, apart from a thin white "witness line" alongthe null point on the airframc leading edges. Retrospectively, it is not difficult to appreciate that such occurrenceswere baffling in the extreme. They were of a kind which has great popular interest, so that many people began to propound panaceas evenwithout being in possession of all available data. The Bristol Aeroplane Company sent a Britannia to Entebbe within a few weeks of B.O.A.C.'s experiencing the trouble, and this confirmed the hypothesis that thephenomenon was due to icing, and to icing of a new form, namely, dry ice crystals. This aircraft was extensively instrumented to measureatmospheric conditions, and carried television equipment for the study of conditions in the powerplant. The initial difficulty in diagnosing the cause of the trouble was thatvery high concentrations of dry ice crystals are often visible only as a thin wispy cloud. A thick industrial fog contains perhaps 0.1 gm ofwater per cubic metre and heavy snow contains about 1 gm. During the Britannia's A.R.B. flying the Proteus was found capable of handlingthe very severe supercooled water content of 2 gm/cu m for a mile and a half (about 20 sec); but the great cu-nim cloud build-ups of theinter-tropical front (such as are met over Africa) can hold as much as 6 gm/cu m of ice crystals—and over distances very much greaterthan a mile and a half. Surprisingly Con first consideration), the greater size of the crystals renders such a high concentration all but invisible. The crystals would not adhere to the airframe, but they would stickto the warm structures crossing the intake of the Proteus and there build up a snowball accretion on the stagnation points. These accretionswould then break free and enter the engine as a solid mass of slush. Opt. Houston comments on the excellent dousing properties of such amixture, and of its ability to blank off the airflow. Once the giant had been nailed he was no longer a giant, but merelyanother complex technical problem for which a solution could be found. [Continued overleaf Developed by Smiths- P K.L.G., the glow-plug used in the Proteus consists of a plati- num-rhodium alloy tube thermally in- sulated from the body of the plug.
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