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Aviation History
1959
1959 - 0345.PDF
COMET DEMONSTRATES DECCA 170 AIR COMMERCE The demonstration approach to L.A.P., via Watford high-level stack (top left) and the centre-lines or Runways 28L, 23R and 23L. Heights and distances are marked along the let-down track. At 75-20 miles from 28L the Flight Log was referenced and the pen moved by itself to the corner of the zone. A positioning error of only about 1mm can be noted carried the aircraft wide on the turns, but thiseffect was immediately noticeable. Operation of the receiver appeared to beextremely simple. Initially, all the switches on the control panel were turned on and the FlightLog pen was set down at one corner of the zone covering the take-off point. When the take-offwas begun, the selector was set to the operating position and the pen immediately moved overto the actual position and began tracking. The three Decometers positively indicated every 20sec whether they were positively set. In case of doubt, the selector could be turned to"reference" and the pen immediately moved itself over to the nearest zone intersection. AnyFlight Log error was shown by a displacement from the exact point of inter-section. At no time during BY the time these words appear the M.o.S. Comet 2EG-AMXD fitted with several Decca receivers will almosthave completed its important series of demonstrations to world airline and civil aviation authorities. Last week Flight tookpart in one of the series of three-hour flights, piloted by Lt-Cdr. "Doc" Stewart, from London Airport to the west coast of Irelandand back via a fictitious holding pattern and dummy approach to Exeter airport. Each flight was preceded by a thorough briefingon Decca Mk 10 operation and the aims of the M.T.C.A. in sup- porting its introduction as an additional international standard.(These aims were recorded in some detail on pages 121-122 of Flight last week.) Of particular interest during the briefing for the demonstrationin which we participated was the news of further Decca develop- ments and the display of various sizes of Flight Log andminiature receiver equipment. The S.B.A.C.-racking version of Decca Mk 10 is now in production and a \\ ATR version willshortly follow it. Later, a transistorized receiver taking half of this volume will permit duplicate installations within the li ATRframework. Flight testing of the H.F. digital data link equipment for auto-matic position reporting by aircraft has begun. Single-sideband will be employed, possibly sharing a speech channel. Identifica-tion of aircraft, or the triggering from the ground of a position report from a particular aircraft, will be achieved with conven-tional Selcal techniques, details of height, position and speed being transmitted and either printed directly on flight-progressstrips or converted into a pictorial display. Both V.H.F. and U.H.F. data links could later be provided for short-range use. One of the points particularly stressed during the briefing wasthat the twin-track airway dimensions proposed for Decca were based on evaluation of operational performance rather than ontheoretical values. All Decca errors and the ability of the average pilot were amply allowed for in defining the two four-mile-widelanes separated by a three-mile buffer zone for both high- and low- altitude airways. During the flight the Mk 10 receiver functioned faultlesslydespite some thunder and lightning in the London area. A single receiving aerial, mounted under the starboard wing, served a Mk 7,two Mk 10s and a Dectra receiver. Seven discharge wicks were attached to the trailing edge of each aileron, and others were fittedto the elevators. Dectra was demonstrated only over the western Atlantic area.Flight Log charts had been prepared to cover the route of the demonstration flight, the fictitious holding pattern near Exeterbeing an easily added feature requiring no equipment on the ground. As will be seen from the actual-size portion of the Deccachart reproduced above, the Comet returned to London Airport following the marked approach track to Runway 28 left, butturned off to land on 23 left, which was at the time the runway in use. The approach was initially made to 23 right, but a rapidside-step took us over to the other centre-line for the landing. During the let-down from the Watford area, a very strong wind wasthe pen more than a milli- metre or so out. When theselector was returned to the operating setting, the pen quickly caught up with the aircraft position and continued tracking. Thewhole operation took about 10 sec. Chart changes were also very simple, taking about 30 sec. Theprocedure was to set the chart selector to the new chart when the pen reached a marked point on the map. The pen was drivenalong a dotted line to the nearest zone intersection on the new chart and then moved itself to the new location and continuedtracking as soon as the selector was operated. When changing chart or chain, or when the Flight Log was being checked, thereseemed to be practically nothing to do and accurate working was immediately apparent. From the pilot's point of view this repre-sents a very considerable advance over the earlier receivers, in which the pen had to be placed on the exact point on the chartbefore accurate tracking could start. Any required information can be marked on the charts, _ sothat holding patterns, overtaking patterns and flight information of a more general nature may be incorporated as required by anyparticular operator. The form of the Flight Log can also be varied, a particular example being the plastic chart and cursor svstem usedby Silver City. For their 20-minute cross-Channel flights it is obviously impractical to use up and throw away a small chart afterevery crossing. The normal charts may, of course, be retained as a permanent record of the track flown, though this with some pilots,might prove unpopular. In the course of the demonstrations the M.T.C.A. has put upa most convincing case for Decca Mk 10, both theoretically and in practice. A combination of Mk 10 and its data link appears tooffer both pilot and controller a happier prospect than Vortac- supported surveillance radar, but it remains to be seen whetherself-evident technical merit will be able to prevail in the inter- national arena at Montreal. .._-... DOG EAT DOG? - HAWAII is a small place to boast two competing airlines. Whenthe traffic density on the inter-is'and services is taken into account there seems little room for two competitors to spreadtheir wings. And when the volume of traffic falters, as it did last year, the pressure starts to bear on the weaker of the two. In the case of Hawaii it is difficult to foresee which carrier isleast likely to succumb. Both admit the financial difficulties that result from such severe competition in a strictly limited market,both are subsidized by the C.A.B. through mail payments, and each expresses a willingness to take over the other. Hawaiian Airlines are the older and larger of the two. Foundedthirty years ago this mpnth, thev had a twenty-year monopoly of scheduled services until Trans-Pacific entered the field in 1949.To meet this new challenge Hawaiian purchased five Convair 340s in 1953. The acquisition bolstered Hawaiian's share of themarket, which had sunk to about two-thirds, to some three- quarters of the total, and this share has since remained more orless unchanged. In addition to the Convair fleet, Hawaiian
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