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Aviation History
1964
1964 - 0476.PDF
FLIGHT International, 20 February 1964 291 task which currently demands an appreciable part of crew member's time in long-range aircraft. This last feature offers the most valuable possibility of automatic position reporting by digital data link, when this is implemented for civil use, with consequent benefits to the traffic control system, and reduction in air-ground communications work-load. The ability of the computer to store datum performance envelopes not only enables it to display to the pilot the appropriate cruise- control information for a particular flight condition, but also to compare the actual aircraft, engine and system performance with the datum. Thus the computer can act as an overall monitor of correct functioning of aircraft and systems and can display this to the crew as a warning or attention-getting display. Used in con- junction with a flight recorder and with the automatic check-out techniques already mentioned, the off-line digital computer could provide a very valuable automatic test facility for the other electronic systems without the need for specialized ground equipment at each civil airfield. It would seem that the first civil application of civil airborne digital computers would be aimed at reducing crew work-load and as a monitor and maintenance aid. These are all desirable objectives for the current generation of aircraft and it would not prove impossible to fit off-line digital systems to existing aircraft. Resulting improvement in navigational and steering accuracy in both horizon- tal and vertical planes could be important in view of increasingly crowded air-space and the trend towards reduced separations. But special input/output sections would be needed in order to avoid the need for modification of existing aircraft equipment to give or accept digital signals; and special electrical power and cooling supplies would have to be provided. A modification of this magnitude would undoubtedly be expen- sive and could cost approximately £50,000 per aircraft. While the experience gained would be valuable for the SST and other future aircraft, the full advantage of the off-line digital computer could probably only be obtained when it was designed into an aircraft from the beginning or if, as seems less likely, the introduction of the computer into existing aircraft were accompanied by a corresponding major change in flight-deck layouts and/or duties. The Future That the concept of the digital system is steadily gaining ground is shown by three of the most advanced strike aircraft in the West, namely, the North American A-5 Vigilante, the Grumman A-6 and the British Aircraft Corporation TSR.2, respectively fitted with digital systems produced by Autonetics, Litton and Elliott Flight Automation. Widespread adoption of digital techniques for ground-based applications is leading to many advances in digital components, not only in capability, but also in quality and price—sometimes in a way which is denied to the analogue system designer. Resultant- reductions in digital equipment prices have greatly increased its competitive position in relation to other equipment. Micro- miniature airborne computers costing between £20,000 and £30,000, when used in a central on-line system, should be no more expensive than the equivalent series of analogue computers, which are possibly less effective. And although it has not until recently been thought economic to build a small digital computer for single specialized tasks normally performed by analogue computers, there are distinct signs that the small digital computer of. say 1,024 words storage capacity, is becoming price-competitive. This in turn opens up several interesting prospects. Although the coupling of computers to autopilots has been mentioned, little has yet been said publicly on the possibility of digital autopilots. Modern autopilots, with gain-scheduling for variations of height and airspeed and a multitude of facilities, are formidable pieces of airborne analogue equipment. Their replacement by a digital auto- pilot offers many potential advantages—and disadvantages. The problems of coupling multiple computers into a real-time, fail-safe system, and the provision of the necessary power-output stage, may prove very different from those associated with analogue systems. Application of small, specialized digital computers for air data systems and for navigation aids, such as Decca Omnitrac, is indicative of the trend towards digital systems and leads to yet another development. As computing becomes more and more digital, there will be an increasing demand for the adoption of digital communication between sensors, computers and crew. At the same time, digital computers will be increasingly used in ground-based organizations for air defence, air traffic control and airline ground handling. The US Sage system, the RAF's Firebrigade, MoA's Euclid and various airline seat reservation systems are early examples. Consequent emergence of a common digital language offers the possibility of much closer and more integrated control of both military and civil air operations. The flight of an aircraft is the result of a process which may have involved many different ground agencies, such as seat-reservation, passenger check-in, airline freight warehouse, flight planning and dispatch and air traffic control. The rapid and efficient flow and use of information between these agencies and the aircraft is essential if the most effective and economic use is to be made of the flight. The digital computer, both in the air and on the ground, provides just that basis of common language which promises to match advances in aircraft speeds with comparable advances in ground-control and services. Fig 4 Off-line computing system for a jet transport r - AIRCREW-BASIC INFORMATION DISPLAY o o o o © FUEL GAUGES GAUGING SYSTEM Cl THRUST ANDFUEL FLOW SENSORS FUaFLOWMETERING SYSTEM THRUST METER UNIT e DERIVEDINFORMATION DISPLAY PITOT AND STATICTRANSDUCERS SENS0fl_gB2JJP AIR DATACOMPUTER BASIC DATA GROUP \ I \ I COMPUTERCONTROL UNIT INPUTOUTPUT SECTION COMPUTER STABILIZEDPOWER SUPPLES AIRCRAFTSUPPLIES COMPUTING GROUP
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