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Aviation History
1996
1996 - 0380.PDF
AVIONICS Honeyivell/GEC head-up display: the first step towards enhanced vision where die ILS will become untenable before die GLS is available. The strategy means that some airlines will be operating into airports with differ ent landing systems. This is generating the need for an MMR, whether an ILS/GLS, ILS/MLS, or ILS/MLS/GLS receiver. Use of the GPS as a landing aid is already growing. General aviation has led the way in using the GPS for non-precision approaches. At several US hospitals, for example, emergency- medical-service helicopters, equipped with approach-certificated GPS receivers from AlliedSignal Aerospace, Arnav Systems or Garmin International, can now operate in reduced visibility. Airlines are exploiting the capability of the GPS for non-precision approaches, particularly to airports where siting problems prevent the use of an ILS. In 1995, Boeing and Smiths Industries demonstrated unaided GPS approaches to a 300ft decision height at Juneau, Alaska. The air craft, an Alaskan Airlines 737-400, had dual modified Smiths flight-management computers and a single Honeywell GPS receiver. Two distinct avenues to Cat I precision- approach capability using the GPS are being pur sued. In the USA, the intention is to achieve Cat I standard using the wide-area augmentation sys tem (WAAS), which will improve GPS integrity, availability and, eventually, accuracy. Wilcox Electric was awarded a $475 million contract in 1995 to implement the WAAS, with the system to be available by earlv 1998 and capable of providing Cat I by 2000. In the near term, and for many countries out side the USA, the likely route to Cat I GLS is through local-area augmentation using differ ential GPS (DGPS). Several manufacturers are developing airborne receivers and ground sta tions meeting the US Special Category I (SCAT I) specification. This uses a VHF datalink to transmit DGPS error-corrections to incoming aircraft. Certification of several SCAT I instal lations, in the USA and elsewhere, is expected during 1996. The feasibility of Cat Will GLS continues to be evaluated. In 1995, the FAA completed flight tests to determine the feasibility of Cat Illb automatic landings using different DGPS tech nologies. Both trials, by E-Systems and Wilcox, demonstrated the accuracies required for Cat III. Also in 1995, Boeing conducted its own Cat III GLS automatic-landing trial, using NASAs 757 and prototype equipment supplied by three teams: Collins/Daimler-Benz Aerospace (DASA), Honeywell/Pelorus and Litton/ Wil cox. An Interstate Electronics/Airport Systems International team also participated in the Boeing trial, which demonstrated Cat III accu racies. Analysis of both trials continues, along with further simulation work, as the industry works towards a standard for Cat II/III GLS. Internationally, interest in the GLS is increasing. Trials are under way at Munich Airport, in Germany, to collect DGPS data from aircraft flying ILS approaches, for direct comparison. Collins/DASA equipment is being used. Swiss regional Crossair plans SCAT 1 GLS trials at Lugano, Switzerland, for comparison with earlier MLS tests. These will use a Saab 2000 fitted with an Interstate FMS/GPS, and an Airport Systems DGPS ground station. Airbus Industrie is being aggressive in its pur suit of Cat I DGPS capability, and has conducted demonstrations, including automatic landings, as far afield as China and South Africa. The trials, using an Airbus A340, have involved both Honeywell and Litton GPS receivers and Sextant and Thomson/Wilcox DGPS ground- stations. Airbus plans to certificate a Cat I DGPS capability on its aircraft by the end of 1997. The European manufacturer is the first to seek industry proposals for an MMR, which it plans to certificate by the end of 1997 and which will consist of an FM-immune ILS and Cat I GLS, initially, with MLS available only as an option. British Airways and KLM, meanwhile, are the first airlines to seek an MMR, in their case a unit combining an ILS and an MLS. Even in the USA, interest in the MVIR is emerging as airlines tackle the issue of how ulti mately to transition from the ILS to the GLS. Already Collins has announced plans to develop the GLU-900 MMR, which will have the ILS and GLS as standard, with the MLS as an option. The unit will provide Cat Illb capability and is scheduled to be available by late 1997/early 1998. INTERNATIONAL TCAS With the US air-transport fleet now fully equipped with the traffic-alert and collision- avoidance system (TCAS), attention has switched to the international arena. Some 6,000 aircraft are already fitted with the TCAS 2, and estimates suggest that at least another 6,000 aircraft world wide will be equipped with the system. So far, only Australia has announced a dead line for TCAS installation — the year 2000 — but Europe's Eurocontrol has recommended that TCAS 2 be mandatory by January 2000, on all aircraft with 30 or more seats, and by January 2005 on all aircraft with 19 or more seats. China, India, Japan and Russia are all consider ing TCAS and several Asia-Pacific airlines are already moving to install the system. The International Civil Aviation Organ isation has adopted the US TCAS 2 specifica tion as the international standard for what it calls the airborne collision-avoidance system (ACAS). The present ACAS specification is based on the current standard of the TCAS 2, Version 6.04, but this will be updated to the lat est software iteration, Change 7, after US test ing is completed at the end on 1996. Change 7 is intended to remove anomalies still present in TCAS 6.04, eliminating conflict- 44 FLIGHT INTERNATIONAL 14 - 20 February 1996
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