DEEP DIVISIONS, between US and European authorities, seem unavoidable at the key international meeting, to decide the future of precision-landing systems, now under way in Montreal.
A US Federal Aviation Administration team has been visiting European authorities in a search for areas of agreement, but papers presented at the meeting will reveal a wide gulf in thinking.
European aviation authorities and industry are already preparing to step up development of the proposed multi-mode receiver (MMR) as soon as the International Civil Aviation Organisation's (ICAO) Special Communications/Operations meeting (COM-OPS 95) finishes on 7 April.
European nations, led by the UK, are still sparring with the USA over numerous technical issues and remain deeply divided over the feasible timetable for the use of global navigation satellite systems (GNSS), such as the global-positioning system (GPS), for Category III approaches.
FAA GPS programme manager Dick Arnold says that the USA's first Cat III GPS approach is planned to be operational in 2001. Results of trials of the competing "pseudolite" and "non-pseudolite" augmentation systems will be presented at COM-OPS 95. One system will be selected this year.
Arnold says that the USA will make a "high-level statement" on the proposed GPS wide-area augmentation system (WAAS) in Montreal. The ground-based WAAS will increase GPS integrity and accuracy, allowing Cat I operations and the statement is expected to be an agreement, between the US Departments of Defense and Transportation, allowing the FAA to broadcast differential-GPS corrections, using the WAAS.
The FAA's WAAS testbed is demonstrating the required integrity and 7m vertical accuracy, says Arnold, and an agreement with the Pentagon will allow it to award the WAAS contract in late April/early May, for operation in late 1997.
The USA intends to begin phasing out the instrument landing-system (ILS) in 2005, starting with Cat I installations, and with Cat III units to be removed when GPS technology allows - also possibly as soon as 2005.
A key paper presented by UK Civil Aviation Authority deputy director of navigation engineering Jim Lawson will give an estimate of a best possible GNSS-capability timetable of sole-means Cat II landing (which he predicts will be 2009), and for Cat IIIa (forecast for 2013); and Cat IIIb (estimated at 2015).
The paper says: "Reports that GNSS has already demonstrated its capability as a precision aid are encouraging, but misleading. There are no short cuts to success. The consequences if a new system fails to do the job properly are the risks to safety of life, nugatory investment and harm to the future of precision-approach operations."
In another paper, the UK claims that there are numerous GNSS shortcomings, including susceptibility to interference, inadequate availability and questionable continuity and integrity.
The UK, explicitly supported by France, Germany and the Netherlands, will argue for ICAO to permit use of the microwave-landing system (MLS) and to support the MMR concept to cater for the transition from the ILS as the latter becomes progressively unsustainable because of interference and multi-path effects.
British Airways, which has just completed an MLS cost-benefit study - understood to have found that the MLS would pay for itself within about a year - will strongly support the UK CAA position. It will claim that the ILS aircraft flow-rate reduction of two-thirds in Cat III conditions "...would almost be restored by MLS".
The UK airline is part of the evolving MMR team which includes Thomson-CSF, GEC-Marconi Avionics and the aviation authorities of the UK, France, Netherlands and others. In the USA, AlliedSignal is supportive.
MMR supporters were surprised to be denied funding by the European Commission (EC) which, ironically, is more interested in funding satellite-based-navigation development. Nevertheless, all the players say that they will continue the effort with or without EC money.
Source: Flight International
