Kieran Daly/LONDON

Frequency congestion in Europe is giving the future air-navigation system a bad name and delaying its implementation.

Progress towards use of the future air-navigation system (FANS) continues to prove slow for regulator and airline alike. Operators and governments remain reluctant to make the early moves - except, perhaps, in the Pacific.

The difficulty with VHF communications in Europe is the sort of medium-technology/high-emotion issue which makes the airlines wonder aloud just how much they will be expected to contribute to make the more exotic elements of the FANS work.

European nations will almost certainly receive permission in March to reduce VHF channel spacing in upper airspace, from 25kHz to 8.33kHz, starting from 1 January 1998. That is because the growth in traffic and an increase in air-traffic-control (ATC) sectors, caused by the unforeseen growth in the number of nations, are rapidly exhausting the supply of frequencies.

The emergence of data-linking would help, but operational use of the most promising system - the time-division multiple-access data-link, which permits four digital-voice communications on a channel simultaneously - is perhaps ten years away. The unavoidable result is an expensive update programme for the airlines, with the added sting that, if they do not make an expensive leap to next-generation voice-data radios (VDRs), then they will face a repeat performance at a later date.

Operators say that fleet-wide modification is impracticable before 2000. Worse still, non-European long-haul airlines will have to perform the work just to serve Europe. Some are even considering the uncomfortable option of Europe-dedicated fleets.


Rockwell-Collins manager of avionics marketing Paul Healey says that the company could offer 12.5kHz spacing immediately, as a "quick and dirty" solution, but that that is not accepted as adequate in an 8.33kHz environment. Healey also notes that neither 12.5kHz nor 8.33kHz spacing will permit the continued use of the climax system, by which ground transmitters are offset from their nominal frequencies by ±7.5kHz, to allow their multiple use.

Collins is diplomatically trying to help customers, who understandably resent the enforced expenditure. It is widely agreed that older aircraft with ARINC 500-series equipment cannot practicably be modified because of the re-wiring entailed. Healey explains, however, that all other aircraft - analogue or digital - can be modified.

Collins' current product, the VHF900 digital VDR, can already be used on 8.33kHz-spaced channels. It can also throughput ARINC 750 high-speed data, likely to be used in the USA in due course and current low-speed data. Airlines believe, however, that VDRs will cost them some $60,000 per shipset and generally expect to incur total bills of about $70,000 an aircraft, even if some work can be incorporated in scheduled major maintenance.

AlliedSignal business development and marketing manager Ron Carlson says that his company's VDR is also capable of 8.33kHz spacing. He notes: " overkill for older-generation aircraft. However, if you are looking in the long term, then you are going to need it. Over the next few years, with the advent of FANS and 8.33, it is putting the airlines in the position of spending a larger percentage of their revenue on avionics than at any time in their history."

The International Air Transport Association's regional technical director for Europe, George Oliver, says that the carriers would much prefer to go straight to VDR, but cannot make the timetable work.

Oliver understands the problem and recognises that the solution will be costly. He says that "...blocking 8.33 would cause ATC delays, which are very costly, but, then, 8.33 is going to cost us money, too. It is our assessment that the least costly solution is 8.33. We don't like it, but we really have no option."

The airlines understandably resent the chaotic development of European ATC which has ultimately resulted in their having this cost foisted on them. One engineering manager says: "The question is: 'who pays?' The input for the ground [service] providers is also enormous. Do they pay, and then we will go off and fit VDRs and we are happy, but they have a big bill? Or do we take the 8.33 interim step, which has a bigger input on us than on them?"

In the background are the producers of the Contran system, which is intended to prevent simultaneous transmissions or "step-ons" on a frequency. The system, has been proved to work and the surface element has been bought, by two UK airports. Widespread use of the airborne element, which works independently, holds out the possibility of markedly more efficient frequency utilisation.

Penny & Giles Avionic Systems has marketing rights for the airborne Contran and sales director Kevin George explains that, if any given frequency is used more efficiently, then it is less likely that it will need to be split and so will soften the drive towards 8.33kHz separation. That is in addition to Contran's primary safety advantage. Nevertheless, it seems, 8.33kHz splitting is coming sooner or later, with hefty costs for the airline community.

Source: Flight International