Julian Moxon/PARIS

The attempt to introduce the new basic radio-navigation (B-RNAV) standards into European airspace by January 1998 has been termed a "chaotic mess" by the avionics industry as it faces a last-minute change of specification from the European Joint Aviation Authorities (JAA).

B-RNAV avionics will be required to enable aircraft to navigate en route more precisely in the increasingly crowded European airspace. Modern aircraft equipped with flight-management systems (FMS)comply without difficulty. Many operators of older, noisy, airliners soon to be banned from European airspace, along with the business-aircraft community, are unwilling to spend at least $60,000 to fit FMS, however. They plan to use global-positioning-system (GPS) receivers instead, which can cost around one-sixth as much.

Although the GPS has been approved for B-RNAV use by Eurocontrol (the Brussels-based air-traffic-control organisation), the JAA decided in March that two changes to the specification had to be made before the 29 January deadline for B-RNAV introduction is reached.

Both modifications (health word checking and pseudo-range detection) relate to the system used for checking the accuracy of the positioning data which GPS receivers pick up from satellites. A Trimble-built device is available, but it costs twice as much as some systems.

According to an industry source it is "very difficult" to modify the receivers quickly to the new standard. The change is threatening several manufacturers, including one of the most popular suppliers of low-cost GPS receivers, Garmin - even though the company was the first to be approved for precision-area-navigation operations in the USA and has had approval "in intent" from the UK and French civil-aviation authorities.

Now, the UK and France have given JAA co-member Germany the responsibility of confirming that Garmin's B-RNAV technology is adequate for navigation in European airspace.

German doubts about Garmin's original B-RNAV test procedures, however, have resulted in a request to the FAA, asking it to confirm that the company's receivers are suitable for use in European B-RNAV airspace. "There's not much chance of that," says an industry source. He adds that "-the FAA is hardly likely to interfere in a European operational matter, especially when it could become a major legal issue".

Meanwhile, equipment installers say that "-time is running out fast" for airlines wishing to install GPS or FMS receivers for B-RNAV operations. "There are virtually no workshop slots within the five months left", one says.

The situation is complicated by the fact that the European nations have failed to agree on what airspace will actually be covered by the B-RNAV rules. France has said that it is considering B-RNAV operations above flight level 245 (24,500ft/7,500m) while Switzerland and the UK say that it should come into effect above 9,500ft. Germany has yet to produce its own requirement. "The result is that most operators don't know which way to turn," says the source. He adds that "-the entire implementation programme is ill-considered-we were told that the requirement [to fit B-RNAV] has existed for seven years. Now, just before it comes into effect, they've turned the tables".

Source: Flight International