Airspace Management

Over the years, the FRP has recognised many changes in the US navigation system mix, brought about not only by new technology, but driven in large part by user pressure. Loran C, for example, was included in the FRP as a somewhat specialised marine navaid for several years until it suddenly took off like wildfire within the American general aviation community. Much the same effect has been true of GPS, except that in this case the projected user community is virtually anybody who moves on or over this planet.

The FRP contains a wealth of information about the United States’ navigation policies and the planning philosophies behind them. It includes detailed, non-technical descriptions of each system’s characteristics, including accuracy, availability, coverage and other factors. It also includes the expected phase-out dates of navaids that have been superseded by newer technology such as the Global Navigation Satellite System (GNSS), which in turn helps operators plan ahead for new equipment installations and/or retrofits.

The 1996 FRP will be different from previous editions, with an almost obituary-like flavour to its list of phase-out dates for every navigation system we have come to know and love. In fact, there are many who have witnessed the birth and death of radionavaids in their lifetime. The home-grown Australian DME being a recent example. Born 1953 — Died 1995.

Yet from the US government’s point of view, it makes solid, economic sense. Satellite technology has shown itself potentially capable of meeting — and usually exceeding — the capabilities of all of the traditional radio aids.

Unfortunately, this brave new world of navigation poses a number of problems for those involved in day-to-day operations in the current environment. A fundamental concern is the planned future reliance on a single source of positioning, with no alternate backup.

The US Aircraft Owners and Pilots Association (AOPA) is especially critical of this approach, which will see the termination of the US government’s support in the year 2000 of Loran C, a system on which a large number of AOPA members depend. The 1992 FRP had set the phase-out in 2015. The Association is concerned that safety could be compromised when an alternative navaid is no longer available.

At the other end of the aviation spectrum, cost becomes a key consideration. Major airlines know that avionics changes can represent very large investments that, in some cases, can even impact their aircraft fleet makeup. British Airways spokesman noted that the $US100,000 cost of retrofitting GPS equipment in the Boeing 747-400 did not cover the removal of each aircraft from service and the resulting significant loss of revenue. BA was particularly upset with the FRP process that, in 1992, forecast Omega to continue until 2005 but in 1994 accelerated the shutdown to September 1997.

With a large 747 fleet, BA is now faced with a major unplanned expenditure on its 747s to replace Omega with GPS over a short space of time. Even worse, the BA representative pointed out, was the fact that his airline’s 60 737s also depend on Omega on certain routes and these, too, would now need to be GPS equipped. However, since the book value of these aircraft averages only $1 million each, the airline might be better off selling the whole fleet and starting anew.

Federal government officials at a FRP hearing allowed that the accelerated phase-out of Omega was unfortunate, but necessary in view of government cost-cutting requirements. Major changes in phase-out dates would not be acceptable in the future, stated one official, adding that the earlier forecast closure date of 2015 for Loran C was a “gross miscalculation” at the time.

Will user concerns cause the FRP authorities to push back some of the phase-out dates? Omega could get a reprieve for a few years because of an unusual function it supports in weather monitoring.

Under the World Weather Watch, hundreds of thousands of upper air sounding balloons are launched every year around the globe to provide a virtually continuous picture of the earth’s climate — vital intelligence for aviation, shipping, agriculture and a host of other industries. Most of these balloons are tracked by Omega, in what might be viewed as one of the earliest applications of Automatic Dependent Surveillance technology.

Can’t GPS do this? Not yet, according to experts. The Omega tracking device carried aloft weighs just a few ounces and costs less than $5, which is a major challenge for GPS designers.

Finally, there could be a small cloud on the GPS horizon. A US DoD spokesman confirmed what has been rumoured in the industry: the Block IIR satellites that will slowly replace the Block II versions now in orbit will transmit at lower power levels. This has raised concern that some lower cost GPS general aviation and handheld units may operate less well in the future Block IIR environment.

The spokesman disagreed with this, stating that the present Block IIs are transmitting at higher power than called for in the DoD signal specification, with which receiver manufacturers are required to comply. Only time will tell.