Paris 2011: Natnav Coming of Age
It is only in the past few of years that GPS approaches, pioneered in Alaska in the 1990s, have started to become available. These form another element of a future, efficient system where aircraft are managed in time as well as space, take efficient paths and don’t waste burning fuel in unnecessary holds. Also, ADS-B has been rolled out as an alternative surveillance system to radar, based on digital information rather than crude, pulse-firing technology where aircraft identification can take up precious time.
With approaches, the WAAS system in the U.S. has allowed differential correction of GPS position errors and with Egnos (European geostationary navigation overlay system) coming online this year the first approaches are coming on line at locations such as Pau is southern France, for initial testing. Also under development is Europe’s own GPS system, Galileo, although that is bogged down in funding issues.
Nevertheless, the true potential of GPS technology will soon start to be seen and even the smallest, most remote airfields could benefit from ILS-like approaches (in fact, what pilots see will be no different with current ILS systems).
Larger airfields can look forward to Category III precision approaches to a decision height of 50 feet or less, with ground-based augmentation systems (GBAS), although to date GBAS has entered general use only for so-called special Category I (SCAT I) approaches (for example, Wideroe Dash 8s can use this at six airports already). The ability to support multiple approach paths is a big advance on current ILS systems.
GBAS is just one technology being advanced through SESAR–and, for example, through the program Park Air Systems is developing a Cat II/III-capable GPS-only GBAS for first installation at Germany’s Frankfurt Airport in 2013. Egnos provides wide coverage (eventually extending from western Europe to Africa, eastern Europe and Russia) but less accuracy–down to from 10 meters to two meters or less. This means it will also support RNP 0.3 which is good enough for LPV approaches. It opens up possibilities for curved approaches, ideal for airfields where ILS is not ideal or was never an option–or just for fitting in with noise abatement and more fuel-efficient approaches at any airport. In fact, with the support of the ACCEPTA project, more than 50 LPV approaches using Egnos are lined up for completion this year–and it is just the start.