Following a successful eight-month trial period, North Atlantic tracks (NAT) working to reduced vertical-separation minima (RVSM) are to be declared fully operational on 27 March. Plans have also been announced to extend the RVSM vertical band in 1998.

The NAT RVSM vertical band is now FL330-FL370 (33,000-37,000ft/10,060-11,280m). This is to be extended to FL310-FL390, the levels between which most airliners cruise. Only aircraft with high-accuracy altimetry are supposed to fly in RVSM bands, because the usable flight levels are separated by 1,000ft instead of the traditional 2,000ft. This allows more traffic to use the tracks, and enables optimum flight levels.

The decisions have been made by the NAT Implementation Management Group (IMG) after finding that operational height- keeping accuracy is on target. The hope is to extend the band down to FL310 as early as 23 April, but definitely by 8 October, when the upward extension to FL390 will be implemented. The NAT IMG says that it has considered objections by business-jet operators who cannot yet meet RVSM specifications, but believes that the airlines deserve a return on RVSM investments. The final NAT extension to encompass FL290-FL410 will take place when Europe adopts the RVSM, estimated to be 2001.

Source: Flight International