Upgrade follows tests at Lhasa airport in Tibet which allow operation with significantly lower weather minima

Air China Boeing 757s are being modified to allow them to perform required navigation performance (RNP) approaches to the mountainous Lhasa airport in Tibet following demonstration flights in late April.

The upgrade follows the completion of tests by a team involving Air China, Boeing Flight Ser­vices Group, the Civil Aviation Admini­stration of China (CAAC) and Naverus, the UK-based provider of satellite-based navigation procedures that helped develop RNP approaches for Canada's WestJet. The CAAC believes the pilot project with Air China could lead to expansion of the safer approach procedure throughout the region.

CAAC vice-minister Wang Changshun says the success of the RNP test flights has "significant implications for constructing and developing airports in difficult terrain in western China and can help open up new flight routes for busy hubs in eastern China".

Using satellite navigation data and on-board sensors, the flight management system (FMS) ensures the aircraft safely follows required flight profiles by continuously com­paring aircraft position to defined RNP lateral and vertical containment boundaries and alerting crews to deviations. In the case of the new Lhasa RNP 0.15 approach, this means aircraft must be within 0.15nm (278m) laterally of the track centreline with a 95% probability.

Boeing says the flight procedures will allow airlines to operate with significantly lower weather minima at airports such as Lhasa and "should significantly reduce flight turnbacks, delays and cancellations while enhancing safety". Boeing Flight Services, part of Commercial Aviation Services group, is also working on several other RNP projects, some of which are designed to help ease congestion at major US airports.

Although it declines to identify specific projects, they are believed to include work with Continental Airlines on a series of RNP approaches to its main base at Houston International. Continental was unavailable to comment when contacted by Flight International. Alaska Airlines, an early RNP developer because of the extreme approaches to some of its destinations such as Juneau, is also close to gaining US Federal Aviation Administration approval for an RNP approach to San Francisco's parallel runway 28R.

The RNP 0.11 procedure would be the lowest in the USA, and could allow runways to accept the standard 60 approaches an hour, versus half that number when weather conditions reduce visibility below a 3,000ft (915m) ceiling.


Source: Flight International