By David Jensen
LONG BEACH, Calif., 4 March, 2010. The transition to required navigation performance (RNP) – which enables a more efficient operation of airplanes in a defined airspace – is complex and doesn't happen overnight. However, no RNP program is as large and complex, however, as Southwest Airlines', according to officials at Boeing Commercial Aircraft Services (BCAS) in Long Beach, Calif.
"It's the mother RNP upgrades," says Rudy Bracho, senior manager of business development for BCAS.
More than half of Southwest's fleet of about 500 B737s came factory equipped for RNP, so the carrier already enjoys the fuel-saving benefits of RNP. But to gain full advantage, the carrier is upgrading its 215 737 Classics. The low-cost carrier's $175-million modernization program has the front end of these aircraft gutted to accommodate GPS receivers, digital displays, new processors and software, new wiring and battery power.
The program also has Southwest's about 6,000 pilots in simulators and classrooms taking RNP training. The airline's goal is to achieve an RNP.1 capability, meaning its aircraft will remain within a 10th of a nautical mile of its authorized flight path.
RNP.1-level represents the ultimate level of performance-based navigation. However, according to Ken Shapero, Naverus' director of marketing communications, "You can gain the most benefits with RNP.3 [one-third of a nautical mile] and below."
To upgrade an aircraft for RNP, a carrier seeks from the original equipment manufacturer (OEM) service bulletins for an amended type certificate. BCAS and Airbus' Toulouse-based Airbus subsidiary, QuoVadis, provide a range of RNP services that can accompany the service bulletins.
The extent to which the operator's aircraft must be modernized can vary. "It should be known that rarely is upgrading an aircraft to RNP straightforward. You can't use the catalog approach," says Bracho.
"With newer aircraft, little may have to be done," he adds. "But then there's the opposite extreme, like Southwest's program."
Bracho warns that operating a single model does not mean all upgrades for that model would be identical. "Not all models were advanced [technologically] at the same pace," he explains. "The 737NGs are RNP capable, but to what degree? It varies.
"Not All NGs are the same, in part because the operator purchasing the aircraft had options in equipage," Bracho continues. "I would say that if a customer has 100 aircraft, maybe 10 could share the same modernization design work."
The desired level of RNP also impacts a modernization program, particularly in software development for the FMC. Some levels are more complicated and, therefore, more expensive. "I give our customers extreme examples, for instance, the constrained RNP.15 approach into Innsbruck [Austria] or Juneau [Alaska] as opposed to a public RNP approach where there are no obstacles, a flat terrain, and where a missed approach would be simple."
When an operator selects a level of RNP that suits his needs, Boeing or Airbus issues service bulletins, which include wiring diagrams, a modification spec sheet, brackets, connectors and installation instructions. Add the avionics and appropriate software from Honeywell, Rockwell Collins, Thales, GE, Garmin or another cockpit systems manufacturer, and you have an aircraft equipped for RNP.
A check ride, making sure the modification works appropriately, follows the upgrade, according to Bill Syblon, flight operations specialist at Boeing. "After that, the operator's only concerns [regarding equipage] are to amend the aircraft's minimum equipment list and carry out standard maintenance of the systems," he adds.
