RNP Revs Up

The Federal aviation Administration (FAA) has sharpened its focus on publicly supported, required navigation performance (RNP) procedures and formed an RNP program office to speed the process along. FAA pledged in July 2002 to develop and implement a plan to establish RNP in the succeeding 12 months.

RNP values indicate the accuracy with which an aircraft can navigate from point to point in space, an ability known as area navigation (RNAV). (RNP 0.3, for example, means that an aircraft must fly within 0.3 nautical mile [nm] of the centerline of the flight path, with a 95 percent probability of that accuracy.) RNP benefits include:

• Reduced terrain, obstacle and aircraft separation standards;

• Increased levels of navigation accuracy and flight predictability; and

• Increased airspace capacity, efficiency and safety.

The new program office, a division in FAA’s Air Traffic Planning and Procedures unit, will be closely supported by the Flight Standards, Aircraft Certification and Aviation Systems Standards organizations.

FAA plans a two-phase RNP strategy, the first of which runs from fiscal year 2003 to FY 2005. The agency aims next year to complete an aircraft equipage inventory, "so we’ll know better what capabilities [aircraft] have and what benefits we can provide," says John McGraw, manager of the Flight Technologies and Procedures Division of the Flight Standards Service.

Aircraft with dual flight management systems (FMS), dual GPS and high-level inertial navigation systems (INS) might be qualified down to a very low RNP approach value, perhaps to RNP 0.1 or 0.15.

FAA next year targets implementation of en-route RNP at routes along the west coast and inland, in the Las Vegas area, says Mike Cirillo, program director for air traffic planning and procedures. Part of the high-altitude national airspace redesign, RNP 2.0 procedures will be implemented first at flight levels (FL) 390 and above, and later at FL-350. Eighty to 90 percent of FL-390 airspace users could take advantage of RNP 2.0, he estimates.

The first public RNP/RNAV approaches, at RNP 0.3, are expected by early 2004. "For users with higher levels of equipage, there may be lower minima, but with some special aircraft and aircrew authorization to use [them]," McGraw says. Meanwhile, pioneer Alaska Airlines is developing private RNP procedures that will add to the knowledge base (see story, page 13).

FAA is casting its net wide on RNP approaches, McGraw says. "We believe for 0.3 RNP...some general aviation aircraft will be able to participate.

"We think that probably aircraft with GPS [technical standard order] C129-approved boxes would have the capability to participate in basic RNP 0.3 approaches. We’re not assuming that they have WAAS [wide area augmentation system equipment] to participate."

TAOARC Work Schedule

The Terminal Area Operations Aviation Rulemaking Committee (TAOARC), created to solve RNP/RNAV implementation, avionics and operational issues, has completed work on advisory circular, AC 120-29A (dated Aug. 12, 2002), which includes some RNP criteria.

A terminal instrument procedures (TERPS) order for RNP is expected in 2003, providing instrument approach design criteria down to RNP 0.3. Participants hope later to put in provisions for smaller RNP values–probably down to RNP 0.1 or 0.15. After the TERPS order, TAOARC will finalize operational approval and certification criteria documents to further spur RNP procedure development.

Phase 1 RNP Strategy (FY 03 to 05)*

Approach: Public RNP 0.3
Aircraft: GPS or RNP-certified, using DME/DME/Inertial

RNP Parallel Approach Transition: Public RNP 0.3
Aircraft: GPS (may require VNAV) or RNP-certified, using DME/DME/Inertial

Terminal Arrivals and Departures: RNP 2.0
Aircraft: GPS, RNP-certified, some DME

En Route: RNP 2.0 (8-nm aircraft separation)
Aircraft: GPS, RNP-certified, some DME

*Phase 2 (FY 05 and on) adds items such as RNP 1.0 arrival/departure and en-route procedures.