Jeppesen using RAIM to fine tune RNP
Several elements of the Next Generation Air Transportation System depend on GPS-based area navigation (RNAV) and required navigation performance (RNP). RNP is essentially RNAV with onboard performance and alerting capability. The ability of the aircraft's own navigation system to monitor its navigation performance and to inform the crew if the required performance is not being met is a defining capability of RNP operations. The technology that assesses the integrity of GPS signals within a GPS receiver is called receiver autonomous integrity monitoring, or RAIM.
Englewood, Colorado-based Jeppesen (Booth No. 3004) is introducing here at NBAA a new product that improves upon the company's current RAIM prediction technology, which provides predictions of GPS satellite availability while assessing the integrity and accuracy of GPS-based navigation signals. Called the Jeppesen FlitePlan RNP Predictor, the RAIM prediction product was developed jointly by Jeppesen and its technical-support partner, DW International (DWI), a consultant on air navigation, civil air communications and air traffic management. Southwest Airlines is the first civil aviation customer for the product, which is also designed for use by general aviation operators.
The FlitePlan RNP Predictor predicts the availability of a certain level of RNP along a route of flight, which includes the departure and arrival procedure phase of the flight. Using such factors as aircraft type and configuration at a particular time and place and current GPS satellite status, the RNP Predictor computes a prediction report of the aircraft's actual navigation performance (ANP). This enables operators to comply with all FAA, European, ICAO and other global RAIM prediction requirements.
By taking all route details from the flight plan and calculating RAIM availability for all route types (oceanic, en route, terminal and approach), the RNP Predictor allows flight planners, dispatchers and aircrew to plan around periods of reduced GPS availability. It does this on a leg-by-leg basis and includes destination and alternate airports for RNAV and RNP operations anywhere in the world.
The Jeppesen prediction tool calculates RAIM at each waypoint at the time the aircraft is expected to arrive. In addition, it checks RAIM 15 minutes before and 15 minutes after the estimated arrival at a configurable interval for each waypoint. The tool fills in calculation points between waypoints so the minimum sample time is maintained between calculation points.
The RNP prediction report can be included as part of a flight plan so the crew can see RAIM availability. Once in flight, the aircraft flight management system monitors the actual navigation performance and the crew can verify the prediction with actual observations. If the ANP value falls below the required RNP value, the crew must take action. The RNP prediction reports help dispatchers and crews understand areas where the RNP values may fall below required levels, and re-plan routes if necessary.
The tool has two main elements, according to Jeppesen. The "airport watch" service monitors a customer's regular airports in real time. As Notice Advisory to Navstar Users (NANUs) are received by the tool, the status of any affected airport is relayed back to the user's dispatch or flight planning system, either textually or graphically. The second element is the request/reply service, in which a single airport, group of airports or entire flight plan can be submitted to the tool for analysis.
By using RNP procedures, pilots can fly more precise routes and approaches based on satellite data, thus reducing fuel consumption, emissions and noise effects. "Through reduced fuel burn, flying RNP procedures will also allow airlines to operate in a more environmentally friendly manner," said Thomas Wede, Jeppesen senior vice president and general manager, aviation.
Said Jeff Martin, assistant director of operations for Southwest Airlines, "The Jeppesen FlitePlan RNP Predictor enables us to capitalize on our significant investment in RNP approaches and will produce a bottom-line improvement within Southwest Airlines' operations."
Southwest Airlines, Jeppesen and DWI worked closely together to integrate the tool into Southwest's local systems, including its in-house dispatch tool and Jeppesen Flight Planning system. When a flight plan is run, a request can be made to include RNP prediction, and this report is then included as part of the flight plan. The RNP prediction system resides locally at Southwest and communicates with the air operations center and flight planning systems through a Jeppesen messaging protocol.
Jeppesen expects that dispatchers working for airlines or business aviation operators with larger fleets will be the primary users of the RNP predictor. However, "pilots could potentially self-brief and self-dispatch." The RNP Predictor currently works only with Jeppesen's Jetplan flight planning service, but it is designed so that it can be integrated with other systems using standard XML technology.
The FlitePlan RNP Predictor does not require user customization for RNP values above 0.3. "For values below that level, to enable precision approach analysis, details of the aircraft FMS are needed and some set-up may be required," explained a Jeppesen spokesman.
"Costs for the service are still being finalized," said the spokesman, "but we plan to make them competitive and commensurate with the value the service provides. The fees are expected to reflect fleet size and will be on a subscription basis."
Updates are managed by Jeppesen and DWI and coordinated with the customer in the case of a locally installed system. The subscription charge will cover any regular updates. Customer specific updates may be chargeable on a time and materials basis.