RNP Navigation

[Tony Forrest]

In response to many questions about RNP/RVSM/GNSS/INS Navigation, the following is the first of a series of articles to hopefully clear up any misunderstanding.


From WIKI (with minor edits)

Required Navigation Performance (RNP) is defined by ICAO as "a statement of the navigation performance
necessary for operation within a defined airspace". Part of a broader concept called "Performance-based
Navigation," RNP is a method of implementing routes and flight paths that differs from previous methods in
that not only does it have an associated performance specification that an aircraft must meet before the
path can be flown but must also monitor the achieved performance and provide an alert in the event that
this fails to meet the specification. It is the monitoring and alerting facility that distinguishes RNP
from RNAV (aRea NAVigation) from which it developed. RNP equipped aircraft can safely operate routes with
less separation than previously required which is significant because it increases the number of aircraft
that can safely use a particular airspace and therefore accommodate the increasing demand for air traffic
capacity.

Under the ICAO definitions, GNSS is the primary navigation system to support currently defined RNP
standards. Before the introduction of GNSS, aircraft navigated using ground-based navaids or Inertial
Navigation Systems (INS), and the degree to which they follow an assigned track was based on the accuracy
of those systems. These assumptions on the accuracy and precision to which an aircraft could fix its
position in three dimensions in turn drove the size of the protected airspace which needed to be
maintained around each aircraft. On many densely traveled routes, such as those over the northern Atlantic
Ocean North Atlantic Tracks (NAT) connecting the United States and Europe, aircraft were packed as tightly
as the separation rules allowed during peak times thus limiting the number of flights which could travel
that route per day.

RNP changes those assumptions. Under RNP, the nature of the navigational aids is not specified, rather the
volume of airspace around the aircraft is, and this volume may be smaller (in some cases much smaller)
than that of conventional navigation. In practice, the RNP aircraft is assumed to be navigating using a
combination of ground-based navaids (radio navigation), GPS, and inertial guidance systems, which give far
greater precision than previously possible. This allows air traffic control to reduce the spacing between
aircraft without compromising safety. Certain blocks of airspace are being designated with RNP standards;
only aircraft meeting the designated RNP level for that airspace will be allowed to operate in that area.

The performance required to fly an RNP route is generally specified in nautical miles, e.g. RNP 4 which
implies that the total system error will be no greater than 4 NM for 95% of the time. The RNP
specification requires that if the error exceeds or is likely to exceed twice the specified value (i.e.
8NM for RNP 4) then an alert must be generated. Since the deviation is likely to exceed the alerting
deviation before the error can be rectified, route spacing must be sufficient to ensure that two aircraft
deviating to the alert level toward one another will remain safely separated. RNP 4 thus supports 30 NM
lateral or longitudinal spacing.


Benefits of RNP In The Terminal Area
Operators who implement the methods and standards of RNP may gain benefits in operating efficiency,
improved access to airports, and safety.

Compared to routes that rely on ground-based navigation aids, RNP approaches in the terminal airspace
offer potentially shorter routes, resulting in reduced fuel consumption. This represents an economic
benefit for operators, and reduced emissions of CO2 and NOx for the environment.[citation needed]
Approach procedures based on RNP often provide improved minima compared to the existing non-precision
approaches, in many cases comparable to existing ILS approaches. This allows aircraft to complete landings
in a broader range of weather conditions.
RNP approaches typically incorporate a Continuous Descent Approach (CDA) right to the runway, which is
safer, more fuel-efficient and quieter than current stepped-descent or "dive and drive" approaches that
require the aircraft to maneuver at low level and low speed in the airport vicinity before final approach
to the runway.

RNP, together with other technologies such as ADS-B, also offers a means to support greater capacity and
less airspace congestion in crowded environments. It features prominently in the FAA’s roadmap for its
Next Generation Air Transportation System (NextGen), intended to modernize US airspace through 2025.

Implementing RNP

Operators seeking to implement RNP currently face three basic hurdles: aircraft eligibility, operational
approval to conduct RNP operations, and publication of airport-specific RNP approach procedures.

Aircraft eligibility: The aircraft and its avionics must be certified by the FAA, EASA or other relevant
regulatory agency that it is capable of meeting the requirements of performance-based navigation. Specific
combinations of flight management systems, navigation sensors, flight guidance systems, cockpit displays
and other equipment are required, together with the monitoring and alerting capabilities that distinguish
performance-based navigation from other satellite-based navigation methods such as RNAV. Aircraft
certification typically specifies an accuracy level, such as RNP 0.10 or RNP 0.30, at which the aircraft
can navigate.

Operational approval: The operator must gain operational approval from its regulator to conduct RNP
operations. In addition to having an eligible fleet, the operator must incorporate changes to aircrew
procedures, dispatch, maintenance, and other areas of operations, similar to the requirements necessary to
conduct ILS CAT II/III operations. The operator must also meet stricter requirements for monitoring the
integrity of navigation databases and flight-specific availability of levels of RNP performance based on
satellite conditions.

Airport-specific approach procedures: The operator must have access to RNP approach procedures that are
designed for the specific runway end they intend to use. These procedures may be tailored to their
specific aircraft and operations, or be public procedures available to all approved operators at that
airport.

There is a fourth component to RNP operations which has to be considered. Integration of RNP operations in
the terminal environment in busy terminal airspace. A trial wass conducted at Brisbane Airport (Australia)
integrating RNP operations into terminal airspace. The trial ran for a year (from 18 January 2007). It was
successful and RNP operations are standard within the Australian air spaces.

RNP Implementation Worldwide
Implementation of RNP in the terminal airspace began in 1996 with a program by Alaska Airlines to address
challenges it faced in Juneau, Alaska. In recent years, operators in Australia, Canada, China, New Zealand
and the US began RNP operations, while both ICAO and the FAA made significant progress on evolving the
procedure design criteria and other requirements for RNP. Key milestones in RNP implementation worldwide

include:

Australia/New Zealand: Qantas and Air New Zealand launched efforts in the region with RNP procedures at
Queenstown, New Zealand. RNP-AR operations are being progressively deployed at 15 airports in Australia.
To date terminal RNP procedures are conducted at Cairns, Townsville, Brisbane, Gold Coast, Alice Springs,
Ayers Rock, Sydney, Canberra and Hobart. January 2008 saw operations commencing at Mount Isa, Broome,
Kalgoorlie and Karratha. Melbourne, Adelaide, Darwin and Port Hadland followed later in 2008. To date, in
excess of 120,000RNP procedures have been flown.

Jetstar commenced RNP operations at Brisbane and Gold Coast in March 2008.

Canada: WestJet has deployed RNP procedures at 22 airports in their Canadian network

China: Air China conducts RNP operations at multiple airports including Lhasa, Linzhi and Jiuzhaigou. The
Linzhi airport, opened in 2006, is notable for allowing only RNP-based operations, since reliable
navigation using ground-based navigation aids is not feasible there due to surrounding terrain.

US: Alaska Airlines conducts RNP operations at 12 US airports in Alaska and the continental US, and
credits the technology with 1300 “saved” operations in 2006 due to improved access in marginal weather.
Alaska’s sister airline Horizon Air gained approval to conduct RNP operations at specific airports in late
2006. In 2007, Hawaiian Airlines fleet of B767-300 aircraft are already upgraded with RNP enable Flight

Management Systems (Honeywell Pegasus) and is seeking certification approvals. Southwest Airlines
announced plans to upgrade its entire fleet to RNP capability, and commissioned development of RNP
procedures for all airports it serves. On December 22, 2008, Southwest announced that the Boeing Co. would
be the lead integrator in the RNP program for the 737-300 aircraft. The -300 models will be retrofitted
with a new flight deck, including hardware and software, to make all the -300's compatible with the 737-
700 and allow both types to use the same preferred airspace.[1] American Airlines, Continental Airlines
and Delta Airlines have announced similar plans for equipment upgrades and RNP operational approval.

Europe: Transavia has 40 pilots trained specifically to operate flights to/from Innsbruck (Austria) under
heavy weather conditions under RNP procedures. This airport is known for its challenging approach, as it
is located on the bottom of the Inntal valley, where snow and fog can heavily reduce sight.


From the AIP Website

INTRODUCTION OF
REQUIRED NAVIGATION PERFORMANCE (RNP)
APPROACH AND DEPARTURE PROCEDURES
WITHIN AUSTRALIA
1. INTRODUCTION
1.1 Approach and Departure procedures using Required Navigation
Performance Authorisation Required (RNP--AR) criteria have been
designed for several Australian aerodromes for use by operators approved
by the Civil Aviation Safety Authority (CASA).
1.2 These procedures are nowin operation at a number of airports and are
being progressively implemented at other airports.
1.3 These procedures are named as RNAV (RNP), with an appropriate
identifier of either U, M or P eg. RNAV--U (RNP).
1.4 The procedures can only be performed by approved operators in
appropriately equipped aircraft.
2. BACKGROUND
2.1 Required Navigation Performance (RNP) is a statement of the
navigation performance necessary for operation within a defined airspace,
a route, or procedure.
2.2 RNP is based on area navigation (RNAV) and adds on--board
monitoring of the aircraft’s navigation performance to alert the pilotwhen the
RNP specified for the airspace, route or procedure may not be achieved.
(AIC H08/09) Page 2 of 3
Use of an on--board performance monitoring and alerting capability can
reduce reliance on increased route separation and/or air traffic control
intervention to maintain the overall safety of the operation.
2.3 Basic RNP procedures are based on a 2 x RNP lateral containment
area plus a buffer area.
2.4 For RNP--AR procedures (RNP values equal to or less than 0.3 and
greater than or equal to 0.1) the buffer area is eliminated and additional
certification, approval and crew training requirements on specific aircraft
types ensure containment to the appropriate level of safety without the
buffer.
2.5 RNP approach and departure procedures provide for a high level of
aircraft containment which is beneficial in obstacle rich environments.
Additionally, the procedures provide containment for the aircraft not only in
the approach, but in themissed approach segment. This applies equally to
all engine and engine out procedures for RNP--AR.
2.6 As a result, procedures have been developed for a number of
Australian aerodromes which will afford higher safety for operators.
3. LOCATIONS
3.1 QANTAS using B737--800 aircraft and/or JetStar using A320 aircraft
are conducting RNP--AR approaches and departures at several airports.
3.2 At a later date,Virgin Blue usingBoeing 737--700 and 737--800 aircraft
are expected to conduct RNP--AR operations.
3.3 Pilots will be alerted that RNP approaches are in progress at a
particular port when pilots of participating aircraft use the phraseology
“Request RNP approach”.
4. IMPLEMENTATION
4.1 The RNAV (RNP--AR) procedures will be promulgated by AIP SUP as
each aerodrome is authorised, where there is no ATC, or non--continuous
ATC. Eventually, all procedures will be incorporated into DAP.
4.2 “Trigger” NOTAMs will be issued advising pilots that new RNAV
(RNP--AR) procedures have been issued. Pilots should refer to the SUP for
an airport to determine where the RNP tracks will be in relation to their
intended operation.
Page 3 of 3 (AIC H08/09)
5. CANCELLATION
5.1 This AIC self cancels on 31 January 2011.
6. DISTRIBUTION
By AVFAX and Airservices Australia website only.