Required Navigation Performance-4 (RNP-4)
Normal Procedures: Airspace
- Accuracy / Performance Standards
- Qualification Criteria / Operational Approval
- Example Compliance
[ICAO Doc 7030, §MID/ASIA, ¶220.127.116.11.2] For flights on designated controlled oceanic routes or areas within the Auckland Oceanic, Brisbane, Fukuoka, Honiara, Melbourne, Nauru, New Zealand and Port Moresby FIRs, a longitudinal separation minimum of 55.5 km (30 NM) derived by RNAV may be applied between RNAV-equipped aircraft approved to RNP 4 or better, in accordance with the provisions of the PANS-ATM, 18.104.22.168.
[ICAO Doc 7030, §PAC, ¶22.214.171.124.2] For flights on designated controlled oceanic routes or areas within the Anchorage Arctic, Anchorage Continental, Anchorage Oceanic, Auckland Oceanic, Nadi, Oakland Oceanic and Tahiti FIRs, a longitudinal separation minimum of 55.5 km (30 NM) derived by RNAV may be applied between RNAV-equipped aircraft approved to RNP 4 or better, in accordance with the provisions of the PANS-ATM, 126.96.36.199.
In both the Asia and Pacific instances, the 30 NM longitudinal separation "may be applied." If you do not have RNP-4 authorization the following PANS-ATM provisions are cited:
[ICAO Doc 4444, ¶188.8.131.52] LONGITUDINAL SEPARATION MINIMA BASED ON DISTANCE USING RNAV WHERE RNP IS SPECIFIED
184.108.40.206.2.2 Direct controller-pilot communications shall be maintained while applying a distance-based separation minima. Direct controller-pilot communications shall be voice or CPDLC. The communication criteria necessary for CPDLC to satisfy the requirement for direct controller-pilot communications shall be established by an appropriate safety assessment.
220.127.116.11.3 Longitudinal distance-based separation minima in an RNP RNAV environment not using ADS
18.104.22.168.3.1 For aircraft cruising, climbing or descending on the same track, the following separation minimum may be used:
|Separation minimum||RNP type||Communication requirement||Surveillance requirement||Distance verification requirements|
|93 km (50NM)||10||Direct controller-pilot communications||Procedure position reports||At least every 24 minutes|
22.214.171.124.4 Longitudinal distance-based separation minima in 126.96.36.199.4 an RNP RNAV environment using ADS
188.8.131.52.4.3 For aircraft cruising, climbing or descending on the same track, the following separation minima may be used:
|Separation minimum||RNP type||Maximum ADS periodic reporting interval|
|93 km (50NM)||10||27 minutes|
|93 km (50NM)||4||32 minutes|
|55.5 km (30NM)||4||14 minutes|
If you do not have ADS and are not RNP-4 authorized, the controllers have the option of accepting you but using increased separation standards provided: you are RNP-10 qualified, you are in direct communications with the controller, and you make position reports at least every 24 minutes.
Accuracy / Performance Standards
System Performance, Monitoring, and Alerting
[ICAO Doc 9613, Volume II, Part C,¶184.108.40.206]
- Accuracy: During operations in airspace or on routes designated as RNP 4, the lateral total system error must be within ±4 NM for at least 95 per cent of the total flight time. The along-track error must also be within ±4 NM for at least 95 per cent of the total flight time. An FTE of 2.0 NM (95 per cent) may be assumed.
- Integrity: Malfunction of the aircraft navigation equipment is classified as a major failure condition under airworthiness regulations (i.e. 10–5 per hour).
- Continuity: Loss of function is classified as a major failure condition for oceanic and remote navigation. The continuity requirement is satisfied by the carriage of dual independent long-range navigation systems (excluding signal-in-space).
- Performance monitoring and alerting: The RNP system, or the RNP system and pilot in combination, shall provide an alert if the accuracy requirement is not met, or if the probability that the lateral TSE exceeds 8 NM is greater than 10–5.
- Signal-in-space: If using GNSS, the aircraft navigation equipment shall provide an alert if the probability of signal-in- space errors causing a lateral position error greater than 8 NM exceeds 10–7 per hour (Annex 10, Volume I, Table 220.127.116.11-1).
Note.— Compliance with the performance monitoring and alerting requirement does not imply an automatic monitor of flight technical error. The on-board monitoring and alerting function should consist at least of a navigation system error (NSE) monitoring and alerting algorithm and a lateral deviation display enabling the crew to monitor the flight technical error (FTE). To the extent operational procedures are used to monitor FTE, the crew procedure, equipment characteristics, and installation are evaluated for their effectiveness and equivalence as described in the functional requirements and operating procedures. Path definition error (PDE) is considered negligible due to the quality assurance process (1.3.6) and crew procedures (1.3.4).
These requirements are duplicated in Advisory Circular (AC) 20-138( ), Airworthiness Approval of Positioning and Navigation Systems.
[ICAO Doc 9613, Volume II, Part C,¶18.104.22.168] It is important to understand that additional requirements will have to be met for operational authorization in RNP 4 airspace or on RNP 4 routes. Controller-pilot data link communications (CPDLC) and automatic dependent surveillance — contract (ADS-C) systems will also be required when the separation standard is 30 NM lateral and/or longitudinal. The on-board navigation data must be current and include appropriate procedures.
This is a potential "gotcha" in the works. You can have an OpSpec/MSpec/LOA for RNP-4 authorization without CPDLC and ADS. (Some POIs will not permit this, but some will.) There are locations in the world where the requirement for RNP-4 authorization assumes CPDLC and ADS.
Qualification Criteria / Operational Approval
[AC 90-105A, App. F, ¶F.2]
- F.2.1 Statement of Compliance (SOC). Aircraft with an SOC with RNP 4 criteria in Advisory Circular (AC) 20-138( ), Airworthiness Approval of Positioning and Navigation Systems, in their Airplane Flight Manual (AFM), Airplane Flight Manual Supplement (AFMS), pilot’s operating handbook (POH), or the operating manual for their avionics meet the performance and functional requirements of this appendix.
- F.2.2 Statement from the Manufacturer. Aircraft with a statement from the manufacturer documenting compliance with the RNP 4 criteria in AC 20-138( ) meet the performance and functional requirements of this AC. These statements should include the airworthiness basis for compliance. Compliance with the sensor requirements will have to be determined by the equipment or aircraft manufacturer, while compliance with the functional requirements in this appendix may be determined by the manufacturer or by inspection by the operator.
- F.2.3 Navigation Equipment Requirements. Navigation equipage for all RNP 4 operations in oceanic and remote continental areas must have at least dual independent long-range navigation systems (LRNS). Global Navigation Satellite System (GNSS) must be used as either a stand-alone navigation system, as one of the sensors in a multisensor system, or as part of an integrated GNSS/inertial system.
Note: RNP 4 operations are based on Global Positioning System (GPS) positioning. Positioning data from other types of navigation sensors may be integrated with the GPS data provided it does not cause position errors exceeding the Total System Error (TSE) budget. Otherwise, means should be provided to deselect the other navigation sensor types.
Operational Approval - 14 CFR 91
- 7.1 Part 91 Operators. A letter of authorization (LOA) is not required for Title 14 of the Code of Federal Regulations (14 CFR) part 91 operators (other than part 91 subpart K (part 91K)) except for oceanic operations (see Appendices E, F, and G) or if required in foreign airspace. Part 91 operators (other than 91K) should comply with the aircraft eligibility and operational guidance in this advisory circular (AC).
- 7.2 Operational Authorization. To obtain operational authorization, aircraft eligibility must be determined in accordance with the applicable appendix of this AC. Operational authorizations issued under a previous version of this AC or other canceled ACs does not need to be reissued or reevaluated.
Note: Previous approvals under FAA Order 8400.12C, Required Navigation Performance 10 (RNP 10) Operational Authorization, and FAA Order 8400.33, Procedures for Obtaining Authorization for Required Navigation Performance 4 (RNP-4) Oceanic and Remote Area Operations, are still valid for these operations. Operators must ensure their operations remain consistent with the performance and functional requirements of this AC.
Operational Approval - 14 CFR 91K, 121, 125, 129, and 135
[AC 90-105A] Parts 91K, 121, 125, 129, and 135 Operators. Title 14 CFR parts 91K, 121, 125, 129, and 135 operators receive approval to fly RNP operations as described in this AC via operations specifications (OpSpecs), management specifications (MSpecs), or LOAs as follows:
- OpSpec/MSpec/optional LOA, paragraph C063, Area Navigation (RNAV) and Required Navigation Performance (RNP) Terminal Operations;
- OpSpec/MSpec, paragraph B035, Class 1 Navigation in U.S. Class A Airspace Using Area or Long-Range Navigation Systems;
- OpSpec/MSpec/LOA (to include Part 91 operators), paragraph B036, Oceanic and Remote Continental Navigation Using Multiple Long-Range Navigation Systems (M-LRNS); or
- Helicopter Specification (HSpec)/LOA, paragraph H123, Class I Navigation Using Area or Long-Range Navigation Systems with Wide Area Augmentation System (WAAS) for Rotorcraft Required Navigation Performance (RNP) 0.3 En Route and Terminal Operations.
[FAA Order 8900.10 Vol 3, Chapter 18, Part B, §B036, ¶k)] OpSpec/MSpec Entries.
- For RNP 4 operations, an aircraft must meet a cross-track keeping accuracy and along-track positioning accuracy of no greater than +7.4 km (4 NM) for 95 percent of the flight time. Different routes that require RNP-4 may have different separation, equipment, and communications requirements. It is possible in the future that a route or airspace could be established that would require RNP-4 navigation capability with VHF communication and radar. Some examples of routes that require RNP-4 are:
- Australian Tasman Sea; detailed guidance is contained in Australian Government, Civil Aviation Authority, AC 91U-3(0), Required Navigation Performance 4 (RNP-4) Operational Certificate;
- Easter Russia, the Magadan region; requires FANS 1/A-equiped aircraft; and
- Western region of China and north of the Himalayas, Route 888; because of the remoteness of the area, RNP-4 CPDLC, and ADS are required.
"Easter Russia" is probably a typo, most likely means eastern Russia.
- For RNP-4 operations in oceanic or remote airspace, at least two fully serviceable independent LRNS, with integrity such that the navigation system does not provide misleading information, must be fitted to the aircraft. These will form part of the basis upon which RNP-4 operational approval is granted;
- For aircraft incorporating GPS, AC 20-138A or equivalent documents provide an acceptable means of complying with installation requirements for aircraft that use but do not integrate the GNSS output with that of other sensors. AC 20-130A describes an acceptable means of compliance for multi-sensor navigation systems that incorporate GPS; and
- Flightcrew training and operating procedures for the navigation systems to be used must be identified by the operator.
Figure: Limitations Extract, from G450 Airplane Flight Manual, §1-03-10, ¶13.]
Portions of this page can be found in the book International Flight Operations, Part III, Chapter 9.
Advisory Circular 20-138D, Positioning and Navigation Systems, 5/8/12, U.S. Department of Transportation
Advisory Circular 90-105A, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace, 3/7/2016, U.S. Department of Transportation
FAA Order 8400.33, Procedures for Obtaining Authorization for Required Navigation Performance 4 (RNP-4) Oceanic and Remote Area Operations, U.S. Department of Transportation, 9/15/05
ICAO Doc 4444 - Air Traffic Management, 16th Edition, Procedures for Air Navigation Services, International Civil Aviation Organization, October 2016
ICAO Doc 7030 - Regional Supplementary Procedures, International Civil Aviation Organization, 2008
ICAO Doc 9613 - Performance Based Navigation (PBN) Manual, International Civil Aviation Organization, 2008