Introduction to Navigation Specifications

Learning Objectives Organisation of PBN Manual Vol II Vol II Part A, General PBN concept review Navigation performance System performance error components Role and application of on-board performance monitoring and alerting Use of navigation specifications Relationship with existing criteria Vol II Parts B and C Summary

Organisation of PBN Manual, Volume II Part A: General Part B: Implementing RNAV (including RNAV Specifications) Part C: Implementing RNP (including RNP Specifications) Attachment A: Barometric VNAV

PBN Concept Review 3 2 1 NAVIGATION APPLICATION NAVAID NAVIGATION SPECIFICATION 2 NAVAID INFRASTRUCTURE 1 As you know, a Navigation Application is the application of a navigation specification and associated navaid infrastructure to ATS routes, instrument approach procedures and/or defined airspace volume. In simple terms a Navigation Specification describes in detail the requirements for an Area Navigation (RNAV) System for operation along a specific ATS route or procedure.

PBN Concept Review Requirements placed on the RNAV system Performance required for accuracy, integrity, continuity and availability Functions available to achieve required performance Navigation sensors to achieve required performance Flight crew procedures to achieve required performance RNP specifications require on-board performance monitoring and alerting…RNAV specifications do not

Navigation Performance System performance error components Lateral navigation errors Longitudinal navigation errors On-board performance monitoring and alerting Role Application

System Performance Error Components (1) Lateral navigation errors (95%) 3 main errors: PDE, NSE and FTE The inability to achieve the required lateral navigation accuracy may be due to navigation errors related to aircraft tracking and positioning. The three main errors in the context of on-board performance monitoring and alerting are Path Definition Error (PDE), Flight Technical Error (FTE), and Navigation System Error (NSE). The distribution of these errors are assumed to be independent, zero-mean and Gaussian. Therefore, the distribution of Total System Error (TSE) is also Gaussian with a standard deviation equal to the Root Sum Square (RSS) of the standard deviations of these three errors. PDE occurs when the path defined in the RNAV system does not correspond to the desired path i.e. the path expected to be flown over the ground. Use of an RNAV system for navigation presupposes that a defined path representing the intended track is loaded into the navigation database. NSE refers to the difference between the aircraft’s estimated position and actual position. Note. – NSE is sometimes referred to as Positioning Estimation Error (PEE) FTE relates to the air crew or autopilot’s ability to follow the defined path or track, including any display error (e.g., CDI centering error). FTE can be monitored by the autopilot or air crew procedures and the extent to which these procedures need to be supported by other means depends, for example, on the phase of flight and the type of operations. Such monitoring support could be provided by a map display. Note. – FTE is sometimes referred to as Path Steering Error (PSE)

System Performance Error Components (2) Longitudinal navigation errors (95%) Along-track navigation errors (NSE) No FTE in longitudinal dimension No current navigation specifications require 4-D control The accuracy requirement of RNAV and RNP specifications are defined for the lateral and along-track dimensions i.e., NSE is considered as a radial error and PDE is considered negligible. There is no declared FTE in the longitudinal dimension. It is really a time differential. Note: The on-board performance monitoring and alerting requirements of RNP specifications are defined for the lateral dimension. However, because NSE is considered as a radial error, the on-board performance monitoring and alerting is effectively provided in all directions. Longitudinal performance implies navigation against a position along the track (e.g., 4-D control). At the present time, there are no Navigation Specifications requiring 4-D control.

Role of On-board Performance Monitoring and Alerting (1) The PBN concept uses “on-board performance monitoring and alerting” instead of “containment” The associated ICAO terms were previously containment area, contained airspace, containment value, containment distance, obstacle clearance containment Replaced by the navigation accuracy of TSE The PBN concept uses “on-board performance monitoring and alerting” instead of “containment” Avoids confusion between existing uses of “containment” in various documents by different areas of expertise For example: a) Containment has referred to the region within which the aircraft will remain 95% of the time. The associated terms have been containment value and containment distance and the related airspace protection on either side of a RNAV ATS route. b) Within PANS-OPS material, containment has referred to the region used to define the obstacle clearance, and the aircraft is expected to remain within or above that surface (regardless of alerting) with very high probability. c) Within the industry standards of RTCA/DO-236() and EUROCAE/ED-75, containment referred to the region that the aircraft will remain when there is no alert (0.99999 probability). The associated terms are containment limit, containment integrity, containment continuity, and containment region.

Role of On-board Performance Monitoring and Alerting (2) Allows the flight crew to determine whether the RNP system satisfies the navigation performance required in the navigation specification Dependent on system architecture Relates to both lateral and longitudinal navigation performance

Role of On-board Performance Monitoring and Alerting (3) “On-board” means the performance monitoring and alerting is on-board the aircraft “Monitoring” relates to NSE and FTE PDE is constrained through database integrity and functional requirements on the defined path “Monitoring” refers to the monitoring of the aircraft’s performance; ability to determine positioning error and/or to follow the desired path “Alerting” is related to monitoring Flight crew alerted if navigation system not performing to requirement “On-board” means the performance monitoring and alerting is on board the aircraft and not elsewhere (e.g., using a ground-based route adherence monitor or ATC surveillance) “Monitoring” relates to FTE and NSE PDE is constrained through database integrity and functional requirements on the defined path, and is considered negligible. “Monitoring” refers to the monitoring of the aircraft’s performance as regards its ability to determine positioning error and/or to follow the desired path.

Application of On-board Performance Monitoring and Alerting (1) Aircraft (or aircraft and pilot in combination) Required to monitor TSE Provides an alert if accuracy requirement is not met, or if probability that TSE exceeds 2x accuracy value is larger than 10-5 Net effect of RNP navigation specifications is to bound TSE distribution PDE negligible; FTE known; NSE varies Recall error components: PDE FTE NSE Since PDE is assumed to be negligible, reduced to FTE and NSE. FTE is assumed to be a function of a given flight control mode (e.g., Manual, or Flight Director, or Autopilot). However, NSE distribution varies over time due to changing characteristics, most notably from Selected NAV sensors Relative geometry (GNSS, DME)

Application of On-board Performance Monitoring and Alerting (2) RNP navigation specifications provide assurance that TSE is suitable for the operation Aircraft TSE remains ≤ required accuracy for 95% of flight time; and Probability TSE for each aircraft exceeds specified TSE (2xRNP) without annunciation is < 10-5 Performance monitoring is not error monitoring Typically, the 10-5 TSE requirement provides the greater restriction on performance. For example, any system with Normal distribution of XTKE, the 10-5 monitoring requirement constrains the standard deviation to be 2 x (accuracy value) / 4.45 = accuracy value / 2.23, while the 95% requirement would have allowed the standard deviation to be as large as the accuracy value / 1.96. While these characteristics define the minimum requirements that must be met, they do not define the actual TSE distribution. Actual TSE distribution may be expected to be typically better than the requirement, but there must be evidence on the actual performance if a lower TSE value is to be used. There can be significant variability in how individual errors are managed Some systems monitor actual XTKE and ATKE individually, while others monitor the radial NSE to simplify the monitoring and eliminate dependency on aircraft track (e.g., based on typical elliptical 2-D error distributions) Some systems include FTE in the monitor, by taking current value of FTE as a bias on the TSE distribution For Basic GNSS systems, the accuracy and 10-5 requirements are met as a by-product of the ABAS requirements, defined in equipment standards, and the FTE distribution for the standardized CDI displays. Performance monitoring is not error monitoring Performance monitoring alert issued with the system cannot guarantee, with sufficient integrity, that the position meets the accuracy requirement. When such an alert is issued, probable reason is loss of capability to validate the position data (insufficient satellites). For such a situation, most likely position of aircraft is what is shown on display. Likelihood of TSE exceeding twice accuracy value just prior to alert is approximately 10-5 However, cannot assume that simply because there is no alert, the TSE is less than twice the accuracy value. Example: Aircraft accounting for FTE based on fixed error distribution. If FTE grows large, no alert is issued by the system even when the TSE is many times larger than the accuracy value. For this reason, operational procedures to monitor FTE are important.

Application of On-board Performance Monitoring and Alerting (3) Safety assessment Performance monitoring and alerting for RNP 4, Basic-RNP 1 and RNP APCH does not obviate need for safety assessments Cannot assume appropriate route spacing is 4xRNP Navigation database errors not covered by nav specs RNP AR APCH Additional requirements to more tightly control each error source Risk Evaluations Cannot assume appropriate route spacing is 4xRNP, because: Collision risk depends on probability of loss of separation in dimension under consideration, and the exposure to that loss of separation. Exposure may be evaluated over time (i.e., to conduct an instrument approach), or over the number of risk events (e.g., number of aircraft that will be passed in an hour). RNP AR APCH Requirements can be tighter and a number of additional requirements are applied to more tightly monitor or control each error source. 2 ways to determine obstacle clearance through analysis 1. Derive obstacle clearance from TLS, given predetermined aircraft requirements and operational mitigations 2. Derive aircraft requirements and operational mitigations from TLS, given predefined obstacle clearance criteria. Methodology applied for RNP AR used this second method. RNP AR APCH operations was first established to have a total width of 4x the accuracy value (+/- 2x accuracy value centered on the path), after which the aircraft requirements and operational mitigations were then developed to satisfy the TLS.

Use of Navigation Specifications Use and scope of navigation specifications by flight phase Relationship with existing criteria Vol II, Parts B and C organisation Navigation specification template

Use and Scope of Navigation Specification by Flight Phase PBN Manual includes airworthiness, operational and training guidance NAVIGATION SPECIFICATION FLIGHT PHASE En Route Oceanic / Remote En Route Continental ARR APPROACH DEP Initial Intermed Final Missed RNAV 10 (RNP 10) 10   RNAV 5 5* 5 RNAV 2 2 RNAV 1 1 1b RNP 4 4  Basic-RNP 1 1a,c 1a 1a,b RNP APCH 0.3 RNP AR APCH 1 - 0.1 0.3 - 0.1 Notes: The numbers given in the table refer to the 95% accuracy requirements (NM) RNP 2 and Advanced-RNP 1 are expected to be included in a future revision of the PBN Manual; 1a means that the navigation application is limited to use on STARs and SIDs only; 1b means that the area of application can only be used after the initial climb of a missed approach phase 1c means that beyond 30 NM from the airport reference point (ARP), the accuracy value for alerting becomes 2 NM * Means Above MSA THIS IS A REVIEW Incorporate existing operations as practical RNAV 10 (designated and authorized as RNP-10) B-RNAV renamed as RNAV 5 RNP APCH includes existing RNAV(GNSS) approaches Additional guidance on barometric VNAV Harmonized European and US RNAV Volume II, Part B, Chapter 3: RNAV-1 and RNAV-2 Considered limited terminal arrival/departure ATS surveillance Volume II, Part C, Chapter 3: Basic RNP-1

Use and Scope of Navigation Specifications ICAO navigation specifications do not address all airspace requirements (e.g., comm, surv) necessary for operation in a particular airspace, route or area These will be listed in the AIP and ICAO Regional Supplementary Procedures Incumbent upon States to undertake a safety assessment in accordance with provisions outlined in Annex 11 and PANS-ATM, Chapter 2 ICAO PBN Manual provides a standardized set of criteria, but is not a stand-alone certification document Examples: RNP 4, RNAV 1, RNP AR APCH

Navigation Specifications and the Approval Process Navigation specifications are used by States as basis for aircraft certification and operational approval A navigation specification does not in itself constitute regulatory guidance material Aircraft approved by State of manufacture Operators approved in accordance with their National Operating Rules Compliance with one navigation specification does not guarantee compliance with another Navigation specification do not in itself constitute regulatory guidance material against which the aircraft or operator will be approved For example, with RNAV 2/ RNAV 1, there is still a need to have an approval process. This could be either through a dedicated approval document or through recognition that existing regional RNAV implementation certification documents (TGL No. 10 and AC 90-100) can be applied with the necessary differences, to satisfy the objectives set out in the PBN Navigation Specification. Compliance should be determined against each relevant Navigation Specification.

Relationship with Existing Criteria Not re-inventing the wheel Taking existing criteria e.g., Orders, ACs, AMC, and TGL etc. A more logical structure Common format and content More complete to enable uniform implementation

Common Organisation of Volume II, Parts B and C Where “X” represents the chapter number: X.1 Introduction X.2 ANSP Considerations X.3 Navigation Specification X.4 References X.1 Introduction Background Purpose X.2 ANSP Considerations Navaid Infrastructure Considerations Communication and ATS Surveillance Considerations Obstacle Clearance and Horizontal Separation Additional Considerations Publication Controller Training Status Monitoring ATS System Monitoring X.3 Navigation Specification Approval Process Aircraft Eligibility Operational Approval Description of aircraft equipment, training documentation, operations manuals and checklists, minimum equipment list considerations Aircraft Requirements Operating Procedures Pilot Knowledge and Training Navigation Database Oversight of Operators X.4 References

Air Navigation Service Provider Considerations Navigation infrastructure Sufficient for proposed operation, including reversionary modes Communication and ATS surveillance Determine reliance on radar Obstacle clearance and route spacing References PANS-OPS Publication Incorporation into AIP, and reference to ICAO Annex 15

Air Navigation Service Provider Considerations Controller Core training and training specific to the Nav Spec Status monitoring Navaid infrastructure monitoring ATS System monitoring

Overview of Specific Navigation Services  D/D/IRU RNP AR APCH RNP APCH RNP-1 RNP-4 RNAV-1 RNAV-5 RNP-10 D/VOR D/D IRU GNSS

Navigation Specification Background Approval process Aircraft requirements Operating procedures Pilot knowledge and training Navigation database Oversight of operators

Approval Process Aircraft Eligibility Operational Approval Can be based on Aircraft Flight Manual or supplemental information Operational Approval Operating procedures Flight crew training Control of navigation database process, where required Approval obtained in accordance with State operating rules

Aircraft Requirements Performance Requirements Accuracy, Integrity, Continuity, GNSS signal-in-space Performance monitoring and alerting Only applicable for RNP systems Criteria for Specific Navigation Services Defines allowable systems and required performance Functional requirements Just as important as performance Navigation database requirements

Operating Procedures Pre-flight planning General operating procedures Performance expectations (deviation from path) Pilot has critical role in performance monitoring Contingency procedures

Pilot Knowledge and Training Lists training tasks considered important, which may already be part of operator’s training program System-specific information on how navigation system functions is vital to success

Summary PBN Concept = navigation specification + navaid infrastructure + navigation application Navigation performance System performance error components On board performance monitoring and alerting Use of navigation specifications Navigation Specification provides implementation guidance for PBN operations -- not a stand-alone certification document Relationship with existing criteria Common organisation of Vol II Parts B and C ANSP considerations, navigation specification

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