1. Introduction to Navigation Specifications

2. 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

3. 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

4. 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.

5. 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

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

7. 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)

8. 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.

9. 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 ( probability). The associated terms are containment limit, containment integrity, containment continuity, and containment region.

10. 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

11. 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.

12. 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)

13. 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.

14. 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.

15. 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

16. 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
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

17. 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

18. 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 ) 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.

19. 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

20. 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

21. 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

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

23. 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

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

25. 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

26. 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

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

28. 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

29. 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

30. Feedback and Questions