58TH ANNUAL CONFERENCE, Conchal, Costa Rica, 20-24 May 2019
Agenda Item: B.5.5 – WP No. 90
Compatibility in Clearances Issued
Presented by TOC
RNP approaches have been implemented, while it is not always possible for the controller to check whether or not the aircraft/crew are capable of complying with the requirements of the said type of RNP approach.
1.1 At the 2007 36th International Civil Aviation Organization (ICAO) General Assembly, States agreed to Resolution 36/23, which urges all States to implement routes and airport procedures in accordance with the ICAO PBN criteria. Regional PBN Implementation Task Forces were developed to coordinate the regional implementation programs.
1.2 Pilots and air traffic controllers are the end-users of PBN, each having their own expectations on how to use it and the capability of the RNP system to support their working methods and everyday operations.
1.3 This paper is intended to clarify whether or not air traffic controllers should be responsible for verifying the aircraft or/and crew capabilities/requirements by checking the flight plan for a given flight, before issuing clearances specifically for RNP procedures in a given airspace. In many cases the ATM automation supports checking 8,33 KHz, RVSM or Mode S conformance as this information is provided at CWP (for instance, for the Indra ATM System, they are contained in the “aircraft equipment in relation with RVSM, 8.33 KHz, P_RNAV, Mode S” field). Sometimes checking a flights’ capabilities can be easy if the automation system displays this information in a readily discernable manner; however, some systems may leave it to the controller to interpret the alpha-numeric codes in the flight plan which might not even be accessible from the CWP but have to be retrieved through a different console.
1.4 An annex is added to the present paper, containing technical information on the PBN, R-NAV and RNP concepts.
2.1 The ICAO PBN requirements are meant to facilitate the integration within the operational environment of new and modern technologies. Regardless of the aircraft operators’ choice of technology provider, strongly influenced by cost effectiveness, or the States’ means of implementation, the accuracy, integrity, continuity and functionality imposed by the PBN requirements within a given airspace concept are clearly set.
2.2 There are various policies adopted by IFATCA in respect with the use of RNP/PBN.
|Working procedures and/or systems should provide the approach capability of the flight to relevant controllers.|
(IFATCA. (2018). TPM, 2018 Ed., ADME 2.10)
Implementing new technologies oftentimes increases controllers’ work and responsibilities. Therefore, a balance should be achieved in accommodating additional information and new procedures in the ops room.
|Controllers should be presented with information, by any suitable means, concerning navigational capability of aircraft under their control. […]
PBN route structures must be designed to ensure that ATC workload is not increased when compared to previous conventional route structures and, where possible, it is reduced in spite of increased traffic. RNAV and RNP standards should be harmonized throughout the world and included in the PBN Manual. Harmonization will result in common standards, decreasing the diverse types of RNAV and RNP procedures that are currently encountered by air crews operating around the world. The development, validation and implementation of PBN procedures should involve all affected parties, in particular, local operational controllers and representatives of airspace users.
Organizational processes and support should exist for operational staff to initiate airspace and procedure changes. The introduction of PBN procedures shall be accompanied by training for controllers and pilots that is commensurate with the complexity of the procedure.
(IFATCA. (2018). TPM, 2018 Ed., AAS1.4)
|RNP based operational procedures should be developed in parallel with new approach aids, such as GNSS.|
(IFATCA. (2018). TPM, 2018 Ed., ADME 2.9)
Regarding the required navigation performance for approach and landing IFATCA TPM states that:
|A monitoring and interpretation service should be established to monitor the status of all elements of the GNSS and interpret this information in a manner that provides relevant information to pilots and ATC. The information disseminated from the monitoring service or displayed at controller positions must be expressed in operational terms.
ATC procedures must be established for the use of GNSS and must cover the failure or degradation of the system. When ATC is informed of a change in the status of the GNSS by the monitoring service or by display equipment, specific procedures associated with that change must be implemented. Should it not be possible to achieve the RNP in airspace, an alternative RNP should be declared.
(IFATCA. (2018). TPM, 2018 Ed., AAS 1.7)
|The variety of approach types, and the associated complexity to the controller, should be reduced. The type of approach sub-category should be transparent to the controller in order to maintain an acceptable workload. The approach sub-category and the associated minima should be determined by the aircrew based upon equipment fit and training.|
(IFATCA. (2018). TPM, 2018 Ed., ADME 2.10)
ICAO PBN Manual (Doc 9613)
2.3 Crew and operator responsibilities are set within the Implementation of PBN in Doc 9613.The responsibility for the preparation of the flight and the compliance with the required navigation performance rests with the operator and the pilots.
|Before conducting flights into an airspace, the appropriate State regulations of that airspace require that operators and pilots take account of all operational documents relating to that airspace.|
(ICAO Doc 9613 PBN Manual (Vol I Vol II) Fourth edition 2013 Part B Chapter 3 Implementing RNAV1 and RNAV2, 22.214.171.124)
|Requirements for navigation applications on specific routes or within a specific airspace must be defined in a clear and concise manner.This is to ensure that the flight crew and the air traffic controllers (ATCOs) are aware of the on- board RNAV or RNP system capabilities in order to determine whether the performance of the RNAV or RNP system is appropriate for the specific airspace requirements.|
(ICAO Doc 9613 PBN Manual (Vol I Vol II) Fourth edition 2013, Executive Summary)
ICAO 2012 Flight Plan
2.4 Since 2012, in terms of providing information on aircraft navigation capabilities within the FPL, some changes were made to ITEM 10 and ITEM 18 of the FPL format (the former P-RNAV Item 10a code no longer exists; the meaning of the Item 10a code „R‟ was changed from indicating “RNP type certification” to “PBN approved”; specific PBN capabilities were amplified in Item 18; flight plans may be rejected if R is filed in Item 10a and no PBN information is filed in Item 18).4 For each phase of the flight the PBN NAV special “approvals” are to be identified and correctly filed into the FPL.
|4.4.4 FLIGHT PLAN
126.96.36.199 An operator shall, prior to departure:
a) ensure that, where the flight is intended to operate on a route or in an area where a navigation specification is prescribed, it has an appropriate RNP approval, and that all conditions applying to that approval will be satisfied;
b) ensure that, where the flight is intended to operate in reduced vertical separation minimum (RVSM) airspace, it has the required RVSM approval;
c) ensure that, where the flight is intended to operate where an RCP specification is prescribed, it has an appropriate approval, and that all conditions applying to that approval will be satisfied.
d) ensure that, where the flight is intended to operate where an RSP specification is prescribed, it has an appropriate RSP approval, and that all conditions applying to that approval will be satisfied.
(Doc 4444 Procedures for Air Navigation Services — Air Traffic Management (PANS-ATM) 16th edition 2016, 4.4, 188.8.131.52.)
Filing a FPL does not guarantee its acceptance by the receiving ATS unit as there are a few conditions to be met:
|4.4.3 Acceptance of a flight plan
The first ATS unit receiving a flight plan, or change thereto, shall:
a) check it for compliance with the format and data conventions;
b) check it for completeness and, to the extent possible, for accuracy;
c) take action, if necessary, to make it acceptable to the air traffic services; and
d) indicate acceptance of the flight plan or change thereto, to the originator.
(Doc 4444 Procedures for Air Navigation Services — Air Traffic Management (PANS-ATM) 16th edition 2016, 4.4, 4.4.3)
The above refers to the AIS/Network Manager (“The Network Manager carries out air traffic management network functions for the European Commission, on behalf of EUROCONTROL which was nominated for this task. Working with its stakeholders, the Network Manager develops and runs the European ATM network (covering 43 countries), with the aim of meeting the Single European Sky’s performance targets” (https://www.eurocontrol.int/network-manager)) checking the FPL for certain errors before validating it (such as syntax errors). The matter of navigational capabilities (RNP approval) requires a different kind of validation/ check by the ATS unit(s) concerned (ATC or ATM system check) whenever possible.
(TOC, WP90, Compatibility in clearances issued, 2019)
New airspace concept
2.5 The new airspace concept may require changes to the ATC system interfaces and displays to ensure controllers have the necessary information on aircraft capabilities.
(ICAO Doc 9613 PBN Manual (Vol I Vol II) Fourth edition 2013)
2.6 For the PBN approach navigation specifications, be it RNAV 1, RNAV 2, RNP 1, A- RNP, RNP AR (authorization required) APCH the following requirements must be met:
|Preflight planning: it is the operators and pilots’ responsibility to insert into the FPL the appropriate application for the given RNP operations;
General operating procedures:
a) Operators and pilots should not request or file RNP routes, SIDs, STARs or approaches unless they satisfy all the criteria in the relevant State documents
Either for departure or arrival, the flight crew should always verify that their aircraft navigation system is operating properly and the correct departure/arrival procedure are entered and depicted properly.
Contingency procedures: The pilot must notify ATC of any loss of the RNP capability (integrity alerts or loss of navigation), together with the proposed course of action. If unable to comply with the requirements of an RNP SID or STAR, pilots must advise ATS as soon as possible. The loss of RNP capability includes any failure or event causing the aircraft to no longer satisfy the A-RNP requirements of the route.
In the event of communications failure, the pilot should continue with the RNAV route in accordance with established lost communications procedures.
(ICAO Doc 9613 PBN Manual (Vol I Vol II) Fourth edition 2013 Part B Chapter 3 Implementing RNAV1 and RNAV2)
Air traffic controllers should take appropriate action to maintain separation and to coordinate with other ATC units as appropriate, when informed that the flight is unable to maintain the prescribed level of navigation.
ATC vs PIC responsibility
2.7 No air traffic controller should/ would knowingly issue a clearance/ authorization/ instruction that would contradict crew and/or aircraft capabilities.
Aircraft capabilities are becoming increasingly complex, and it is therefore reasonable to suspect that ATM systems are not always keeping up with the pressure from the aeronautical industry. In this matter, regardless of the information provided by operators (via FPL), it is only fair to assume that this would/ should not always translate into full ATC awareness.
The confirmation of acceptance of a given instruction/ clearance lies with the pilot-in-command, and a clearance does not relieve him/her of any responsibility whatsoever in connection with a possible violation of applicable rules. So if an ATCO issues a clearance for a procedure for which the aircraft and/or the pilot are not certified and approved, it cannot be used as justification for breaking the rules.
|4.5 AIR TRAFFIC CONTROL CLEARANCES
4.5.1 Scope and purpose
184.108.40.206 Clearances are issued solely for expediting and separating air traffic and are based on known traffic conditions which affect safety in aircraft operation. Such traffic conditions include not only aircraft in the air and on the maneuvering area over which control is being exercised, but also any vehicular traffic or other obstructions not permanently installed on the maneuvering area in use.
220.127.116.11 If an air traffic control clearance is not suitable to the pilot-in-command of an aircraft, the flight crew may request and, if practicable, obtain an amended clearance.
18.104.22.168 The issuance of air traffic control clearances by air traffic control units constitutes authority for an aircraft to proceed only in so far as known air traffic is concerned. ATC clearances do not constitute authority to violate any applicable regulations for promoting the safety of flight operations or for any other purposes; neither do clearances relieve a pilot-in- command of any responsibility whatsoever in connection with a possible violation of applicable rules and regulations.
(Doc 4444 Procedures for Air Navigation Services — Air Traffic Management (PANS-ATM) 16th edition 2016, Chapter 4, 4.5)
The requirements on early provision of type of approach to be expected (as early as in the en- route flight phase) are in place to assist the pilot to know what to expect and also to have time to notify ATC if unable to comply or if a different clearance is required:
|6.5 PROCEDURES FOR ARRIVING AIRCRAFT
22.214.171.124 At aerodromes where standard instrument arrivals (STARs) have been established, arriving aircraft should normally be cleared to follow the appropriate STAR. The aircraft shall be informed of the type of approach to expect and runway-in-use as early as possible.
6.5.4 Instrument approach
126.96.36.199 The approach control unit shall specify the instrument approach procedure to be used by arriving aircraft. A flight crew may request an alternative procedure and, if circumstances permit, should be cleared accordingly.
(Doc 4444 Procedures for Air Navigation Services — Air Traffic Management (PANS-ATM) 16th edition 2016, Chapter 6, 6.5)
More on the pilot and operator responsibilities is found in Doc 9613:
|188.8.131.52 Operator responsibilities
a) Each operator is responsible for the training of pilots for the specific RNP AR APCH operations exercised by the operator. The operator must include training on the different types of RNP AR APCH procedures and required equipment. Training must include discussion of RNP AR APCH regulatory requirements. The operator must include these requirements and procedures in their flight operations and training manuals (as applicable). This material must cover all aspects of the operator’s RNP AR APCH operations including the applicable operational authorization. An individual must have completed the appropriate ground and or flight training segment before engaging in RNP AR APCH operations.
(ICAO Doc 9613 PBN Manual (Vol I Vol II) Fourth edition 2013)
With regard to pilot responsibilities, ICAO is clarifying the issue in the latest version of Doc 8168, Procedures for Air Navigation Services — Aircraft Operations (PANS-OPS), effective November 2018.
1.7.6 PBN operational approval
184.108.40.206 Pilots shall verify, before operating on any PBN route or procedure, that they have approval to operate on the navigation specification used. Where there are additional restrictions, for example sensor use or optional functionality as discussed in 1.8.2 above, the pilot shall also verify that these restrictions are complied with.
1.5.3 PBN operational approval
220.127.116.11 Pilots shall verify, before operating on any PBN route, that they have approval to operate on the navigation specification(s) used. Where there are additional restrictions, for example sensor use or optional functionality, the pilot shall also verify that these restrictions are complied with.
1.4.5 PBN operational approval
18.104.22.168 The pilot shall verify, before operating on any PBN route or procedure, that they have approval to operate on the navigation specification used. Where there are additional restrictions, for example sensor use or optional functionality as discussed in 1.4.2, the pilot shall also verify that these restrictions are complied with.
1.3.6 PBN operational approval
22.214.171.124 The pilot shall verify, before operating on any PBN route or procedure, that they have approval to operate on the navigation specification(s) used in the design of the procedure. Where there are additional restrictions, for example sensor use or optional functionality as discussed in 1.3.2, the pilot shall also verify that these restrictions are complied with.
7.6.6 PBN operational approval
126.96.36.199 The pilot shall verify, before operating on any PBN route or procedure, that they have approval to operate on the navigation specification used. Where there are additional restrictions, for example sensor use or optional functionality as discussed in 7.6.2, the pilot shall also verify that these are complied with.
(ICAO Doc 8168, Procedures for Air Navigation Services — Aircraft Operations)
From all of the above one can conclude that “it is unreasonable to expect that, in every case, ATC will be in a position to check whether clearances issued by ATC conform to aircraft and/or aircrew capabilities.”
3.1 It is crews’ and operators’ responsibility to ensure that the aircraft and the flight crew are certified and qualified to operate in the airspace, on a procedure or along an ATS route.
3.2 Crews should always be aware of the approach procedures in use and they should also notify air traffic controllers whenever, for whatever reasons (malfunctions), discrepancies between FPL data and on-board capabilities arise.
3.3 Controllers assume that the aircraft and flight crews are suitably certified and qualified for PBN operations.
3.4 Controllers should also be trained in basic understanding of area navigation concepts, the relationship and fundamental differences between RNAV and RNP operations, and how their implementation affect control procedures, separation and phraseology.
3.5 Aircraft capabilities should be known by ATC in advance and easily accessible to the controller without creating additional clutter on the CWP. As air traffic controllers use information collected from the FPL and processed within the ATM system, the system itself should be provided with the capability to crosscheck or compare FPL data regarding aircraft navigational capabilities against procedures or airspace requirements in force.
3.6 Automation should be in place to automatically detect if, according to flight plan information, an aircraft is unable to execute a PBN procedure cleared by ATC.
4.1 It is recommended that:
Air traffic controllers shall be able to issue any clearance to an aircraft based on the capabilities in its flight plan. Automation should be in place to detect if, according to flight plan information, an aircraft is unable to execute any procedure in use.
is inserted as the second paragraph to IFATCA TPM, ATS 3.42.
4.2 It is recommended that existing IFATCA ADME 2.10 policy:
The variety of approach types, and the associated complexity to the controller, should be reduced. The type of approach sub-category should be transparent to the controller in order to maintain an acceptable workload. The approach sub-category and the associated minima should be determined by the aircrew based upon equipment fit and training.
is amended to read:
The variety of approach types, and the associated complexity to the controller, should be reduced. The type of approach sub-category should be transparent to the controller in order to maintain an acceptable workload.
Even if they are being provided with all the necessary information on an aircraft navigational capabilities (FPL, displayed info) air traffic controllers should not be responsible to check aircraft or air crew navigational capabilities prior to issuing an approach clearance as it is the responsibility of operators and crews to comply with the PBN requirements for the given airspace.
and is included in the IFATCA Technical and Professional Manual, ADME 2.10
IFATCA Technical and Professional Manual, 2018 edition.
ICAO DOC 4444 Procedures for Air Navigation Services — Air Traffic Management (PANS-ATM) 16th Edition 2016.
ICAO DOC 9613 PBN Manual, (Vol I Vol II) Fourth edition 2013.
ICAO DOC 7030 Regional Supplementary Procedures, 5th edition 2008.
ICAO DOC 8071 Manual on Testing of Radio Navigation Aids Vol II 5th edition 2007.
ICAO DOC 8168 Procedures for Air Navigation Services — Aircraft Operations, (PANS-OPS), Volumes I (5th edition 2006) and II (6th edition 2014).
ICAO DOC 9426 Air Traffic Services Planning Manual, 1st provisional edition 1984.
ICAO DOC 9689 Manual on Airspace Planning Methodology for the Determination of Separation Minima 1st edition 1998.
ICAO DOC 9849 Global Navigation Satellite System (GNSS) Manual 3rd edition 2017.
ICAO DOC 9859 Safety Management Manual (SMM) 4th edition 2018.
ICAO DOC 9905 Required Navigation Performance Authorization Required (RNP AR) Procedure Design Manual 2nd edition 2016.
ICAO DOC 9992 Manual on the Use of Performance-Based Navigation (PBN) in Airspace Design 1st edition 2013.
ICAO Annex 4 — Aeronautical Charts 11th edition July 2009.
ICAO Annex 6 — Operation of Aircraft Part I 11th edition July 2018.
ICAO Annex 8 — Airworthiness of Aircraft 12th edition July 2018.
ICAO Annex 10 — Aeronautical Telecommunications, Volume I — Radio Navigation Aids 7th edition July 2018.
ICAO Annex 11 — Air Traffic Services 15th edition July 2018.
ICAO Annex 15 — Aeronautical Information Services 16th edition July 2018.
ICAO Annex 17 — Security 10th edition April 2017.
ICAO Circular 336 2015.
EASA European Plan for Aviation Safety EPAS 2018–2022.
EASA AMC 20-26.
Commission Regulation (EU) No 1178/201189i8.
Commission Regulation (EU) 2016/539.
Guidance for the provision of NAV/COM/SUR information in the New ICAO 2012 Flight Plan.
PBN NAVIGATION OPERATIONAL APPROVAL HANDBOOK.
Crew briefing flying to Nice (2018).
A few considerations on the PBN concepts
PBN defines aircraft navigation requirements in terms of the accuracy, integrity, continuity and functionality required for the proposed operations. ICAO DOC 9613 PBN Manual states that:
|PBN definition: Area navigation based on performance requirements for aircraft operating along an ATS route, on an instrument approach procedure or in a designated airspace.|
Alongside Communications, ATS Surveillance and ATM, PBN is one of the components of the Airspace Concept. The latter is composed of three parts: The Navigation Specification, the Navaid Infrastructure and the Navigation Application.
PBN encompasses two types of navigation specifications: RNAV (aRea NAVigation), and RNP (Required Navigation Performance). The difference between the RNAV and RNP navigation specifications is that onboard performance monitoring and alerting is required for RNP but not for RNAV operations.
Warnings will be triggered should the accuracy of the aircraft’s position fall outside a defined limit. For instance, setting an RNP value of 0.3 NM means that the on-board performance monitoring will alert the pilot if it estimates the error of the navigation system to exceed 0.3 NM.
To ATC, the RNP navigation offers a significantly greater confidence that aircraft will maintain a given route more accurately, thus making it possible to design routes closer to one another and increase airspace capacity.
These are a set of aircraft and flight crew requirements needed to support performance-based navigation operations in a defined airspace.
As mentioned before, there are two types of navigation specifications:
a) Required Navigation Performance (RNP) Specification – Area navigation specification that includes the performance control and alerting requirement, designated by the prefix RNP; e.g., RNP 4, RNP APCH, RNP AR (authorization pending) APCH.
b) Area Navigation (RNAV) Specification – Area navigation specification that does not include the performance control and alerting requirement, designated by the prefix RNAV; e.g., RNAV 5, RNAV 2, RNAV 1.
(ICAO Doc 9613 PBN Manual (Vol I Vol II) Fourth edition 2013)
In the table below there are some examples of the required navigation specifications over different phases of flight.
(ICAO Doc 9613 PBN Manual (Vol I Vol II) Fourth edition 2013)
As shown in the drawing below different RNP specifications may be used for the different phases of the flight:
(Doc 9613 Figure II-A-1-1)
RNP AR (Authorization Required) approaches include unique capabilities that require special aircraft and aircrew authorization similar to Category (CAT) II/III ILS operation.
Benefits of implementing PBN:
Among the benefits of implementing PBN are:
- more efficient design of airspace and procedures which collectively result in improved safety, capacity, predictability, operational efficiency, and environmental impacts.
- environmental benefits because aircraft are able to reduce emissions and fuel consumption.
- Increase safety through continuous descent procedures that reduce the risk of controlled flight into terrain and loss of control.
- Improve airport and airspace access in all weather conditions.
- PBN together with GNSS allow straight-in approaches to be designed for most runways. ICAO data shows that straight-in approaches are 25 times safer than circling approaches.
- RNP and RNAV-based arrival and departure routes can complement, and even replace, radar vectoring, thereby reducing approach and departure controller workload and/or frequency congestion.
(PBN Implementation from Industry Perspective (Airbus Pro Sky) Nov 2015)
Last Update: October 2, 2020