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Towards a safer sky with EGNOS
Europe’s progress towards a full scale LPV implementation – Current status(fi rst implementations), lessons learnt and challenges for the future |
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The European Geostationary Navigation Overlay Service (EGNOS) is Europe’s first venture into satellite navigation, providing an augmentation signal to the Global Positioning System (GPS) Standard Positioning Service (SPS). It has been a long way for Europe, since the beginning of the EGNOS programme in the late 90’s, culminated with the declaration of availability of the three EGNOS Services:
• The Open Service (OS), targeting mass market applications, declared available by the European Commission on the 30th of October 2009.
• The Safety of Life (SoL) Service, which main objective is to support civil aviation operations down to LPV (Localiser Performance with Vertical guidance) minima, declared available by the European Commission on the 2nd of March 2011.
• The EGNOS Data Access Service (EDAS) declared available by the European Commission on July 2012, is oriented to users in different domains of application such as Location Based Services (LBS), Assisted-GNSS (A-GNSS) concepts, a broad range of services in professional GNSS markets, and related R&D activities.
As most of the Satellite Based Augmentation System (SBAS) systems around the world, EGNOS was defined, designed and developed to be used primarily for aviation. Therefore the SoL Service is “the service” that EGNOS was originally meant to provide, justifying its very existence. Thus, the introduction of the EGNOS SoL Service in the EATMN (European Air Traffic Management Network) was, maybe, the most important milestone for the whole EGNOS project.
From the 2nd of March 2011 onwards all European Air Navigation Service Providers (ANSPs) were enabled to proceed with EGNOS based procedures publications, with the LPV procedure in Pau (France) being the first operational procedure on the 17th of March 2012.
European Framework for LPV Implementation
EGNOS benefits for aviation
During the International Civil Aviation Organisation (ICAO) 36th Assembly in September 2007, it was discussed about the growing importance of Performance Based Navigation in respect to aviation safety. The recommendations laid down to States in Resolution 36-23 on Performance Based Navigation (PBN) goals were of particular interest at that time. The Assembly urged States to complete PBN implementation plans by 2009 to achieve “Implementation of approach procedures with vertical guidance (APV) (Baro-VNAV (Vertical Navigation) and/or SBAS) for all instrument runway ends, either as the primary approach or as a back-up for precision approaches by 2016 with intermediate milestones as follows: 30 per cent by 2010, 70 per cent by 2014”.
The ICAO 37th Assembly in October 2010 amended the above mentioned resolution by adding, concerning APV, “implementation of straight-in Lateral Navigation (LNAV) only procedures, as an exception, for instrument runways at aerodromes where there is no local altimeter setting available and where there are no aircraft suitably equipped for APV operations”
EGNOS, as Europe’s SBAS, guarantees the level of vertical performance required for PBN with the potential to lower pilot’s decision height down to 250 feet (200 feet in the future) without the need for ground navigation aids like ILS. Baro- VNAV performance will not allow APV Baro minima lower than 250 ft. EGNOS provides real benefits to airspace users in terms of accessibility of airports, reducing delays, diversions and cancellations while maintaining today’s high safety levels.
In addition, EGNOS is free of charge and will allow for savings in maintenance costs associated with ground-based conventional navigation aids used for approach. It increases safety by allowing Instrument Flight Rules (IFR) approaches at difficult locations or under meteorological conditions where previously such approaches were not possible due to safety concerns. In addition, EGNOS provides a convenient and inexpensive back up for runways already equipped with ILS ensuring IFR approach capability even when the ILS is not available.
An independent cost-benefit analysis commissioned by the European GNSS Agency (GSA) indicated that the benefits for Europe’s aviation sector will add up to €2.4bn by 2030. Of this, about €1.2bn will be saved due to reduced flight delays, diversions and cancellations. Another €900m in benefits will be due to the reduction of Controlled Flight Into Terrain (CFIT) accidents. And €300m will be saved due to the phasing out of infrastructure navaids.
Another study by EUROCONTROL and Helios compared the use of Baro vertical navigation technology with a satellitebased augmentation system (SBAS) such as EGNOS for APV landings. APV Baro provides vertical navigation by measuring changes in air pressure with altitude. For airports that lack ILS on all runway ends, the benefits of using APV Baro for landings can range from €50,000 to €200,000 a year in savings (estimated benefit of reduced aircraft disruptions). Cost savings will depend on the airport traffic level, the number of ILS installed, the airport topography (and its impact on the minima that can be achieved) and local meteorological conditions. Using EGNOS in addition to APV Baro can provide an additional €20,000 a year in benefits, compared to using only Baro-VNAV.
European pre-operational past experiences
A number of R&D projects cleared the way to the adoption of EGNOS in European aviation, addressing the needs of all involved stakeholders and evidencing the already mentioned benefits EGNOS brings to aviation.
We could highlight GIANT-2 project, which introduced EGNOS enabled operations to end users within identified niche markets, by using integrated avionics onboard and performing preoperational flight demonstrations, before EGNOS certification.
In particular, a Cessna 172 airplane performed 9 LPV approaches and demonstrated EGNOS’ potential in helping small and medium airports run more safely and efficiently.
Complementarily other GIANT-2 trial tests involved Search and Rescue (SAR) helicopters (Agusta Westland) in order to use the navigation technology for maritime search and rescue by the Italian Coast Guard. Emergency services rely on the speed and versatility of helicopters, because of their ability to reach locations without landing aids, but suffer from the impact of adverse weather conditions which can often stop them landing because instrument approaches are not available.
The purpose of these flight tests was to assess the vertical guidance offered, and to examine the impact on improved safety for helicopter approaches.
Pilots and air traffic controllers (ATCOs) provided very positive feedback being enthusiastic about the benefits this new navigation capability would bring to European civil aviation.
On rotorcraft’s side, HEDGE project explored EGNOS exploitation for rotorcraft operations.
As of today, helicopters are underserved by the current European ATM system which was really designed for fixed wing aircraft. EGNOS allows the development of high performance operations, including approaches to places which cannot install traditional navigation aids such as hospitals and oil rigs, as validated in HEDGE.
LPV approaches and the PBN concept
PBN represents a fundamental shift from sensor-based to performance-based navigation. Significantly it is a move from a limited statement of required navigation accuracy to a more extensive statement of required performance of the area navigation system in terms of accuracy, integrity and continuity. PBN describes how this performance is to be achieved in terms of aircraft and crew requirements.
ICAO sees PBN as the vehicle to promote global interoperability world-wide. PBN provides a set of navigation specifications for different phases of flight which can be used as needed by regions and States, thereby avoiding the proliferation of different certification and operational approvals.
The ICAO PBN Manual (Doc 9613) replaced the Required Navigation Performance (RNP) Manual in 2008, with the objective to further improve safety, provide an enabler for extra airspace capacity improve interoperability and consequently reduce costs for operators.
Approach has been historically sensor driven, but will become performancedriven with the introduction of the RNP APCH and RNP AR APCH navigation specifications, fully in line with the ICAO Assembly Resolution A37-11.
At the end of 2012 and the update to the PBN Manual, the RNP APCH navigation specification will officially include approach to all 4 minima: LNAV, LP (Localizer Performance), LNAV/ VNAV and LPV minima (Volume II, Part C, Chapter 5 [1]). Approaches to LNAV and LP minima are Non Precision Approaches, whereas approaches to LNAV/VNAV and LPV are APV (Approach with Vertical guidance).
Despite they are true RNP applications (with monitoring and alerting functions) RNP APCH procedures are published on charts with the title Area Navigation (RNAV) (GNSS) RWY XX. Consequently and according to PANS-ATM [3] section 12.3, clearance by ATC to perform an RNP APCH procedure is given in terms of “clearance to RNAV approach RWY xx”.
These approach charts can have one or several minima lines to accommodate the needs and capabilities of the different airspace users on the final approach segment towards the runway. Note that the design of the Initial approach segment and the missed approach can either be done according to RNP APCH criteria (common to all “types” of RNP APCH) or to other criteria like RNAV 1.
With the aim to reinforce Europe’s commitment towards PBN Implementation, EUROCONTROL received a mandate from the European Commission (EC) to draft an Implementing Rule (IR) on PBN for Europe. The IR will define navigation requirements and identify the functionalities required in en-route and terminal air-space, including arrival and departure, and also approach. Eurocontrol delivered a Regulatory Approach Document (RAD) which was accepted by the EC in March 2013 and will produce a final report, by the end of 2013, aimed at being the basis of the PBN IR to be finally published by the EC in 2014.
Drafting the IR will account for the outcomes of an analysis of the areas of the regulatory provisions that could be covered (on the ANSP and/ or on the airspace users) to ensure the desired interoperability. Finally, the overall goal of the implementing rule will be to ensure harmonised and coordinated implementation of ICAO Assembly Resolution AR 37/11 within the European (ATM) Network.
The LPV Implementation Process
The ANSP Perspective
There are two ANSPs involved in the implementation of EGNOS based operations in Europe (in particular LPVs):
• ESSP, the EGNOS Service Provider, in charge of the EGNOS SoL navigation service. All ESSP oversight activities have been taken over by European Aviation Safety Agency (EASA) since the end of 2012.
• The Air Traffic Services (ATS) Service Provider responsible for the LPV procedure publication and the corresponding ATS services, referred hereafter as “the ANSP”. The competent supervisory authority for the ANSP will be its National Supervisory Authority (NSA role played by the corresponding State’s Civil Aviation Authority in most cases) referred hereafter as “the NSA”.
As key prerequisites for EGNOS based operations implementation:
• The NSA needs to agree to the use of GNSS in their airspace.
• The required EGNOS SoL Service availability at the aerodrome concerned must be confirmed in the EGNOS Safety of Life Service Definition Document [6], published by the EC with the support of ESSP. A signal availability and spectrum check should be performed as well but a real time GNSS signal monitoring is not required, as integrity is monitored on board the aircraft.
Both ANSPs’ activities are ruled by the Single European Sky (SES) provisions where we can highlight the following required processes specifically linked to the LPV implementation process:
• The certification of ESSP, as EGNOS Service Provider (the ATS provider is supposed to be certified as well) as required by European Union (EU) Regulation No 1035/2011 [4].
• The establishment of the socalled “EGNOS Working Agreement” (EWA) between these two ANSPs containing:
– ESSP SoL Performance commitment, in line with the EGNOS SoL Service Definition Document [6]
– ESSP-ANSP coordination for contingency management.
– ESSP-ANSP working arrangements including:
– EGNOS NOTAM (Notice to airmen) Proposals provision (when required)
– GNSS Data recording: in the context of post accident/ incident investigations
– Collaborative Decision Making (CDM): enabling the ANSP involvement in ESSP decision making process to minimize potential impact of ESSP planned activities in the corresponding EGNOS based operations.
• The issuance of the EGNOS system Declaration of Verification (DoV) by ESSP, ensuring its compliance with EU Regulation No 552/2004 [5].
• The rest of activities linked to the LPV procedure publication following the same approval process defined for any other approach procedure publication in line with the procedure design criteria provided in ICAO PANS-OPS [7].
The operator perspective
From an operator perspective there are two possibilities in terms of GNSS (GPS/ WAAS/EGNOS) avionics certified equipment, stand-alone or integrated, meeting the applicable European Technical Standard Orders (ETSOs):
• ETSO-C145: Airborne Navigation Sensors using the GPS augmented by WAAS.
• ETSO-C146: Stand-Alone Airborne Navigation Equipment using the Global Positioning System (GPS) Augmented by the Wide Area Augmentation System (WAAS).
These regulations refer to RTCA DO- 229 [8], which is the current requirement for GPS receivers having the WAAS/ EGNOS capability, and is the certification basis for ETSO-C145 (DO-229A) and ETSO-C146 (DO-229B). Once a certified EGNOS enabled avionics equipment is selected to be installed, the operator must obtain the following approvals:
• The Airworthiness Approval applying for the corresponding Type Certificate (TC), Restricted Type Certificate (RTC) or Supplemental Type Certificate (STC) to European Aviation Safety Agency (EASA).
To ease this process EASA has generated an Acceptable Means of Compliance (AMC) standards to support and facilitate the implementation of EGNOS based operations within the context of the European Air Traffic Management Network (EATMN). These AMCs ([9] and [10]) provide some acceptable means that can be used to obtain airworthiness approval also defining the operational criteria necessary to conduct safely such approach operations in designated European airspace.
Complementarily to [9], EASA published a Certification Memorandum (CM) clarifying the acceptability of the use of GPS/EGNOS geometric altitude as a source of altitude for approaches to LNAV/VNAV minima.
Applications for Airworthiness Approval can be made to EASA on the basis of a Certification Review Item (CRI). In fact, a number of certification projects have been already completed, under Type Certificate (TC) or a Supplemental Type Certificate (STC) projects together with the validation of Garmin’s FAA All Model List (AML) STC for the GTN series.
• The Operational Approval: The avionics installation involves not only the technical aspects directly related to the airworthiness of the aircraft but also addresses those aspects related to the changes that such modification could induce in its operation.
Those changes must be fully assessed in order to ascertain that the aircraft modification does not pose additional hazards and therefore that the appropriate safety level is maintained.
To this purpose, an Aircraft Operational Qualification is intended to assess all the elements relating to the training and qualification of flight crews (both cockpit and cabin), all elements of compliance with operational rules including normal, abnormal and emergency procedures, and to update the required operational documentation (POH (Pilot Operating Handbook), AFM (Aircraft Flight Manual), MEL (Minimum Equipment List)). This process is managed by the National Supervisory Authority (NSA) of the aircraft’s State of registry based on [9], [10] and [11].
Today’s GNSS penetration in the global aviation market is approximately 90%, mainly driven by the large sales volume in General Aviation (GA), as described in the GNSS Market Report issue 2, published by GSA in 2012. Over the last few years the penetration of GNSS in commercial aviation has increased with sustained sales, and it is expected to increase from 70% to 90% by 2020.
The expected shipments of EGNOS enabled devices is expected to dominate the market through the regional, business and general aviation segments in the next decade. The penetration of SBAS enabled units in regional aviation is estimated as close to 9% and is expected to increase up to 39% by 2020. Sales already achieved within business and general aviation can now be operationally used to deliver benefits, and is expected to increase from some 26% in 2012 to 77% in 2020.
Business and general aviation are key niche markets for EGNOS based operations introduction at this early stage. Today, almost all new navigation equipment sold by general aviation manufacturers is SBAS capable and IFR pilots can decide to install a stand-alone SBAS enabled receiver for a relatively small price.
A survey performed by GSA confirmed that the vast majority of the European GA IFR community (85%) is interested in installing and using SBAS or have at least considered it before. Indeed, approximately 48% of participants indicated that their aircraft are already SBAS approved, although it does not necessarily imply that they have operational approval to fly LPV approach procedures.
Availability of approach procedures and equipage/certification costs are the main barriers dissuading non-SBAS equipped GA users from upgrading.
In order to tackle these issues, GSA has launched a roadshow, in collaboration with EASA, in order to increase awareness on the safety benefits provided by EGNOS, providing practical guidance on how to certify an aircraft and facilitate getting EGNOS-specific landing procedures published and available for general aviation.
EGNOS SoL Service Roadmap
In close coordination with the European Commission (responsible for the EGNOS Programme Management) ESSP has recently published the EGNOS Services Roadmap documents (available at http:// www.essp-sas.eu/printed_documents).
These documents provide a high-level overview of the three EGNOS services’ current status and their expected evolution, linked to the consecutive EGNOS system releases (ESR) deployment and the information/interfaces improvements described therein, structured in 4 different categories: Service Area, Service Level, Service Robustness and User Interfaces.
Particularly the EGNOS SoL Service roadmap shows the following planned milestones up to 2015, materializing how the SoL service is expected to evolve in the short-midterm and specifically where and when LPV capability will be enabled in the different EU member States areas:
• Service Area: Two main service area extensions linked to the deployment of the following ESRs:
– ESR v2.3.1: Deployed in February 2012 introducing a relevant coverage extension mainly to the south and east of Europe. Figure 2: EGNOS APV-I availability with ESR v2.3.1
– ESR v 2.4.1: To be deployed in the beginning of 2015 targeting to provide APV-I availability to EU28 Member States.
• Service Level: The most relevant improvement included in this category is the introduction of LPV 200 capability in the beginning of 2015.
• Service Robustness: Several robustness improvements associated with the following ESRs deployment:
– ESR v 2.3.2: To be deployed in October 2013
– Inclusion of 2 new Ranging and Integrity Monitoring Stations (RIMS) stations
– Improved Ionospheric monitoring
– ESR v 2.4.1: To be deployed in early 2015
– Inclusion of 2 new RIMS stations
– SES ASTRA (SES-5) replacing PRN 120
– SES ASTRA 5-B replacing PRN 124 (Artemis)
– EGNOS Wide Area Network enhancement
• User Interfaces:
– The EGNOS helpdesk (egnoshelpdesk@ essp-sas.eu) extended its operating hours to H24 every day of the year being available to receive user requests via phone call and e-mail since July 2012.
– The EGNOS User Support Website (http://egnos-user-support.esspsas. eu) is being re-organised to provide specific contents for each EGNOS Service in a differentiated way before the end of 2013.
– Interfaces within the EGNOS Working Agreement (EWA). Main improvements:
– Improved Contingency Communication to ANSPs achieved in September 2012.
– Progressive improvements to EGNOS NOTAM proposals generation.
European LPV Implementation Status
ESSP has concluded 12 different EGNOS Working Agreements, since the SoL Service was declared available in March 2011, with the following ANSPs: DSNA (France), Skyguide (Switzerland), Guernsey Airport (Bailiwick of Guernsey, Channel Islands), DFS (Germany), ENAV (Italy), Austrocontrol (Austria), NATS (UK), AENA (Spain), PANSA (Poland), ANS CR (Czech Rep), HIAL (UK) and EDAL (UK). On the ground of these EWAs the following EGNOS based approaches have been published in Europe up to now:
• DSNA (France): 50 LPV procedures in 39 airports.
• Skyguide (Switzerland): 4 LPV procedures in 4 airports.
• Guernsey Airport (Bailiwick of Guernsey): 2 LPVs in Alderney Airport.
• DFS (Germany): 73 APV Baro- VNAV procedures authorized to be flown with EGNOS vertical guidance in 32 different airports plus 14 LPVs in 9 of them.
• ENAV (Italy): 7 LPV procedures in 4 airports.
• AENA (Spain): 2 LPV procedures at 1 airport.
These pioneer EGNOS based operations implementations are paving the way for the coming ones that, in line with the different European ANSP’s plans shared in different fora and the European funded implementation projects’ objectives, will triple current figures in the short term generating a snowball effect that will be extended soon all across Europe.
ESSP makes this information available through its website (http://www.essp-sas.eu/) where an “EGNOS based procedures map” is displayed together with a detailed table listing these procedures already in place.
At a higher level, EUROCONTROL has developed an interactive map called the “PBN Approach Map Tool”. The tool provides a means to illustrate the implementation status and plans for PBN Approaches, including RNP APCH (to all 4 minima: LNAV, LP, LNAV/ VNAV and LPV) and RNP AR APCH.
Implementation status information is factual (approach procedures are available in national AIP (Aeronautical Information Publication)). Implementation plans are collected from individual countries. Whether these publication plans will materialise and when is dependent on a number of factors (e.g. difficulties to collect obstacle data for procedure design, unforeseen issues faced in the procedure design phase or delays in the approval for publication by the supervisory authority) and should not be considered as commitments by a country.
The tool shows information about individual types of approaches or of APV in general. This also shows the evolution over time of the percentage of runways ends where approaches are published.
This is freely available to any user of the EUROCONTROL extranet (Onesky Online) at the following link: https://extranet.eurocontrol.int/http:// prisme-newgis.hq.corp.eurocontrol.int/pbn/.
Guidance Material, Supporting Cells and Existing Incentives
EGNOS based operations adoption is in its initial stage. Except for those States/ANSPs most active in GNSS, involved in EGNOS research & development projects for long, most European States/ANSPs/operators start now to assess the feasibility and cost/benefits of implementing EGNOS based operations to fulfill ICAO 37th Assembly Resolutions on what regards to APV implementation.
There is a huge effort being done by the European Commission for the dissemination and awareness of the aviation community on EGNOS with the lead of the GSA and the support of ESSP.
ESSP SoL Users’ consultation 2012 revealed a clear need, as identified by the European ANSPs consulted, for support and guidance to boost EGNOS based operations implementation towards ICAO Assembly resolutions in coordination with existing funding programmes and implementation initiatives.
Complementarily, although there is a clear recognition of the current effort being done up to now, more effort on guidelines / awareness material generation and dissemination is requested.General and Business aviation operators flying to small-medium regional airports are clearly identified as best candidates obtaining higher benefits from LPV early adoption. Therefore, an improvement on the support/link with these aviation communities to provide guidelines/awareness material to trigger the necessary decisions (CBAs (Cost Benefit Analysis), technical guidelines, awareness material, etc.) is requested.
What is being done to answer this need?
• Guidance Material: EUROCONTROL, the European Organisation for the Safety of Air Navigation, led the development of “Guidance material for RNP APCH (Approach) implementation” which was published by ICAO as the ICAO EUR DOC 025. The guidance are to assist first in identifying the type of approach which is the most relevant to publish at the airport (EGNOSbased LPV is one option) and then guides through the implementation process. These guidelines are making reference to other reference material amongst which:
– APV SBAS Concept of Operations – APV SBAS generic safety assessment
– European GNSS NOTAM concept
• Supporting Cells:
– ICAO PBN TF: Under the chair of the European and North Atlantic (EUR/NAT) Office, this Task Force is focused on monitoring the deployment of PBN applications (in all phases of flight, and including but not limited to EGNOS-based operations) in the ICAO EUR/ NAT Region. This collects the national PBN implementation plans as requested by ICAO and assist together with the Go- Teams and EUROCONTROL individual countries in the move towards PBN.
– EUROCONTROL RNAV Approach implementation Support Group (RAiSG): The objective of the group is to coordinate the activities necessary for the implementation of RNAV Approaches, including RNP and RNP AR (Authorisation Required) approaches. In coordination with the appropriate (international/ global) organisations, the tasks of the RAiSG include in particular:
– providing a forum for sharing lessons learned – contributing to improving the awareness on RNAV approaches
– monitoring/tracking the deployment progress and plans;
– and supporting/conducting all sorts of technical and experts’ types of activities dealing with operational concepts, infrastructure and airport requirements, procedure design, support to certification, flight inspection, ATC procedure, AIS and NOTAMS, safety assessments, etc.
• European incentives towards EGNOS adoption in Aviation
– ACCEPTA: A co-funding incentive scheme has been established through ACCEPTA project to support ANSPs and airports to design, develop, check, verify and publish EGNOS LPV approach procedures at selected European airports. In addition, the project also supports the installation of EGNOS enabled avionics, certification and operational approval to perform LPV approaches with a number of aircraft of the involved operators. In total, 71 runways at 39 airports and 44 aircraft from 11 operators and end-users are receiving co-funding.
– SHERPA: This project is undertaking specific capacity building activities in Easter Europe countries to map the implementation of EGNOS into the States PBN strategy.
– FILGAPP: Looking at operations evolutions, curved approaches enabled by EGNOS are being investigated and several flight trials will be performed in 2013.
– HEDGE NEXT: It targets the operational implementation of EGNOS into the rotorcraft domain, by supporting the certification of helicopters and APV implementation in selected sites from Spain, Poland and Switzerland, involving national rotorcraft leader operators on emergency services. Moreover, HEDGE NEXT is creating lowlevel RNAV routes that intercept previous SOAP (SBAS Offshore Approach Procedure) procedure criteria implemented in the North Sea and moves forward on the development, test and validation of curved approaches for helicopters using GPS and SBAS as sensor (PinS and advanced PinS concepts)
– SIRAJ supports the EGNOS service extension to the areas covered by ACAC and ASECNA by promoting and demonstrating the benefits of EGNOS for civil aviation in a real environment.
Other SBAS based operations implementation
APV Baro-VNAV
In addition to APV SBAS, the use of SBAS on RNAV(GNSS) approach procedures is also possible for performing APV Baro-VNAV procedures down to the published LNAV/VNAV minimum. Anyhow, the State publishing the procedure has to confirm that they allow APV Baro procedures to be flown with either Baro-VNAV or SBAS equipment. In this case, EGNOS NOTAMs are provided accordingly to inform on a possible unavailability of the procedure down to LNAV/VNAV. In the US this is also permitted and the PANS OPS procedures design criteria allow this possibility.
Class 2, 3 or 4 approved SBAS aircraft avionics are a requirement for the use of vertical guidance with EGNOS on APV Baro-VNAV procedures.
As an example, there are 73 APV Baro-VNAV procedures authorized to be flown with EGNOS vertical guidance in Germany. Other countries, as France, also authorise the use of EGNOS for APV Baro-VNAV and more procedures will be available in the near future throughout Europe.
PinS
The Point in Space (PinS) concept consists in flying under Instrument Meteorological Conditions (IMC) to/ from a Point-in-Space located in the vicinity of the landing/departure site. The segment joining the PinS and the landing/departure site is flown visually but does not require VFR minima. The main advantage is that PinS procedures allow IFR flights to/from non-IFR sites (aerodromes, heliports, helidecks).
PinS LPV approach procedures are progressively being introduced for helicopter operations providing clear benefits for Search and Rescue (SAR), SBAS Off Shore Approach Procedures (SOAP) and Helicopter Emergency Medical Services (HEMS).
Challenges for the future
There are currently a number of areas of research on future SBAS-based operations: surveillance, advanced approach procedures as well as instrument approaches at small airfields.
Surveillance
The high accuracy and integrity of SBAS-based positioning enable to enhance both surface and airborne (e.g. ADS-B) surveillance functions.
Advanced approach procedures
In the frame of the Single European Sky ATM Research Programme (SESAR) 5.6.3 project a new advanced instrument approach procedure based on SBAS is been researched. This advanced procedure is an extension of the ‘ILS-look-alike’ APV SBAS approach by making use of the RF functionality within the RNP APCH navigation specification. Radius to Fix (RF) legs are possible in the initial and intermediate segments as well as in the final phase of the missed approach. The vertical profile of the initial and intermediate segments is flown with the CDA technique (based on barometric vertical positioning) whereas the final approach segment is an APV SBAS down to LPV minima.
Instrument approaches at small airfields
The implementation of LPVs at noninstrument aerodromes is a clear challenge. The minimum runway infrastructure and the minimum level of ATS are key issues to work on.
In the UK, the Civil Aviation Authority (CAA) is developing a policy regarding instrument approach procedures to aerodromes without an instrument runway and/or approach control. A riskbased approach will be followed to regularise existing discrete Instrument Approach Procedure (IAPs) and when considering other aerodromes meeting specific criteria. Mitigation against inferior runway or ATS will be derived subject to an acceptable safety assessment. A consultation was performed over the summer of 2012 and the publication of the Policy and Guidance is expected in 2013.
In addition, the ACCEPTA project is also assessing the operational implementation of EGNOS-based instrument procedures down to LPV in small airfields in Europe that are typically restricted to operate under Visual Flight Rules (VFR).
Acknowledgements
The author would like to thank the following people that have provided an invaluable support in the preparation of this paper: Carlos J. Hernando (Ineco), Juan Vázquez (ESSP SAS), Miguel A. Sánchez and José Luis Fernández (ESSP SAS).
References
[1] ICAO, Performance-Based Navigation Manual, Volume II, Implementing RNAV and RNP (Doc 9613).
[2] ICAO Assembly Resolutions A37-11 and A36-23
[3] ICAO, Doc 4444, Procedures for Air Navigation Services, Rules of the Air and Air Traffic Services (PANS-ATM)
[4] Regulation (EU) No 1035/2011 laying down common requirements for the provision of air navigation services
[5] Regulation (EU) No 552/2004 on the interoperability of the European Air Traffic Management network (the interoperability Regulation)
[6] Safety of Life Service Definition Document (EGN-SDD SoL, v1.0)
[7] ICAO, Doc 8168, Procedures for Air Navigation Services – Aircraft Operations (PANS OPS)
[8] RTCA DO-229 Minimum Operational Performance Standards for Global Positioning System / Wide Area Augmentation System Airborne Equipment
[9] EASA AMC 20-27 Airworthiness Approval and Operational Criteria for RNP APPROACH (RNP APCH) Operations Including APV Baro-VNAV Operations
[10] EASA AMC 20-28 Airworthiness Approval and Operational Criteria for RNP APPROACH (RNP APCH) Operation to LPV minima using SBAS
[11] Commission Regulation (EEC) No. 3922/91 Annex III (EU-OPS) and its subsequent amendments
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