optimal final recommendations - deliverable...

EUROCONTROL Status: Approved /51

This investigation has been carried out under a contract awarded by the European Commission, contract number AIP3-CT-2004-502880

No part of this report may be used, reproduced and/or disclosed, in any form or by any means without the prior written permission

of Airbus France and the OPTIMAL project partners. 2008 - All rights reserved

Document Description: This document presents the re commendations that have been found along the OPTIMAL project. They refer to procedure design, aircraft and rotorcraft airborne systems, as well as ground functions.

Programme: Sixth Framework Programme - Strengthening the competitiveness Contract Number: AIP3-CT-2004-502880 Project Number: FP6-2002-Aero-1-502880 Project Title: Optimised Procedures and Techniques for the Improvement of Approach and Landing Project Acronym: OPTIMAL Deliverable: D8.3 Document Title: Final OPTIMAL recommendations - Deliverable D8.3 Document ID: WP8.3-EEC-066-V1.0-ED-PU Date: 31/10/2008 Status: Approved Classification: PU File Name: OPTIMAL-WP8.3-EEC-066-Final OPTIMAL recommendations-V1.0-ED-PU.doc

OPTIMAL Project Co-ordinator: Airbus

Yohann Roux: [email protected]

Contributing Partners:

EEC, AIF, DLR, INE, ECF, TAT, ISD, NLR, AEN

Approval status

Author Responsible Partner Verification

Project Approval

EEC FRÉDÉRIQUE AYACHE PMC

OPTIMAL final recommendations - Deliverable D8.3

Title: Final OPTIMAL recommendations - Deliverable D8.3 OPTIMAL Project

Date: 31/10/2008 Id: WP8.3-EEC-066-V1.0-ED-PU

/51 Status: Approved EUROCONTROL




Distribution list

COMPANY

Company’s Short Name

NAME

AIRBUS France AIF Yohann Roux

DLR DLR Bernd Korn

INECO INE Luis Chocano, Luis Pérez; José Manuel Álvarez

EUROCOPTER FRANCE ECF Michel Authesserre, Philippe Rollet

THALES ATM TAT Xavier Jourdain

ISDEFE ISF Nicolas Suarez

NLR NLR Robert de Muynck

AENA AEN Aitor Alvarez Rodriguez

EUROCONTROL ERC Frédérique Ayache; Louis Sillard

THALES AVIONICS TAV Didier Hainaut

EUROCOPTER DEUTSCHLAND ECD Wolfgang Kreitmair-Steck

ONERA ONR Claude Barrouil

UNIVERSITY OF LIVERPOOL UoL Gareth Padfield

SMITHS AEROSPACE SIA Peter Allsop

AGUSTA AGU Giuseppe Pagnano

DFS DFS Olaf Weber

SENASA SEN Antonio Pelaez

LVNL LVN

DAVIDSONLtd DAL Jeremy Davidson

GMV GMV Manuel Toledo

SPERRY MARINE SPM Paul Stevens

Northrop Grumman NG David Schooley ; Serge Perrussel

ENAV ENA Giovanni Del-Duca

AIRBUS CENTRAL ENTITY AIC Marcel Garcia

SICTA SIC Claudio Vaccaro

OPTIMAL Project Title: Final OPTIMAL recommendations - Deliverable D8.3

Id: WP8.3-EEC-066-V1.0-ED-PU Date: 31/10/2008





Document Change Log

Version Date Modified Pages

Modified Sections

Comments

0.1 29/03/06 All All Creation

0.2 All Incorporated comments from AEN, INE, AIF and ECF

0.3 06/10/08 All Added EVS section and last comments

1.0 31/10/08 Approved version







TABLE OF CONTENTS

1 LIST OF FIGURES _____________________________________________________ 7

2 LIST OF TABLES_____________________________________ _________________ 7

3 LIST OF ABBREVIATIONS ______________________________ ________________ 8

4 REFERENCES _______________________________________________________ 10

5 INTRODUCTION______________________________________________________ 11

6 CONTINUOUS DESCENT APPROACH PROCEDURES ______________________ 13

6.1 Procedure Overview _______________________________________________________ 13

6.2 Recommendations for operational implementation ______________________________ 14

6.3 Recommendations from airborne functions ____________________________________ 14

6.4 Recommendations from procedure applied to Schiphol airport____________________ 15

7 GNSS-BASED PROCEDURES __________________________________________ 16

7.1 Approach procedures based on GBAS ________________________________________ 16

7.1.1 Procedure overview_____________________________________________________ 16

7.1.2 Recommendations for operational implementation_____________________________ 17

7.1.3 Recommendations from Malaga RWY 13 GBAS PA procedure __________________ 17

7.2 Procedures based on SBAS__________________________________________________ 18



7.2.3 Recommendations from San Sebastian RWY 04 SBAS APV Procedure____________ 19

7.3 Procedures based on ABAS _________________________________________________ 20


7.3.2 Recommendations from procedure design ___________________________________ 21

7.3.3 Recommendations from airborne functions __________________________________ 21







8 ENHANCED VISION SYSTEM___________________________________________ 22

8.1 Overview of the concept ____________________________________________________ 22

8.2 Guidelines for the operational implementation _________________________________ 23

8.3 Open issues_______________________________________________________________ 23

9 DUAL/DISPLACED THRESHOLD OPERATIONS ________________ ___________ 24

9.1 Overview ________________________________________________________________ 24

9.2 Guidelines for the operational implementation _________________________________ 24

9.3 Open issues_______________________________________________________________ 25

10 RNP-AR PROCEDURES _______________________________________________ 26

10.1 Overview of RNP-AR approach procedures____________________________________ 26

10.1.1 Straight-in RNP-AR approach procedures ___________________________________ 26

10.1.2 Curved RNP-AR approach procedures ______________________________________ 27

10.2 Recommendations for RNP-AR procedures____________________________________ 28


10.2.2 Recommendations from airborne functions __________________________________ 30

10.3 Recommendations from applied procedures ___________________________________ 30

10.3.1 Specific curved procedure for RWY 22 in San Sebastian________________________ 30

10.3.2 Specific curved procedure for RWY 31 in Malaga _____________________________ 31

11 ROTORCRAFT SPECIFIC IFR APPROACHES _________________ ____________ 32

11.1 Steep straight-in final approach procedure ____________________________________ 32


11.1.2 Further possible research_________________________________________________ 33

11.1.3 Guidelines for the operational implementation ________________________________ 33

11.2 Curved final approach procedure ____________________________________________ 34










11.2.4 Open issues ___________________________________________________________ 36

11.3 SNI operations ____________________________________________________________ 36

11.3.1 Overview of the concept _________________________________________________ 36



11.3.4 Open issues ___________________________________________________________ 38

11.4 Time-referenced (4D) operations _____________________________________________ 38

11.4.1 Overview _____________________________________________________________ 38


11.4.3 Open issues ___________________________________________________________ 40

12 GROUND FUNCTIONS AND ATC TOOLS _____________________ ____________ 41

12.1 GBAS ___________________________________________________________________ 41

12.1.1 Generic GBAS recommendations __________________________________________ 41

12.1.2 Recommendations from Malaga GBAS ground station performance evaluation ______ 42

12.2 Recommendations related to SBAS ___________________________________________ 43

12.3 Arrival management tools (AMAN) __________________________________________ 45

12.4 Converging runways and final approach display aid (CORADA) __________________ 46

12.5 Advanced safety nets and monitoring aids _____________________________________ 47

12.5.1 Extended OPTIMAL validation activities____________________________________ 47

12.5.2 WTEA further improvement ______________________________________________ 48

12.5.3 Tuning _______________________________________________________________ 48

12.5.4 Training ______________________________________________________________ 48

12.5.5 EUROCONTROL Specification ___________________________________________ 49

12.5.6 Summary from SESAR Master Plan ________________________________________ 50







1 LIST OF FIGURES

Figure 1: Nominal and Optimised CDA procedures ..............................................................13

Figure 2: Simulated EVS image with head-down symbology................................................22

Figure 3: Displaced threshold approach on a dependent runway system [FlughFrank1999] 24

Figure 4: OPTIMAL Curved RNP-AR approach procedure ...................................................28

Figure 5: Rotorcraft steep approach procedure ....................................................................32

Figure 6: Rotorcraft curved approach procedure ..................................................................34

Figure 7: Rotorcraft SNI operations ......................................................................................37

Figure 8: CORADA Dual mode.............................................................................................46

Figure 9: CORADA master/slave mode ................................................................................47

2 LIST OF TABLES

Table 1: Safety Requirements (GBAS PA) ...........................................................................18

Table 2: Safety requirements (SBAS PA) .............................................................................20

Table 3: Input data availability for the Prediction function .....................................................44

Table 4: Input data availability for the Real Time Monitoring function. ..................................45







3 LIST OF ABBREVIATIONS

ABAS Aircraft Based Augmentation System A-CDA Advanced Continuous Descent Approach ADD Aircraft Derived Data AGL Above Ground Level AMAN Arrival MANager ANSP Air Navigation Service Provider AOB Angle Of Bank APV Precision) Approach with Vertical Guidance ATC Air Traffic Control ATCo Air Traffic Controller ATM Air Traffic Management AWOSG All Weather Operations Steering Group CAT Category CFIT Controlled Flight Into Terrain CORADA COnverging Runways and Approach Display Aid CRC Cyclic Redundancy Check CSPR Closely SPaced Runways DA/H Decision Altitude / Height DAP Downlink Aircraft Parameters DMAN Departure MANager DME Distance Measuring Equipment DT Dual/Displaced Threshold EASA European Aviation Safety Agency ECAC European Civil Aviation Conference EDAS EGNOS Data Access System EGNOS European Geostationary Navigation Overlay Service EVS Enhanced Vision System FAA Federal Aviation Authority FAP Final Approach Point FAS Final Approach Segment FATO Final Approach and Take Off area FMS Flight Management System FPAP Flight Path Alignment Point ft Feet (1 metre = 3.2808 ft) GBAS Ground Based Augmentation System Geo Geostationary GNSS Global Navigation Satellite System GPS Global Positioning System HMD Head Mounted Display HUD Head Up Display ICAO International Civil Aviation Organisation







IFPP Instrumental Flight Procedure Panel IFR Instrumental Flight Rules ILS Instrument Landing System IRU Inertial Reference Unit JAA Joint Aviation Authorities LAAS Local Area Augmentation System (FAA) LLZ Localizer LNAV Lateral NAVigation LPV Localizer Performance approach with Vertical guidance MAPt Missed Approach Point MDA/H Minimum Decision Altitude/Height MLS Microwave Landing System MSAW Minimum Safe Altitude Warning NM Nautical Mile/s (1 NM = 1852 meters) NOTAM NOtice To AirMen NSE Navigation System Error NTZ Non Transgression Zones OAS Obstacle Assessment Surfaces OCP Obstacle Clearance Panel OPS Operations OPTIMAL Optimised Procedures and Techniques for the Improvement of Approach and Landing PA Precision Approach RDH Reference Datum Height RF Radius to Fix RIMS Ranging and Integrity Monitoring Station RNAV Area Navigation RNP Required Navigation Performance RPI Reference Path Identifier RTA Requested Time of Arrival SAAAR Special Aircrew and Aircraft Authorization Required SBAS Space-Based Augmentation System SNI Simultaneous Non Interfering (Approaches) STCA Short Term Conflict Alert TCAS Traffic Collision Avoidance System TMA Terminal Manoeuvring Area TWR Tower VDB VHF Data Broadcast VNAV Vertical NAVigation VPA Vertical Path Angle WTEA Wake Turbulence Encounter Advisory WVE Wake Vortex Encounter







4 REFERENCES

1. OPTIMAL Deliverable D2.0 V1.1 Final WP2 report including guidelines and recommendations

2. OPTIMAL Deliverable D2.2.1-2 V1.1 Aircraft Procedure Definition - DT

3. OPTIMAL Deliverable D2.2.1-3 V1.1 Aircraft Procedure Definition - EVS

4. OPTIMAL Deliverable D2.2.-4 V1.0 Aircraft straight-in final LPV approach procedures based on ABAS

5. OPTIMAL Deliverable D2.2.1-5 V1.1 Aircraft straight-in final LPV approach procedures based on SBAS

6. OPTIMAL Deliverable D2.2.1-6 V1.1 Aircraft straight-in final precision approach procedures based on GBAS

7. OPTIMAL Deliverable D2.2.1-8 V1.0 Aircraft procedure definition – Straight-in Final RNP-RNAV

8. OPTIMAL Deliverable D2.2.1-9 V1.0 Aircraft procedure definition – Curved Final RNP-RNAV

9. OPTIMAL Deliverable D2.2.1-11 V1.2 Aircraft procedure definition - ACDA

10. OPTIMAL Deliverable D2.3.1 V1.0 Rotorcraft procedures definition

11. OPTIMAL WP5 recommendations to WP8.3

12. OPTIMAL Deliverable D5.0.1 WP5 Final report V1.0

13. OPTIMAL Deliverable D3.1.4 WP3 Contribution to Normalisation and Standardisation

14. OPTIMAL GBAS Malaga Performance Comparison

15. OPTIMAL San Sebastian Airport Environmental Assessment Data

16. OPTIMAL Safety aspects of ACDA approaches at Schiphol

17. OPTIMAL Safety Assessment of the proposed GBAS-PA procedure for runway 31 at Malaga airport

18. OPTIMAL Safety Assessment of the proposed SBAS-APV procedure for runway 04 at San Sebastian airport

19. OPTIMAL Malaga airport capacity simulation results

20. OPTIMAL San Sebastian airport capacity simulation results

21. EUROCONTROL - Specification for Short Term Conflict Alert, Edition 1.0, 22 Nov 2007

22. EUROCONTROL - Organisational Support for STCA (Guidance Material)

23. SESAR Definition Phase Deliverable 5 - SESAR Master Plan (DLM-0710-001-02-00)







5 INTRODUCTION

OPTIMAL is an air-ground co-operative project aimed at defining and validating innovative procedures for the approach and landing phases of aircraft and rotorcraft in a pre-operational environment. The goal is to minimise external aircraft/rotorcraft noise nuisance and increase the ATM capacity while maintaining and even improving safety. Those achievements will be enabled by available precision approach landing aids as well as new technologies (such as SBAS, GBAS, ABAS), more accurate navigation means (low RNP) and enhanced airborne and ground systems. The target time frame for the operational implementation of the OPTIMAL proposed operational concept is 2010 and beyond, it will therefore contribute to reaching the targets for airport capacity developments identified in the ATM 2000+ Strategy and in the ACARE Strategic Agenda.

OPTIMAL developed generic approach procedures that were then applied to specific airports. In parallel, new airborne aircraft and rotorcraft functions were developed, as well as new ground functions, to support the new procedures. Studies, fast time and real time simulations, and flight trials were conducted in order to evaluate these approach procedures.

This recommendations document gathers all the recommendations that came up along the different OPTIMAL activities. The recommendations are grouped per approach procedure type and present in a same section all the recommendations linked to a procedure type together with the related airborne recommendations. The recommendations linked to the ground functions are given in a separate section as they are transversal to all procedures.

The structure of the document is:

• Section 1: List of figures

• Section 2: List of tables

• Section 3: List of abbreviations

• Section 4: References

• Section 5: Introduction

• Section 6: Continuous Descent Approach Procedures

• Section 7: GNSS-Based Procedures

• Section 8: Enhanced Vision System

• Section 9: Dual/Displaced Threshold Operations

• Section 10: RNP-AR procedures

• Section 11: Rotorcraft Specific IFR approaches

• Section 12: Ground Functions and ATC tools.

Sections 6 to 10 include when appropriate:







• Recommendations coming from procedure design

• Recommendations for operational implementation

• Recommendations coming from airborne functions

• Recommendations coming from applied procedure to specific airport.







6 CONTINUOUS DESCENT APPROACH PROCEDURES

6.1 PROCEDURE OVERVIEW

Within the OPTIMAL project, the development of the advanced Continuous Descent Approach has multiple aspects. OPTIMAL focuses on two compatible variants of Continuous Descent Approach.

The “nominal” CDA consists of a fixed earth referenced descent path of 2 degrees initially from the start of the CDA, changing to a 3 degrees path below an altitude of 3000ft. The CDA descent profile transitions into a conventional instrument final approach. Due to the fact that the procedure may be flown with a near-idle thrust setting, depending on the initial speed, the profile provides some control capability with respect to the deceleration profile to the ATC controller.

The deceleration profile can either be flown with idle thrust, optimized by using the FMS for determining the configuration changes, while the profile can also be flown more conservatively for ATC sequencing reasons. Under such circumstances, imposed by other traffic, it may be necessary to initiate an earlier than optimum deceleration to a lower speed and perform a constant speed descent along the 2 deg gradient.

The “optimised” CDA provides even more environmental protection as it is flown at relatively low speeds while maintaining the cleanest possible configuration and considering actual wind conditions. The vertical profile will be variable depending on actual wind conditions until transition to the fixed 2/3 degrees approach is made.

Figure 1: Nominal and Optimised CDA procedures

For more information refer to [1] and [9].







6.2 RECOMMENDATIONS FOR OPERATIONAL IMPLEMENTATION

Present as well as past studies on Continuous Descent Approach procedures have shown the need to work on standardization to support CDA implementation:

From an aircraft operational point of view, the CDA procedure is mostly an advanced flying technique. On the other hand, successful operation of such procedures at a given airport highly depends on the ATM environment in which the procedure is being flown.

A standardized mode of CDA operation has not yet been internationally defined. It is recommended that international bodies develop guidance material for drawing and coding CDA approaches.

CDA procedures will be operated by making use of available RNAV transition routes from TMA entry or the initial approach fix to the final approach. As a result, the following minimum list of requirements and enabling technology will be necessary:

• RNAV routing infrastructure in the TMA, which shall be used to be able to plan and execute a CDA profile using the onboard FMS

Onboard the aircraft, the following requirements apply:

• RNAV capability

• FMS capable of planning and executing a CDA profile

In addition, when operating these procedures in a busy environment, ATC will need sufficient means to allow the operation of CDA approaches with minimum need to act on the sequence after starting the CDA descent. Depending on the amount of traffic, this requires:

• Accurate arrival planning, i.e. a good AMAN, enhanced by air-ground datalink of flight plan data

• Arrival sequencing and monitoring tools, where necessary

• RTA capability within the FMS.

The operational implementation of day-to-day CDA operations will be encouraged by the definition of (P-RNAV) transition routes from entering the terminal airspace to the final approach point/fix.

While the use of P-RNAV transitions alone, i.e. without CDA descent profiles, will not be beneficial compared to present day vectoring, the advantages will become clear to ATC and the operators when CDA procedures can be flown on a more regular basis.

6.3 RECOMMENDATIONS FROM AIRBORNE FUNCTIONS

The acoustic analyses have demonstrated that the current FMS profiles are already noise efficient compared to standard vectorised approach. Therefore, as the ACDA procedure will require the airborne capacity (upgraded FMS with ACDA capacity), it is recommended to apply in the meantime the current available FMS profiles which are already noise efficient compared to standard vectorised approach.







The acoustic results has shown that very large noise benefits can be obtained with advanced FMS CDA functions able to optimise and adapt CDA profiles to the aircraft performance of the day. However, it is important to mention that acoustic benefits and optimised profiles strongly depend on aircraft type. It is recommended to design the CDA procedures to take into account the aircraft performances in order to avoid non-flyable CDAs for aerodynamically efficient aircraft or to avoid sub-efficient CDAs in terms of noise reduction.

Acoustic analyses have shown the importance of the time of configuration extensions; that’s why it is recommended to delay the configuration extensions as much as possible during the approach. This will be managed by the CDA capable FMS but it is recommended that flight crews should be made better aware of the main sources of aircraft noise during the approach as well as flight techniques that could be safely applied to minimize noise.

Since CDA is a brand new function, no CDA data is exchanged between the ATC and the aircraft, although it would be very beneficial for both ATC and aircraft to get access, through data link, to several CDA related data (aircraft speed, RTA…).

6.4 RECOMMENDATIONS FROM PROCEDURE APPLIED TO SCHIPHOL AIRPORT

The OPTIMAL project conducted a study to assess flight performance and in-trail separation during continuous descent approaches in a variety of contextual conditions, such as wind, path deviations, aircraft weight and initial separation, at Schiphol airport. Continuous descent approaches with and without speed constraints have been assessed.

It is already manifest from the current research that the wind has a strong effect on the evolution of continuous descent approaches. In this study specific wind data at the ground level of Schiphol Airport has been used in combination with a general model that describes the wind at larger heights. It is advised to obtain specific wind data for larger heights in future research.

Given the considerable effect of the wind on the continuous descent approaches, the feasibility of using wind predictions in the arrival manager planning tool should be considered in future research. Using such wind predictions may support reduction in the variance in separation distances and thereby an increase in the arrival capacity.

The study of continuous descent approaches without speed constraints has focused on some particular contextual conditions. The results show the separation during approaches for particular constant wind conditions and aircraft weights. In order to evaluate the effects of continuous descent approaches without speed constraints on the arrival capacity, knowledge is required on the probability density of separation distances. To this end, Monte Carlo simulations should be done that account for the variability of key factors in these approaches (e.g. wind, aircraft weight, lateral separation). As part of such analysis, the uncertainty in the data required for this method (e.g. wind predictions) should be accounted for.

The presented results primarily consider the separation between pairs of aircraft in an open loop control situation. Future research may further address the possibilities of closed loop control actions imposed by air traffic controllers or airborne systems. This research should address the effect of closed loop control actions on the probability density of separation distances. This should be done for pairs of aircraft as well as for streams of aircraft.







7 GNSS-BASED PROCEDURES

The GNSS-based approach procedures developed in OPTIMAL are based on ABAS, SBAS or GBAS. This section presents separately the recommendations for each case.

7.1 APPROACH PROCEDURES BASED ON GBAS

7.1.1 Procedure overview

Within the context of the OPTIMAL project, only GBAS PA Straight-in Final Approach aligned with the runway centre line have been considered. However, offsets up to 5º are admissible.

7.1.1.1 Final Approach segment

The Straight-in Final GBAS PA is based on GNSS information plus GBAS local corrections for both lateral and vertical guidance.

Final Approach Segment (FAS) Geometry is defined in the FAS Data Block and broadcast by the GBAS local station (VDB message). Once the VDB transmission is processed, the Path Identifier will be displayed, allowing visual cross-check against the chart by the crew.

An instrumental GBAS PA procedure is characterized by the ILS Look-alike concept. This concept is understood in the way that the objective is to apply the GNSS (GBAS) technology in such way that modifications respect to conventional ILS approach procedures be minimized and make the “transition” affordable. The “transition” refers to an evolution towards a future scenario in which the GNSS will be the “sole” navigation system mean, as recommended by ICAO:

• The flight crew displays are similar to the ones used in conventional ILS PA procedures, that is, simulating angular deviations which converge in the direction of the approach to the touchdown point.

• FAS Data Block contains all the information required for the definition of the Glide Path and the emulation of a converging guidance to the pilot whose sensibility increases in the approach direction.

• Obstacle assessment is based on the OAS, which are identical to ILS CAT I OAS

7.1.1.2 Initial, Intermediate and Missed Approach Segments

Within the context of OPTIMAL project, the rest of the segments involved in the procedure are also based on the RNAV concept and GNSS as positioning system (LNAV only)

At the same time, the OPTIMAL project considers that GBAS corrections are usable up to 4NM beyond the FPAP for the straight missed approach. That is, reversion from GBAS to other mean of navigation should be performed before that limit. This criterion derives from a combination of ICAO GBAS and FAA LAAS coverage criteria, as explained in D2.2-1-6.

Refer to [1] and [6] for more information.







7.1.2 Recommendations for operational implementation

7.1.2.1 Guidelines for the operational implementation

Although GBAS Straight-In PA operation is very similar to ILS, some ATC and aircrew training is required. Operators shall amend their Airline Operating Manual (AOM) according to the change of cockpit procedures and the installation of a GBAS system onboard. ATC must also be trained in the procedures and work processes, especially about the interface to the GBAS ground subsystem, and the procedures for the case of a GBAS and/or GNSS failure.

After the selection of the GBAS approach by the crew, the display of the Reference Path Identifier (RPI) indicates that VDB transmission was valid and is being processed. Cross-check of the RPI against the chart by the crew is the main and the only required check. However, this check covers the validity of data as usable FAS data, but it does not cover issues related with content integrity and updating (data changes without notification, or other potential sources of failure).

ATC must be provided with GBAS PA procedure availability information (in a similar way to current ILS status information). Information about failures from the Space or Ground Subsystem must be passed to ATC in a way that does not need interpretation (“procedure available/non available”). Mixed mode operation (GBAS/ILS) imposes coordination needs, not only between aircraft and ATC, but also between APP ATC and TWR ATC.

7.1.2.2 Open issues

The question of the availability of alternate approach procedures for the case of GBAS or GNSS failure is not closed and this issue could need local solutions for each scenario.

At present ILS OAS are used for designing the GBAS procedure and computing the OCA/H value. It is known that the GBAS system meets at least, the same technical performance as ILS CAT I, however it is also recognized that the protection areas defined for ILS may be improved in terms of adapting them to the GBAS operation and actual performance. In that sense, some research activities should be carried out in order to define the own GBAS OAS.

7.1.3 Recommendations from Malaga RWY 13 GBAS PA pr ocedure

The following table exposes the safety requirements depending on the scenario. In the table, the requirements have been grouped depending on the domain and the sub domain where they are involved. The hazards have been assessed with a likelihood ensuring minimum occurrence likelihood for a safe operation.

There are also some recommendations for different mitigation means that can be implemented in order to guarantee the requirement fulfilment and the safe behaviour of the system.







Table 1: Safety Requirements (GBAS PA)

7.2 PROCEDURES BASED ON SBAS


Within the context of the OPTIMAL project, only APV/SBAS Straight-in Final Approach aligned with the runway centre line have been considered. However, offsets up to 5º are admissible.

7.2.1.1 Final Approach segment

The straight-in Final SBAS/APV Approach is based on SBAS positioning information for both lateral and vertical guidance.

Final Approach Segment (FAS) Geometry is defined in the FAS Data Block and contained in the onboard data base.

An instrumental APV procedure is characterized under the ILS Look-alike concept. This concept should be understood in the way that the objective is to apply the GNSS (SBAS) technology in such a way that modifications respect to conventional ILS approach procedures be minimized and make the “transition” affordable. The “transition” refers to an evolution towards a future scenario in which the GNSS will be the “sole” navigation system mean, as recommended by ICAO:







• The flight crew displays are similar to the ones used in conventional ILS PA procedures, that is simulating angular deviations which converge in the direction of the approach to the touchdown point.

• FAS Data Block contains all the information required for the definition of the Glide Path and the emulation of a converging guidance to the pilot whose sensibility increases in the approach direction.

Obstacle assessment is based on APV OAS, which are derived from ILS OAS, taking into account that:

• Lateral guidance is considered to have LLZ performance

• Vertical guidance does not meet PA CAT I performance, hence implying more restrictive obstacle clearance assessment.

7.2.1.2 Initial, Intermediate and Missed Approach Segments

Within the frame of OPTIMAL project, the rest of the segments involved in the procedure are also based on the RNAV concept and SBAS as positioning system (LNAV only)

Refer to [1] and [5] for more information.

7.2.2 Recommendations for operational implementation


Although APV/SBAS operation is very similar to ILS one, some ATC and aircrew training is required. Operators shall amend their Airline Operating Manual (AOM) according to the change of cockpit procedures. ATC must also be trained in the procedures and work processes, especially for environments where different types of RNAV approaches (LNAV/VNAV, LNAV….) are involved at the same time.

Related to the previous point, the information about system availability/reliability should be transmitted to ATC in a way that is free of interpretation, giving an indication of procedure availability/non availability as clear as possible.

7.2.2.2 Open issues

The need of conventional aids (DME, markers…) for altimeter-distance cross-checks, in addition to the APV/SBAS “distance to THR” constant indication, is not closed.

Availability of alternate approach procedures for the case of GNSS failure or guidance degradation: this issue, which is not closed, could need local solutions depending on each scenario.

7.2.3 Recommendations from San Sebastian RWY 04 SBA S APV Procedure

The following table identifies a summary of the requirements specified for the conflict scenarios. These requirements have been defined at a functional level and are allocated among the appropriate domain. The values shown in the table indicate the least likelihood required to ensure a safe operation.







Regarding navigation sensors (SBAS and backup), the ground element (signal) of the system has been included in the appropriate sub domain, with the same minimum safety requirements of the on-board element.

For every requirement, when appropriate, associate candidate mitigation is noted.

Table 2: Safety requirements (SBAS PA)

7.3 PROCEDURES BASED ON ABAS


A straight-in final LPV approach procedure is an instrument approach procedure that is provided, within the final approach phase, with lateral and vertical guidance, that does not meet the performance requirements established for Precision Approach operations. So it cannot be classified as a conventional Precision Approach (PA).

The LPV procedure is based on the RNAV (Area NAVigation) concept. It is characterized by the ILS look-alike concept that consists in minimizing differences with conventional ILS approach procedures. The final approach segment is identical to an ILS PA. It is aligned (potentially with an offset) with the runway centreline and measures at least 4NM. From an operational stand point, it finishes at the Decision Altitude/Height (DA/H) where the pilot must determine whether visual references are on sight in order to decide to continue the approach procedure or to perform a missed approach procedure. The ABAS solution implemented in Optimal, based on lateral and vertical hybridization of GPS and inertia, provides lateral and vertical guidance with sufficient performance to meet LPV criteria. For more information, refer to [1] and [4].







7.3.2 Recommendations from procedure design


In terms of procedure design, a straight in LPV ABAS approach procedure is similar to LPV SBAS procedure and was designed considering the material developed by ICAO OCP for straight-in LPV SBAS procedure.

Despite the fact that LPV procedures are performance-based approaches, the standards take into account only the SBAS as a mean to fly LPV approaches. Therefore the implementation of LPV ABAS would require an update of the standard.

For operational implementation, the LPV ABAS procedure requires an aircraft with APV1/APV2 performance, which means upgraded avionics systems in particular with an ABAS advanced hybridization algorithm.

7.3.2.2 Open issues

In the LPV procedure design, ICAO has kept the sensor-based approach defining the requirements based on SBAS. The DO229 provides requirements in terms of NSE. In the direction of performance-based concept, a set of TSE (=NSE+FTE) should be established from simulations. And the LPV procedure design could be reconsidered in light of these new TSE requirements.

7.3.3 Recommendations from airborne functions

In the frame of OPTIMAL, the aircraft capacity to fly LPV procedure has been developed. The ABAS capacity is here based on upgraded avionics with a tight hybridisation between inertia and GPS data both in lateral and vertical (no Barometric guidance). In order to meet APV performance, a specific hybridisation algorithm is required with specific interface between inertial system and GPS receiver. This algorithm has demonstrated the capacity to meet APV performance criteria but it is now recommended to work on the certificabilty of the system to demonstrate that the performance achievement guarantee is equivalent to SBAS.







8 ENHANCED VISION SYSTEM

8.1 OVERVIEW OF THE CONCEPT

The EVS concept developed in the frame of the OPTIMAL project focuses on the use weather penetrating sensor technology and the presentation of the image to the pilot on a head-down display.

The final rule of the FAA for Enhanced Flight Vision Systems (EFVS) (released in 2004) clearly acknowledges the operational benefits of such a technology but the use is restricted to head-up displays and U.S. aircraft operating within national airspace.

The All Weather Operations Steering Group (AWOSG) of the JAA has proposed some amendments towards an international standard acceptable by the ICAO but also with the restriction to head-up display technology.

Figure 2 : Simulated EVS image with head-down symbology

For more information, refer to [3].







8.2 GUIDELINES FOR THE OPERATIONAL IMPLEMENTATION

Results from OPTIMAL studies show that the limitation to head-up display technology should be changed to a broader requirements definition that does not prevent the use of head-down displays but rather specifies a display technology that allows the pilot to safely manoeuvre the aircraft below the MDA or DH. The OPTIMAL simulation trails clearly demonstrated that together with an appropriate crew procedure EVS head-down approaches could be flown with the same performance and workload as with EVS-head up approaches. It revealed as well that a switch over of controls from pilot flying to pilot not flying (e.g. at EVS transition height) should not be part of the procedure.

Also the new rule should specify some minimum symbology requirements that encourage the use of display features that are available on head-down displays such as colorized lines and symbols or pseudo-colour infrared imagery.

8.3 OPEN ISSUES

This first investigation about the EVS head down crew procedure showed very interesting and promising results. It is of course necessary to increase the number of subjects and trials for more consolidated conclusions.

Besides the feasibility of flying EVS head-down, pilots stated as well that they even prefer the EVS head down display rather than the EVS head-up display. The transition from head-down to head-up could be done without any problems identifying the runway visually. This process is supported by the proposed crew procedure which does not really differ from existing standard crew procedures. Pilots emphasized the need of training to get familiar with EVS imagery and the symbology. Although they achieved rather good results using EVS together with the non precision VOR/DME approach, pilots would prefer to have as well additional vertical guidance, be it provided by ILS or by satellite navigation (ABAS, SBAS). They recommended as well integrating the EVS imagery and symbology into the standard PFD. As a next step, flight trials under different visibility conditions need to be conducted to further verify these results. Based on the results of described investigations, we are confident that EVS head-down together with the proposed crew procedure does provide the same level of performance as the currently existing EVS Head-Up procedure of the FAA EFVS rule.







9 DUAL/DISPLACED THRESHOLD OPERATIONS

9.1 OVERVIEW

At the end of the 90's a landing procedure called HALS/DTOP was developed in cooperation by the Frankfurt Airport AG and the Deutsche Flugsicherung GmbH (DFS – German Air Navigation Services) for the Frankfurt Airport. The objective of the work done in the frame of the OPTIMAL project is to describe how a second threshold on a runway can be operated, which benefits can be expected and which restrictions have to be considered under the different conditions of a single runway airport or a parallel runway system.

The basic idea of a displaced or dual/displaced threshold is the invention of a second threshold on a long runway at least 1500m from the original one, so that the displaced glideslope is approximately 260ft above the other.

Figure 3 : Displaced threshold approach on a dependent runway system [FlughFrank1999]

For more information refer to [1] and [2].

9.2 GUIDELINES FOR THE OPERATIONAL IMPLEMENTATION

Besides the installation activities for required navigation aids and lighting systems and runway markings, the DT is about operational aspects rather than procedure design aspects. DT uses straight in precision approaches including standard transitions (or even vectoring) to the final approach fixes. Of course, both controllers and pilots need to be trained for these operations. A proper TMA route structure (RNAV transitions, trombones), to facilitate the sequencing tasks should be implemented. If controller support tools (AMAN, DMAN, etc) are in use, they have to be adapted to take into account the new threshold systems and the new possibilities to reduce separation distances. As a final step, coordination between AMAN and DMAN is recommended to ensure optimal use of the runway.







9.3 OPEN ISSUES

DT procedure leads to a better utilization of the runway. Consequently, a higher amount of runway operations will take place creating an additional operational challenge. The severity of runway incursions might increase (not necessarily the number of incursions). This has to be taken into account when introducing DT operations and is not yet fully addressed. Whether or not having two approach light systems on the same runway active at the same time does have an impact on flight crew performance that needs further investigations. There are good reasons that appropriate training will overcome potential problems but this has still to be proven.

So far, it is recommended to integrate the planning scheme of arrival and departure management in order not to sacrifice the higher arrival rate by a reduction of departures on the runway system. Whether or not this will be successful needs respective validation activities.







10 RNP-AR PROCEDURES

The OPTIMAL project developed three types of RNP-AR final approach procedures:

• Straight-in procedures

• Curved procedures.

At the beginning of Optimal Project, Segmented Final Approaches were thought as a possible type of procedures to be analysed. During the development of OPTIMAL, ICAO developed the PBN, in which it is now prohibited to use fly-by and fly-over transitions in the final segment. Moreover, the flyability of segmented final approaches was not demonstrated. The objective is not to promote Segmented Final Approach Procedure against Curved Final Approach Procedures, so finally segmented procedures were not considered in the project.

The following section 10.1 gives an overview of each type of procedure. Section 10.2 presents the recommendations for all cases as they are common to all types of RNP-AR procedures. Finally, recommendations coming from curved procedures applied to San Sebastian and Malaga airport are given in section 10.3.

10.1 OVERVIEW OF RNP-AR APPROACH PROCEDURES

The Final RNP-AR Approach Procedure is defined based on RNP (AR) which represents RNP where Aircrew and Operational Authorization are required (Special Aircraft and Aircrew Authorization Required SAAAR). RNP AR operations utilize high levels of RNAV capability and aspects of the operation must meet relevant requirements. RNP AR tries to exploit advanced aircraft navigation capabilities on procedures and top utilize advanced attributes of RNP, such as RNP values less than 0.3, radius to fix paths within the final approach segment, and performance based lateral and vertical navigation in final and lateral guidance in the missed approach.

10.1.1 Straight-in RNP-AR approach procedures

Within the context of the OPTIMAL project, a procedure will be considered as Straight-in Final Approach when the Final Approach Segment (FAS) is aligned with the runway centreline.

Initial, Intermediate and Missed Approach Segments are based on RNP-AR (Lateral only).

Two types of Final Approach Segment are proposed:

• RNP (AR) lateral only and vertical guidance is based on Baro-VNAV (VEB).

• RNP (AR) lateral and Vertical. Although there are not any standard for the use of Vertical RNP it is proposed in the document as long term.

Barometric vertical navigation (Baro-VNAV) is a navigation system that presents to the pilot computed vertical guidance referenced to a specified vertical path angle (VPA), nominally 3º. The computer-resolved vertical guidance is based on barometric altitude and is specified as a vertical path angle from RDH. If the navigation system is not capable of temperature







compensation, the approach can be performed only in a certain range of temperatures. That range will be included in the approach chart. Aircraft provided with temperature compensation may disregard that limitation, provided that the flight crew is properly trained on the use of that function. Temperature compensation is applicable to VNAV guidance and it does not substitute the flight crew compensating for the effects of cold temperatures on minimum altitudes or decision heights.

For more information, refer to [1] and [7].

10.1.2 Curved RNP-AR approach procedures

Within OPTIMAL, a curved final approach procedure is a procedure involving a fixed radius leg on the final approach segment. The roll-in waypoint is the Final Approach Fix and the roll out waypoint is located at the runway centreline at a distance closer than 4NM from the threshold.

Initial, Intermediate and Missed Approach Segments are based on RNP-AR (Lateral only).

As stated in paragraph 3.2.5 of the ICAO Manual on RNP (Doc 9613-AN937), vertical RNP is not currently considered. Besides that, two types of Final Approach Segments have been proposed within optimal project:

• Final Approach Segment RNP (AR) lateral only and vertical guidance based on Baro-VNAV (VEB).

• Final Approach Segment RNP (AR) lateral and vertical. There is not any standard for the use of Vertical RNP. Nevertheless it is proposed in the document as long term.

Barometric vertical navigation (Baro-VNAV) is a navigation system that presents to the pilot computed vertical guidance referenced to a specified vertical path angle (VPA), nominally 3º. The computer-resolved vertical guidance is based on barometric altitude and is specified as a vertical path angle from RDH. If the navigation system is not capable of temperature compensation, the approach can be performed only in a certain range of temperatures. That range will be included in the approach chart. Aircraft provided with temperature compensation may disregard that limitation, provided that the flight crew is properly trained on the use of that function. Temperature compensation is applicable to VNAV guidance and it does not substitute the flight crew compensating for the effects of cold temperatures on minimum altitudes or decision heights.

These types of Curved Final RNP-AR could be also divided into:

• A completed RNP-AR final segment

• An RF RNP-AR leg plus a transition to a short xLS straight-in Leg.

The classification of curved RNP approach procedures can be depicted as follows:

1. An RF leg and a short aligned leg, both RNP-AR (AR) with vertical guidance based on Baro-VNAV (VEB).

2. An RF leg and a short aligned leg, both with lateral and vertical RNP guidance.







3. An RNP-AR (AR) RF leg with vertical guidance based on Baro-VNAV (VEB) plus a short xLS leg.

4. An RF leg with lateral and vertical RNP guidance plus a short xLS leg.

In the implementation options 3 and 4, that is, with transition to xLS, it is recommended that the transition from xLS to RNP is automatic as soon as the Missed Approach is engaged.

Figure 4: OPTIMAL Curved RNP-AR approach procedure

Refer to [1] and [8] for more details.

10.2 RECOMMENDATIONS FOR RNP-AR PROCEDURES

10.2.1 Recommendations for operational implementati on


Aircraft should be equipped with the necessary RNAV system. The RNAV/RNP system should meet a set of basic performance and functional requirements as required by the procedure.

The RNP navigation system must have the ability to monitor its achieved navigation performance and must have an alerting function.

The reliability of the navigation system must be very high. Operation on this type of approaches typically requires redundant equipment. No single-point-of-failure can cause the loss of guidance compliant with the RNP value associated with the approach.

Typically, the aircraft must have at least the following equipment (IRU):

• dual GNSS sensors,

• dual flight management systems,

THR

RF Centre

RWY

PFAF

PFAF

RWY

DA/DH

50 ft

Final Straight-in Leg

Curved Leg

THR

less than 4NM







• dual air data systems,

• dual autopilots,

• a single inertial reference unit.

The RNP-AR system should have a navigation database and should support each specific path terminator required.

Operator and Flight crew are responsible for checking that the installed RNAV system is the appropriate.

The State of the operator is the responsible for the flight operations approval, which has to satisfy adequate operation programs and evaluate the training programs and operational manuals.

Aircrew and air traffic controller must receive the appropriate training.

Flight evaluation for procedure and obstacle validation prior to publication is recommended. It should include a check-up of: track lengths, angles of bank, descent gradients, runway alignment and compatibility with predictive terrain hazard warning functions.

This kind of procedure shall not be used in areas of known navigation signal (GNSS) interference.

Close terrain and obstacles should be published.

10.2.1.2 Open issues

A complete loss of RNP capability or degradation beyond the maximum prescribed RNP level (0.3) is not foreseen. The procedure design and protection assumes that during the approach procedure the navigation system performance will be solid enough to sustain this consideration. Therefore the case of degradation beyond that limit is not covered. Safety analyses should be done about this issue for curved and segmented approaches since the fact that this problem may occur during the RF leg or during the transition constitutes a substantial difference from final Straight-in approaches.

There are not any standard for the use of Vertical RNP . Within OPTIMAL project the possibility of applying RNP containment concepts for ensuring vertical guidance is considered. The way to apply the vertical containment limit, its shape and figures of vertical RNP are open issues.

For a curved or segmented final approach procedure in which exist an RNP-AR RF leg plus a short xLS leg, it is supposed that the transition occurs at the Roll-out waypoint. Nevertheless, a transition time is needed for LOC effective engagement due to systems reconfigurations. This time corresponds to a distance, during which both types of protection should be considered.

Also for this type of procedures, the equipment should be capable of performing an automatic transition from xLS to RNP as soon as the Missed Approach is engaged. If so, a time/distance is needed to assure that the RNP guidance is engaged, and there are not values for this time/distance.







10.2.2 Recommendations from airborne functions

10.2.2.1 RNP-xLS transitions

It could be interesting to reach a common agreement on RNP-xLS transition point (by publication, standard computation, etc), in order to share a common way to define the switching logic between RNP and xLS guidance modes.

This would be beneficial for both the aircraft and the ATC to precisely know when the aircraft quits RNP guidance mode to begin xLS capture, because these two modes do not share the same behaviour and performance. The definition of the containment limit during RNP-xLS transition has to be considered. Indeed, during the initial part of the approach the aircraft is subject to RNP containment rules; during the final approach the aircraft is subject to xLS containment rules. A transition time exists for switching from RNP guidance mode to xLS guidance mode, this distance depends on the manufacturer; the containment limit has to be precisely defined in such a zone, in order to ensure the appropriate protection level along the whole procedure, without any gap.

Note: OPTIMAL RNP definition considered a transition point. However, it shall be noted that according to the on-board technical solution, the need for a transition point could be challenged.

10.2.2.2 Procedure design

In the case of procedures flown in mountainous environment, it is crucial to check that the reference trajectory has not been corrupted. A solution may be to use CRC codes in the same way it is already used for SBAS operations according to SBAS standards.

The use of databases raises the question of its validation. Today, DO200A seems not sufficient enough and database validation is costly for airlines. There is a lot of standardization work to do on this topic.

10.2.2.3 LDEV scale

Currently, the ICAO Performance Based Navigation Manual (working draft 3.1 - September 2006) requires that LDEV scale used for RNP operations shall be variable and depending on the RNP value of the flown procedure.

All the crews involved in OPTIMAL unanimously agree to keep a fixed L/DEV scale with +/-0.2NM as maximum deviation. Since the L/DEV is required by the EASA and FAA to monitor the FTE when flying RNP less than 0.3NM, the range of 0.2NM is a good compromise. Besides, the scale could be graduated in order to make it easier to evaluate. This is a preferred solution against the ICAO variable scale.

10.3 RECOMMENDATIONS FROM APPLIED PROCEDURES

10.3.1 Specific curved procedure for RWY 22 in San Sebastian

For the curved procedure applied to San Sebastian runway 22, a noise study was conducted in the frame of OPTIMAL.







From this study, it can be stated that the noise contours are mainly determined by the altitude profiles; the higher the aircraft, the lower the noise. The OPTIMAL curved approach procedures fly at lower altitude than the baseline arrival procedure during the final segment of the approach. So, the noise contours are slightly bigger for the both curved proposals than for the baseline scenario, increasing the affected population. Therefore, these results should feedback to the procedure design in order to refine them.

10.3.2 Specific curved procedure for RWY 31 in Mala ga

For the curved procedure applied to runway 31 in Malaga, a real time simulation was performed involving controllers from Malaga.

The main concerns identified in the simulation are what is called by OPTIMAL “paralysis” and “blindness” of the controllers about aircraft flying RNP-AR approach. As these two phenomena lead the controllers to non-detection or late detection of potential losses of separation between aircraft or potential CFITs, it is necessary to train the controllers to the particularities induced by RNAV procedures. Controllers must monitor the aircraft flying RNAV procedures even though they should avoid giving them instructions once they are cleared to fly these procedures.

As one of the advantages of curved procedures is to incorporate a late turn, thus allowing for example, avoiding overflying inhabited areas, a tool like CORADA to help controllers mix the curved flow with the runway centreline aligned one, or different curved flows would be a great help.

Besides, for the simulation, some phraseology was developed. It will probably need further consideration.

Finally, further studies seem necessary in particular to determine the human-machine interface that should be used when RNP-AR procedures are mixed with current approach procedures, one of the questions being whether it would be helpful to differentiate the presentation of RNAV aircraft from the non-RNAV ones.







11 ROTORCRAFT SPECIFIC IFR APPROACHES

The OPTIMAL project developed rotorcraft specific approach procedures for improving rotorcraft IFR operations taking benefits of the rotorcraft possibilities:

• Steep straight-in final approach procedures

• Curved final approach procedures

These procedures can be used in operations at airports as well developed in the frame of OPTIMAL:

• Simultaneous Non Interfering (SNI) operations where aircraft and rotorcraft flight paths are geometrically separated and fully independent, thus allowing simultaneous IFR approaches of rotorcrafts and aircrafts towards the same airport.

• Time-referenced (4D) operations where separation between IFR aircrafts and rotorcraft flying to the same airport is achieved by accurate timing.

As for aircraft, studies, real-time simulations and flight trials were run in order to assess these procedures and operations. The following sections give an overview of the procedures and present the fields where further research is possible and the recommendations from all these studies.

More information about the procedures can be found in [10].

11.1 STEEP STRAIGHT-IN FINAL APPROACH PROCEDURE


The main feature that distinguishes these procedures from “normal” ones used by fixed wing aircraft is the steep glideslope angle of more than 3º. Values up to 10º have been evaluated in simulation experiments, and values of up to 9º have been tested successfully in-flight.

Figure 5: Rotorcraft steep approach procedure

� � IF FAF

1000 ft min







11.1.2 Further possible research

11.1.2.1 Rotorcraft

One area of research in OPTIMAL had to do with the intercept of the much steeper glideslope flying a curve through the FMS, and maintaining a low airspeed while descending on a steep slope. It was questionable whether the steep glideslope intercept should be performed in successive steps (2 at the most) or done in one step. EC155 flight trials clearly indicated that a single step would suffice, but this result could be rotorcraft type-specific. More simulations and flight trials would be needed to determine the best profile to capture a steep final slope.

Furthermore, optimising the speed profile for noise minimisation throughout the entire procedure and in particular along the final segment should also be investigated by using appropriate noise prediction tools.

11.1.2.2 Geometric profile

Protection of glideslopes steeper than 6° in the pr ocedures raises an issue. . The current obstacle assessment surfaces (OAS) for ILS or LPV final paths are optimised for 3° standard slope and cannot be extrapolated beyond 6° slope. A redefinition of OAS would be necessary to assess obstacle protection for slopes steeper than 6°. Such redefinition requires a significant effort and should to be conducted in the frame of the ICAO IFPP.

When a slope steeper than 6° is used only to reduce noise nuisances and is not required to clear the obstacles, an alternative could consist to protect the final path using 6° OAS.

11.1.3 Guidelines for the operational implementatio n

The straight-in rotorcraft procedures developed in OPTIMAL mainly require the use of GBAS, SBAS or are based on RNP-AR. If the same GBAS station is used also for other approach procedures on other runways at the same airport, one should consider the case of a common GBAS failure not resulting in simultaneous missed approaches on the different runways, as in that case a traffic conflict can easily arise. However, it is expected that airports will be equipped in the future with redundant GBAS stations to avoid traffic disruptions in case of single equipment failure.

Furthermore main requirements are listed below:

• Failure of the enabling equipment should be graceful and should be detected and announced in the cockpit to the crew as well as to ATC.

• Appropriate phraseology shall be developed to fly each specific procedure to be used by ATC and aircrew.

• The rate of descent for procedure design shall not exceed 1000 fpm on the initial and intermediate segments, and shall not exceed 800 fpm on the final segment.

• A slightly adapted phraseology needs to be introduced for unambiguous communication.







• For the missed approach the navigational system should provide track information to the crew by properly switching NAV routes and selecting the proper route (after the MAPt) automatically or by a simple action by the pilot.

• The rotorcraft will fly the straight-in GBAS or SBAS procedure considering the ILS Look-alike concept. Cockpit crews have to be familiar with the new paragraphs in the Flight Manual.

• The rotorcraft shall meet the standards associated with the processing of SBAS/GBAS signals (ILS Look-alike displays, minimized risk of wrong channel selection, computing the path guidance instructions specified in GBAS messages, etc.).

11.2 CURVED FINAL APPROACH PROCEDURE


When flying curved final approach procedures, rotorcraft are approaching the airport from an angle different from the fixed-wing traffic, which are all aligned with a specific landing runway. At some distance from the airport a curved segment aligns the rotorcraft with the FATO approach direction while staying clear of nearby approaching fixed-wing traffic, landing on a nearby runway.

Because of the curved segment in final approach, this procedure is necessarily of RNP-AR type, thus requiring the helicopter navigation system to be eligible for such operations.

Figure 6: Rotorcraft curved approach procedure


11.2.2.1 Rotorcraft

From the minimum IFR speed defined per rotorcraft, which depends upon the quality of the airspeed sensing equipment, autopilot functions, etc., the associated maximum glideslope angle is determined from the limiting ROD (Rate Of Descent) value (of 800 ft/min). All speeds in the procedure are referenced to the ground, since with the relatively low airspeeds involved the effect of wind will be relatively large.

The radius of the curves in the curved procedure could be based on a rate one-half turn rate (i.e. 1.5º.s-1) rather than on geometric considerations (e.g. the closeness of obstacles) in







order to have a built-in turn rate margin. With this radius any deviations from the curved track, for whatever reasons, will not likely result in corrective pilot actions that could result in turn rates in excess of the standard “rate-one” turn.

11.2.2.2 Procedure profile

With the final approach fix altitude being in the order of 2000 ft or 3000 ft AGL, there is in general “room” for implementing only one curved segment/RF leg, with any substantial heading/track change when on a steep glideslope. The RF leg starts at the Roll-In Point (RIP), and finishes at the Roll-Out Point (ROP). In order to avoid having to start the turn as well as the descent simultaneously, the start of the turn occurs after the descent has started, i.e. after the Final Approach Fix (starting both of them together would unduly increase the pilot’s workload).

Much of the acceptability ratings of a particular procedure layout is, or has been obtained from simulated or flight experiments using test pilots. A decelerating curved-final approach, where the airspeed is reduced while descending along the curve, was the hardest thing to do in terms of pilot workload and was strongly discouraged, in favour of a constant-speed approach.

11.2.2.3 Air traffic control

For the air traffic controller, it remains a problem of having confidence in the rotorcraft’s properly tracking the RF leg when supposed to do so, and not to continue straight on and so make an overshoot. The solution could be a safety net feature which warns the ATCo when the rotorcraft deviates from the prescribed track.

However, with the RNP concept, the rotorcraft cannot exit the containment zone without being warned itself by the on-board monitoring system.


The curved-final rotorcraft procedures developed mainly require the use of RNP-AR because of the RF segment. If GBAS is used also for guidance on the very final straight xLS segment after the curve, then, if other approach procedures on other runways at the same airport are in effect, one should consider the case of a common GBAS failure not resulting in simultaneous missed approaches on the different runways, as in that case a traffic conflict can easily arise. However, it is expected that airports will be equipped in the future with redundant GBAS stations to avoid traffic disruptions in case of single equipment failure.

Furthermore main guidelines listed below are similar to the ones given for the straight-in steep procedures, i.e.:

• Failure of the enabling equipment should be graceful and should be detected and announced in the cockpit to the crew as well as to ATC.

• Appropriate phraseology shall be developed to fly each specific procedure to be used by ATC and aircrew

• The rate of descent for procedure design shall not exceed 1000 fpm on the initial and intermediate segments, and shall not exceed 800 fpm on the final segment.







• When executing a decelerating steep final approach extra rotorcraft provisions should be provided for the pilot/crew to reduce workload. Notably a 4-cues flight director or autopilot or similarly augmented flight control modes should be available.

• For the missed approach the navigational system should provide track information to the crew by properly switching NAV routes and selecting the proper route (after the MAPt) automatically or by a simple action by the pilot.

• The FMS must be able to navigate RF legs, and be able to provide proper navigational data, such as deviations from present (curved) track, as well as display the data with the curved path on a display for the pilot to use during the approach.

• The rotorcraft shall be certified for RNP-AR operations.

11.2.4 Open issues

Issues still open with regard to the application or the design of the curved final procedure are:

• The lowest altitude [ft AGL] where the ROP should be located. A value of 500 ft had been designed (and tested in the simulations), however, from pilot comments it is arguable to increase this to at least 700 ft AGL, if not 1000 ft AGL.

• Moreover, the main issue is that an Inertial Navigation System (INS) comparable to transport airplanes is today required to fly RNP-AR procedures. Such equipment is not present in civil IFR helicopters because of excessive cost. Consequently, the possibility to fly RNP-AR operations relying only on SBAS, or GBAS, should be investigated.

11.3 SNI OPERATIONS

11.3.1 Overview of the concept

The aim of the concept is to remove IFR rotorcraft from the runway traffic by using rotorcraft specific non dependent procedures. Any of the procedures described in sections 11.1 and 11.2 can be flown in SNI operations.







Figure 7: Rotorcraft SNI operations


11.3.2.1 Rotorcraft

Refer to section 11.1.2.1.

11.3.2.2 Procedure profile

Refer to section 11.1.2.2.

11.3.2.3 Air traffic control

The task load of the ATCo could be more or less, depending upon the individual layout of the procedure in relation to other fixed-wing procedures. Since, in general, the slower rotorcraft traffic has been taken out of the mainstream of fast(er)-flying jets, the control and monitoring of the rotorcraft flight is less demanding, as long as the SNI does not “truly” interfere with that other traffic. When it does, then the workload of the ATCo will increase rather than decrease. With proper and careful design this non-interference can be achieved, thus leading to a potential increase in airport capacity.


Care should be taken in locating the procedure such that no interference will occur not only with approaching traffic (the basis of SNI) but also with departing traffic. Since departing traffic on a SID cannot receive additional clearances when still below 3000 ft the only option for ATC to avoid conflicts with approaching traffic on the procedure is to delay conflicting take-offs. Therefore also departure routes will need to be scrutinized for possible conflicts.







11.3.4 Open issues

The amount of additional rotorcraft traffic on the SNI operations that are driving the decision to have an additional controller is still unknown. First results have shown that 8 additional rotorcraft flights per hour have been managed by the existing ATCo team. The “maximum allowable” convergence angle is unknown, neither are there any guidelines or criteria for that.

The issue of TCAS-generated alerts in a converging layout/situation needs to be addressed further. Experience from fixed wing aircraft “normal convergence” operations can be taken into account.

11.4 TIME-REFERENCED (4D) OPERATIONS

11.4.1 Overview

Regarding mixed operations of aircraft and rotorcraft approach traffic at airports, the following typical cases may occur in which 4D guidance becomes a necessity:

• Case A: Simultaneous and interfering operation

With the rotorcraft flying in-trail with the other fixed-wing traffic this is the worst operational scenario that may occur. Separation problems need to be avoided by increasing the time delays between flights. This reduces the airport’s overall traffic flow. Also controllers have to be aware of the different approach speeds. Precise 4D scheduling is required here. In addition, rotorcraft are demanded to fly as fast as possible while at the same time using the shallow slopes originally introduced for the usually much faster aircraft – definitely a far less than optimal solution for all participants.

In such a case, 4D concept of operations can help to enable precise scheduling but:

• Optimum sequencing not possible

• Worst operational solution

• 4D guidance required to provide safe separation

• Negative impact on airport capacity

• Wake vortex encounter problems likely to occur.

• Case B: Simultaneous operation with narrow lateral separation (CSPR)

The mixed approach traffic streams are not completely independent due to the closely-spaced runways (CSPR) and FATO area locations. This is a situation in which wake-vortex problems are very likely to occur, depending on the types and classes (heavy, medium, light) of aircraft and rotorcraft involved as well as on the actual meteorological situation (wind direction and velocity). To avoid these difficulties, the approaching traffic needs to be staggered in sequence by making use of exactly defined time slots for each vehicle, thus requiring accurate an 4D guidance and planning system.

In that case as well, 4D concept of operations enables precise scheduling but:

• Optimum sequencing not possible







• Worst operational solution

• 4D guidance required to provide safe separation

• Negative impact on airport capacity

• Wake vortex encounter problems may occur.

• Case C: RPAT operational example procedure for CSPR

The operational scenario demonstrates the simultaneous operation of mixed approach traffic flows which are not completely independent due to the closely-spaced parallel runway and FATO area locations (CSPR-like scenario). This is a situation in which wake-vortex problems are very likely to occur. To avoid these vortex hazards, the approaching traffic needs to be staggered in sequence by making use of exactly defined time slots for each vehicle, thus requiring an accurate 4D guidance and planning system. The approach procedure defines Non-Transgression Zones (NTZ) in the 4D airspace. Fixed-wing aircraft practically stop generating vortices when the nose gear touches the runway, thus a late steep descent for rotorcraft to the FATO (at 6° or more) helps to reduce probability of WVE.

4D concept of operations provides precise scheduling for optimum use of airport and ATC capacity but:

• 4D guidance being required to provide safe separation means unequipped traffic cannot operate in this scenario (if unable to maintain required accuracy when flying manually)

• In case of a rotorcraft missed-approach after the curved approach segment, the rotorcraft needs to fly straight ahead in the direction of the FATO while initiating the climb.


For the implementation of fully automatic 4D time-referenced rotorcraft operation under instrument flight rules (IFR), the following requirements need to be fulfilled.

11.4.2.1 Airborne system requirements/recommendations

The rotorcraft needs to be equipped with a 4D-capable flight management system (4D-FMS).

11.4.2.2 Optional (desirable) airborne system requirements

• HUD- or HMD-projected flight path visualization (tunnel display recommended) for the flight crew.

• Data-link avionics equipment for communication with ATC.

11.4.2.3 General procedure design requirements

The procedure must be designed with respect to the flight performance envelope and handling characteristics of the specific rotorcraft category and its operational limitations.







As with 4D the more challenging aspects are of operational nature, the environment (especially the ATC procedures) has to be ready for 4D operations. At least the concept of time base operation including RTAs (required time of arrival) has to be in use for fixed wing traffic so that the 4D r/c operations can be added seamlessly.

11.4.3 Open issues

The 4D trajectory and its use in future ATM is regarded as one key element considered by SESAR. Consequently, it is currently not fully defined, how the 4D trajectory based operations will look like for rotorcraft. The above described rotorcraft aspect of 4D might have to be modified according to the final 4D concept of SESAR.







12 GROUND FUNCTIONS AND ATC TOOLS

On the ground side, OPTIMAL considered both equipment to guide the aircraft and tools to help the controllers manage the procedures developed in the project:

• Equipment:

• GBAS station

• SBAS

• Controller tools:

• Arrival management tools (AMAN)

• Converging runways and final approach display aid (CORADA)

• Advanced safety nets and monitoring aids.

This section presents the recommendations coming out from the different studies, simulations or flight trials that used the functions or tools developed in OPTIMAL.

12.1 GBAS

The following recommendations have been written taking into account that the objectives defined for the OPTIMAL activities are, at this first stage, purely experimental and learn-oriented (although the final objective of the GBAS CAT I project at Malaga airport is to become operational).

It is to be noted that the first GBAS CAT I system will be certified in 2009 (by the FAA) and therefore this system will be used operationally in Europe from 2009 onwards.

The GBAS CAT I on-board equipment was certified (at least Rockwell Collins MMR) and Boeing and Airbus offer it as an additional capability (e.g. B-737-NG, A-380) in some airplanes and as basic equipment in some others (B-787, A-350).

The GBAS CAT II/III system is being developed and it is expected to be certified in 2012-2014.

The GBAS CAT II/III system is the one which maximises the GBAS operational benefits, as there is no sensitive area (Localiser Sensitive Areas) to protect in LVP operations, and then the capacity of the airport is not so dramatically reduced as in the case of ILS.

As OPTIMAL also performed an evaluation of the Malaga GBAS station, some recommendations are specific to that case. They are presented in section 12.1.2.

12.1.1 Generic GBAS recommendations

The generic recommendations from OPTIMAL for GBAS are given below:

• For airports with commercial traffic (Boeing or Airbus type) without an ILS in any runway (or only one), it is recommended to assess the possibility to install GBAS CAT







I, by analysing whether the system is able to be installed and whether the users (airlines) can achieve operational benefits. This is specially stressed for those airports where an ILS system is not possible to be installed due to sitting constraints.

• For airlines in the process to procure a new aircraft (Boeing or Airbus) it is recommended to assess the possibility to ask for the GBAS capability taking into account the possible benefits in the airports network today (CAT I only) but taking into account that when GBAS CAT II/III is certified, the retrofit will be easier (less costly) for those already equipped with GBAS CAT I equipment as well.

• For ANSPs involved in the operational approval of GBAS operations, it is recommended to use an Independent Monitor Station to obtain:

• An independent source of data

• An independent monitoring of main performance (including radio frequency interference detection)

These features can be used to monitor the GBAS performances during an acceptable period (3 months) before the system become operational. Besides that this station can be used to confirm/supervise some Site Acceptance Tests results.

• It is recommended to use / procure a PORTABLE Independent Monitor Station. This station is used before the system becomes operational and after that, during some periodic tests. Due to this temporary usefulness if the station can be moved to other locations, its utility will be optimised.

12.1.2 Recommendations from Malaga GBAS ground stat ion performance evaluation

The dynamic and static tests performed within OPTIMAL are almost the same as for the ICAO Document 8071 Vol. II.

The main differences are in the list of parameters that have to be recorded. ICAO Doc. 8071 Vol. II is only indicating a limited number of parameters which are sufficient to show the proper working of a station. Most of these parameters provide analysis capabilities in the position domain; only a few of them allow the detailed investigation for anomalies such as interference (signal-to-noise, spectrum analyser, etc.).

But these parameters are not sufficient to make investigations if any problem occurs during the evaluation of the recorded data. That is why the OPTIMAL project recommends the recording of more parameters on the first flight trials with a new GBAS ground station – particularly in the range domain (i.e. ephemeris, range and carrier phase measurements, correction data transmitted and received). If the station has shown that all checked parameters are well inside the specified limitations a reduction of recording parameters to the minimum requirements of ICAO Doc. 8071 Vol. II will be sufficient.

More specifically to the Malaga evaluation, a number of issues were found which can be linked to the prototype status of the station. It is recommended that these are reviewed during the certification activities.







12.2 RECOMMENDATIONS RELATED TO SBAS

It is to be noted that the EGNOS (SBAS system in Europe) will be certified to be used by Civil Aviation by 2009. The main approach procedure based on EGNOS is called LPV (Localiser Performance with Vertical guidance) and provides a vertical guided approach procedure to runways with a Decision Height of 250 feet.

The SBAS LPV on-board equipment is being certified for Regional users (Bombardier CRJ-200…) as well as some GPS receivers used by General Aviation are already certified (e.g. Garmin receivers).

The list of recommendations for SBAS is:

• For airports operators, it is recommended to assess the possibility to develop a LPV procedure(s), analysing whether the users can achieve operational benefits. This is specially stressed for those airports with regional carriers or high General Aviation traffic.

• For regional airlines in the process to procure new aircraft to assess the possibility to ask for the SBAS capability taking into account the possible benefits in the airports network.

For ANSPs in the process to approve SBAS operations, it is mandatory to provide NOTAM for the LPV procedures. OPTIMAL findings were used as inputs for the development of the EUROCONTROL GNSS NOTAM tool specifications. In these specifications, a centralised tool for Europe is recommended.

Therefore it is recommended to contact EUROCONTROL before the development of a national tool in order to use the EUROCONTROL specifications to develop this tool, supporting the development of a European centralised tool.

• For ANSP in the process to approve SBAS operations, it is not clear whether it is mandatory to provide LPV operational status to ATC Tower controllers, as it currently done for conventional navaids. The OPTIMAL findings on this aspect recommends that:

• Perform a Safety analysis and decide whether the real time monitoring is needed or not (preferred solution not to be needed)

• If needed, look for a centralised solution (server) to provide this service to the maximum number of airports.

• Secure that an appropriate level of training is provided to both server operators and information recipients (ATC and AIS staff): rudiments of GPS, EGNOS, air data information management and flight operations are needed to successfully exploit the benefits of the EGNOS ATC I/F.

• Secure that an appropriate level of training is provided to both server operators and information recipients (ATC and AIS staff): rudiments of GPS, EGNOS, air data information management and flight operations are needed to successfully exploit the benefits of the EGNOS ATC I/F.

• Safeguard the provision of input data with enough availability and integrity







ICAO annex 10 says that States should notify on both predicted and non-scheduled outages. Both kinds of outages are forecast by a Prediction function, but the former (predicted outages) takes into account only predictable parameters (such as orbits) and scheduled notifications (e.g. NANU), and the latter (non-scheduled outages) takes into account this information and the inputs from a Real Time Monitoring function, which detects anomalies in the system in real time.

The data needs showed that the inputs needed to issue the first kind of outages (predicted outages) are the following:

• GPS data

• GPS unavailability notice

• GPS Almanac

• EGNOS data

• GEO SIS unavailability notice

• RIMS unavailability notice

whereas the data needed to issue the second kind of outages (non-scheduled outages) are, in addition to the data listed above, the following:

• GPS data

• GPS real-time status information

• GPS Ephemeris

• EGNOS data

• GEO SIS real-time status information

• RIMS real-time information

• Real-time EGNOS messages

Possible sources of these data are depicted in the following tables:

GPS Almanacs GPS Ephemeris SBAS

messages NANUs

GEO SIS

availability notes

G/S assets

availability notes

EDAS X X X

INTERNET X X

Local receiver X X X

MMI X X X

Table 3: Input data availability for the Prediction function

GPS Ephemeris SBAS

messages GEO SIS real-time status information

G/S assets real-time status

information







GPS Ephemeris SBAS

messages GEO SIS real-time status information

G/S assets real-time status

information

EDAS X X X X

Local receiver X X X

Table 4: Input data availability for the Real Time Monitoring function.

As it can be seen, EDAS is of utmost importance for EGNOSATC. Therefore, to assure the availability of these data, both first level maintenance layer (operators’ daily support) and specially the second level maintenance layer (manufacturer’s support) of EDAS must be fully guaranteed. In addition, communication links must not be unduly discontinued.

To assure the integrity of the data, data coming from the internet and input to the MMI must be thoroughly checked: e.g. NANU predictions of GPS outages must be cross-checked by the operator. Or: the impact assessment of GEO or G/S maintenance actions carried out in EGNOS daily operations should be fed back to the operation of EGNOS ATC I/F to have a way to confirm these outage notices.

12.3 ARRIVAL MANAGEMENT TOOLS (AMAN)

OPTIMAL improved AMAN in order to support the displaced threshold operations. Several real-time simulations were run in that context that gave the following recommendations for the use of AMAN with displaced threshold operations:

• A coordinator tool for the approach controller (feeder/director) is necessary, which suggests gaps (arrival free intervals) for departures. In this case the following aircraft on the left runway should avoid using the displaced threshold.

The validations results of OPTIMAL (and the previous results of FRAPORT/DFS) showed that without a well balanced trade-off between inbound and outbound flow, we get no benefits for the whole airport, even more an increase of the inbounds may result in a dramatic decrease of the outbound flow.

• The controller needs the possibility to fix a subsequence or it should be possible to fix the sequence number for an inbound entering the downwind.

Without additional inputs the AMAN does not know whether the controller performs an intended action or if a manoeuvre is not intended (a mistake). In the first case the AMAN normally should adapt its sequence and in the second case the AMAN should keep the sequence stable and calculate only new advisories to compensate the deviations. Without further inputs the AMAN always guesses and wrong guesses result in no help for the controller.

• The controller needs the possibility to fix an assigned runway or the assigned runway should be fixed for an inbound entering the downwind. See above.

• The controller needs the possibility to shift two aircraft in a sequence (sequence move). See above

• The controller needs the possibility to change the assigned runway. See above







• If the AMAN provides advisory information then electronic flight strips instead of paper flight strips are mandatory.

Without electronic flight strips no feedback concerning the advisories exists between the controller and the AMAN.

• The controllers that participated into the simulations considered very important to have speed and turn to base advisories, whereas altitude advisories were considered as dispensable.

12.4 CONVERGING RUNWAYS AND FINAL APPROACH DISPLAY AID (CORADA)

OPTIMAL as well developed a controller tool called CORADA in order to help controllers merge traffic streams on a point or on converging runways. The tool proposed several options in the way of displaying the information to controllers and the operational experts involved in the real-time simulations run using CORADA gave the following recommendation:

• the dual mode that was implemented by OPTIMAL was too difficult to use and was showing too much information (ghosts on each flow of aircraft) to be handled by the controllers. The master/slave mode seems more appropriate but new tests would be necessary to validate this opinion. See pictures below.

A’

A

BB’ C

C’

D

D’

E

Figure 8: CORADA Dual mode







Figure 9: CORADA master/slave mode

12.5 ADVANCED SAFETY NETS AND MONITORING AIDS

OPTIMAL improved the performance and accuracy of Safety Nets and Monitoring Aids in approach areas, and adapted them in order to support the new approach procedures developed by the project.

Real-time simulations have been run in order to assess the improved tools. Several recommendations came out from these tests. They are presented in the following sections.

12.5.1 Extended OPTIMAL validation activities

The aim of the Real Time Simulation (RTS) carried out in OPTIMAL was to assess the benefit of the implementation of multi-hypothesis algorithms either in the horizontal plane or the vertical plane in the Short Term Conflict Alert (STCA) and Minimum Sade Altitude Warning (MSAW) ground-based safety nets.

It also included the study of the relevance of using Aircraft Derived Data (ADD), also called Downlink Aircraft Parameters (DAP), in such algorithms.

Analysis of the results has demonstrated that the new algorithms fit the need of following evolutionary air traffic either in the horizontal plane or in the vertical plane.

Moreover, the use of Aircraft Derived Data by ground-based safety nets allows to accurately follow a sequence of manoeuvres and to enhance the trajectory predictions.

The ATC operational experts gave a positive feedback on the OPTIMAL enhancements relative to the diminution of the false alarm rate either in STCA or MSAW. Indeed, this increases their confidence in such functions, relieving them from analysing alarm raised by Safety Nets to state whether they are false or genuine alarm. This saves them more time to focus on their own traffic control missions and on the specific Safety Nets topic, to determine the best resolution strategy when a genuine alarm shows up.

All these results need now to be consolidated by complementing the verification / validation activities based on simulated data, with verification / validation exercises using recorded data: real air traffic data and real Aircraft Derived Data.







This will enable to confirm and/or refine the results already obtained, and possibly to adjust the algorithms that have been implemented.

Using real ADD will also make it possible to undertake statistical analysis on the ratio of equipped aircraft and the compliance of the ADD to the standards.

12.5.2 WTEA further improvement

The WTEA (Wake Turbulence Encounter Advisory) function has been appreciated by the ATC operational experts involved in the RTS. This functionality allows them to obtain a real-time confirmation that the separation applied between two aircraft meets the ICAO separation standard, while warning them in case this one will no more be fulfilled in a short time frame.

The ATC Operational experts recommend to enhance the WTEA function by making use of meteorological data (e.g. forecast and now cast), and real-time wake vortex data in the Safety Nets.

12.5.3 Tuning

Due to the continuous air traffic increase resulting in traffic density raise, and in order to fit complex approach operations resulting from intricate airspace and airport configurations, ANSPs may decide to replace their basic safety nets (STCA, MSAW, etc.) by advanced ones implementing new algorithms enabling drastically decrease the false alert rate while keeping an adequate warning time, such as those developed in OPTIMAL.

In order to prepare this transition, it is recommended that the ANSP undertake a tuning phase of the new safety nets in order to adapt to the specificity of their airspace, followed by a comparison of the basic safety nets and the new ones.

For this purpose it is recommended to apply an evaluation method consisting in a statistical analysis based on tracking and alert recording. This method allows comparing the performance of the two STCA (or more generally or two safety nets). The performance of the new STCA can be assessed with live data. Using this method, a smoothed transition can be achieved by harmonisation of the STCA behaviours in simple situations.

12.5.4 Training

Once the enhanced safety nets (e.g. STCA, MSAW) have been installed validated, and tuned, it is recommended that an adequate training be provided to the Air Traffic Controllers and the engineers (i.e. the operational analysts responsible for the setting up, optimisation and maintenance of the STCA system).

• Training for the ATCO's (example for the STCA, cf. ref [21]):

The primary goal of the training is to develop and maintain an appropriate level of trust in the STCA, i.e. to make controllers aware of the likely situations where they will be effective and, more importantly, situations in which STCA may reach some limitations.

• How STCA detects conflicts







• Which aircraft are eligible for STCA

• The volumes of airspace in which STCA is active, and differences in performance in various parts of airspace

• How STCA alerts are displayed and acknowledged

• How STCA performs in various situations (play back of STCA situations helps here)

• What action to take in the event of an alert

• What action to take in the case that STCA is not available

• Procedures for feedback of STCA performance (this helps further optimisation)

Note: when changing from a "basic" STCA to an STCA implementing the advanced features developed in OPTIMAL, a number of false alerts previously generated will no longer exist thanks to the improved algorithms. This new situation should be presented to the ATCO's being trained.

• Training for the engineers (example for the STCA derived from ref [21]):

Engineers should understand how their STCA system works; requiring that they become familiar with their STCA specification. If no specification is immediately available, then the manufacturer should be able to supply one.

Some description of algorithms is essential for teaching new technical staff about the STCA system.

Engineers should then be provided with the tools and take time to become skilled in STCA alert analysis and parameter optimisation.

It is a useful exercise to collect and analyse all STCA alert situations, not only to aid parameter tuning, but to provide informative examples than can be shown to engineers, ATCOs and other staff.

12.5.5 EUROCONTROL Specification

The SPIN (Safety nets: Planning Implementation and eNhancement) Task Force was instrumental in the development of standards and guidance material for ground-based safety nets.

The SPIN Task Force was established in 2005. Its purpose was to:

• prepare draft standards and guidance material for the ground-based safety nets STCA, MSAW and APW

• propose ECIP Objectives and their Lines of Action for ECAC-wide implementation of these standards and of the recommendations of the guidance material

• maximise opportunities for early enhancement of existing safety net implementations.

When installing basic or advanced safety nets, it is recommended that ANSPs take into account the following documents developed as part of the SPIN Task Force:







• EUROCONTROL - Specification for Short Term Conflict Alert, Edition 1.0, 22 Nov 2007

• EUROCONTROL - Organisational Support for STCA (Guidance Material)

EUROCONTROL - Specification for Short Term Conflict Alert specifies the minimum requirements for the development, configuration and use of Short Term Conflict Alert (STCA) by all Air Navigation Service Providers (ANSP) in the European Civil Aviation Conference (ECAC) area.

The European Convergence and Implementation Plan (ECIP) contains a pan-European Objective (ATC02.2) for ECAC-wide standardisation of STCA in accordance with the EUROCONTROL Specification of Short Term Conflict Alert. This document specifies, in qualitative terms, the common performance characteristics of STCA as well as the prerequisites for achieving these performance characteristics.

It should also be noted that Regulation (EC) No 552/2004 of the European Parliament and of the Council of 10 March 2004 on the interoperability of the European Air Traffic Management network (the interoperability Regulation) contains inter alia the following essential requirements:

• “Systems and operations of the EATMN shall achieve agreed high levels of safety. Agreed safety management and reporting methodologies shall be established to achieve this.”

• “In respect of appropriate ground-based systems, or parts thereof, these high levels of safety shall be enhanced by safety nets which shall be subject to agreed common performance characteristics.”

The Specification for Short Term Conflict Alert facilitates harmonisation of the STCA elements of the ground based safety nets and sets up the prerequisites for the refinement, in quantitative terms, of the common performance characteristics which might be developed in a further step in response to the requirements of the SES interoperability Regulation.

EUROCONTROL - Organisational Support for STCA (Guidance Material) contains guidance related to the organisational support required for the development, configuration and use of Short Term Conflict Alert (STCA) in the ECAC area. Specifically, the report contains a guidance related to the STCA life cycle, including:

• Organisational issues.

• Procurement and improvement.

• Verification, tuning and validation.

• Management and training.

12.5.6 Summary from SESAR Master Plan

This recommendation is a list of the Research and Development topics extracted from the SESAR Master Plan ([R3]), for Line of Change #9 - Independent Cooperative ground and airborne safety nets:







• STCA Using Enriched Surveillance Information: Improve ground based safety net performance using widely shared aircraft position and intent data.

• Display ACAS Resolution Advisories to Controllers: Introduce Resolution Advisory (RA) downlink informing Controllers automatically when ACAS (airborne collision avoidance system) generates an RA.

• Develop and validate provision to controllers of a reliable alerting system based upon all the surveillance information available.

• Develop and validate the coordination of ATC and flight deck warnings as well as appropriate presentation, so that the nuisance alert rate can be optimised. Analyse possible information overload for the controller due to the RA Downlink.

• Specify principles for Resolution Advisory (RA) priority over any instruction that may be triggered by ground safety nets or ATC tools.

• STCA adapted to new Separation modes: Adapt the STCA function to new separation modes in particular if lower separation minima is considered.

• Compatibility between Airborne and Ground safety nets: Introduce improved compatibility between airborne and ground safety nets. Although ACAS and STCA are and need to stay independent at functional level there is a need for better procedures in order to avoid inconsistent collision detection and resolution.

• Enhance STCA function so that it is able to recognise the new separation modes and avoid triggering false alarms and hence optimising the nuisance alarm rate for the controller’s benefit.

• Analyse the impact of ACAS on ATC systems. Improve means to avoid inconsistent collision detection and solution by ACAS and STCA. Develop and validate a prioritisation process, which shall be followed by airborne and ground safety nets when operating together.

optimal final recommendations - deliverable...

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