AMC 20-XX Version 1 “Approval of GNSS system for RNAV/GNSS approaches”

1. AMC 20-XX Version 1“Approval of GNSS system for RNAV/GNSS approaches” B. RABILLER / DGAC CNS/ATM Steering Group meeting Hoofdorp, 21-22 June 2005

2. Overview • Introduction of AMC 20-XX Version 1 • The missed approach issue • Vertical navigation discussion • Generality • NPA Baro-VNAV • APV Baro VNAV • AMC 20-XX Synthesis table • Miscellaneous.

3. AMC 20-XX Version 1Introduction • A stand-alone document (is now separated from PP 32). • Incorporate comments from last CNS/ATM steering group meeting • Incorporate comments received from AEA and AIRBUS • Is mature for the Lateral navigation part. • Still need discussion for the vertical part. • To issue AMC 20-XX for the lateral part only OR • To postpone issuance of AMC 20-XX in order to address the Vertical part

4. AMC 20-XX Version 1 Missed Approach wording • New wording used in AMC 20-XX : « The missed approach should be flown in accordance with the published procedure. The crew should respect all published constraints. Use of the RNAV system during the missed approach is acceptable provided: * the RNAV system is operational (e.g no loss of function, RAIM available, no failure indication,..). * the whole procedure (including the missed approach) is loaded from the navigation data-base and fully respect the complete published procedure. « 

5. AMC 20-XX Version 1 Vertical navigation discussion • Vertical guidance is based on barometric (Baro VNAV) or geometric altitude (SBAS) • Different accuracy • Different integrity • Different performance • Performance of Baro-VNAV may be affected by: • Altimeter setting error (QNH selection) • Non standard atmosphere (in particular for low Temperature) • Altitude error (e.g static ports iced/partially blocked) • Horizontal error (coupling) • ….

6. AMC 20-XX Version 1 Vertical navigation discussion • These problems are already discussed in many panels (ICAO, JAA, FAST, Eurocontrol,…). • But no clear position or decision on these issues so far • Three vertical navigation concept: • The « NPA Baro-VNAV » • The « APV Baro-VNAV » • The « APV SBAS » • It exists procedure design criteria (PANS-OPS) for APV Baro-VNAV. • At the last OCP, APV SBAS procedure design criteria have been accepted.

7. AMC 20-XX Version 1 Vertical navigation discussion • Baro VNAV system are already fitted onboard Air Transport aircraft and business jet. • Operators/Airlines want to use this vertical navigation function. • Aviation Authority promote the CDFA concept in order to reduce CFIT • What Should be our answer ? • Analyze the different vertical guidance possibilities focusing as a first step on baro-altimetric technology • Define performance criteria and airborne system functionalities to accommodate these different operational concept. • …

8. AMC 20-XX Version 1 NPA Baro-VNAV versus APV Baro-VNAV Conventional NPA NPA BaroVNAV 2 APV BaroVNAV 1 Runway 1 NPA Obstacle surface APV Baro-VNAV Obstacle surface 2

9. AMC 20-XX Version 1 NPA-Baro VNAV • Applicable only to conventional NPA (ex VOR/DME, NDB,..). • No specific procedure design criteria. • A continuous descent path is « defined » in order to respect altitude constraint of the published approach (respect of step down fix, altitude at FAF,…) • Issues to be addressed: • Use of DA(H) in lieu of MDA • Crew training and qualification • Following subject should be discussed but are not blocking point for NPA Baro-VNAV (Temperature correction, Altimeter setting,…) • For NPA Baro VNAV operation, altimeter remains the primary means to control the descent.

10. AMC 20-XX Version 1 NPA Baro-VNAV FAF

11. AMC 20-XX Version 1 NPA-Baro VNAV • What are the recommendation proposed in AMC 20-XX for NPA Baro VNAV (§ 9.8) • Certification criteria • Based on AC 20-129 performance • Operational approval criteria • Based on HBAT 99-08 and AC 90-97 • It is proposed to use those document as a basis except that visual segment obstacle assessment should be based on OCP 14 material instead of HBAT 99-08

12. AMC 20-XX Version 1 APV Baro-VNAV • Approach designed with specific PANS-OPS criteria. • Baro-VNAV approach procedures are classified as instrument procedures in support of approach and landing operations with vertical guidance (APV). • Use of a DA(H) • Approach plate indicates that this approach is an “APV Baro-VNAV” approach: • Defines « LNAV/VNAV » minima in the minimum box • VPA (°) • RDH (Wpt coordinates, height) • Minimum temperature • Navigation data base should contained WPTs and RNAV/VNAV information (RDH and VPA) for the procedure and the missed approach. Note: There is no protection as for APV-SBAS where the FAS data block is protected (CRC)

13. AMC 20-XX Version 1 APV Baro-VNAV • For APV Baro-VNAV, it is necessary to address specific issues: • Temperature correction, • Altimeter setting procedure, • Horizontal coupling error (ATK error impact on vertical positioning), • Specific altimeter maintenance procedure? (static source, etc), • …. • Baro-VNAV shouldn’t be considered anymore as a supplemental means. • Performance criteria should be defined and consistent with PANS-OPS • Functional criteria should be developed • If necessary operational limitation or procedures should be established • This Work should be done before incorporating any certification and operational criteria to AMC 20-XX for the APV Baro_VNAV use

14. AMC 20-XX Version 1 Vertical navigation discussionConclusion for NPA Baro VNAV • AMC 20-XX incorporates criteria for the approval of NPA Baro VNAV operation • Para 9.8 “Baro VNAV use on NPA -general criteria” • Appendix 2 “Obstacle Visual segment assessment” • VNAV performance based on AC 20-129 criteria • Basis for operational approval: • Use of DA(H) in lieu of MDA if visual segment obstacle assessment is done. OR • DA = MDA + 50 ft • AMC 20- XX NPA Baro VNAV criteria should be consolidated by OPS people and OCP members

15. AMC 20-XX Version 1 Vertical navigation discussionConclusion for APV Baro VNAV • Presently APV Baro-VNAV criteria are TBD in AMC 20-XX • Certification and operational criteria should be consistent with PANS-OPS • Some work should be done to define: • Airborne APV Baro-VNAV performance criteria (accuracy, integrity, continuity,…) • Airborne system functional criteria (required, recommended) • Some work should be done to assess impact of certain parameters on the baro VNAV and find a solution to mitigate the impact: • Altimeter setting • Navigation data base • Temperature effect • Horizontal coupling error • ……

16. AMC 20-XX Version 1 Synthesis Table

17. AMC 20-XX Version 1 Miscellaneous • FTE requirement is 0.25 Nm whereas it’s 0.2 Nm in PANS-OPS. • Navigation data base process (§9.5) • Is it sufficiently clear? • Do we need a specific guidance? • See Magali’s paper.

18. AMC 20-XX Version 1Conclusion • LNAV part is mature. • Use of Baro VNAV on NPA is addressed and is completed. • APV SBAS criteria (e.g. Annex 10, DO 229(), AC 20-138A) are available and therefore AMC 20-XX airborne criteria could be developed rather easily. • Airborne criteria for APV Baro VNAV don’t exist (e.g Accuracy, functional requirement,.) • Should be developed • Need a coordinated work (OPS, Airworthiness, procedure designer,..)

19. QUESTIONS ?