RNAV Overlays 1

1. 1 RNAV Overlays (1) Definition History of RNAV overlay 5 evolutionary steps to RNP What the system can do What the system is allowed to do Lack of legislation Use of the available system Development of �Soft� coding ARINC 424 developments

2. 2 RNAV Overlays (2) Problems with RNAV overlay FMS errors

3. 3 RNAV OverlayDefinition A route designed in accordance with non RNAV design criteria, being stored in a navigation database with or without State involvement

4. 4 RNAV Overlays5 evolutionary steps to RNP (1) Conventional procedure, not coded Conventional procedure flown by RNAV system, coded to ARINC 424 (no State involvement) Conventional Procedure meeting RNAV criteria coded to limited set ARINC 424 (State involvement) RNAV Procedure (not RNP) RNP-RNAV Procedure

5. 5 RNAV Overlays5 steps to RNP (2) Step 2 (conventional + overlay) No State involvement Coding is a private matter Pilot is and can be made responsible for monitoring accuracy using the underlaying conventional route

6. 6 RNAV Overlays5 steps to RNP (3) Step 3 (conventional + Overlay+ ) State involvement (learning phase) Publication of waypoints, allowing �FMS friendly� coding (turn anticipation, DF legs) Smooth transition towards RNAV via long(er) dead reckoning segments Control over coding via Source publication (charted and textual) Pilot is and can be made responsible for monitoring accuracy using raw data

7. 7 RNAV Overlays5 steps to RNP (4) Step 4 (RNAV) Heavy State involvement (State takes responsibilities) Coding (shared responsibility between the State and the database supplier) Testing Ground/space sensor availability Less possibilities for the pilot to monitor accuracy, more reliance on quality of the process

8. 8 RNAV Overlays5 steps to RNP (5) Step 5 (RNP) Heavy State involvement in all phases of the whole process Pilot to rely heavily on technical support and quality assurance of the whole process and all systems

9. 9 RNAV OverlaysWhat the system can do Route design flexibility: �any route in space� Direct approaches (no course reversals) Accurate track keeping (follows a �line on a map�) Random ad-hoc routing (ATC flexibility: �waypoints treated as VOR/DME�s�)

10. 10 RNAV OverlaysWhat the system is allowed to do Limited due to lack of integrity total system Software level C Software complexity Database complexity Route design mismatch with coding

11. 11 RNAV OverlaysLack of legislation DC10 RNAV as from 1970 Legislation lacking behind technical possibilities JAA PRNAV TGL-10 allows optimisation of what is available for 30 years Late return on investment

12. 12 RNAV OverlaysUse of the available system Solution: overlay of existing routes Requirement to check with raw data by the crew Trial and error coding development Increase complexity coding required (ARINC 424 evolution) Danger of the high expectations by the crew (99.xx% correct coding)

13. 13 RNAV OverlaysDevelopment of �soft� coding (1) Underlaying legal conventional route allowed �soft coding� Tendency to code difficult/not codable routes (�code what should not be coded�) AIRINC 424 increased in complexity to cope with flexible conventional route design

14. 14 RNAV OverlaysDevelopment of �soft� coding (2) Increased expectations by the crew Lack of experience in �out of FMS flying� However, ultimate responsibility rests at the crew

15. 15 RNAV OverlaysAIRINC 424 developments (1) Coping with expectation that all routes must and can be loaded Departures become more complex due to environmental pressure Continuous increase in complexity of coding rules

16. 16 RNAV OverlaysAIRINC 424 developments (2) Errors in coding Unexpected (some) aircraft behaviour Different in coding options for the same �problem� Different aircraft: different behaviour

17. 17 RNAV Overlays Problems with RNAV Overlay (1) Overlay coding not tested for flyability All lead radials/turn fixes coded as fly over waypoints Automatic turn anticipation feature of the RNAV System ignored Unintended destabilisation after fly-over waypoints

18. 18 Problems with RNAV Overlay (2) Impossible to apply �and-and� commands (�turn at.. not before..�) Unintended intercept heading Possible mismatch between conventional description and coding result �Price of overlay system�

19. 19 RNAV OverlaysFMS ERRORS (1) Four error sources Database Position Update FMC program / Database stored data interaction Pilot error

20. 20 RNAV OverlaysFMS ERRORS (2) Database Error Typing errors Incorrect way point / fix position calculation Magnetic variation Coding not in accordance with ARINC 424 Incorrect source documentation Too complex procedures Non adherence to ICAO or ARINC 424 Specifications

21. 21 RNAV OverlaysFMS ERRORS (3) Position Update Error Incorrect position DME station stored Movable TACAN Inadvertent update-station frequency change Duplicate frequencies combined with station shut-down Test emissions �covered� by TEST ident

22. 22 RNAV OverlaysFMS ERRORS (4) Position Update Error (2) Out of DME coverage flying Entering DME coverage area Update out of DME usable sector VOR/DME update Unknown sources

23. 23 RNAV OverlaysFMS ERRORS (5) FMC program / Database stored data - interaction Complex procedures may interact with aircraft performance limitations Aircraft performance overrules FMC commands Unintended aircraft response Automation �surprises�

24. 24 RNAV OverlaysFMS ERRORS (6) Pilot error Human Factor issues Pilot<>FMC interface Lack of commonality between systems Paper Chart versus Nav display System handling complexity Mode complexity Automation management

25. 25 RNAV OverlaysFMS ERRORS (7) ATC �interference� Last minute changes / re-programming Forced change in level of automation

26. 26 RNAV Overlays