Visibility Chain at Regional Airports in the Netherlands Wiel Wauben R&D Information and Observation Technology
Introduction • KNMI automated the aeronautical observations at regional civil airports, the so-called AUTO METAR system. • During the evaluation many questions related to visibility arose. • It was realized that documentation was scattered between departments and incomplete; not always verified against current practices or ICAO requirements and recommendations; background of deviations were sometimes unclear (requirements old system or by local agreement? ). review of visibility chain against WMO 2008, 2010, ICAO 2005, 2006, 2010 and KNMI handbooks, reports and (manufacturer’s) system documentation, work instructions and configurations. 2 TECO 2012 | Visibility Chain
Visibility Chain • Public KNMI internal document (http: //www. knmi. nl/bibliotheek/knmipub. IR/IR 2012 -02. pdf • Contents 11. Server and client network systems 1. Introduction 2. Sources of meteorological information for users 12. System monitoring and data validation 13. Continuous remote verification 3. Definitions of visibility 14. Derivation of VIS and RVR 4. Causes of visibility reductions 15. Averaging of VIS and RVR 5. Visibility requirements 16. Selection and backup of VIS and RVR 6. Sensors for the measurement of MOR 17. Available VIS and RVR variables 7. Calibration of MOR measurements 18. Meteorological reports 8. Maintenance and effect of contamination 19. Technical infrastructure 20. Data flow 9. Sensor locations 21. Conclusions and recommendations 10. SIAM sensor interface and MUF cascade 3 TECO 2012 | Visibility Chain
Visibility requirements • WMO (2008) specifies the range of RVR as 10 to 1500 m, whereas ICAO (2010) recommends a RVR range from 50 to 2000 m. • The requirements for background luminance are not clearly stated. Range given in examples and ICAO (2006) only mentions that an uncertainty of ± 10 % is considered acceptable. 4 TECO 2012 | Visibility Chain
Calibration of MOR measurements • A field reference setup of TMM and FS is used the transfer the calibration of the TMM to the FS by means of a so-called Transmitter ↑ SB receiver ↑ scatter plate. LB receiver → FD 12 P ↑ • Reference restricted to MOR < 1500 m and without precipitation!? Furthermore the linearity of the sensor over the MOR range is not verified. • Background luminance checked via calibrator of manufacturer. Traceability is currently under review. 5 TECO 2012 | Visibility Chain
linearity FS 6 TECO 2012 | Visibility Chain
Maintenance and effect of contamination • Describes the maintenance and monitoring of lens contamination level and the effect of contamination of the MOR measurements. • Flying insects in the measurement volume of the FS sensor can give significant reductions of the MOR. • The solution. . . 7 ? see poster P 1(28)! TECO 2012 | Visibility Chain
Selection and backup of VIS and RVR • No backup of VIS/RVR at touchdown by FS at other end of RWY in local MET report (arrival). • Backup of background luminance is allowed. • Usage of video camera’s to determine whether VFR conditions apply in case of sensor failure, but quality images too poor. 8 TECO 2012 | Visibility Chain
Data flow 9 TECO 2012 | Visibility Chain
Conclusions • The review of the visibility chain was appreciated by internal and external users. • During the review some errors in the chain could be pointed out. Some of these were directly solved, but others require consensus between parties involved and/or further investigations. • The recommendations (37) are managed in a spreadsheet. Persons have been assigned, but items have not yet been prioritised and sometimes their impact is unclear. Meanwhile new items have been added to the list. • The maintenance of the document is still under discussion. Inclusion in Dutch handbook on observations versus coupling to documentation of the underlying systems, regulations and agreements. 10 TECO 2012 | Visibility Chain
A useful contribution • Track changes in WMO / ICAO documentation e. g. used in proposals for the amendment of Annex 3 and including rationale! 11 TECO 2012 | Visibility Chain
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