CAP 670 Part C, Section 2: NAV 01: Engineering Requirements for Instrumented Runway Visual Range (IRVR) Systems
June 2019 Page 2
NAV01.7 For existing systems, IRVR values calculated using 40 per cent of the averaged beam intensity of the specified inner ellipse for runway edge lights (as defined in Appendix 6A of CAP168, “Aeronautical Ground Lighting Characteristics”) will be permitted following the submission to the CAA of results obtained by either photometric measurement or following the “block replacement” of those lights (1644).
Note 1: For new and existing systems, the initial de-rating factor of 40% is based upon the minimum serviceability requirements set out in Chapter 6 of CAP 168 (Licensing of Aerodromes) and continuing operation at this level will depend upon satisfactory evidence of on-going inspection and subsequent maintenance programme being presented to the CAA. A more pessimistic de-rating factor will be ascertained in the absence of such evidence.
Note 2: CAA staff will determine whether continued operation at the initial de-rating factor is justified or whether the de-rating factor can be increased upward toward the ICAO recommended maximum of 80% (Doc 9328 Chapter 6.5, “Light and Light Intensity”).
Note 3: The number of inspections required in each calendar year will depend upon the nature and frequency of aircraft operations from that aerodrome but a minimum of 4 photometric inspections (one in each quarter) should be taken during each 12 month period and the results submitted to the appropriate CAA RO.
NAV01.8 The sensor output shall be sampled at a minimum rate of once per second
