FAA test methods for Runway Visual Range visibility and ambient light sensors

As part of the procurement process for a new Runway Visual Range (RVR) system, the Unites States (US) Federal Aviation Administration (FAA) has developed a formal Operational Capability Test (OCT) procedure for evaluating candidate visibility sensors (VS) and ambient light sensors (ALS) relative to the requirements in the FAA RVR system specification. In order to avoid the possibility of lengthy sensor modifications after contract award, the FAA chose to conduct a series of qualification tests on candidate sensors as part of the vendor evaluation process prior to contract award. Not all sensor requirements were to be evaluated during the relatively short test period (six months) at a single site. Rather, the focus was on 26 core requirements identified as being essential to VS and ALS performance. The test period was selected to include the possibility of severe winter weather that presents the most challenging conditions for sensor performance while also ensuring high probability of experiencing a number of significant fog events. An OCT was conducted this past winter (2003-2004) at the Otis Weather Test Facility on Cape Cod, MA. The test methods are described and sample test results presented to illustrate the data-gathering and analytical procedures employed. The test results utilize data from the current FAA New Generation RVR (NG-RVR) sensors as opposed to any of the candidate sensors used during the actual OCT, since the latter are necessarily proprietary and outside the public domain. The tests were divided into three categories: 1) Tests based on naturally occurring events during the six-month test period; 2) Tests based on artificially applying contaminants to the sensor windows; and 3) Tests conducted during installation and at 90-day maintenance intervals.