3.1 GENERAL.
This Chapter provides criteria for placement of sensors at airports based upon runway category (i.e., visual/nonprecision, precision without Runway Visual Range (RVR) instrumentation, and precision with RVR instrumentation). Special care is necessary in selecting appropriate locations for installation of sensors to assure that the resultant observations are representative of the meteorological conditions affecting aviation operations. Users, in applying these criteria, should consider future plans for the airport that could impact placement of sensors, e.g., installation of an Instrument Landing System (ILS), Microwave Landing System (MLS), runway construction, etc.
The site chosen for locating backup sensors shall be within 11,000 feet (3.4 kilometers) of the primary sensor array and shall have exposure and terrain equivalent to the primary sensor array site.
3.2 CLOUD HEIGHT, VISIBILITY, WIND, TEMPERATURE, DEW POINT, AND PRECIPITATION SENSORS.
3.2.1 General. No sensor siting shall violate runway or taxiway object free areas, runway or taxiway safety areas, obstacle free zones, or instrument flight procedures surfaces as described in AC 150/5300-13, Airport Design, or FAA Handbook 8260.3, TERPS. These sensors (cloud height, visibility, wind, temperature, dew point, and precipitation) should be located together near available power and communications. However, the temperature, dew point, and precipitation sensors can be placed at any convenient location on the airport that meets the sensor exposure criteria outlined in Chapter 2. FAA Sector Manager approval is required for the use of any FAA facilities, such as power, communications, shelters, towers, etc.
3.2.2 Airports with Only Visual and/or Nonprecision Runways. The preferred siting of the cloud height, visibility, and wind sensors and associated data collection platform (DCP) is adjacent to the primary runway 1,000 feet (300 meters) to 3,000 feet (900 meters) down the runway from the threshold. The primary runway is considered to be the runway with the lowest minimums. The minimum distance from the runway centerline shall be 500 feet (150 meters); the maximum distance shall not exceed 1,000 feet (300 meters). The minimum distance of 500 feet (150 meters) assumes flat terrain. If the elevation of the wind sensor site is above or below the runway elevation, then the minimum distance is adjusted by 7 feet (2.1 meters) for every foot (0.3 meters) of elevation difference. The adjustment is negative (i.e., the minimum distance
is less than 500 feet [150 meters]) if the sensor site elevation is less than the runway elevation. The adjustment is positive (i.e., the minimum distance is greater than 500 feet [150 meters]) if the sensor site elevation is greater than the runway elevation.
The preferred siting should be appropriate for most airports with only visual and/or nonprecision runways. If this siting proves to be unnecessarily restrictive, the cloud height, visibility, and wind sensors and associated DCP may be sited at an alternate location on the airport provided the alternate location: (1) will assure that the resultant observations are representative of the touchdown zone of the primary runway, and (2) meets the sensor exposure criteria outlined in Chapter 2. In no case shall the site selected result in a violation of a runway or taxiway object free area, runway or taxiway safety area, obstacle free zone or instrument flight procedures surfaces described in AC 150/5300-13, Airport Design, or FAA Handbook 8260.3, TERPS.
3.2.3 Airports with Precision Instrument Runways and Without RVR Instrumentation. There are two preferred options for siting at these airports.
3.2.3.1 Option #1.
The cloud height, visibility, and wind sensors and associated DCP shall be located adjacent to the primary instrument runway 1,000 feet (300 meters) to 3,000 feet (900 meters) down the runway from the threshold. The minimum distance from the runway centerline shall be 750 feet (230 meters); the maximum distance shall not exceed 1,000 feet (300 meters). The minimum distance of 750 feet (230 meters) assumes flat terrain. If the elevation of the wind sensor site is above or below the runway elevation, the minimum distance is adjusted by 7 feet (2.1 meters) for every foot (0.3 meters) of elevation difference. The adjustment is negative (i.e., the minimum distance is less than 700 feet [213 meters]) if the sensor site elevation is less than the runway elevation. The adjustment is positive (i.e., the minimum distance is greater than 750 feet [230 meters]) if the sensor site elevation is greater than the runway elevation. In no case shall the site result in a violation of a runway or taxiway object free area, runway or taxiway safety area, obstacle free zone, or instrument flight procedures surfaces as described in AC 150/5300-13, Airport Design, or FAA Handbook 8260.3, TERPS.
3.2.3.2 Option #2.
The cloud height and visibility sensors and associated DCP shall be located behind the glide slope shelter/MLS elevation station used for the primary precision instrument runway (area "B", Figure 1).
The wind sensor shall be located either on the glide slop antenna tower or on a separate tower. The preferred location is on the glide slope antenna tower as this eliminates the potential safety concerns caused by a separate wind sensor tower. This option shall be implemented at airports that have FAA Airway Facilities technicians available and who will not be relocated as a result of remote maintenance monitoring. Under no conditions shall anyone have access to an FAA glide slope antenna tower without an FAA technician being present.
When mounted on the glide slope antenna tower, the wind sensor shall: (1) not extend above the top of the tower, (2) be mounted on a boom a minimum of 3 feet (1 meter) laterally from the tower, (3) be a minimum of 3 feet (1 meter) vertically from any antenna, and (4) be mounted on the side of the tower opposite from the glide slope antenna face.
If joint use of the glide slope antenna tower is not practical, a separate wind sensor tower shall be installed immediately behind the glide slope antenna tower (area "A", Figure 1). The height of the complete installation (i.e., tower plus air terminal(s) and obstruction lights) shall not exceed the height of the glide slope antenna tower when installed in this area.
Exceptions: Sensors shall not be sited in area "A" or "B", Figure 1, if the glide slope installation is in violation of a runway or taxiway object free zone, runway or taxiway safety area, obstacle free zone, or instrument flight procedures surfaces as defined in AC 150/5300-13, Airport Design, or FAA Handbook 8260.3, TERPS. An OE/AAA study shall be performed if the glide slope installation is decommissioned or relocated subsequent to the siting of the sensors in areas "A" and "B", Figure 1.
One of the above options should be appropriate for most airports with precision instrument runways and without RVR instrumentation. If both options prove to be unnecessarily restrictive, then the cloud height, visibility, and wind sensors and associated DCP may be sited at an alternate location on the airport provided the alternate location: (1) will assure that the resultant observations are representative of the touchdown zone of the primary instrument runway and (2) meets the sensor exposure criteria outlined in Chapter 2. In no case shall the site selected result in a violation of a runway or taxiway object free area, runway or taxiway safety area, obstacle free zone, or instrument flight procedures surfaces as described in AC 150/5300-13, Airport Design, or FAA Handbook 8260.3, TERPS.
3.2.4 Airports with Precision Instrument Runways and With RVR Instrumentation.
The cloud height, visibility, and wind sensors and associated DCP shall be sited at a location on the airport that will assure the resultant observations are representative of the meteorological conditions affecting aviation operations, and that meets the sensor exposure criteria outlined in Chapter 2. No sensor siting shall violate runway or taxiway object free areas, runway or taxiway safety areas, obstacle free zones, or instrument flight procedures surfaces as described in AC 150/5300-13, Airport Design, or FAA Handbook 8260.3, TERPS.
3.3 PRESSURE, LIGHTNING DETECTION SENSORS.
3.3.1 Pressure. The pressure sensors are not functionally constrained to be at any specific location and may be located anywhere that meets the exposure requirements in paragraphs 2.2 and 2.2.1.
3.3.2 Lightning Detection (Thunderstorm). The single station detection sensor shall be installed at any convenient location on the airport and in accordance with requirements described in paragraph 3.3.2.
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