13.6 Approach categories with the corresponding minimum RVR values are listed in TBL GEN 3.5.6.
TBL GEN 3.5.6
Approach Category/Minimum RVR Table
Category Visibility (RVR)
Nonprecision 2,400 feet
Category I 1,800 feet*
Category II 1,000 feet
Category IIIa 700 feet
Category IIIb 150 feet
Category IIIc 0 feet
* 1,400 feet with special equipment and authorization
13.7 Ten.minute maximum and minimum RVR values for the designated RVR runway are reported in the body of the aviation weather report when the prevailing visibility is less than 1 mile and/or the RVR is 6,000 feet or less. ATCTs report RVR when the prevailing visibility is 1 mile or less and/or the RVR is 6,000 feet or less.
13.8 Details on the requirements for the operational use of RVR are contained in FAA Advisory Circular 97.1, “Runway Visual Range (RVR).” Pilots are responsible for compliance with minimums prescribed for their class of operations in appropriate Federal Aviation Regulations and/or operations specifications.
13.8.1 RVR values are also measured by forward scatter meters mounted on 14.foot frangible fiberglass poles. A full RVR system consists of:
13.8.1.1 Forward scatter meter with a transmitter, receiver and associated items.
13.8.1.2 A runway light intensity monitor (RLIM).
13.8.1.3 An ambient light sensor (ALS).
13.8.1.4 A data processor unit (DPU).
13.8.1.5 A controller display (CD).
13.8.2 The forward scatter meter is mounted on a 14.foot frangible pole. Infrared light is emitted from the transmitter and received by the receiver. Any obscuring matter such as rain, snow, dust, fog, haze, or smoke increases the amount of scattered light reaching the receiver. The resulting measurement along with inputs from the runway light intensity monitor and the ambient light sensor are forwarded to the DPU which calculates the proper RVR value. The RVR values are displayed locally and remotely on controller displays.
13.8.3 The runway light intensity monitors both the runway edge and centerline light step settings (steps 1 through 5). Centerline light step settings are used for CAT IIIb operations. Edge light step settings are used for CAT I, II, and IIIa operations.
13.8.4 New Generation RVRs can measure and display RVR values down to the lowest limits of Category IIIb operations (150 foot RVR). RVR values are displayed in 100.foot increments and are reported as follows:
13.8.4.1 100.foot increments for products below 800 feet.
13.8.4.2 200.foot increments for products between 800 feet and 3,000 feet.
13.8.4.3 500.foot increments for products between 3,000 feet and 6,500 feet.
13.8.4.4 25.meter increments for products below 150 meters.
13.8.4.5 50.meter increments for products between 150 meters and 800 meters.
13.8.4.6 100.meter increments for products be-tween 800 meters and 1,200 meters.
13.8.4.7
200.meter increments for products be-tween 1,200 meters and 2,000 meters.
14.
Reporting of Cloud Heights
14.1 Ceiling, by definition in Federal Aviation Regulations, and as used in Aviation Weather Reports and Forecasts, is the height above ground (or water) level of the lowest layer of clouds or obscuring phenomenon that is reported as “broken,” “overcast,” or “the vertical visibility into an obscuration.” For example, an aerodrome forecast which reads “BKN030” refers to heights above ground level (AGL). An area forecast which reads “BKN030” states that the height is above mean sea level (MSL). See FIG GEN 3.5.24 for the Key to Routine Aviation Weather Reports and Forecasts for the definition of “broken,” “overcast,” and “obscuration.”
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