時間：2011-04-18 00:50來源：藍天飛行翻譯 作者：航空 點擊：次
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7.1.15. Runway Visual Range (RVR)There are currently two configurations of RVR in the NAS commonly identified as Taskers and New Generation RVR. The Taskers are the existing configuration which uses transmissometer technolo-gy. The New Generation RVRs were deployed in November 1994 and use forward scatter technology. The New Generation RVRs are currently being deployed in the NAS to replace the existing Taskers. a. RVR values are measured by transmissometers mounted on 14.foot towers along the runway. A full RVR system consists of: 1.Transmissometer projector and related items. 2.Transmissometer receiver (detector) and related items. 3.Analog 4. recorder. 5.Signal data converter and related items. 6.Remote digital or remote display program-mer. b. The transmissometer projector and receiver are mounted on towers 250 feet apart. A known intensity of light is emitted from the projector and is measured 7.1.38 Meteorology by the receiver. Any obscuring matter such as rain, snow, dust, fog, haze or smoke reduces the light intensity arriving at the receiver. The resultant intensity measurement is then converted to an RVR value by the signal data converter. These values are displayed by readout equipment in the associated air traffic facility and updated approximately once every minute for controller issuance to pilots. c.The signal data converter receives information on the high intensity runway edge light setting in use (step 3, 4, or 5); transmission values from the transmissometer and the sensing of day or night conditions. From the three data sources, the system will compute appropriate RVR values. d.An RVR transmissometer established on a 250 foot baseline provides digital readouts to a minimum of 600 feet, which are displayed in 200 foot increments to 3,000 feet and in 500 foot increments from 3,000 feet to a maximum value of 6,000 feet. e.RVR values for Category IIIa operations extend down to 700 feet RVR; however, only 600 and 800 feet are reportable RVR increments. The 800 RVR reportable value covers a range of 701 feet to 900 feet and is therefore a valid minimum indication of Category IIIa operations. f.Approach categories with the corresponding minimum RVR values. (See TBL 7.1.5.)TBL 7.1.5 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 g.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 one 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. h.Details on the requirements for the operational use of RVR are contained in FAA AC 97.1, “Runway Visual Range (RVR).” Pilots are responsible for compliance with minimums prescribed for their class of operations in the appropriate CFRs and/or operations specifications. i.RVR values are also measured by forward scatter meters mounted on 14.foot frangible fiberglass poles. A full RVR system consists of: 1.Forward scatter meter with a transmitter, receiver and associated items. 2.A runway light intensity monitor (RLIM). 3.An ambient light sensor (ALS). 4.A data processor unit (DPU). 5.Controller display (CD). j.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. k.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. l.New Generation RVRs can measure and display RVR values down to the lowest limits of Category IIIb operations (150 feet RVR). RVR values are displayed in 100 feet increments and are reported as follows: 1.100.feet increments for products below 800 feet. 2.200.feet increments for products between 800 feet and 3,000 feet. 3.500.feet increments for products between 3,000 feet and 6,500 feet. 4. 25.meter increments for products below 150 meters. 5. 50.meter increments for products between 150 meters and 800 meters. Meteorology 7.1.39 6.100.meter increments for products between 800 meters and 1,200 meters. 7.200.meter increments for products between 1,200 meters and 2,000 meters. 7.1.16. Reporting of Cloud Heights a. Ceiling, by definition in the CFRs 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 “obscuration,” e.g., an aerodrome forecast (TAF) which reads “BKN030” refers to height above ground level. An area forecast which reads “BKN030” indicates that the height is above mean sea level. REFERENCE. AIM, Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR), Paragraph 7.1.30, defines “broken,” “overcast,” and “obscuration.” |
