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之前对于为什么RVR能够替代的问题咨询了FAA当局，近期有了回复，整体上和笔者查询的资料内容差不多，同样是从RVR系统本身的作用范围和航空器运行中的重要性进行了解释，原文附在最后，其中的参考文件也欢迎感兴趣的朋友自行学习，前文可以参见文章： 对于起飞和着陆运行都可以允许有RVR替代的存在，也就是跑道上的某一段的RVR数值替代另外一段的做法，使用中间端RVR进行替代首先要基于FAA6560 order的RVR传感器设备的位置规定，在安装位置的基础上，可以发现在一个2000ft半径的范围内，是可以共享RVR数值的，同时一个接地端的RVR传感器是安装在跑道入口0-2500ft的范围内，而中间端是安装在跑道中间点1000ft的范围内，这就是一个RVR有效的范围半径，所以可以替代。 对于起飞滑跑来说，起飞阶段是非常缓慢的，所以机组有大量的时间来评估能见度，让航空器与跑道对正，同时基于上述的规定的RVR安装位置，允许运营人使用中间端代替接地端，也就是说首先第一段解释了RVR系统的作用范围在设备上是允许的，其次第二段解释了中间端的替代主要是因为机组可以有大量的时间来确定航空器的滑行状态，同样在着陆的时候，对于中间端和接地区之间也是可以替代。 末端的RVR不能作为替代RVR，这是因为航空器在接地区的RVR情况是最重要的，末端的RVR情况明显不能有效覆盖接地区的RVR情况，所以可以知道在国内文件或者国际文件中，不管是起飞还是着陆，接地区的RVR不工作时，只有中点端的可以替代，但是千万不要忘记一个前提，那就是RVR传感器的位置设置严格符合FAA Order 6560.10的要求。 原文如下： Thank you for your inquiry on the RVR readout values for TDZ and Midpoint RVR. For both takeoff and landing operations there are authorizations to allow RVR substitutions as you mentioned. Using a MID RVR may be authorized (depending on the OpSPec and/or the procedure) based on the RVR siting requirements of FAA Order 6560.10. Within the RVR siting requirements we find that we can share RVR’s within a 2,000 foot radius. A Touchdown RVR sensor is located within 0 to 2,500 feet from the threshold and the midpoint is within 1,000 feet of the center point of the runway. This shows an effective radius of the RVR system. During takeoff runs, the aircraft begins slowly so there is plenty of time for the pilot to evaluate visibility and aircraft alignment with regards to the runway centerline. This, combined with the siting requirements; allows operators to be authorized to substitute the Midpoint RVR for a Touchdown. The reverse is true for landing when substitution is authorized; the aircraft is slowing to taxi speeds at the end of the runway. A rollout RVR VS is not authorized as an RVR substitute due to the fact that the RVR is most critical at the touchdown of the aircraft. The requirements of 91.175 Takeoff and Landing Under IFR place emphasis on what the pilot is required to see in order to proceed safely. 参考文献： FAA Order 6560.10 Runway Visual Range FAA Order 6750.24 Instrument Landing System and Ancillary Electronic Component Configuration and Performance Requirements Advisory Circular (AC) 120-118 FAA Order 8260.3, United States Standard for Terminal Instrument Procedures (TERPS) The Instrument Procedures Handbook (IPH) The Pilot’s Handbook of Aeronautical Knowledge The Aeronautical Information Manual (AIM) |
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