关于两个ILS/DME程序共用一个DME的问题

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Sometimes, there are 2 ILS/DME approachs on opposite ends of a runway, with 2 different ILS frequencys, but with same DME (a DME arc). 在计算备降标准时，算作一套设备还是两套设备？

​Brett是这样回答的：

The determination of whether it is two different navaids is based upon the primary component of the approach in question. The DME is not considered primary, but rather the localizer would be what this is based on. So as long as it’s two different localizers, then it’s fine.

因此，这种共用一个DME的情况，可以算作两套设备。

《关于两个ILS/DME程序共用一个DME的问题》上有5个想法

  2. Definition of “Two Operational Facilities.” The words “two operational facilities” mean that in the event there is a single failure of one facility, the other would be operational. In the situation where both instrument landing system (ILS) facilities share a single transmitter, they are “one operational navigational facility” because both ILSs would become inoperative in the event of a single transmitter failure. The two ILS identifiers would have to be different even though the ILS transmitter frequency is the same for both. The instrument approach charts indicate to the pilot whether there is one frequency or two; thus, one or two navigational facilities.
    上面摘自8900.1 Vol.12
    如果需要DME定位的且仅有DME能提供定位信息的，DME失效时，程序当然也就失效。这时，另一套设备自然也失效。
    再追问一下？搞不好能问出DME定位对程序的影响。

    • 这个问题老师已经解释过了。
      Q: Do I need to check the frequencies of each localizer when looking for different runways/approaches/navaids?

      A: NO. There is no such thing as a 2-frequency rule. Often, both localizers on opposite ends of a runway will be operating a different frequency, many times the same frequency. Does not matter – they can never BOTH be on at the same time unless ATC policy now calls for head-on collisions due to head-on converging approaches. You can check the localizer ID on the IAP for each approach if you really want to verify if you have 2 different navaids, but unless you have a Localizer Back Course approach on one runway and an ILS on the opposite end of the pavement (1-nav rule here), you are wasting time.
      只要是两头盲降的，就可以算成两套设备，即使频率一样也没关系。只有Back Course才算成一套设备。
      相比之下，我更关心DME的问题。我觉得Brett的回答只是他一家之言，因为我没找到什么书面的依据。如果能多找几个美国签派问问就好了。

      • 额，上面问的就是DME的事。根据8900.1来看，就是一套中的设备失效是否会影响另一套设备工作。如果会，那么就算一套。对于共用一个且只有一个DME的，且两头程序均基于该DME定位的，我认为根据上述定义，只能算一套。

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