DME/DME RNP-0.3 NA

Discussion in 'Cleared for the Approach' started by JasonM, Aug 23, 2014.

  1. JasonM

    JasonM Pattern Altitude

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  2. poadeleted20

    poadeleted20 Deleted

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    If you don't know what to do with it, the answer to what you do with it is "nothing". RNP approaches require special certification for aircraft and training for the crew. If you'd had that training, you'd know what this means. Since you don't, you haven't, and you're not flying RNP approaches, so it doesn't affect anything you do.

    That said, it means if the RNP system you're using to fly RNP approaches is based on DME/DME with RNP-0.3 accuracy, you can't use that system to fly this particular RNP approach even though you can normally use a DME/DME-0.3 RNP system to fly RNP approaches.
     
  3. JasonM

    JasonM Pattern Altitude

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    ah thanks. Trying to grasp all the details at any airport my check ride may include and noticed this. Now I want to learn more about it.
     
  4. poadeleted20

    poadeleted20 Deleted

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    See AIM Section 5-4-18 for the short story and the Training material here for the fuller story.
     
  5. JasonM

    JasonM Pattern Altitude

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    Thanks. I will check it out.
     
  6. azure

    azure Final Approach

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    That was my DPE's "stump the dummy" question for me on my IR checkride. I offered that it doesn't apply to me, and he was satisfied with that and then used it as a teaching moment. Basically, what he told me is what C'Ron said.
     
  7. aterpster

    aterpster Pattern Altitude

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    I don't know of any RNAV approach that permits use of DME/DME 0.30, do you?

    And, certainly RNP AR does not permit it. It requires two GPS receivers, and a whole lot of other redundancy. Light airplane GA will never be able to fly RNP AR.

    Advanced RNAV is coming along one of these days, though, which some light airplanes will be able to fly, once the feds can agree on the ground rules for flying RF legs for non-RNP AR aircraft.
     
  8. John Collins

    John Collins Pattern Altitude

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    DME/DME is a technology that mostly airliners and some corporate aircraft have installed that permits them to navigate using RNAV routes. It is based on a FMS (Flight Management System) that receives multiple DME stations to triangulate the aircraft position. The DME frequencies, locations and identifiers are stored in the FMS database and are used to make the position determination. It only works where there are sufficient DME locations in order to determine a fix, such as over land. In the case of RNAV (GPS) approaches, there are rarely sufficient DME's in the immediate area to be able to maintain a valid position. DME/DME RNP 0.3 is a statement of a Navigation specification that requires a position to be determined within +/- 0.3 NM. An RNAV (GPS) approach with LNAV lateral is technically an RNP 0.3 approach in ICAO terminology.
     
  9. John Collins

    John Collins Pattern Altitude

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    In ICAO terminology, an RNAV (GPS) approach is RNP 0.3, see AC 90-105. You are thinking of RNAV (RNP) which require authorization.
     
  10. poadeleted20

    poadeleted20 Deleted

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    I assumed without looking that the approach which the OP was discussing was an RNAV(RNP) approach, and now that I look further, it isn't. As an RNAV(GPS) approach, Wally is correct -- you must be using GPS as the primary sensor on the final segment, so I can't imagine why that note is there.

    Of course, the answer about what that Note means to the OP is still "nothing", since the OP almost certainly isn't flying an RNP aircraft with DME/DME-0.3 capability.
     
  11. poadeleted20

    poadeleted20 Deleted

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    However, unless I'm missing something, one is not authorized to use DME/DME RNP to sub for GPS on an RNAV(GPS) approach, since it doesn't say anything but "GPS" in the title.
     
  12. John Collins

    John Collins Pattern Altitude

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    The last part of the statement is not strictly true, as any navigation system that meets the RNP 0.3 criteria in theory could fly the procedure, but I am not aware of any such example.

    This is from AC 90-105:

    In a note, they go on to say in the AC:


    This is from the Jeppesen description:

    Regardless, I agree that it doesn't apply to the OP and he can ignore the note.
     
  13. aterpster

    aterpster Pattern Altitude

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    The first few years after GPS became operational a few carriers that did not have GPS, but had DME/DME/IRU RNAV were authorized to fly GPS approaches. One airline had such a significant map shift on approach in your next of the woods, they came close to hitting a tower 1 mile, or so, off to the side. This event ended DME/DME for approaches.

    Thus, the note, because there are still some of those old pre-GPS FMSes flying around.
     
  14. poadeleted20

    poadeleted20 Deleted

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    That's the part I didn't know -- that it was possible to have approval to fly an approach without the equipment specified for lateral guidance on the final segment (in this case, DME/DME subbing for GPS). Thanks for pointing it out.
     
  15. aterpster

    aterpster Pattern Altitude

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    If you find one, let me know. I'd like to see one.
     
  16. poadeleted20

    poadeleted20 Deleted

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    Guess you'll have to ask John, since he's the one who pointed it out.:wink2:
     
  17. JimNtexas

    JimNtexas Pattern Altitude

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    Here is how I parse 'DME/DME RNP-0.3 NA', please correct me if I'm wrong:

    'DME/DME' refers to flight management systems that derive position from two different DME stations, as discussed above.

    RPN-0.3 refers to a 'Required Navigation Performance' device that is accurate to +/- 0.3 to 1.0nm along a route.

    NA means 'not authorized'

    So if you bought an old Learjet for $600K it might have an RNP 0.3 DME/DME flight management systems, but no GPS. If so you can't fly this approach.

    Now if you just bought a G650 for $650M that has an RPN 0.1 nav system and GPS is notam'd out, maybe you could fly this. I'll leave that discussion to the Gulfstream pilots and hanger lawyers.
     
  18. aterpster

    aterpster Pattern Altitude

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    You got most of it.

    The fact the G650 can do RNP 0.10 works only if GPS is working. So, if GPS is notam'd OTS, the G650 crew will have to shop for an LNAV approach with DME/DME 0.30 authorized. I think they will run out of gas first. :wink2:
     
  19. John Collins

    John Collins Pattern Altitude

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    RNP 0.3 specification means that the navigation equipment meets the accuracy performance of +/- 0.3 NM 95 percent of the time and incorporates associated on-board performance monitoring and alerting features to notify the pilot when the RNP specification is not being met.