LPV approaches ... GPS altitude?

Discussion in 'Cleared for the Approach' started by alanbreck, Jun 24, 2019.

  1. jordane93

    jordane93 Final Approach

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    The 121 world is highly regulated. Any slight change to any manual or procedure is kind of a headache so it wouldn’t be cake just to implement authorize the use of LPV approaches. It took my companies months just to change the way we flew non precision approaches from dive and drive to a constant angle approach. We didn’t add any new approach authorizations. We just changed the way we shot a LOC, RNAV, VOR, etc.
     
  2. N1120A

    N1120A Line Up and Wait

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    Not necessarily. Just unable to use the minimums. They can use LNAV/VNAV.
     
  3. aterpster

    aterpster Pattern Altitude

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    And, that is not WAAS LNAV/VNAV.
     
  4. olasek

    olasek Pattern Altitude

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    Most likely they wouldn't even be able to load it, it would not show up in their database. The same way I don't see RNP approaches in my Cirrus' nav database.
     
  5. aterpster

    aterpster Pattern Altitude

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    Not really the same. The RNP AR database is loaded separately only on aircraft that have jumped through all the hoops. Then, not all RNP AR approaches are in those databases, rather only those for which the aircraft/operator have qualified for. Each such approved approach has to be verified by an independent qualification entity as to continuity and flyability with the specific FMS in the aircraft.
     
  6. N1120A

    N1120A Line Up and Wait

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    That's not true. Most, though not all, LPV RNAV approaches also have some combination of LP, LNAV/VNAV, LNAV and even Circling minimums. Very few are solely LPV approaches. That way, aircraft that are non-WAAS can still fly them.
     
  7. aterpster

    aterpster Pattern Altitude

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    That's correct, but you'll never see a procedure with both LPV and LP.
     
  8. write-stuff

    write-stuff En-Route

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  9. luvflyin

    luvflyin Final Approach

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    What site is that from? I think their 'summary' is wrong.
     
  10. aterpster

    aterpster Pattern Altitude

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    It is wrong as to LNAV/VNAV. Depending on the airplane, LNAV/VNAV may, or may not, require WAAS.
     
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  11. luvflyin

    luvflyin Final Approach

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    Yeah. That Approach does have Baro-VNAV notes pertaining to Temperature and Altimeter Source but WAAS wouldn't be required if you were within the temperature range and using the correct Altimeter. What about LNAV+V? Not pertinent to that Approach but I think it's the same. WAAS not required unless it is for a particular Approach.
     
  12. MauleSkinner

    MauleSkinner Final Approach

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    It’s more about your equipment installation...some boxes use Baro input for LNAV/VNAV, others use a WAAS input. Some WAAS boxes allow you to deselect WAAS input and force the use of Baro input for LNAV/VNAV minimums.
    I believe “LNAV+V” is a Garmin term, and Garmin boxes without WAAS don’t give you the “+V”. Many systems can or do use Baro VNAV for advisory glidepath information.
     
    Last edited: Jun 30, 2019
  13. chemgeek

    chemgeek Cleared for Takeoff

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    LNAV+V is LNAV with vertical ADVISORY information. Garmin boxes will do this for certain approaches. The +V is not part of the official approach design, and is safely ignored. The +V gives you guidance for something like a 3 degree vertical descent from the FAF to the runway. Or, if you just want to break out quicker, you can do a "dive and drive" at each of the stepdown fixes while ignoring the vertical advisory information. You are still on your own for complying with stepdown altitudes. In other words, LNAV+V is just an LNAV approach.

    If you follow the vertical advisory guidance below the MDA you can become a statistic. The GPS 7 to Sidney NY (N23) (in my area) is a good example, and this and other various concerns about the approach got it marked N/A at night for a while. Yet, it is quite safe if you just follow the stepdown fixes and don't go below DA until the airport is in clear sight.
     
  14. luvflyin

    luvflyin Final Approach

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    and @MauleSkinner . Got it now. I didn't know that LNAV+V was a Garmin gadget. Come to think of it I couldn't recall any Approaches that have LNAV+V line of Minimums.
     
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  15. MauleSkinner

    MauleSkinner Final Approach

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    Spending some time in the POH/Supplement would probably help clarify that.

    I know that sounds snarky, but it’s not intended to be.:cool:
     
  16. luvflyin

    luvflyin Final Approach

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    Lol. Snark away. Anyway, thanks
     
  17. chemgeek

    chemgeek Cleared for Takeoff

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    To be fair, the LNAV+V is described in the "fine print" of the GNS-430 manual, and most instrument instructors will inform their students about how it works as well. In addition, the topic has been covered in the instrument rags as well. But if you trained IFR before WAAS, you would have to figure this out on your own or perhaps stumble across it during an IPC or in your subscription to IFR magazine or the like. It is important to know about if you fly IFR, as the vertical guidance coming alive is alluring, and is in my opinion potentially confusing. When I first got my GNS-430, I flew a bunch of LNAV+V approaches in my area in VFR conditions out of curiosity using the +V to see what it would do if you followed it down to the runway. Basically, it will take you right to the threshold--very impressive. HOWEVER, the +V knows nothing about terrain, so there are some places (Sidney being one) where following the +V advisory glideslope will take you straight into an intervening hillside. THIS is why you should be knowledgeable about the LNAV+V function, and of course why you should adhere to stepdown fix limitations and the DA.

    Personally, I wish I could just disable the LNAV+V function. I don't mind "dive and drive."

    Cheers, and be careful out there...
     
  18. MauleSkinner

    MauleSkinner Final Approach

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    I’d agree with most of that, but instructors, Instrument rags, an IPC, etc., are not the official source. The POH/Supplement is, and therefore it’s important for a pilot using the equipment to “stumble across” the fine print of the GPS documentation.
     
  19. luvflyin

    luvflyin Final Approach

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  20. MauleSkinner

    MauleSkinner Final Approach

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  21. luvflyin

    luvflyin Final Approach

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    Not about ‘correcting’ you. Was just wondering so looked it up. Garmin doesn’t own the Sky, yet:D. It’s like Vise Grips or Crescent wrenches, we all call em that even though others manufacture whatever their generic names are. Seems relatively new compared to Garmin. I wonder if Garmin has it patented and if Avidyne and others pay to use the concept.
     
  22. aterpster

    aterpster Pattern Altitude

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    An example?
     
  23. MauleSkinner

    MauleSkinner Final Approach

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    Collins and Honeywell have had it for over 20 years. Not positive, but we think Universal did, too.
     
    Last edited: Jul 1, 2019
  24. aterpster

    aterpster Pattern Altitude

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    Okay. Thought you meant procedural.
     
  25. N1120A

    N1120A Line Up and Wait

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    Interestingly, there was a NOTAM on a non-LPV approach that I've used for training and in non-WAAS airplanes that listed the 3 degree altitude from the FAF to a fix between the FAF and the MAP that is where the LNAV+V would take you as the step down altitude (about 60 feet higher), but they removed it.
     
  26. azure

    azure Final Approach

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    As is the RNAV 35 to my home base, KMPV (Montpelier, VT). There was a video on the AOPA website (I think it was from FAAST), might be still available, that showed a couple of pilots that nearly bought it flying that approach at night. There is elevated terrain about a mile south of the field that will eat you if you try to cheat the MDA. Night landing to 35 (and 05, same reason) is NA now on that approach.
     
  27. chemgeek

    chemgeek Cleared for Takeoff

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    The FAA made quite a few approaches N/A at night for a while a few years ago because of this and similar issues. It took a while to convince the FAA to let up. For us and others, it required that the VASI/PAPI systems be functional to allow night approaches.

    RIght now, the FAA is on a mission to align VASI/PAPI lights with the glide angle (GA) for LPV approaches. We are one of he first airports to be affected. Our GA is 3.08 degrees (PAPIs are at 4.0 degrees), but apparently, there are some obstructions (trees) that conflict with current design safety limits. In order to keep reasonable minimums, we are going to have to raise our glide angle to get past the obstructions (to 3.5 or 3.77 degrees) and will have to re-align the PAPIs to the same value to make everything kosher. This issue, along with a long-ago, ill-advised wind farm on the missed approach course, will probably raise our minimums from 250 AGL to something closer to 400 AGL. Hopefully, it will impact class A aircraft less than class C aircraft. We'll have to see what the approach designers come up with.
     
  28. aterpster

    aterpster Pattern Altitude

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    Picking at nits: Approach Category, not Class. "Class" is used for airport standards for aircraft size related to runways and taxiways, not instrument approach or departure procedures.
     
  29. olasek

    olasek Pattern Altitude

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    Well, it knows about the terrain up to MDA, below MDA - you must fly visually anyway.
     
  30. chemgeek

    chemgeek Cleared for Takeoff

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    Yeah, too lazy to look up the appropriate terminology. Just got a gander at the proposed changes today and the underlying issues causing them via our airport consultant. Our RWY 35 approach gets raised to 450 AGL (without some tree amelioration which might help slightly) and for some reason the RWY 17 gets LOWERED to 300 AGL. (Go figure.) The windfarm impacts the missed approach for 35, which in turn affects the allowable MDA for that approach in order to assure appropriate clearance. Our ODPs will get changes as well. Still trying to understand why the FAA let the windfarm go up 3 miles north of the airport. We had to beg them to change the ODP years ago when local pilots noted that the published ODPs were...up close and personal with the windmills. Now the current interpretation of the TERPS will initiate additional changes. Oh well...
     
  31. aterpster

    aterpster Pattern Altitude

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    There would have been a Part 77 Aeronautical Study and presumably a determination of no hazard. Airport managers should be on top of Part 77 proposals affecting their airport. Sadly, that only happens at air carrier airports where the airport management has a staff specialist who know where to look on a timely basis.
     
  32. sonopoa

    sonopoa Pre-Flight

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    There is a Book Club ? - care to post the link to that ?
     
  33. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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    My pleasure. (It is 'buried' in Hangar Talk)
    Here it is
     
  34. aterpster

    aterpster Pattern Altitude

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    Thanks for the tip. It's on my to-do list. In the banner it mentions, among other things, on-line banking. I had on-line banking via dial-up modem before GPS. Perhaps they meant via the Internet. There were also many bulletin board systems during the dial-up modem days. Remember Hayes kept improving the speed in spite of Bell folks saying it couldn't be done?