Would you give up ILS for LPV approaches?

Discussion in 'Avionics and Upgrades' started by Chip Sylverne, Mar 31, 2019.

  1. Palmpilot

    Palmpilot Touchdown! Greaser!

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    I'd be a lot more concerned about the actual interference testing by the U.S. military than a hypothetical attack by the Russians.

    [​IMG]
     
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  2. John Collins

    John Collins Pattern Altitude

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    There are currently 3998 LPV and 1549 ILS. Pretty much all runways that have an ILS also have an LPV.
     
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  3. John Collins

    John Collins Pattern Altitude

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    I have not flown an ILS since 2008 in actual conditions. I regularly practice an ILS, but if ATC is using an ILS, I will request the RNAV. I have never been turned down, although vectors to final is the normal method of joining the approach because the path will overlay the ILS and I won't interfere with others flying the ILS. All that said, I would keep my ILS/VOR system as a backup. In the older installations with a separate GPS and Nav/Com, the primary CDI is usually switched between GPS and Nav and in most cases, the relay has spare poles to add the GS signals. If not, update the relay and keep the SL30, after all you still need a Com unit.
     
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  4. Walboy

    Walboy Cleared for Takeoff

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    I see these notices all the time and I have yet to lose a signal. I think a lot of the arrival/departure procedures into and out of the LA Basin are RNAV...do they quit using those during the testing period? :dunno:
     
  5. Chip Sylverne

    Chip Sylverne En-Route PoA Supporter

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    Fear is the poison of our lives.
    The fly in that ointment is the 175/375 isn't approved in the AFMS as a switched source, and it doesn't have the required annunciation pinouts. But I think I've decided to go with the 175 to drive my 525A and stec 60-2 for lpv appchs. Keep one sl30 as a separate loc/ils capability, and the second SL30 as a nav/com without a cdi, so if tshtf I can cross check radials using the integrated display and be on my merry way /A.
    Thanks for the input, John.
     
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  6. John Collins

    John Collins Pattern Altitude

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    The AFMS does not limit if the CDI source is switchable from GPS or VLOC. So there is no reason not to have one of your SL30 as a VLOC source and a switch/relay/Source annunciator to switch between GPS and VLOC.

    The external CDI is mentioned in a few places in the Limitations section of the AFMS, see this partial quote (reformatted):

    Although not a limitation (which is a legal requirement), section 4 of the AFMS for Normal Procedures deals with the topic of HSI/EHSI Operation. The caution note make no sense unless the installation supported a capability to select the source of GPS or VLOC on the same HSI.

     
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  7. Chip Sylverne

    Chip Sylverne En-Route PoA Supporter

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    Fear is the poison of our lives.
    Then I'm a little confused as to why the source switching wasn't spec'd in the external switching section, as it was in the GNS 4xx/5xx manual or the GTN 6xx/7xx manual, nor are there any interconnect diagrams as there are in the GX series IM's. The only source switching shown in the IM is for the Ki208A and 209A.

    As a practical matter, 12v remote solenoids are difficult to find and very expensive, and add significantly to the complexity of the install. I'm not sure the juice is worth the squeeze.
     
  8. N1120A

    N1120A Line Up and Wait

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    Unless you were based at VNY, MCC or any other of the very rare airports that don't have a decent (or any) GPS approach, you are getting much more if you choose LPV over ILS. Not only are you getting LPV, but all the non-LPV GPS approaches. Those are generally superior to some crappy VOR or even LOC only approach.

    On the first point, I totally agree. GPS approaches simply don't have the radio sensitivity issues that ILS approaches do, and light aircraft with GPSS autopilots fly them much better when you need to shoot with a little help than they do an ILS. Your information from the CDI is always going to be correct, no matter how close you get to the radio.

    On the second, when you have an LPV overlaid on an ILS, there is zero reason for a controller to deny. They use the same waypoints and even FAFs. More and more, I'll even have controllers clearing "ILS or RNAV." If a controller is denying in that situation, they are just being jerks.

    If you have WAAS and an LPV approach, you don't need a backup.

    We get those all the time and I've never (knock wood) had an issue.
     
  9. JohnAJohnson

    JohnAJohnson Cleared for Takeoff

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    I wonder if that includes the cost of satellite maintenance, Air Force staff required to monitor the system, and other required GPS costs. I think you'd have to for an apples to apples.


     
  10. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    Not from an FAA perspective. The GPS constellation is going to exist for the military regardless of other users. Might as well take advantage of it if you're the FAA. No more electronic stuff to maintain, just flight test it every so often and you're good.
     
  11. Martin Horton

    Martin Horton Filing Flight Plan

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    I'm just getting back into flying again, so not totally up to speed, so I might be way off. But I am looking to buy an airplane that is equipped with two NavComs but lacks a GPS and ADSB.
    So it occured to me that a GNX 375 would be great. But then I realized it wouldn't do ILS. But the ILS approaches are in the database, just come with a warning that it's for monitoring only. So it occurred to me that you could allow the GPS to provide guidance to the AP but you would have to have a NavCom tuned to the ILS and displayed on an indicator. Then you could let the AP fly the LPV provided you monitor the ILS indicator to be sure you are following LOC and GS.

    Am I crazy, misinformed, or would that work and be legal. It seems to me that as long as the ILS indications are in the right place, how you achieve that is up to you.
     
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  12. Chip Sylverne

    Chip Sylverne En-Route PoA Supporter

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    Fear is the poison of our lives.
    Martin, apparently great minds think alike ;)