Why buy new VHF Nav?

Discussion in 'Avionics and Upgrades' started by CRQFlier, Dec 29, 2020.

  1. CRQFlier

    CRQFlier Pre-takeoff checklist

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    I've been planning a panel upgrade for a few months. The goal is light IFR capability. The plan includes a new audio panel, GPS, and comm plus an indicator (G5, E5, 275, 106b - not sure which). I had planned on keeping my Narco 12D that includes GS and DME. But... the Narco has gotten squirly with intermittent lost comm. Not good.

    So I "assumed" I should just get a GNC255 replacement and tie it to whatever indicator i buy - easy. But then I started thinking - when exactly do I use VHF nav only? I initially thought, well it's good backup if gps goes down, I can run an ILS or LOC. But reviewing dozens of approaches they all require DME (or GPS). So the backup idea doesn't hold water for IFR.

    Is VHF nav really just a VFR dinosaur at this point? Keep it if you got it, but don't buy new?

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  2. AlphaMike

    AlphaMike Pre-takeoff checklist

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    Fallowing! I’m in the same place. Backup GPS or GNC255
     
  3. gsengle

    gsengle Pattern Altitude

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    Depends on the flying you do. Personally I still want to be able to do an ILS. But as a practical matter they all have LNAV/VNAV / LPV overlays in the USA these days, so I’d be tempted to go dual gps and be done. Not sure if there is a regulatory reason you can’t do that part 91..


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  4. Arrow76R

    Arrow76R Pre-takeoff checklist

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    With all the military jamming "tests" of GPS it would be advisable to have a backup! But I err...they tend to do those "tests" only in the "fly-over" parts of the country.
     
  5. Groundpounder

    Groundpounder En-Route

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    I would be very reluctant to go with no VHF nav abilities at all. In addition to the times when GPS may be unavailable, there may be times when you are going to somewhere that is advertising the ILS, and for whatever reason won't let you shoot the RNAV.
     
  6. CRQFlier

    CRQFlier Pre-takeoff checklist

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    I was planning to keep that narco for exactly the ILS reason - it has DME. But the GNC255 does not, so you need GPS for every ILS/LOC i looked at. So if GPS is down - either the box or system - you need dme for the ILS, technically. That's why I'm rethinking even needing VHF nav.

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  7. CRQFlier

    CRQFlier Pre-takeoff checklist

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    I haven't found an ILS (nearby) that doesn't require DME or GPS. Also haven't found an airport that has ILS but no VNAV/RNAV and usually LPV. Found a few LOC that don't require the DME/GPS.

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  8. Groundpounder

    Groundpounder En-Route

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    So get a GNC355, which will give you a GPS and a COM, and then get a GNC255, which will give you a VOR/ILS receiver and a com #2.
     
  9. asicer

    asicer Final Approach

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    What about VOR approaches that don't require DME?
     
  10. gsengle

    gsengle Pattern Altitude

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    GPS


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  11. CRQFlier

    CRQFlier Pre-takeoff checklist

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    That's what I originally thought. But then I wondered what I'm I really getting, when do I use VHF only nav - without dme or gps? Cost wise the 255 is maybe $3-4k more than a 225 when you include fresh install.

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  12. CRQFlier

    CRQFlier Pre-takeoff checklist

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    I suppose that's probably it if GPS is inop. Pretty rare bird.

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  13. asicer

    asicer Final Approach

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    What about VOR approaches that don't require DME for when the GPS is being jammed?
     
  14. asicer

    asicer Final Approach

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    Perhaps, but not rare enough for the FAA to stop worrying and discontinue their MON program.
     
  15. gsengle

    gsengle Pattern Altitude

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    If you’re that unlucky, divert.


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  16. gsengle

    gsengle Pattern Altitude

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    I have 3000 hours. I’ve flown one VOR approach that wasn’t part of a check ride ever. Not sure if it required DME or not.


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  17. asicer

    asicer Final Approach

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    A VHF NAV receiver can be helpful when you divert due to a jammed GPS :)
     
  18. bluesky74656

    bluesky74656 Line Up and Wait

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    It seems that there is some condition that would allow an ILS approach to an airport but not allow an RNAV approach. The RNAV (GPS) 24R into Burke Lakefront (BKL) is NOTAMed unavailable, but the ILS 24R is available. If you don’t have an ILS, you can’t shoot an approach to that airport.
     
  19. RussR

    RussR En-Route

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    As a kind of side note, If you can get radar vectors, no ILS procedure really requires DME or ADF, even if it says it does. All you really need to be able to do intercept the glideslope and ride it down. If your primary navigation radio fails, you have the ability to treat it as an emergency anyway, and do what you need to. Safely.
     
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  20. gsengle

    gsengle Pattern Altitude

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    It’s almost always the other way around...


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  21. Groundpounder

    Groundpounder En-Route

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    If you truly want to fly IFR, and reliably get to your destination each and every time, $3-4k is short money. If you're OK with there being times you can't get there from here, well.....
     
  22. hindsight2020

    hindsight2020 Final Approach

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    He can keep the narco 12D as-installed for cheap and retain VHF nav capes.Way cheaper than reinventing the wheel with a fresh high faluting garmo moneybag navcom box. Furthermore, the OPs concern for DME is moot in the first place, if he's committed to install a GPS in the plane. Post 19 already explained the real-world flying reasons why.
     
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  23. CRQFlier

    CRQFlier Pre-takeoff checklist

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    I agree 3-4k isn't much in the broader picture. But my use case is light IFR - meaning a marine layer or MVFR when I'd rather be IFR. I don't do single engine IMC over mountains any more - so I'm pretty limited anyway.

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  24. CRQFlier

    CRQFlier Pre-takeoff checklist

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    This might be the way to go.

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  25. asicer

    asicer Final Approach

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    I concur, but didn't you say in post #1 that it was giving you problems? I thought Narco's were pretty much un-repairable at this point in time?
     
  26. CRQFlier

    CRQFlier Pre-takeoff checklist

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    Yes, the comm in intermittent inop. The nav has been OK - as far as I know. But honestly, I gotta think the nav is next - might already have issues, but we haven't noticed since we rarely use it. Bevan will repair still, but that's likely good money after bad.

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  27. Ravioli

    Ravioli Ejection Handle Pulled

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    The odds of both ground based and satellite based navigation going dark simultaneously are pretty low.

    So... Dual GPS only protects against your equipment failing. Having GPS and NAV gives a backup for things outside your cockpit.

    Seams like cheap insurance to me.
     
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  28. geezer

    geezer Line Up and Wait

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    As RussR pointed out, if there is radar coverage, they will vector you to the ILS intercept, so lack of DME is not too important.

    I have been vectored to the intercept several times, they did not want me flying the whole procedure. I have not flown a plane with DME, except when training for the IFR add on.
     
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  29. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    Like California. :(
     
  30. SCCutler

    SCCutler Administrator Management Council Member PoA Supporter

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    The 12D is a solid radio, and is certainly repairable. Bevan (among others) can certainly renew the Mark 12D.

    That’s what I’d do.
     
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