Brian E.

Perspective needed: WAAS only GPS Navigator or Nav with legacy NAVAIDS

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Happy holidays -  I'm getting close to narrowing down my avionics shop as I try to bring my M20C up to date.  I currently have 2 KX155s feeding a dual VOR setup with one that has a glideslope.  I'm second guessing my choice to replace both KXs with modern radios and pull both VORs and replace with a GNX375.  The only reason I'm wavering is due to the IFR weather alternate requirements for WAAS equipped aircraft.  WIth that in mind I'm reconsidering installing a navigator that will take advantage of the VOR and ILS antenna such as an Avidyne  440 or 540.  To help frame this a bit better I'm not necessarily looking to shoot approaches to minimums and really think that non-precision alternate minimums should be sufficient but I wanted another perspective to ensure I'm not being short sighted.

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I can't really give you an answer to your particular question, but in my plane, the KX-155 seems to pick up comms better than my 430.  I don't know if that's across the board with everyone or just my particular plane.  It's enough to make me ask before I dump the KX-155.

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@rbridgesGood point on the radio as I've heard the 155s are better sounding than most modern radios.  I also realize they are old radios and Comm 1 is losing the top segment of the 1st digit occasionally--transmits and receives well.  Comm 2 is money, display is clear and knobs are smooth.  I was going to use a GTR225 to replace Comm. My goals was to get in and get our and not have to go back any time soon.

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46 minutes ago, rbridges said:

I can't really give you an answer to your particular question, but in my plane, the KX-155 seems to pick up comms better than my 430.  I don't know if that's across the board with everyone or just my particular plane.  It's enough to make me ask before I dump the KX-155.

A lot of pilots have had the same reaction.  I bought the 430 AW, the “A” being the 16 watt transmitter, just so that I would have plenty of radio power.  Unfortunately it does nothing for reception.  Mine went back to Garmin several years ago and was found to be “out of spec” on the bench, was adjusted, and went back in the plane.  I still have an issue with receiving ATC when I get a long way from the ground transmitter, or if there is weather around and thus interference.  I am looking at a GTN750, which would result in pulling the old King that I have, and I don’t relish that thought because as old as it is, it is my “go to” when the Garmin radio in the 430 isn’t doing its job. I am hoping Garmin has gotten the message and the newer radios are better??

WAAS on the other hand, is really really useful. You don’t have to shoot any approach down to minimums if you don’t want to.  I wouldn’t be without VOR/ILS capability though.  What happens if you lose GPS guidance, i.e. there is an outage? And there are lots of trafficked airports where ATC would rather have you on the ILS with everyone else. Personally, I prefer ILS approaches to GPS approaches.

Edited by jlunseth

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Why not go with just adding a GPS 175 and leave everything else as is? Or compromise and pull the non-glidesloped kx 155 and indicator and install the GNC 355?

Sent from my LM-V405 using Tapatalk

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So...

The only thing you need is to add a WAAS source?  Helps with 2020 compliance...

 

Get an all in one box... because it does everything... in the smallest amount of panel space...

On a budget, go used 430W...

Less of a budget restriction, go Avidyne...

no budget restriction, go big G...

Otherwise you run out of room for everything you want...

 

If you fly IFR a lot... it is nice to have two precision resources to get to the ground...  ILS or WAAS...

installation costs... you are not paying for things you don’t get...


Check to see if your home drome has a WAAS approach...

 

 

Lets start with...

What are you trying to get out of your panel project...?

  • WAAS for ADSB/2020...
  • WAAS for vertical guidance on approaches...
  • Approach capable GPS.... no vertical guidance...
  • Transponder/WAAS/GPS/weather/traffic...

I simply added a WAAS box repeater to go with my existing transponder... 2020 compliant, but, not flying IFR at this time...

Figure out what you want, then check in with Alan to see what’s on the trade shelf...

Sorry if I missed the objective... :)

Best regards,

-a-

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I faced a similar dilemma with my airplane. I was IFR equipped with the dual NAV/COMs, dual VORs, ADF, glideslope, etc. I had already met the ADS-B requirements with a Lynx 9000 NGT.

My NAV/COMs were 17 and 18 years old, respectively, and starting to be a little finicky at times. I made up my mind that I wasn’t going to spend any more money on old technology that added zero value or capability to the airplane. I sure wasn’t interested in purchasing old gear that might have a limited remaining useful life to it.

I opted for a new GTN 650, GI106B indicator and a GMA 342 audio panel to provide a built-in intercom and facilitate the removal of my remote 1975 era marker beacon receiver. I retained the best of my two NAV/COMs, the remote glideslope receiver and the VOR head with the cross pointer. Consequently, I now have dual independent ILS capability as well as all the RNAV approaches available with the GTN. I am really enjoying this set up and the GTN in particular. The new gear is fun and easy to use. RNAV approaches and holding procedures are a snap. The capabilities that it provides will spoil you quickly. 
 

Now, when I am looking at the for sale ads, I find myself quickly dismissing anything with old radio gear in it. Once you have the new stuff, you just don’t want to go back.

 

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My airplane is headed for the radio shop next week.  When I get it back it will have the old KX-155, new GTX375 (driving the old HSI and Stec AP) and a PAR200B audio panel/comm radio. I too was concerned about keeping an ILS receiver.  All the other old stuff will be gone: audio panel, Mac1500, KR87 ADF, KN62 DME, KT76 transponder.

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Not saying it is prophetic, but this was the title on a FAA Safety Team seminar email I received this morning:

"No GPS Signal-Now What?"
Topic: Old school navigation when the government shuts down the GPS signal in a region

 

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I'm following this as well. Barring any unforeseen expenses the plan is to put in some avionics and get the IFR done this year. I have a VOR/ILS head and a Narco Mark 12D. Number one radio is a Garmin SL-40. Plan to keep the SL-40 and replace the Narco 12D with something, just trying to decide what that something is going to be, maybe GNC 355, GTN 650, or IFD 440.

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44 minutes ago, Oldguy said:

Not saying it is prophetic, but this was the title on a FAA Safety Team seminar email I received this morning:

"No GPS Signal-Now What?"
Topic: Old school navigation when the government shuts down the GPS signal in a region

 

There are so many financial, commercial, transportation, and safety functions that are dependent on GPS that I think the likelihood of the gov ever turning it off are pretty much zero.

 

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44 minutes ago, EricJ said:

There are so many financial, commercial, transportation, and safety functions that are dependent on GPS that I think the likelihood of the gov ever turning it off are pretty much zero.

 

I would agree long term, but we are consistently seeing where they are doing something to interrupt the signal at various times and altitudes in different locations. There are usually NOTAMs associated with the outages, but they do occur.

Something like this:

 

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2 minutes ago, Oldguy said:

I would agree long term, but we are consistently seeing where they are doing something to interrupt the signal at various times and altitudes in different locations. There are usually NOTAMs associated with the outages, but they do occur.

Something like this:

 

"Outage" means different things in different applications, though, and the integrity checking standard for airborne navigation will fail before a handheld or a timing application.   We see those notams in the southwest all the time, and while it does happen, I've not personally experienced a nav failure because of them.    It's pretty rare that I check notams for a trip and not see these warnings, though.   So I think whatever they're doing isn't sufficient to drop most applications.

Just a quick link that illustrates some of the examples of how extensive the reliance on GPS timing goes:

https://qz.com/1106064/the-entire-global-financial-system-depends-on-gps-and-its-shockingly-vulnerable-to-attack/

 

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1 hour ago, EricJ said:

"Outage" means different things in different applications,

 

Yes, I'm curious if the above outage will have an effect on ATL, CLT, CHS, etc.  That's a big swath of airspace with decent traffic in it.

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Thanks for all the replies.  I'm really trying to get away from all of the legacy gear and clean up the panel and not have to fix things twice.  I see more GPS approaches at the places that I fly than VORs and more GPS/VOR than ILS ten fold.  This leads me to question the need to invest in a secondary and tertiary navigation means.

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3 hours ago, Brian E. said:

This leads me to question the need to invest in a secondary and tertiary navigation means.

my wife always laughs about me wanting a backup to the backup to the backup.

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I don’t know about anyone else’s experience, but for me the ILS approaches are a lot shorter than GPS. Its still easier to get a VTF ILS, get right on the approach and get down, than it is to get VTF for an RNAV.  We have one at FCM where it is common, the approach is from the side of the airport where the MSP Bravo is located and they want to keep you away from the landing Bravo ring.  Otherwise its a long ride to the FAF and down.

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I bought a J, upgraded the panel, flew it 5 years and sold it. Then I bought a K and upgraded it's panel. So I've done it twice. 

My priorities were safety, reliability, and redundancy. I really don't want to be on  trip and dealing with a radio failure. All of the old King radios I removed had issues, either TX or RX. I know people love them, but I just didn't want that old stuff. I don't want to keep spending $ and time repairing old radios.  Finally I don't want any single failure to be an emergency. So 2 certified independent boxes that can navigate and communicate. I don't think one needs both boxes to be GPS/NAV/COM however. 

In the J I put a single Aspen, GTN650, and SL30. I thought that was the best bang for the buck.

In the K I put 3 Aspens, and 2 GTN650's. I wanted more redundancy and capability in a more capable airplane.

Now for the question you didn't ask. Do you have a single vacuum driven AI? I would bet the failure of that system has killed more pilots than any nav/com failure. I think dual certified AI's would be required in any IFR panel.

Larry

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14 hours ago, larryb said:

 

Now for the question you didn't ask. Do you have a single vacuum driven AI? I would bet the failure of that system has killed more pilots than any nav/com failure. I think dual certified AI's would be required in any IFR panel.

Larry

sorry for the thread drift, but that's a good point.  I ponied up for the dual MAX units to be vacuum free, but even one will get you out of an emergency.

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On 12/11/2019 at 3:49 AM, larryb said:

In the K I put 3 Aspens, and 2 GTN650's

You do set the bar high.. :)

 

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Think of it this way, for modern IFR, these days a realistic  minimum equipment list should be:

Dual COM's and Nav's

At least 1 WAAS GPS, two is better

Backup electric attitude is a must with a legacy vacuum instruments; or preferably glass G5's w/ battery backup

AP - preferably 2 axis. But some AP is pretty essential flying in IMC and needing to multi-task
ADS/B Out transponder

Engine analyzer- you want to know before you might have an emergency and these days many of us are looking to replace all our factory gauges too.

When you fit these things into a clean panel configuration, the more you can combine the more space efficient the panel is and often the easier to operate it as well.

So best options are usually the Garmin GNS-xxxW's or GTN's or Avidyne's, that combine COM/NAV/GPS into one box, then spend what you can afford on instruments for better reliability and utility like G5 attitude and HSI's of G3X's or Aspen(s) etc. Think long term plans to minimize overall installation and multiple re-wiring jobs to make piece meal changes to the panel - each mod over time often degrades the wiring since you often no longer have clean unspliced wire cable runs when several patch jobs have been done. 

I went with GTN750 & 650 and G500.

With one GPS, going with the bigger screen GTN750 or Avidyne 540 will also give you all the MFD capabilities including charts and weather which is really helpful - otherwise you'll be relying on your iPad for all that. Its only money! 

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One way to combine things is the  PS engineering PAR300.   Remote mount transceiver that combines with the audio panel.   Downside is you lose the NAV side of things.

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On 12/9/2019 at 8:55 PM, rbridges said:

I can't really give you an answer to your particular question, but in my plane, the KX-155 seems to pick up comms better than my 430.  I don't know if that's across the board with everyone or just my particular plane.  It's enough to make me ask before I dump the KX-155.

Funny, I have the same experience.  Not sure whether this is because of antenna locations or simply the 430W not doing as well as the KX.

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