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  #1  
Old 06-09-2014, 06:41 PM
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CharlieWaffles CharlieWaffles is offline
 
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Default GPS Only IFR - Alternate Airports

What is the current set of regulations around IFR only GPS, specific to alternate airports. I know that GPS only IFR is allowed, but I have seen some articles that said the alternate could not also be GPS approach (either/or only). But I also saw some articles that said some TSOs allowed both approaches to be GPS only. In my case, I have a GTN750.
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  #2  
Old 06-09-2014, 07:12 PM
BobTurner BobTurner is offline
 
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The original, non-WAAS GPS boxes approved under TSO 129 were to be used only as "supplemental" navigation. Other nav boxes (e.g., VOR) had to be on board and useable over the route flown. If an alternate airport was required, then the aircraft had to be capable of flying a non-GPS approach at that alternate (and that approach had to have appropriate alternate minimums).

No new boxes can be certified under TSO 129.

Newer boxes, such as the 400W series and the 650 series, are certified under TSO 145 (or is it 146?). They may be used as "sole source" of navigation, and all the above restrictions do not apply.

Whether or not the risk-benefit ratio for this type of operation is suitable is left to the PIC.

Last edited by BobTurner : 06-09-2014 at 07:15 PM. Reason: typos - left out the W
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  #3  
Old 06-09-2014, 07:15 PM
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rleffler rleffler is offline
 
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Quote:
Originally Posted by CharlieWaffles View Post
What is the current set of regulations around IFR only GPS, specific to alternate airports. I know that GPS only IFR is allowed, but I have seen some articles that said the alternate could not also be GPS approach (either/or only). But I also saw some articles that said some TSOs allowed both approaches to be GPS only. In my case, I have a GTN750.
I don't have the regs handy, but the GTN series can use a GPS as an alternate, whereas the older GNS series can't.

I'm sure that somebody will follow up with the details.
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  #4  
Old 06-09-2014, 07:29 PM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by rleffler View Post
I don't have the regs handy, but the GTN series can use a GPS as an alternate, whereas the older GNS series can't.

I'm sure that somebody will follow up with the details.
By "older GNS" series you mean the non-WAAS boxes, that is correct.
The 400W series are TSO'd to 145 and can use an alternate with GPS only.

Note the rule with TSO 129 boxes is for flight planning (and fuel-carrying) only. You need to have enough fuel to make it to a suitable alternate with your 129 GPS inoperative; plus reserves. If it's working, you can still use it to shoot a gps approach at an alternate. You just have to have a backup, too.
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  #5  
Old 06-10-2014, 06:57 AM
Soju Hunter Soju Hunter is offline
 
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Quote:
Originally Posted by CharlieWaffles View Post
What is the current set of regulations around IFR only GPS, specific to alternate airports. I know that GPS only IFR is allowed, but I have seen some articles that said the alternate could not also be GPS approach (either/or only). But I also saw some articles that said some TSOs allowed both approaches to be GPS only. In my case, I have a GTN750.
Why ask the question when your box is equipped with radio NAV? Antenna not installed?
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  #6  
Old 06-10-2014, 09:00 AM
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Quote:
Originally Posted by Soju Hunter View Post
Why ask the question when your box is equipped with radio NAV? Antenna not installed?
Typically the minimums are greater for the non-precision approaches, such as VOR, NDB, etc. If the alternate is a small airport, it may not have an ILS, making the GPS/RNAV the preferred approach.
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  #7  
Old 06-10-2014, 10:13 AM
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CharlieWaffles CharlieWaffles is offline
 
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Quote:
Originally Posted by Soju Hunter View Post
Why ask the question when your box is equipped with radio NAV? Antenna not installed?
Correct, I did not install a NAV antenna, cable, etc...
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  #8  
Old 06-10-2014, 10:43 AM
DGlaeser DGlaeser is offline
 
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Quote:
Originally Posted by CharlieWaffles View Post
Correct, I did not install a NAV antenna, cable, etc...
As noted earlier, since you have a WAAS GPS, there is no requirement to have another nav system (i.e. VOR/LOC), for either the primary or alternate airport.

Without the VOR/LOC antenna installed, you are 'limited' to selecting only GPS approaches (your database will have all the non-GPS approaches as well of course). These days it is not much of a limitation, but something to verify at your intended destinations.
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  #9  
Old 06-10-2014, 10:53 AM
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KatieB KatieB is offline
 
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Quote:
Originally Posted by CharlieWaffles View Post
Correct, I did not install a NAV antenna, cable, etc...
GPS outages are rare, but they can happen. Since you already have VOR/LOC, why not stack the cards in your favor? The antenna install might be a pain but you might come to rely on it as your backup someday.
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Last edited by KatieB : 06-10-2014 at 10:55 AM.
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  #10  
Old 06-10-2014, 11:13 AM
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CharlieWaffles CharlieWaffles is offline
 
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Quote:
Originally Posted by DGlaeser View Post
As noted earlier, since you have a WAAS GPS, there is no requirement to have another nav system (i.e. VOR/LOC), for either the primary or alternate airport.

Without the VOR/LOC antenna installed, you are 'limited' to selecting only GPS approaches (your database will have all the non-GPS approaches as well of course). These days it is not much of a limitation, but something to verify at your intended destinations.
Any chance you know the specific FAR or publication from the FAA that confirms this? This is my understanding but I have to admit I cant find it in the FARs.
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