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GPS only equipment for IFR

FireMedic_2009

FireMedic_2009

Well Known Member
I’ve seen this before but haven’t really asked the question to get an answer.

So if you fly IFR and your plane only has a gps navigator and your intended airport requires you to file and alternate it states in the regs that you can’t plan to fly a gps approach at both places.

Online explanation states, “ that means with GPS only you can only fly RNAV approaches and you can’t plan IFR flights that require an alternate”.

So does the above statement mean if your intended destination requires you to file an alternate airport you can't file IFR? So if you only have a GPS navigator you can only fly IFR if an alternate airport is NOT required. Is that correct? Does it still apply if you have a Waas gps navigator?

Here is Advisory Circular, AC No 90-105A, dated 3/17/16.
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_90-105A.pdf#page28

I’m not sure what it means but does it allow you to fly gps approaches at both locations if you have a waas gps?

Pg 29 of 129

9.5.1.2 Pilots with WAAS receivers, TSO-C145( ) or TSO-C146( ), may flight plan to use any IAP authorized for use with their WAAS avionics as the planned approach at a required alternate, with the following restrictions. When using WAAS at an alternate airport, flight planning must be based on flying the RNAV (GPS) LNAV or circling minima line, or minima on a GPS approach procedure, or conventional approach procedure with “or GPS” in the title. Properly trained and approved, as required, TSO-C145( ) and TSO-C146( ) equipped users (WAAS users) with and using approved baro-VNAV equipment may plan for LNAV/VNAV DA at an alternate airport. Specifically authorized WAAS users with and using approved baro-VNAV equipment may also plan for RNP 0.3 DA at the alternate airport as long as the pilot has verified RNP availability through an approved prediction program. Code of Federal Regulation (CFR) Part 91 nonprecision weather requirements must be used for planning. Upon arrival at an alternate, when the WAAS navigation system indicates that LNAV/VNAV or localizer performance with vertical guidance (LPV) service is available, then vertical guidance may be used to complete the approach using the displayed level of service.
 
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FireMedic_2009 said:
So if you fly IFR and your plane only has a gps navigator and your intended airport requires you to file and alternate it states in the regs that you can’t plan to fly a gps approach at both places.
……….


Here is Advisory Circular, AC No 90-105A, dated 3/17/16.
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_90-105A.pdf#page28

I’m not sure what it means but does it allow you to fly gps approaches at both locations if you have a waas gps?.
.
Click to expand...

The first statement is not true. But it used to be true. If you have a TSO 129 (older, non-WAAS) gps, then for ifr you were (and still are) required to have the capability to shoot a non-gps approach at either your destination or your alternate. But if you have a TSO 144/145 (WAAS) gps, that is now considered sufficient nav equipment for both the destination and the alternate. As always, the forecast wx at the alternate must be better than the precision minimums; in particular, it has to be at or better than the non-precision gps minimums.
 
So here it goes:

Paraphrased out of the AIM— If you have a non-WAAS (TSO-129/196) IFR GPS:

1. For navigation under IFR the aircraft must be equipped with an alternate approved and operational means of navigation suitable for navigating the proposed route of flight (eg VOR, etc).
2. For flight planning purposes, a non-WAAS equipped users whose navigation systems have fault detection and exclusion (FDE) capability, who perform a preflight RAIM prediction for the approach integrity at the airport where the RNAV (GPS) approach will be flown, and have proper knowledge and any required training and/or approval to conduct a GPS-based IAP, may file based on a GPS-based IAP at either the destination or the alternate airport, but not at both locations. At the alternate airport, pilots may plan for:
Lateral navigation (LNAV) or circling minimum descent altitude (MDA);
LNAV/vertical navigation (LNAV/VNAV) DA, if equipped with and using approved barometric vertical navigation (baro-VNAV) equipment;
RNP 0.3 DA on an RNAV (RNP) IAP, if they are specifically authorized users using approved baro-VNAV equipment and the pilot has verified required navigation performance (RNP) availability through an approved prediction program.

If the above conditions cannot be met, any required alternate airport must have an approved instrument approach procedure other than GPS-based that is anticipated to be operational and available at the estimated time of arrival, and which the aircraft is equipped to fly.

It should be noted that this alternate prohibition is planning only and doesn’t apply once you’ve airborne— fly whatever IAP works best for the situation.

If you have an IFR WAAS GPS (TSO 145/146) you can use it for sole source nav and the prohibition against planning for GPS approaches at both the destination and alternate is lifted.
 
Thanks Bob and Todd for the info.

I believe the standard min for precision is 600' ceilings and 2 mile vis. Non-precision 800' and 2 miles. Bob, is the reason you said the alternate has to be non-precision mins is because the FAA doesn't consider wass gps a precision approach although many would disagree?

Thanks!
 
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This is one of the best videos I have found that walks you through the legalities of using only a WAAS IFR GPS as your only means of navigation. You can start watching at 2:02 where that discussion starts. It is certainly tempting to build a basic IFR panel with just a GNX 375, which includes the adsb transponder. Good luck!

https://www.youtube.com/watch?v=vQZAm0EnBrc

Fernando

FireMedic_2009 said:
I’ve seen this before but haven’t really asked the question to get an answer.

So if you fly IFR and your plane only has a gps navigator and your intended airport requires you to file and alternate it states in the regs that you can’t plan to fly a gps approach at both places.

Online explanation states, “ that means with GPS only you can only fly RNAV approaches and you can’t plan IFR flights that require an alternate”.

So does the above statement mean if your intended destination requires you to file an alternate airport you can't file IFR? So if you only have a GPS navigator you can only fly IFR if an alternate airport is NOT required. Is that correct? Does it still apply if you have a Waas gps navigator?

Here is Advisory Circular, AC No 90-105A, dated 3/17/16.
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_90-105A.pdf#page28

I’m not sure what it means but does it allow you to fly gps approaches at both locations if you have a waas gps?

Pg 29 of 129

9.5.1.2 Pilots with WAAS receivers, TSO-C145( ) or TSO-C146( ), may flight plan to use any IAP authorized for use with their WAAS avionics as the planned approach at a required alternate, with the following restrictions. When using WAAS at an alternate airport, flight planning must be based on flying the RNAV (GPS) LNAV or circling minima line, or minima on a GPS approach procedure, or conventional approach procedure with “or GPS” in the title. Properly trained and approved, as required, TSO-C145( ) and TSO-C146( ) equipped users (WAAS users) with and using approved baro-VNAV equipment may plan for LNAV/VNAV DA at an alternate airport. Specifically authorized WAAS users with and using approved baro-VNAV equipment may also plan for RNP 0.3 DA at the alternate airport as long as the pilot has verified RNP availability through an approved prediction program. Code of Federal Regulation (CFR) Part 91 nonprecision weather requirements must be used for planning. Upon arrival at an alternate, when the WAAS navigation system indicates that LNAV/VNAV or localizer performance with vertical guidance (LPV) service is available, then vertical guidance may be used to complete the approach using the displayed level of service.
Click to expand...
 
FireMedic_2009 said:
Thanks Bob and Todd for the info.

Bob, is the reason you said the alternate has to be non-precision mins is because the FAA doesn't consider wass gps a precision approach…

Thanks!
Click to expand...

Well, I don’t know what the FAA thinks. But my guess is that they were just trying to be a bit conservative, as alternate wx minimums always are. In particular, the ability to shoot the no-WAAS-required LNAV at the alternate, just in case waas went down. Or maybe they were thinking of the many LPV approaches that don’t really come close to 200’ agl decision heights. As always these are planning requirements, before takeoff. If you end up at your alternate and LPV is available you of course may use it.
Edit. Another theory. There are now so many gps approaches, maybe the faa doesn’t want to list all the non-standard alternates anymore, hence the general ‘LNAV available’ approach.
 
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campi said:
It is certainly tempting to build a basic IFR panel with just a GNX 375, which includes the adsb transponder.
Click to expand...

My airplane is IFR GPS only, and I haven't missed the ILS/LOC/VOR at all in the last 2 years. Outside of world shaking events, the WAAS GPS system is so reliable at this point, I wouldn't install a new panel with ground based NAV. Any airport with an ILS is going to have a RNAV overlay version. Most small airports only have RNAV approaches, either LPV or LNAV (and the modern GPS will simulate a glide slope for you anyway). In addition, VOR's are dropping like flies, MON network notwithstanding.

If the GPS get's nuked enroute, you should have enough gas for ATC to vector you to somewhere with higher ceilings and land VFR.

The alternate requirement is about WX mins AND lost comms, so if you haven't lost comms, your filed alternate will never come into play unless you specifically ask to go there.

ATC doesn't really know what your alternate is without going through some hassle to have it looked up for them from your filed flight plan (source: Opposing Bases podcast). In real life, they are going to ask you what you want to do after going missed: try again, hold, go somewhere else (which you can tell them is your alternate, but they wouldn't know that), or just get a vector to VMC.

campi said:
This is one of the best videos I have found that walks you through the legalities of using only a WAAS IFR GPS as your only means of navigation.
Click to expand...

That is a really good video of this subject, hadn't seen that one before. He really explains it well, and I completely agree with the reasoning of going GPS only. I can finally stop making this argument myself, and just point people to the video :D
 
Untainted123 said:
and I completely agree with the reasoning of going GPS only. I can finally stop making this argument myself, and just point people to the video :D
Click to expand...

Well, as someone who has personally experienced a gps outage at 1100’ agl while on a gps approach, I’m not yet in the gps-only camp. But I also carry more than the minimum instruments required by the far’s and my op limits, too. It’s EAB, and you can choose what you think is best, for you and any passengers.
 
BobTurner said:
Well, as someone who has personally experienced a gps outage at 1100’ agl while on a gps approach, I’m not yet in the gps-only camp. But I also carry more than the minimum instruments required by the far’s and my op limits, too. It’s EAB, and you can choose what you think is best, for you and any passengers.
Click to expand...

EAB doesn't get you anything when the issue is this one. Different issue entirely.
 
BobTurner said:
Well, as someone who has personally experienced a gps outage at 1100’ agl while on a gps approach, I’m not yet in the gps-only camp. But I also carry more than the minimum instruments required by the far’s and my op limits, too. It’s EAB, and you can choose what you think is best, for you and any passengers.
Click to expand...

Same here. I'm not going to live long enough to be convinced to fly IFR without a VHF receiver for an ILS.
 
I am in the GPS only configuration and couldn't be happier. The GNX375 is an amazing solution that provides ads-b in and out, syncs flightplans up/down seamlessly with foreflight and allows me to fly coupled approaches into any airport runway at a 3 degree glideslope. When I look forward at building an RV-15 even as a strictly VFR plan I will probably run the same setup. The ADS-B in and out, plus features of the modern Garmin GPS alone make it worth it.
 
But…..

I’m the contrarian here. If you routinely fly IFR I wouldn’t fly without a VOR /LOC/GS backup. I’ve flown in IMC conditions where for part of the route there were NOTAM’d GPS outages most likely due to military activity. I couldn’t have been able to launch had I not had VOR capability. I concede that GPS is now the primary method to use the system and I use it 99.9% of the time, but I like having options. when I’m in hard IMC. YMMV…..
 
Untainted123 said:
My airplane is IFR GPS only, and I haven't missed the ILS/LOC/VOR at all in the last 2 years. Outside of world shaking events, the WAAS GPS system is so reliable at this point, I wouldn't install a new panel with ground based NAV. Any airport with an ILS is going to have a RNAV overlay version. Most small airports only have RNAV approaches, either LPV or LNAV (and the modern GPS will simulate a glide slope for you anyway). In addition, VOR's are dropping like flies, MON network notwithstanding.

If the GPS get's nuked enroute, you should have enough gas for ATC to vector you to somewhere with higher ceilings and land VFR.

The alternate requirement is about WX mins AND lost comms, so if you haven't lost comms, your filed alternate will never come into play unless you specifically ask to go there.

ATC doesn't really know what your alternate is without going through some hassle to have it looked up for them from your filed flight plan (source: Opposing Bases podcast). In real life, they are going to ask you what you want to do after going missed: try again, hold, go somewhere else (which you can tell them is your alternate, but they wouldn't know that), or just get a vector to VMC.



That is a really good video of this subject, hadn't seen that one before. He really explains it well, and I completely agree with the reasoning of going GPS only. I can finally stop making this argument myself, and just point people to the video :D
Click to expand...


Not every airport with an ILS has an RNAV overlay.

Not sure where you fly but here in the midwest, it is definitely possible to have weather lower than VFR mins covering an area greater than the standard reserve fuel minimums.

Sometimes "getting a vector to VMC" isn't a viable option.

Point is, going GPS only is a personal choice based solely on that person's mission. What is comfortable for one, may not be comfortable for another.

Personally, I would rather have the ILS capability and not need it then need it and not have it...and that is how I equipped my -10, based on my mission.
 
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