IFR equipment question
Votes
Joined 03/28/2020 - 5 Posts
Open
Is a plane legal for IFR flight if it is only equipped for RNAV approaches with a WAAS GPS like a Garmin 420W?  The 420W interfaces with a Dynon Skyview for HSI/CDI and drives AP, including VNAV.  There is no VOR, NDB or ILS equipment installed... only GPS?  A growing number of smaller airports across the country that I frequent have RNAV approaches, which is why I am asking.  
Thanks!
8 Replies
Votes
Joined 06/11/2017 - 789 Posts
Yes.  WAAS IFR GPS units are certified under a different TSO than the earlier non-WAAS units like the KLN-94 and pre-WAAS GNS430/530.  Under that WAAS TSO-146, they are considered "sole source" nav devices and you can legally launch with no other nav gear.  The earlier pre-WAAS TSO-129 units are "supplemental" nav units and you must have an alternative means of IFR navigation available on board.  

One advantage of this is that if your last VOR check was more than 30 days ago, and there's no VOR check available on the ground where you are, you can take off based on that WAAS GPS and then do a VOR check once airborne if needed.  With only a non-WAAS TSO-129 GPS, you'd either be stuck on the ground or have to take off VFR and do a VOR check airborne before picking up your IFR clearance (the latter sometimes being a risky or impossible option depending on weather).

Of course, I personally think it's a poor idea to launch into IFR conditions with only one means of navigation aboard (even a WAAS GPS), but that's a judgement call, not a regulation.  And that's why I've kept both VOR's in my plane and check them periodically.
Votes
Joined 03/28/2020 - 5 Posts
Ron, thank you very much for the TSO-146 sole source nav device information.
Regarding the 30 day VOR check part, I assume you talking about a plane that had a WAAS GPS with VOR capability like the 430W/530W?  The Garmin 420W has no VOR frequency select capability, so I would not be able to perform VOR checks.  I would not be using the VOR system for IFR navigation so hopefully a VOR check would not apply to my setup. Is that correct?  I would only use VOR's as GPS nav waypoints in flight plans.
I understand and agree with your risk point about launching into IFR conditions with only one means of navigation. Living in AZ, I am mostly concerned about getting stuck on top and having a way to get down while on midwestern and southeastern trips. Being IFR capable would also let me launch through overcast layers and get on top instead of scud running like I've done and don't like.  
Thanks again!
Votes
Joined 06/11/2017 - 789 Posts
James Hefner:

Regarding the 30 day VOR check part, I assume you talking about a plane that had a WAAS GPS with VOR capability like the 430W/530W? 
 

Yes, the 30-check VOR only applies if you have a VOR and are going to use it.  If you don't have one, it doesn't apply.

Votes
Joined 03/28/2020 - 5 Posts
Thanks again Ron, you have been very helpful.  Knowing that my plane is legal and capable of IFR flight as equipped, I will assess starting IFR training, which I assume will need to be done in a plane equipped with all the old stuff that I will never use, but will be good to learn.  Hopefully future IFR proficiency checks after attaining the rating can be done in my plane, using the equipment that I fly with.  I will look into what type and frequency of IFR equipment checks that will be required for my WAAS GPS only setup... maybe xpdr and pitot static only.  I have a CFII friend who can help me with dual training in his C182, which is like driving a truck compared to my RV6A.... I don't look forward to that.  😏

Thanks,
Jim
Votes
Joined 06/11/2017 - 789 Posts
Trade that 420W for a 430W and you'll have all you need for IR training and certification.  You'll also have a VOR backup for your GPS when the Marines at Yuma jam GPS (which happens periodically).  In addition, you'll have what you need for an Instrument Proficient Check, which (like an instrument rating practical test) CANNOT be accomplished with only a GPS.

And there are no required periodic checks for the GPS for IFR other than keeping the database current.
Votes
Joined 03/28/2020 - 5 Posts
Thanks for the info about the ongoing proficiency check requirements Ron.  All those reasons will most likely make me decide not to proceed with IFR training.  I don't do enough flights outside the SW each year to be worth a significant amount of expense to equip and stay current for IFR.  I don't need it for flying around AZ, NV, CA, UT, CO, NM where I normally fly and pick my days, being retired.  I will most likely keep doing practice approaches in VFR conditions so I can use it to get down if I ever get stuck on top during trips to Iowa, Ohio and Florida, where I visit family. 
Thanks much for your help!
Jim
 
Votes
Joined 06/11/2017 - 789 Posts
You can stay IFR current IAW 61.56(c) with nothing but RNAV(GPS) approaches.  A 61.57(d) IPC (and thus other types of approaches) is needed only if you go more than six months beyond your instrument currency, i.e., over a year without any instrument work, once you get that instrument rating.  You should still think about the option of trading your 420W for a 430W and getting that instrument rating.  I've trained several people for the IR in an RV-6/9, including one in AZ -- it's very do-able.
Votes
Joined 03/28/2020 - 5 Posts
Ron,
I understand it is doable. It is more of a question in my mind about whether it is worth the time and money investment, given my age (72), where I live (AZ) and the type of x/c flying that I do (2 or 3 trips/yr on my own schedule).
I'll keep my eyes peeled for a bargain on a 430W and will go from there if I get lucky.
Thanks again for your information, advice and encouragement!
Jim
PS: I owned a Cheetah from 2010-14 and regularly followed the GG back then and remember your valuable input there. Keep up the good work and fly safe in your beautiful Tiger! ☺