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Ignorant RV-12/IFR/GPS question...

pstraub

Well Known Member
Hi all, I hope this is not too far off-topic for the RV-12 forum, but I feel comfortable asking it here and I am continually amazed by this group's knowledge. It's embarassing to ask, since I was a practicing CFII until 1988, but I completely missed the GPS revolution (I did not fly between 1993 and 2016). GPS is obviously amazing, I feel like I'm cheating every time I look at my moving map!

So, I never flew a GPS approach or used an on-board unit that had GPS. Now I see all these RNAV (GPS) approaches at little airports that never had anything back in the ILS/VOR/NDB days. I was also confused by the name 'RNAV' because that basically meant VOR/DME back in my day. A couple basic questions....

1. On one of these units I have never used, like the Garmin GNSxxx (excuse my ignorance), would you just enter the name of the approach, like RNAV (GPS)-B at Lodi, CA (1O3) and the GNS would create all the waypoints/fixes for you, based on the approach plate? Or would you have to enter the lat/lon coords yourself to 'build' the approach?

2. I have the Dynon Skyview system (here is the RV-12 content). If it were legal, could I use my WAAS enabled GPS to fly a GPS approach like this one, by manually creating the waypoints in the correct order, in a flight plan? I am assuming the Skyview system has no way to 'load' an approach like this?

Hope these questions even make sense, would love anybody to elaborate and set me straight.

2nm2g5g.jpg
 
In order to legally fly RNAV approaches, you must have an IFR-certified GPS (GNS430/430W, GTN650, etc). Among many other things, they will have all the approaches stored, so that as you mentioned you only enter the name of the approach. Creating your own approach by manually entering the fixes in a non-IFR GPS is not allowed. There are tons of other requirements for IFR GPS units (hence their hefty prices), plus the cost of frequent database updates, but hopefully this answers your main question. Just having a WAAS GPS is not enough.

Chris
 
Great question Paul. For the Garmin GPS units, yes, you would select the approach and all of the waypoints will be populated. I can?t comment on the Skyview system, but you can definitely select and ?roll your own? approach on a G3X. You are correct in your inference that it would not be legal to do in IFR conditions, but you could certainly do the approach in VFR for fun.

I frequently load approaches and fly them for airports I?m not familiar with just to add a margin of situational awareness and I highly recommend doing so in ?marginal? VFR conditions, such as flying at night.
 
Thanks for the replies guys, that pretty much answers my questions. I had some pipe dream that I might be legal in some way, having the SkyView system as primary with a Stratus 2S/Foreflight as backup. So looks like my only option to legally fly an approach is to panel mount a certified solution.

I will at least play with flying some of these approaches (under VFR) by manually creating them. That will be good practice and give me confidence to fly one in an emergency.

If there is a 'silver bullet' solution out there that is certified, semi-affordable, somewhat low power (per my 18A system) and does not take up the whole panel, would love to hear (if that even exists). Thanks again!!
 
If there is a 'silver bullet' solution out there that is certified, semi-affordable, somewhat low power (per my 18A system) and does not take up the whole panel, would love to hear (if that even exists). Thanks again!!

When the previous posters said “approved” or “ifr certified” what they meant was that the box was TSO’d. In principle one might get FAA approval of a non-TSO’d box but to the best of my knowledge that has never happened. Yes, the rules require that all of the approach fixes be called up automatically from the box’s (up to date) database. Because these TSO approvals are very involved and very expensive, competition is limited so even used prices are high. Least expensive might be a used Garmin 300 box (this also includes a com). This is an older, TSO129 box. It’s limited to non-precision gps approaches (LNAV, no LPV) only, and the rules require that you have a VOR on-board as a backup. You will have to pay for a database subscription to use it for ifr approaches (there are different rules for enroute use).
Used Garmin 430Ws (TSO 145/146 WAAS) boxes seem to be going for $6 - $7K. Does that meet your definition of semi-affordable? (It also includes a com and vor/Loc/GS).
Finally, to your other question: when the FAA first started publishing these approaches, they were called “GPS” approaches. Now they’re called “RNAV(GPS)” approaches. I have no idea why the change.
 
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Don?t forget the GPS400W. This is the same box as a 430W minus the nav/comm radios, and can be found in the $5-6k range or maybe less.

Chris
 
Finally, to your other question: when the FAA first started publishing these approaches, they were called “GPS” approaches. Now they’re called “RNAV(GPS)” approaches. I have no idea why the change.

The first GPS approaches were overlays of VOR or NDB approaches, which were not Area Navigation (RNAV) approaches. Approaches created using area navigation rules (complicated, but available online if you’re super bored or need sleep inducing material) are RNAV.

I did manage to squeeze a GTN625 into my panel after buying it for <$5K new, which is a WAAS GPS unit that can be used for LPV approaches. But there are several non-WAAS GPS units out there that could be used for RNAV/GPS approaches, notably the Lodi RNAV approach. A generalization is that all approaches that don’t require vertical guidance can be performed with a non-WAAS unit. There’s a bunch on Barnstormer if you want to go the bargain basement route.
 
To make things more complicated, if you use a non-WAAS IFR GPS, you cannot file an alternate airport with only RNAV approaches. You will need a different method of navigation (ie, VOR). So you may be able to buy the GPS cheaper, but will also need to buy a NAV radio.

Chris
 
There is a big difference between flying the coded approaches out of a database and "rolling your own" by manually loading the waypoints and following a sequential path. Even for the simplest procedure like the depicted one to Lodi, the ARINC coding in the database determines whether the waypoint is a "Flyover" or "Flyby" type, and what type of approach leg is used (usually "track to fix"--TF-- but not always...missed segments are usually "CA" climb to altitude followed by "DF" direct to fix legs). Also, the course needle sensitivity is set by the coding, going from enroute to terminal to approach sensitivity. The TERP protected obstacle areas are built based on those waypoint types and course sensitivities. Approach mode will give you, normally, 0.3 nm needle sensitivity, something you could manually change in some receivers but will automatically be done if you load a database approach. For the more complicated LPV SIAPs. the entire final segment course guidance is predicated on final approach segment (FAS) data that creates the azimuth aiming point, the glide path (based on ellipsoid height, angle, and threshold crossing height) and needle scaling designed to mimic localizer needle scaling, i.e. becomes more accurate the closer you get to the runway.

The coded IFR database is critical to flying RNAV GPS SIAPs as they were designed. You can build your own and fly them VFR but the training value to replicate flying one out of a database is pretty limited.
 
To make things more complicated, if you use a non-WAAS IFR GPS, you cannot file an alternate airport with only RNAV approaches. You will need a different method of navigation (ie, VOR). So you may be able to buy the GPS cheaper, but will also need to buy a NAV radio.

Chris

I?d like to know what your legal reference is for that. There?s nothing in the FAR?s limiting performing RNAV approaches with a non-WAAS GPS unit. You just cannot do the LPV portion. Here?s a little extra info.

https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/factsheets/media/RNAV_QFSheet.pdf

While having a WAAS approach GPS is great, it?s not required. There are definitely alternate airport requirements, but nothing that limits you to the type of equipment you have.
 
I?d like to know what your legal reference is for that. There?s nothing in the FAR?s limiting performing RNAV approaches with a non-WAAS GPS unit. You just cannot do the LPV portion. Here?s a little extra info.

https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/factsheets/media/RNAV_QFSheet.pdf

While having a WAAS approach GPS is great, it?s not required. There are definitely alternate airport requirements, but nothing that limits you to the type of equipment you have.

The last time I looked, TSO 129 boxes were only allowed to be used under ifr if alternate navigation (VOR, or maybe NDB(!)) was on-board, and could be used for an instrument approach at either the destination or the alternate (if required). The regulatory reference is buried in FAR 1.1 (definitions), where it says RNAV rules are what the faa says they are in various publications like the AIM. While normally not regulatory, this FAR reference makes the AIM, for RNAV approaches, ?regulatory by reference?.
 
The coded IFR database is critical to flying RNAV GPS SIAPs as they were designed. You can build your own and fly them VFR but the training value to replicate flying one out of a database is pretty limited.

I disagree. Assuming you have a current navigation database in your VFR GPS unit, if you want to load the approach waypoints in a VFR navigator and fly the route, it will be the exact same route as provided by an IFR TSO?d unit. You can get very good training this way.
 
The last time I looked, TSO 129 boxes were only allowed to be used under ifr if alternate navigation (VOR, or maybe NDB(!)) was on-board, and could be used for an instrument approach at either the destination or the alternate (if required). The regulatory reference is buried in FAR 1.1 (definitions), where it says RNAV rules are what the faa says they are in various publications like the AIM. While normally not regulatory, this FAR reference makes the AIM, for RNAV approaches, ?regulatory by reference?.

Bob, I think you?re trying to refer to the AIM, section 1?1-17 regarding IFR navigation, but you?re really getting off topic. There?s nothing in the AIM or FAR?s that require specific equipment for an alternate approach. You should check out the reference I provided from the FAA.

Paul was asking about whether he could create and fly a procedure in a VFR navigator, and the answer yes - you can. Just not legally under IFR conditions.
 
Check out AC-105A, paragraph 9.5.1 which specifically states:

For flight planning purposes, TSO-C129( ) and TSO-C196( ) equipped users
(GPS users) whose navigation systems have fault detection and exclusion
(FDE) capability, who perform a preflight RAIM prediction 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.

Further, my original caution had nothing to do with whether or not he could use a non-waas gps to practice RNAV approaches in VMC - I was suggesting that a non-waas GPS may not be that cost effective considering another NAV source would still be required. That is straight from AIM 1-1-17 2(a)2, as you suggested:

Aircraft using un-augmented GPS for navigation under IFR must be equipped with an alternate approved and operational means of navigation suitable for navigating the proposed route of flight.

Chris
 
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Ron,
The AIM reference is 1-1-17, subsection 2(a)(2) and 2(a)(3), regarding the availability of non-gps equipment. Of course none of that applies for practice done in vfr conditions.
IMHO setting up a vfr gps box for practice in vmc is of limited value. Once set up, you read the approach chart and follow the needles, like any other approach. 90% of the learning curve is getting the box set up properly. And since they?re all different, doing this on a vfr box is of limited value - unless the button pushing resembles that if a TSO?d box that the pilot intends to transition to.
 
Thanks to all for the very informative comments. Like I said, there is a great depth of knowledge out there and I had a feeling there were not any simple answers, but I am taking it all in. Maybe I just need to keep it light and use what I have for practice and/or an emergency.

If I get up the nerve to build an RV-14, then obviously I will need to step up the panel because that is clearly a very IFR capable platform (nothing against the RV-12, I love it and it exceeds its stated mission profile). I really love this discussion and all the different ideas and angles!!
 
Don?t feel bad, Paul. I?m a CFII that has never flown anything but a six pack approach. The prohibitive cost of an IFR GPS with a data base subscription always put me off.
 
I disagree. Assuming you have a current navigation database in your VFR GPS unit, if you want to load the approach waypoints in a VFR navigator and fly the route, it will be the exact same route as provided by an IFR TSO?d unit. You can get very good training this way.

Yes, your ground track will be the same.

The mechanics of loading the approach with the attendant transition options, the activation of the approach using the correct sequence of button pushing, the changes of modes from enroute to terminal to approach, enabling vertical navigation, the sequencing into the missed approach segment, the changes of scaling of the CDI, the holding pattern entries: not so much.

I guess it depends on what stage of IFR flight the pilot is training for.
 
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