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  #1  
Old 11-26-2017, 01:42 PM
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pstraub pstraub is offline
 
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Default Ignorant RV-12/IFR/GPS question...

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.

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  #2  
Old 11-26-2017, 02:06 PM
YellowJacket RV9 YellowJacket RV9 is offline
 
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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
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Old 11-26-2017, 02:08 PM
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rongawer rongawer is offline
 
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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.
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Old 11-26-2017, 02:22 PM
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pstraub pstraub is offline
 
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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!!
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  #5  
Old 11-26-2017, 03:26 PM
Larco Larco is offline
 
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Could a used 430W and a Dynon Arinc adapter be in the budget?
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Old 11-26-2017, 03:30 PM
BobTurner BobTurner is online now
 
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Quote:
Originally Posted by pstraub View Post
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.

Last edited by BobTurner : 11-26-2017 at 03:46 PM.
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Old 11-26-2017, 03:37 PM
YellowJacket RV9 YellowJacket RV9 is offline
 
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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
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Old 11-26-2017, 04:07 PM
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rongawer rongawer is offline
 
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Quote:
Originally Posted by BobTurner View Post
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.
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  #9  
Old 11-26-2017, 04:32 PM
YellowJacket RV9 YellowJacket RV9 is offline
 
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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
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  #10  
Old 11-26-2017, 04:53 PM
aerovin aerovin is offline
 
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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.
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