Cheapest & Smallest Certified GPS for VNAV

carlmeek wrote:

so i’m wondering what my purchasing options are. I don’t think a fully integrated GTN is the solution here as it’d have to remodel the whole panel and flog half of what i’ve bought.

You could of course get a MGL iEFIS lite (or full). It has 3 axis autopilot with “full 3D” vertical nav, glideslope etc. If it will feed the Dynon? who knows?

Trig has some stand alone GPS receivers used for ADSB out, maybe they can be used?

Carl,

It’s not always true that VFR routings are more complicated than IFR. For instance, the 670 nm from home in the People’s Republic of Alba to Annemasse goes like this, with just five waypoints:

GLE4 NJBRI NAY1 DVR CTL GGE LFLI

…simples! … unless the Jura mountains are socked in, in which case a small detour west of Geneva may save the day.

VS and ALT HOLD are useful for such a flight, but it would be rare that wind and cloud are sufficiently predictable to make following a pre-determined vertical profile a practical option.

USFlyer wrote:

Dynon’s Opinion: It is our opinion that the above requires the navigation system as a whole to be certified, not just the GPS position sensor.

That’s certainly true in Europe.

There is a long tradition with handhelds being able to display an “ILS” to a specified waypoint. I think even my Garmin 496 can do it.

However none have LPV in the specific meaning of it. I don’t know why not, because to implement LPV in a GPS you need the hex data block and that is published. One could thus implement LPV (for all airports that have LPV published) in a phone app (would need an EGNOS GPS to do it “sort of properly”)… One could even implement LPV for airports which don’t have LPV, by generating the data block.

So you are getting H + V guidance in the form of an “ILS” from your current position to the runway but you are not getting the assurance of a surveyed published IAP. It’s an interesting Q whether the HITS trajectory has been checked for obstacle clearance. If it can be commenced from really anywhere then it obviously could not have been, if the GS angle is constant.

So, I guess, all this means is that somebody has done yet another uncertified GPS with an “ILS” capability but with nice graphics.

I wonder if this can drive an autopilot too. Probably it can. In the homebuilt world you don’t have restrictions like that. Whether the LAA approves I don’t know, and their IFR programme is something else to consider when buying avionics.

The 196 will load a pseudo ILS if the approach is in the database, but have not figured out whether you can load an off database pseudo VNAV.

Peter wrote:

Whether the LAA approves I don’t know, and their IFR programme is something else to consider when buying avionics.

Considering there are new systems coming continuously, at least once every year from most manufacturers, and software updates much more often, I have a hard time understanding the rationale behind this “program”. By the time they finish “approving” a system, it will be obsolete or have major software updates in any case. The regulations here (EASA, FAA, but most importantly ICAO and airspace) are very simple; GPS units for IFR navigation have to be certified, transponder is mandatory and must be certified, radio is mandatory and must be certified. This leaves only display technology and gyro, which is 10% hardware and 90% untested and essentially alpha/beta quality software.

The EAA has a nice write up on this, and it’s is no different in Europe (except UK…) You can fly in IMC with a cheap EFIS, but why would you do that? Just about every single homebuilder who installs an EFIS for VFR, also installs some basic backup for alt and in ASI, just in case the big screen should malfunction. We do this even though a total black out is more of an unpleasant inconvenience than a life and death situation. For IFR in IMC, your life depend on that screen not malfunctioning, or the autopilot or the gyro. It makes no sense to me to cheap out on those things. From what I have seen on RVs, they either have old school certified IFR equipment, or they have certified GPS’es and G500s or some mix.

In essence the LAA is saying it is OK to use VFR equipment (experimental EFIS etc exclusively meant and designed for VFR) for “hard” IFR? Based on what experience? This seems to me to be a very odd thing to do.

How does the design of an IFR EFIS vary from the design of a VFR EFIS?

Shorrick_Mk2 wrote:

How does the design of an IFR EFIS vary from the design of a VFR EFIS?

Good question. But take a look at the manufacturers of experimental EFIS’es. They are all made for VFR, and the manuals clearly say so (with perhaps the exception of the G900X). Dynon means that for IFR, all equipment must be certified for instance (EAA does not mean that, but clearly states legal does not equal safe in this respect). My question is, why would you risk your life on alpha/beta quality software functioning 100% at all times, when there are other options that doesn’t even cost that much more (G500, Aspen systems etc). Even I, with my VFR only single seat Onex, have redundancy on the EFIS in case it should black out, or do something else strange, so I can shut it off and look at some other instruments. If I were to build myself an IFR travelling machine, for IMC, I would not put my life on the hands of alpha quality software. I would use true and trusted systems, certified systems like the G500 or Aspen or whatever else is available (high quality AHRS, autopilot and display technology). It is a bit strange the LAA advocate using these experimental systems for IFR IMC.

Perhaps my question was not clear. Is there a clear documented difference between a VFR EFIS and a IFR one? I know what the manual says – obviously if it is not certified it is not going to say IFR despite what is in the box.

Is the software in a VFR box of a demonstrably lesser quality as in a IFR box? If yes – please demonstrate or document the technical differences.