GNC-300XL GPS with GI 106A CDI

[TX7A]

I need some help understanding some of this avionics stuff.
(I'm not an IFR rated pilot, but would like to be some day.)

I am planning on having the GNC300XL coupled to a GI 106A CDI.
The 300XL is non-precision approach IFR certified. Hooked up to the CDI, will the CDI only display horizontal alignment or will it also show the glideslope?
(No NAV radio)

Thanks,
Sam

PS:Is there a good book that explains all this avionics hook-up stuff, what works with what, etc...in layman terms??

[rwtrwtau]

Sam,

The glideslope needle will not be used with this unit. Some systems can do this but is advisary only. Non precision actually refers to the fact that there is no glideslope guidance.

To make a GPS NPA you will need an annunicator panel as well with this unit.

I don't know of any books on avionics. I suspect they would be out of date before they went to print, but the list of required equipment is in the FAR's

Richard

[TX7A]

Originally Posted by rwtrwtau

Sam,

To make a GPS NPA you will need an annunicator panel as well with this unit.

Richard

The Garmin specifications for the GI 106A states the following:
Annunciation: Green for "GPS" course deviation; white for "VLOC" or "NAV" course deviation.

Does that meet the annunciation requirement you are speaking of?

Thanks,
Sam

[Highflight]

Sam,
If you're really serious about getting your IFR ticket in your RV, you should know that GPS approaches are being added as time goes on, but a precision approach is best done with a Nav Radio w/glideslope.

For what you want to do (and it looks like you're trying to save some money as you plan your panel), you'd be better off going with something like the Garmin SL-30 as your primary Nav driving the CDI that will give you your glideslope. You can use a non-certified GPS as guidance as long as you follow the course as indicated by the SL-30 Nav radio.

I started planning on both the GNC300XL and the SL-30, but found that when I factored in the required Annunciator to that package, it cost about the same to step up to the GNS430 and SL-40 as backup Comm because the GNS430 has it's own integral Annunciator.

Actually, I finally decided to bite the bullet and go with the GNS-430 plus the SL-30 anyway because what the heck, this will probably be the last airplane I ever build.

[aadamson]

Originally Posted by Highflight

Sam,
If you're really serious about getting your IFR ticket in your RV, you should know that GPS approaches are being added as time goes on, but a precision approach is best done with a Nav Radio w/glideslope.

Sorry to disagree with you, but that is just plain wrong.... Perhaps you missed a word or two.

GPS approaches are being added all the time is correct, but the whole premise for WAAS GPS is to *replace* the very costly, very aged VOR/ILS system...

Also, let's not confuse GPS approaches with "precision approaches". Or better, let's get educated.

In a VOR/ILS world there are 2 types of approaches, they both use NAV frequencies from a NAV radio. One is a VOR approach and it's considered "non-precision" - this means the the DA (Decision altitude) will be higher than an equivalent approach that is a "precision" approach. An ILS is the later and there are actually various sub categories of it, but as a GA pilot we'll just deal with the one that uses a DH (Decision height above the ground) of 200'

In the GPS world there are actually 4 approaches. A GPS A/B approach the early GPS approaches, they are *all* non-precision approaches and require a GPS device that can perform at the TSO-129a specification. You'll hear them referenced as a certified GPS (also good for enroute too).

Now cross the new technology boundry to WAAS approaches. These require a different reciever, one that conforms to the TSO-145a spec. There are 3 types of approachs here. The first is the LNAV only approach. also an non-precision approach, and it is exactly the same as the TSO-129a GPS A/B approach, same mins, etc. Then there are 2 new approach types, both offering "vertical" guidance via a glideslope, but with differing DA's. The LNAV/VNAV offers glideslope type guidance, but usually (see KSAV GPS 9 approach for an exception) to a non-precision approach altitude (read as not as good as a precision approach). Lastly there is the LPV approach. It's a "precision" approach and in most cases is good to similar ILS standards (usually +50 feet).

The challenge today with GPS recievers is what to buy.... The 300XL, 430, 530, etc are NOT WAAS recievers and only meet the TSO-129a spec (altho Garmin for the last 3 years has said they will update the 430/530 to WAAS). The 480 is a WAAS reciever and it meets the TSO-146a ( a new one because it does LPV which requires meeting both the TSO-145a (the GPS part), and TSO-146a (the Flight Management system part - this included monitoring the internal checks).

One final note. There is also a difference with "primary navigation" vs. "secondary". The TSO-129a only allow for secondary use of the GPS (meaning you'd have to be in radar coverage, or have a Nav radio as well). This is due to the limited integrity checks and having a backup ability if integrity fails. TSO-146a allow for the GPS to be the only and primary navigation means.

Hope all this helps. it's funny that this topic would come up today as I just became educated on all of this as I planned my panel and GPS solutions.

Sorry I picked on Highflight, but let's be clear, and I'm sure this will sound like heracy, the ILS/VOR system as we know it will go away some day, and most likely sooner than later based upon the way the FAA is funding its projects of late. And besides it always bugs me when someone says, learn to fly the ILS and don't worry about GPS..... I think that is *wrong*. Learn to use *all* the facilities that you are given so you have many ways to do the same thing in the case of some sort of ground or air based equipment failure....

[pmathews]

Correct me if I'm wrong, but I'm under the impression that in order to file and fly ifr, you have to have at least one nav radio. You can certainly use a gps enroute and fly a gps approach, but part of the requirement for gps approaches is that you have an alternative approach that does not require gps to be functional. An I think this applies to alternate airports as well when they are required (the 1-2-3 rule).

This is comming back from the cobwebs of my ifr training but that's how I remember it. I wish I could remember the exact FAR I'm thinking of...

If someone knows/thinks differently, please chime in but I'm planing on having at least one nav radio so I can file/fly ifr occasionally.

As far as "light ifr" - it does exist here in southern california. It is also known as "June Gloom" when there are stratus layers at 1000' or more AGL that are a whopping 300' to 1000' feet thick with cavu above and below. That's about the extent of the type of ifr I plan on flying in an RV. Anything more than that is just not my cup of tea without a little more airplane around me.

[Highflight]

Originally Posted by aadamson

Sorry to disagree with you, but that is just plain wrong.... Perhaps you missed a word or two.

Pick away...

The word I may have been missing wasn't a word, but what I thought Sam intended. What it looked like he was trying to do was to go IFR as cheaply as possible.

The GNC300XL, as far as I know but correct me if I'm wrong, is not WAAS capable and I don't believe there is any plan to make it so.

Therefore, and again correct me if I'm wrong, there will never be precision GPS WAAS approaches available to the GNC300XL.

[aadamson]

Originally Posted by pmathews

Correct me if I'm wrong, but I'm under the impression that in order to file and fly ifr, you have to have at least one nav radio. You can certainly use a gps enroute and fly a gps approach, but part of the requirement for gps approaches is that you have an alternative approach that does not require gps to be functional. An I think this applies to alternate airports as well when they are required (the 1-2-3 rule).

If flying with a TSO-c129a certified IFR GPS (approach, enroute, no WAAS), then yes, you need "communications appropriate for the ground based nav facilities". And GPS can never be "primary". A certified WAAS GPS *can* be primary and requires no additional NAV radio (probably not very smart tho).

Originally Posted by pmathews

This is comming back from the cobwebs of my ifr training but that's how I remember it. I wish I could remember the exact FAR I'm thinking of...

If someone knows/thinks differently, please chime in but I'm planing on having at least one nav radio so I can file/fly ifr occasionally.

If it were me, I'd have a Nav radio for backup for now anyway, so a wise move.

Originally Posted by pmathews

As far as "light ifr" - it does exist here in southern california. It is also known as "June Gloom" when there are stratus layers at 1000' or more AGL that are a whopping 300' to 1000' feet thick with cavu above and below. That's about the extent of the type of ifr I plan on flying in an RV. Anything more than that is just not my cup of tea without a little more airplane around me.

Never, never, never, tell yourself there is something known as "light IFR" It simply doesn't exist and is a "concept" that will get you KILLED. Anything that requires you to fly by IFR should be treated that way, as a very serious, deadly proposition. It takes about 3 seconds on the gauges with a vacuum pump failure to put you in a spin. And I would contend that the kind of "june gloom" that exists in the SOCAL area, is the *worst* kind. It's always LOW, thick, and heavy, and Its *always* there. That 3 seconds at those kinds of altitudes is the deadliest kind.

I trained and got my PPL at Montomery field and am all too familiar with june gloom. I got more instrument time with an instructor there than I care to thing about. All just to get to the other side of the mountain and VFR. Scud running the VFR cop-out for "light IFR" kills more pilots in that area, than anything else.

IMHO, DO NOT talk yourself into thinking there are levels of IFR, it simply isn't true and unfortunately statistics backup that up with the wrong numbers!

[aadamson]

Originally Posted by Highflight

Pick away...

The word I may have been missing wasn't a word, but what I thought Sam intended. What it looked like he was trying to do was to go IFR as cheaply as possible.

The GNC300XL, as far as I know but correct me if I'm wrong, is not WAAS capable and I don't believe there is any plan to make it so.

Therefore, and again correct me if I'm wrong, there will never be precision GPS WAAS approaches available to the GNC300XL.

The 300XL *is not* and *will never be* WAAS capable, or certified (means *no* precision GPS approaches). With that as your GPS, you would need a NAV radio and would also need training for VOR/ILS approaches.

[TX7A]

Thanks, Vern & Alan. This discussion has helped me a good bit.
Yes, Vern, I was looking for a less expensive, "beginner-level" IFR package. Also, with the hope of upgrading as funds come available.

What really confuses me is that a Garmin 296/396 is WAAS enabled. What the heck for if it can't be used for IFR...or can it??? Why is it available in a handheld and not in a 300XL or even a 430 for cryin' out loud! I guess I don't get it.

Sam