WAAS GPS for IFR Approaches

Hi everyone, I have been trying to sort through the maze of FAA regs with little in the way of definitive answers.

So far, all I can get after speaking with most of the current EFIS manufacturers, is that you need a WAAS certified GPS radio (e.g. GNS 430W, or GTN 650) to interface with the EFIS in order to shoot a "legal" GPS approach with vertical guidance.

All of the certified WAAS radios are very costly. I noted that there are many WAAS enabled GPS radios for boats that are significantly less expensive. Does anyone know if these units can be used for WAAS GPS information to enable a legal GPS approach?

Thanks!

Roger

They cannot. For an approach you have to be able to retrieve all of the waypoints from the current on-board Nav database which the non-aviation units will not have, plus they have to meet the WAAS TSO (145/146). Finally they will not have the software to provide vertical guidance (LPV, LNAV/VNAV) if that's a capability you want beyond basic LNAV (non-WAAS TSO 129)

WAAS

Do you really need WAAS. The non WAAS 430's are running about 30-40% below the asking price for WAAS version. You can get a Bendix King 90B non WAAS approach certified GPS for 1k and tie it into a separate indicator.

jrs14855 said:

Do you really need WAAS. The non WAAS 430's are running about 30-40% below the asking price for WAAS version. You can get a Bendix King 90B non WAAS approach certified GPS for 1k and tie it into a separate indicator.

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An indicator separate from than the EFIS?

WAAS

Yes, similar to the plain VOR indicators or maybe the same. You will sometimes see the King 90B advertised as a package with indicator and small annunciator which is required for approaches with the King but is self contained with the Garmin 430. Another option is the Garmin 400, GPS only, priced about midway between 90B and non WAAS 430. I use 400, 430 and 530 on a regular basis in King Air. 400 works near identical to 430 except no comm or ILS. Look on Barnstormers for the dealer near Sacramento CA. They usually have several 90B's on their website. The King is not nearly as user friendly as the Garmin but if you're on a budget it gets the job done.

jrs14855 said:

Yes, similar to the plain VOR indicators or maybe the same. You will sometimes see the King 90B advertised as a package with indicator and small annunciator which is required for approaches with the King but is self contained with the Garmin 430. Another option is the Garmin 400, GPS only, priced about midway between 90B and non WAAS 430. I use 400, 430 and 530 on a regular basis in King Air. 400 works near identical to 430 except no comm or ILS. Look on Barnstormers for the dealer near Sacramento CA. They usually have several 90B's on their website. The King is not nearly as user friendly as the Garmin but if you're on a budget it gets the job done.

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Why won't an EFIS HSI not satisfy the separate indicator requirement which I believe is what John was eluding to as the OP implied this would be paired with some type of EFIS?

The background here comes from the AIM, and it's pretty straightforward:

2. IFR Use of GPS
(a) General Requirements. Authorization to conduct any GPS operation under IFR requires:
(1) GPS navigation equipment used for IFR operations must be approved in accordance with the requirements specified in Technical Standard Order (TSO) TSO−C129(), TSO−C196(), TSO−C145(), or TSO−C146(), and the installation must be done in accordance with Advisory Circular AC 20−138(), Airworthiness Approval of Positioning and Navigation Systems. Equipment approved in accordance with TSO−C115a does not meet the requirements of TSO−C129. Visual flight rules (VFR) and hand−held GPS systems are not authorized for IFR navigation, instrument approaches, or as a principal instrument flight reference.

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So, it's not WAAS that you need, which is a technology that is in the cheapest devices today. It's an actual TSO. Not meets the requirements of a TSO, but an actual TSO approval. This is what drives all the cost and makes these devices so expensive. There is no difference in the AIM for type certificated aircraft or experimental.

You can use older non-WAAS certified GPS units for enroute and non-precision approaches, but you asked about an approach with vertical guidance, so yes, you need one of the newer "WAAS" units, but really what you need is a device that holds TSO-C146.

The AIM says nothing about the indicator for the device. It is generally accepted that the HSI/CDI on an experimental EFIS is legal. It's about having the TSO-C146 unit in the plane and using it's databases and software to calculate the deviations.

Auburntsts said:

Why won't an EFIS HSI not satisfy the separate indicator requirement which I believe is what John was eluding to as the OP implied this would be paired with some type of EFIS?

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Exactly. Why would I put an old OBI in a panel when I have all my flight and nav in the EFIS. I have an OBI built into the EFIS as an HSI plus Flight Director if I want it.

Are current databases available for the KLN 90B? It is a discontinued product.

jrs14855 said:

Do you really need WAAS. The non WAAS 430's are running about 30-40% below the asking price for WAAS version. You can get a Bendix King 90B non WAAS approach certified GPS for 1k and tie it into a separate indicator.

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No, you don't really need WAAS in a GPS navigator for it to be useful. You DO need WAAS if you want to get the lower approach minima of LP and LPV approaches, and to my knowledge the non-WAAS navigators do now allow sole-means enroute navigation. Other restrictions would also apply to non-WAAS navigators regarding the available approaches at a filed alternate. Sure they're more expensive, but the modern WAAS IFR navigators make a lot of this planning and decision-making much easier.

In any case, you can only fly the approaches allowed in the approved flight manual supplement for the unit you have.

Here's my take on this: Frequently, I'm stuck waiting for a marine layer to burn off. I only plan to file IFR to get out. I'd prefer to launch knowing I'm heading into VFR at my destination. I'm just not brave enough to fly to a destination that is likely to be IFR on my arrival.

It seems to me an non-WAAS GNS 430 is still gonna have a lot of life left in it for the foreseeable future. And, non-precision RNAV approaches are perfectly fine for the kinda flying I plan on doing. I have a KX-155/GS, KI-209, and MKR BCN that will be kept separate from my EFIS and GPS. And I'll use Skyview stuff for ADS-B out compliance.

Wondering what other builders' thoughts are.

Bubblehead said:

Are current databases available for the KLN 90B? It is a discontinued product.

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I did my IFR training with a KLN-90B tied into my HXr. It works well and King still offers updates for about the same cost as Jepp does for the 430. The UI is a bit less intuitive than the Garmin but not difficult to master. The moving map is useless, but unnecessary with a good EFIS. I also had an SL-30 tied into the HXr for VOR and ILS work.

I ultimately traded up to a 430W as I really like the LPV approaches and their availability.

Larry

Bubblehead said:

An indicator separate from than the EFIS?

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Using the EFIS for your CDI is just fine. You will need an ARINC 429 module if you don't already have one.

NOTE: if you go with a Non-WAAS unit, you will also need a VOR/ILS receiver in addition to your GPS to be legal IFR (the rule change is that either your destination or alternate has to have a ground based approach - used to be just the alternate)

WAAS

I have been using the Garmin 430 for almost 20 years now, 430W for close to 10. I know most of the pitfalls but don't know the issues of connecting a Garmin or a King to a non certified EFIS. I don't think the King will connect to the EFIS but don't know for sure. We are just going thru this with a straight Garmin 400 which was converted to 400W but the connection to the steam Flight Director has turned out to be a real pain.
I was just trying to point out to the OP that there are quite inexpensive non WAAS systems that are still viable.
Personally I am holding out for a 430 connected to Dynon EFIS.
As for the stand alone I think there are quite a few EAB folks flying in the system with just GPS for nav.
Will a hand held VOR receiver make you legal??

jrs14855 said:

I I don't think the King will connect to the EFIS but don't know for sure.

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The KLN-90B uses standard ARINC sentences and will connect to most EFIS' that have an ARINC interface. I successfully had one connected to both a Dynon D100 and a GRT HX. Complete functionality including baro and TAS to the KLN-90.

Larry

KLN 90B

Partsforplanes.com lists five units at $1095, seems to be just the box, no extras. I have seen these as low as $900 on ebay

As for the stand alone I think there are quite a few EAB folks flying in the system with just GPS for nav.
Will a hand held VOR receiver make you legal??

VOR not required. As far as I know, nothing "handheld" qualifies for "required equipment."

flyinga said:

As for the stand alone I think there are quite a few EAB folks flying in the system with just GPS for nav.
Will a hand held VOR receiver make you legal??

VOR not required. As far as I know, nothing "handheld" qualifies for "required equipment."

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I think the poster was referring to non-WAAS GPS boxes which require that you be able to shoot a non-GPS approach at either the destination or alternate. If it's an EAB, tape the handheld to the panel and call it installed.

The OP said " is that you need a WAAS certified GPS radio (e.g. GNS 430W, or GTN 650) to interface with the EFIS in order to shoot a "legal" GPS approach with vertical guidance. "

You can save a lot of $$ with a GTN 625, WAAS and TSO'd.

WAAS

This whole thing got a bit distorted. I was just trying to point out to the op that the 90B is a relatively cheap approach certified GPS if you can live without the glide slope. I did not know if the 90B would connect with a non certified EFIS. Apparently it can.
Someone else commented that an alternate means of navigation is required to be legal for IFR. I asked if a handheld Comm/nav/ils would meet that requirement.
In the last 11 months there have been two incidents of total electrical failure in twin turboprops. One made a safe off airport landing. The other lost control and crashed fatally. If I have a total electrical failure in IMC I don't much care at that point whether my portable EFIS, handheld comm and handheld GPS are legal or not. I am fully prepared to make a GPS approach to 100' if necessary using a handheld GPS in that EMERGENCY situation. I prepare for it as completely as possible and hope it never happens.

N804RV said:

Here's my take on this: Frequently, I'm stuck waiting for a marine layer to burn off. I only plan to file IFR to get out. I'd prefer to launch knowing I'm heading into VFR at my destination. I'm just not brave enough to fly to a destination that is likely to be IFR on my arrival.

It seems to me an non-WAAS GNS 430 is still gonna have a lot of life left in it for the foreseeable future. And, non-precision RNAV approaches are perfectly fine for the kinda flying I plan on doing. I have a KX-155/GS, KI-209, and MKR BCN that will be kept separate from my EFIS and GPS. And I'll use Skyview stuff for ADS-B out compliance.

Wondering what other builders' thoughts are.

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Hi Ken,

Here's my opinion. I have an "outdated" glass panel with a non WAAS 430. It's perfect for everything I do and I can't justify spending big bucks for an updated latest greatest panel or even WAAS. I would way rather spend the money on gas and fly a lot, which I do. In reality around here the instrument rating is really only good for about 6 months due to the MEA's and the freezing level. You'll probably find yourself practicing to stay current/proficient more than anything. If you keep track of the instrument approaches that you actually have to fly in IMC they'll probably be few. (how often do we choose to fly on bad weather days?) But ya, for me the instrument rating is perfect for those marine layer days around here when you just want to get out or back. Usually the LPV approaches are just a few hundred feet lower than LNAV anyway. If you get in a pickle you can always just find an ILS. If you as a sport flyer have to fly an LPV or ILS to minimums you may want to look at your decision making.

Talk to the guys with thousands of hours like Rosie or Turbo not the guys with $50K panels who have never shot an approach.

That said WAAS is great and so are LPV approaches. The latest panels are definately the cat's meow. If you have the money and want the best then by all means go for it. Definitely not required though for the way most of us fly.

At the end of the day, it?s not about the boxes. It?s about your ability to safely operate in the system in IMC. Define your mission and decide if your knowledge, attitude flying skills, and equipment are up to the task and produce a level of acceptable risk to you. Then set and abide by your limitations accordingly.

Thanks everyone for the great replies. I guess my problem is that I'm confused by all the advertising and the hype for all the fancy black boxes. I've had my instrument rating since 1976, and have rarely flown hard IFR, I prefer to file an IFR flightplan just to be in the system especially in the congested northeast where we now call home.

I know this may be opening another can of worms, but if any of you either recently or are currently looking to build an "inexpensive" IFR panel, what would you equip it with? I'd like an EFIS with a nav radio capable of ILS and at least LNAV approaches.

Thanks again for all your help, it's greatly appreciated!

Roger

Roger said:

Thanks everyone for the great replies. I guess my problem is that I'm confused by all the advertising and the hype for all the fancy black boxes. I've had my instrument rating since 1976, and have rarely flown hard IFR, I prefer to file an IFR flightplan just to be in the system especially in the congested northeast where we now call home.

I know this may be opening another can of worms, but if any of you either recently or are currently looking to build an "inexpensive" IFR panel, what would you equip it with? I'd like an EFIS with a nav radio capable of ILS and at least LNAV approaches.

Thanks again for all your help, it's greatly appreciated!

Roger

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For my money I'd go with any of the usual suspects as far as EFIS brands (AFS, Dynon, Garmin, GRT, etc) and pair it with a non-WAAS GNS430. The EFIS choice really boils down to personal preference on features, number of screens, how info is displayed, buttonology, etc which you'll just have to do the research and decide for yourself.

Bear in mind that cheapest option may not be the best option due to lack of product support so make sure future support/database availability is part of your calculus.

Roger - this game of IFR can be really "hard on the head" if one is coming from the staid old days of Cessna or Piper making all the decisions for you.

When you ask the question the way you have, you're going to get answers that range from soup to nuts.

Let me see if I can demystify this for you a little bit.

Firstly, WAAS is just an enabling technology - whether a receiver has a built-in WAAS receiver or not makes little difference. What does make a difference is the TSO to which the receiver is qualified. That TSO tells us the capabilities of the box, and it's those capabilities that dictate the approaches you can fly.

There are older boxes on the market that will allow enroute and non-precision approaches using GPS. There are also older boxes, namely the Garmin GNS480, which will do everything the more modern boxes will do in terms of enroute and approach navigation. I mention the 480 because it's about the best bang for the buck going at the moment. Used 430W's are still commanding a big dollar, big enough that I would spend the extra money to buy a new GTN650 or Avidyne IFD440 rather than buy a multi-year-old box at nearly new prices. The 430W is a good box but, in my opinion, over-priced in today's used equipment market.

GPS navigators are going to have to talk Arinc 429 in order to provide the information needed to perform GPS precision approaches. This means your EFIS selection will also have to include Arinc 429 interface capabilities. Likewise for your autopilot if you wish it to fly coupled approaches.

So how does one get an inexpensive IFR panel? The cheapest way is to go with a VOR/ILS receiver, but we know those approaches and airways are going away, replaced by GPS-based approaches and airways. This being the case, one can spend money now on a VOR/ILS solution but you'll later end up spending the money to get the GPS navigator that will open up all the airports into which you want to fly.

If I were looking at going bargain basement I would likely buy a used legacy GRT EFIS product with Arinc 429 interface and couple it to a used GNS480/CNX80. That way you could upgrade your legacy screens to the newer, higher resolution glass at fairly minimal cost ($2400 each) when money becomes available. Likewise, you could compliment the GNS480 with another box further down the road, even if that other box is a straight 430, an SL30 or similar nav/com. This gives you some redundancy in both navigation and communication.

Keep in mind that the more radios you put in, the more you're going to need a good audio panel to manage them. My best advice to anybody doing a panel upgrade is to start first with the audio system and upgrade it to a full audio panel and equip the audio panel wiring with inexpensive D-Sub connectors which allow you to quickly and easily connect in a new radio when you decide it's time to add a radio to the stack. Don't scrimp on the audio panel - after all, it's controlling the noise that's being piped into your head for every minute you fly your airplane.

How about Garmin get a TSO for the GPS20A and then add the ability to upload IFR approaches with LPV on to the G3X touch.

Ian Coates said:

How about Garmin get a TSO for the GPS20A and then add the ability to upload IFR approaches with LPV on to the G3X touch.

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Great idea, however they would also have to get TSO on the G3X as a flight management system in order to meet the requirements. The GPS20A would be a position "sensor" providing information to the flight management system. It's been done before, but not at anything like "experimental" pricing, so we're right back to spending $10K on a panel-mount TSO'd navigator as being the best option available.

Canadian_JOY said:

Great idea, however they would also have to get TSO on the G3X as a flight management system in order to meet the requirements. The GPS20A would be a position "sensor" providing information to the flight management system. It's been done before, but not at anything like "experimental" pricing, so we're right back to spending $10K on a panel-mount TSO'd navigator as being the best option available.

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And that Sir, is my (our) problem. How to build an IFR panel now that is not going to need extensive replacement in a few years, yet cost in the 5 AMU range?

Roger

Roger - the $5K price point completely rules out TSO C145 GPS navigators since that's about the very bottom end of the price spectrum for that type of device and you'd have to be a good shopper to find one at that price. You'd be left with zero dollars for an EFIS.

Picking up a used legacy EFIS will run you $1-2k. They do come up for sale here from time to time, including recently a dual screen legacy GRT system. With this being the case your budget of $5K leaves you enough money for an EFIS and something like an SL30 NAV/COMM and that's about it.

While your CFO might not like it, stretching the budget to $10K will get you very well into IFR territory with a TSO C145 navigator (which also does VOR/ILS and is a COMM radio, too!).

I updated our panel from a good solid VFR panel with a legacy GRT WS EFIS and an SL30 in it. With the addition of a GNS480, a TruTrak Vizon 385 autopilot, a GRT Mini-X EFIS and an upgrade of the WS EFIS to an HX I came in at a bit over twice your budge but now have a very, very capable airplane with nice redundancy built in.

Roger said:

And that Sir, is my (our) problem. How to build an IFR panel now that is not going to need extensive replacement in a few years, yet cost in the 5 AMU range?

Roger

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Can't be done, legally. It boils down to pay me now or pay me later.

I hear you both and understand. As a ham radio operator and amateur aircraft builder isn't there a way to put together a "kit" of some sorts that may shave a few AMU's off of the panel?

Roger

Roger said:

I hear you both and understand. As a ham radio operator and amateur aircraft builder isn't there a way to put together a "kit" of some sorts that may shave a few AMU's off of the panel?

Roger

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You undoubtably have the skills to build your own audio panel/intercom; parts cost is under $50, and your time is free! But ifr approved GPS? The standards the FAA is holding people to (the TSO 145/146 standards) are so complex that the effort to show compliance is claimed to be in the million dollar range.

OK, so I've been doing some head scratching and research into this perplexing (at least to me) issue.

Seems that there is a blind AHRS box from Talos Avionics (http://www.talosavionics.com/) for less than 1 AMU, that interfaces with either IOS or Android tablets of any size. I realize that this is not a do everything box, but it offers your basic 6 pack of instruments, plus you can dedicate another screen to charts and EIS.

Has anyone done anything like this?

Thanks!

Roger

It's hard to beat the GTN 625 deal ($5495) for a WAAS GPS IFR navigator, if you buy it with a basic G3X system. Grab a handheld NAV/COM for emergencies ($300) and call it good.

Roger said:

OK, so I've been doing some head scratching and research into this perplexing (at least to me) issue.

Seems that there is a blind AHRS box from Talos Avionics (http://www.talosavionics.com/) for less than 1 AMU, that interfaces with either IOS or Android tablets of any size. I realize that this is not a do everything box, but it offers your basic 6 pack of instruments, plus you can dedicate another screen to charts and EIS.

Has anyone done anything like this?

Thanks!

Roger

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Yes, I've seen some panels where something like this was used for backup. Not sure about primary. Remember that if an all-on-one EFIS box fails you may lose everything, so it seems prudent to have one or more backup plans if you are contemplating actual IMC.
OTOH, for about the same $1K (maybe a bit more) price, you can today buy a "mini-EFIS" from Garmin, GRT, Dynon, probably others.

Roger said:

OK, so I've been doing some head scratching and research into this perplexing (at least to me) issue.

Seems that there is a blind AHRS box from Talos Avionics (http://www.talosavionics.com/) for less than 1 AMU, that interfaces with either IOS or Android tablets of any size. I realize that this is not a do everything box, but it offers your basic 6 pack of instruments, plus you can dedicate another screen to charts and EIS.

Has anyone done anything like this?

Thanks!

Roger

Click to expand...

I've flown with the talos in my airplane for awhile - the connectivity is a bit buggy, and it doesn't play real well with other navigation Apps on the iPad. It works for what it is, but I don't think I'd want to depend on it as my last chance backstop in IFR conditions - there are better options.

The Talos was really designed originally for teh European ultralight market as an all-in-one panel solution.

Thanks for the info everyone, great replies. So, here we go again, what does a monetarily challenged builder do to complete a very basic IFR panel that will not be obsolete if and when VORs are decommissioned.

@cofford, do you have a source for the GTN 625 for $5495? I haven't been able to find any at that price.

Thanks again for all your great advice and help!

Roger

Roger said:

Thanks for the info everyone, great replies. So, here we go again, what does a monetarily challenged builder do to complete a very basic IFR panel that will not be obsolete if and when VORs are decommissioned.

@cofford, do you have a source for the GTN 625 for $5495? I haven't been able to find any at that price.

Thanks again for all your great advice and help!

Roger

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That GTN 625 price is a bundle - you have to buy a G3X system with it to get it for $5.5K, otherwise add another 3 AMUs to it.

My advice, get a decent EFIS (most which have VFR GPS to aid in SA), add a couple of NAV/COM radios (the EFIS will have an HSI) and that will give you the minimum but plan your panel with the intent to add an IFR navigator.
Then continue to save until you can add the IFR GPS (something less expensive then a GTN might come along while you save) Seriously doubt we will regress to nothing but the VOR MON before you can save up for the IFR GPS.

Hi Roger, I've got one---a brand new never used GTN 625. I opened the box to say O-o- Ah--pretty, but that's it. I had planned to make my 8 fully IFR, but I'm 74 now, and have begun to realize, I maybe don't have that many more flying days in me to spend all the moola it would take. $6400. (I don't know where the $5495 comes from, last I heard, they were $8300 something)

You can email me or PM me or call if you like. I'm in Atlanta. 770 205 2454

If the Wx was good, and you're serious, I could maybe fly it up to New York for you. Would be a fun trip, but I'd need VFR for at least 2 days.

+1 on Todd's reply, but I would suggest one nav-com, a used SL-30, because it can bring in two VOR signals (or an ILS and a VOR cross fix) at the same time. Make sure whatever EFIS you get that it can display both of these signals (I know my GRT HX can). Get a handheld nav-com for backup; and/or an iPad with GPS for emergencies. Also a mini EFIS with its own battery for backup.

donaziza said:

. $6400. (I don't know where the $5495 comes from, last I heard, they were $8300 something)

ys.

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As Todd mentioned, $5500 is the price if bundled with a new G3X.
Gives you an idea of the profit margin on these boxes.

Great advice. @donaziz, thanks for the offer, but unfortunate;y, I will need to wait and put aside some more money in order to get the GPS Nav. That's why the other suggestions are so timely and appreciated. It will allow me to get in the air with a decent panel and add later on.

Roger said:

Thanks for the info everyone, great replies. So, here we go again, what does a monetarily challenged builder do to complete a very basic IFR panel that will not be obsolete if and when VORs are decommissioned.

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When I was looking into this, cheapest way I could figure to do it:

Apollo GX-50 GPS - can be found for $500-$800, or alternatively a KLN89B for slightly more. Not WAAS, but both are perfectly functional GPS enroute and approach units.

Narco NAV 122 - all in one ILS/VOR receiver with analog needle display built in - can be found for $500 - $800.

Single display GRT HX EFIS - ~$4000, less if you can find a used unit from an upgrade.

For attitude redundancy, I'd also add a GRT Mini X for ~$1400, plus $150 for the moving map and HSI options.

This will offer a no frills basic IFR "starter" panel, with completely separate approach units that do not rely on each other, and with the GRT Mini you are covered if the HX tanks.

You'll be out the cost of the NAV 122 once VORs are decommissioned, but that will be awhile yet.

At some point in the future you can replace the GPS with a WAAS GPS without replacing any of the EFIS units. I replaced my Apollo GX-50 with an Apollo CNX80 (Garmin GNS480) for about $5k, and sold the GX-50 for about what I paid for it.

-Dj

deej said:

Not WAAS, but both are perfectly functional GPS enroute and approach units.

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In what situations would the non-WAAS GPS fall short (vs the WAAS unit)? (I am not yet an IFR pilot).

Nice post on a lower cost IFR panel Deej! That seems like a great way to go for the price.

Andrew, WAAS is a system to increase the accuracy of the GPS signal thereby giving you lower approach minimums, or more accurate positioning while enroute. Very simplistically, if you want to get the equivalent of an ILS approach then a certified WAAS receiver with RAIM is necessary.

Andrew Anunson said:

In what situations would the non-WAAS GPS fall short (vs the WAAS unit)?

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Biggest is no vertical guidance. Non-WAAS GPS approaches are a series of "step down", as in X distance away you drop to a specific altitude, then at Y distance, you drop more, etc.

WAAS gives you vertical guidance all the way down, like an ILS approach.

WAAS will also allow you to do a fully coupled autopilot approach, whereas non-WAAS will only allow the autopilot to do the left-right guidance, and you have to do the vertical altitude manually.

The other unknown is for how long Jeppesen will be releasing updated NAV data for the older non-WAAS GPS units.

-Dj

There's also a regulatory aspect: non-WAAS, you must have a VOR on board. And some rules about non-GPS approaches at your destination or alternate.

Synthetic approach with GRT

I have a non WAAS 430 coupled to a single GRT HX. You can shoot a GPS approach and have the synthetic approach in the EFIS armed. When at the final approach fix just execute the synthetic approach and you are now tracking laterally with the 430 and vertically with the GRT. Can only go to standard dive and drive minimums, but you can do it fully coupled with flight director and autopilot without the dive and drive. Using the GRT in this way makes approaches very safe, relatively simple, and only requires a non WAAS IFR navigator.

Bubblehead said:

Exactly. Why would I put an old OBI in a panel when I have all my flight and nav in the EFIS. I have an OBI built into the EFIS as an HSI plus Flight Director if I want it.

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Because the EFIS may not support it?

RAIM is a lessor form of WAAS... If WAAS is available, RAIM prediction is not required for IFR flight.

WAAS receivers will fall back to a RAIM setup, if WAAS is out of service.

Roger said:

Andrew, WAAS is a system to increase the accuracy of the GPS signal thereby giving you lower approach minimums, or more accurate positioning while enroute. Very simplistically, if you want to get the equivalent of an ILS approach then a certified WAAS receiver with RAIM is necessary.

Click to expand...