GPS... Standalone or Integrated?

[JoeG]

I am in the process of "wish-listing" my avionics and panel gadgets.

The Garmin 430/530 approach is a nice option, but at a steep price. I noticed that GRT sells an "internal WAAS enabled" GPS option with their EFIS.. and its only $450.00!

I realize that nothing in life is free, but what are the real differences? Most of the "overhead" components are already in place with an EFIS, so it seems that all they are providing is a receiver and a little bit of integration software. I guess that's why they can get the price down.

Does anybody have specific experience with the GRT GPS option and could you tell me why I shouldn't buy that instead of the $9000.00 430?

[aadamson]

Originally Posted by JoeG

I am in the process of "wish-listing" my avionics and panel gadgets.

The Garmin 430/530 approach is a nice option, but at a steep price. I noticed that GRT sells an "internal WAAS enabled" GPS option with their EFIS.. and its only $450.00!

I realize that nothing in life is free, but what are the real differences? Most of the "overhead" components are already in place with an EFIS, so it seems that all they are providing is a receiver and a little bit of integration software. I guess that's why they can get the price down.

Does anybody have specific experience with the GRT GPS option and could you tell me why I shouldn't buy that instead of the $9000.00 430?

As a point of reference, all the EFIS systems out there that include a GPS, include a WAAS GPS... You don't have to buy any upgrade to use it VFR. The problem stems from when you try to use it IFR. To do so, it must meet the requirements of the GPS TSO's.

At the current time the GRT option *isnt* available yet. In fact, it's not even been designed yet. So I'm not sure when/if it will be.

I spent a good bit of time talking with them at OSH. I'm not sure that the way they are discussing it currently, that it will meet the TSO 146a (WAAS GPS TSO) that will be required for IFR use. That leaves only the Garmin 480 currently and the recently announced "W" series from Garmin that will meet the WAAS TSO.

As a quick refresher, you need something that will comply with TSO-146a for IFR WAAS usage. TSO-129a for IFR non-WAAS usage.

GRT's literature and the discussion at OSH all centered around 5hz updates, and RAIM support - but, RAIM doesn't have anything to do with WAAS. It's called "integrity monitoring" under WAAS and is lots more complicated than just letting you know if the approach solution is valid or not (what RAIM does for TSO-129a).

Depending on your timeframes, you'll have to factor this into the mix. BTW, I know of NO external (read as portable) GPS (WAAS or not) that meets the TSO-129a or 146a requirements.

So ya kinda have to fall back and punt.... And ask yourself... Do you want IFR GPS or just VFR GPS. The later you can use anything for, but not as primary guidance.