View Full Version : EFIS GPS and ADS-B

04-23-2013, 05:46 PM
If I used a WAAS GPS made and sold by one of the EFIS makers will that satisfy the ADS-B WAAS GPS requirement? (in performance terms)

I know they are not certified but that does not mean they are less accurate does it?

This "Certified" requirement is costing GA flyers an obscene amount of money unnecessarily.

I'm not an IFR pilot and never will be, I think the certified requirement is overkill for a VFR only flyer.


04-23-2013, 05:56 PM
A lot can be written on this subject.. "Performance"-wise, at least what we consider it to be -- yes any of those would work just fine.

I agree with you that this requirement is putting additional burden and increasing overall cost (by at least a grand, if not a little more), but it is what it is. It's important to understand that this has nothing to do with "IFR" so you being VFR doesn't change the reasoning why they require a "certified" one.

Further more, it's not really a requirement that the GPS is certified as standalone.. it can be certified as part of the box (ie NavWorx selling you a box that includes an internal GPS that's approved as source position *for that box*)...

As I said I agree this is not really helping in keeping flying affordable for those who want to participate and fly in airspace that will eventually require ADS-B compliance. Note: participation is not mandatory -- just stay out of the airspace that requires it and you're good.. :)

04-23-2013, 08:27 PM
The simple answer is no. The "performance" they are looking for is not location accuracy when everything is perfect, it's how sure the GPS is of that accuracy at all times, even in degraded situations. This is not a function that commercial GPS units generally provide to the accuracy and standards the TSO requires.

The point of ADS-B out is to keep two aircraft apart, so your IFR or VFR doesn't matter. ATC has to keep that airliner that is IFR away from you when you are VFR, and they need to know your location is accurate. That's why the only three things in a home built that must be certified are the transponder, ADS-B out device, and the GPS. They're the things that don't just keep you safe, they keep the general public safe.

On top of all of that, serial protocols like NMEA flat out don't include the data needed to transmit the ADS-B data, so even if you hooked one up to your ADS-B out device, which must be certified, that certified device won't transmit that data as certified.

ADS-B out is not required for another 2,442 days, and even then it's only required in places where a transponder is required (class B and C airspaces and above 10K feet). That's a long time, and TSO'd GPS prices are likely to come down before then. So why worry about it today?

If all you want to do is "wake up" the ground stations so they will send you traffic, you can use a non-TSO GPS today up until 2020. The ADS-B out data includes data about if your GPS is certified, so the world knows how much to trust it.

--Ian Jordan
Dynon Avionics