Are non-certified devices legal?

[PMcClure]

Curious - can you give examples?

Thanks

On the question of accuracy, I have observed on 2 occasions now where the GPS location shown on my Ipad, using Garmin Pilot App and an external Bluetooth GPS has been inaccurate. in one case, it showed me 3 nmiles east of a localizer when the on board GPS and CDI showed me on path. Another, the Ipad showed me at the IAF while the on board showed me 1 minute to the IAF. Different airports, different data cycles. Since then, I rely a lot less on the Ipad location. Neither case would have killed me because of the terrain but i don't trust the apps as much as before. I called Garmin and made a report. They were quite interested but offered no resolution. 

[Marauder]

Hi Jim - I believe the certification process for a WAAS GPS provided the assurances of accuracy or at least to know when they are not accurate. That is why the error reporting capabilities are built into them (the LOI error messages). Nothing pops up on any of these apps showing GPS integrity, hence the concern that someone may take them as accurate. I always knew there were some differences in accuracy between my panel mounted unit and the apps. Just never knew how much and that is what I am experimenting with. I own a Nexus 7 that is running Garmin Pilot, an iPad 2 running both ForeFlight & Garmin Pilot (don't ask why I have both) and an iPhone 5 with ForeFlight running. I am using an XGPS150 on the iPad but can pair it with the Nexus and iPhone to test the different permutations. My first tests were altitude differences. Still haven't got the iPhone's data, but once I do, I will have a pretty good idea of how things shake out. I noticed location inaccuracies a few times with the georeferenced charts running but obviously was concentrating on the panel mount unit to fly the approach. Once I get a handle on how they perform, I will write up a summary.

[PMcClure]

Very interesting.  I have never experienced this or, at least, I have never noticed it if I have. 

 

But how do you know that it was the on board GPS that was correct?  That is the real question.  Has anyone with triple GPS redundancy experienced this who could at least apply majority logic?  Even then it would seem that the problem could be hardware and/or software based and could be common to similar systems.  

 

Jim

I had the same question. For the localizer, it was a VFR day. I had visual references, the localizer, the G530 and the G430 all showing my exact position on the localizer. But my little ship on the Ipad was way east of the localizer. So I am certain the Ipad was in error. The other was in hard IFR and I was cross checking the 530 to the geo referenced charts. The chart showed me just past the IAF but the 530 showed 1:xx till next. But 100's of other times, it has been dead on. I still use my Ipad as it is a great tool, but I have stopped relying on it for exact location. 

[bd32322]

The accuracy of GPS units is expressed as x feet y % of the time. So 99% of the time it will be accurate to within 300 feet (or some equally large number)

95% of the time it will be accurate to 100 feet

 

You get my drift - as the accuracy increases - the percentage of time the receiver can maintain the accuracy decreases.

 

For the real accuracy figures - you will need to google it - sorry too lazy

[Hector]

I have not seen these inaccuracies either using geo-referenced plates in ForeFlight with iPad and external Bluetooth GPS. With the needles centered the iPad always has shown me straight down the localizer. Altitude is a different story and we all know the GPS is not going to display pressure altitude.

[midlifeflyer]

I have not seen these inaccuracies either using geo-referenced plates in ForeFlight with iPad and external Bluetooth GPS. With the needles centered the iPad always has shown me straight down the localizer. Altitude is a different story and we all know the GPS is not going to display pressure altitude.

I've had the same experience as you. Zero difference between what's depicted on the iPad and what's depicted on certified GPS-based avionics.

[N601RX]

I noticed something several years ago as I was flying up north with a garmin 396.  I had never left Alabama/Florida  with it before and just used the antenna on the back of it.  It always worked fine.  The further north I got the weaker the signal became.  It went from 3D to 2D and then dropped out.  I plugged in the remote antenna and it came back up.  I was curious and made a mental note of were it happened. On the way back home I tried it several times with the remote antenna unplugged and it started back working in about the same place.   Anone else ever noticed anything like this.  It was in a high wing plane.

 

For the people who have had problems with the IPAD and Foreflight, what was forflight reporting as the accuracy when you saw the errors?

[carusoam]

I had a narco radio that would interfere with a portable's GPS reception. It happened in the same place as I tuned in a particular frequency. It didn't matter which GPS antenna I used, on the back or sitting on the glare shield...

When you lose GPS signal strength, try turning off your radios, momentarily of course.

Best regards,

-a-

[Marauder]

Well, the test results are in...

 

Quick summary; I noticed some altitude differences between my iPad running ForeFlight & Garmin Pilot and my Nexus 7 running Garmin Pilot. On the Nexus, using the internal GPS antennae, I was seeing between 400 to 500 feet difference the altitude it reported versus what the iPad running Garmin Pilot with an external XGPS150 antennae.

 

I also suspected there were some issues with the GPS position reports as I saw on the georeferencing on both devices. To get to somewhat accurate answer to both of these concerns, I set up both units to determine what the differences were for both.

 

For the location tests, I set up the Nexus 7 with the internal GPS using Pilot and recorded the lat/long for the position I was at (stationary, on the ground). I did the same with XGPS150 antennae connected first to the Nexus and then to the iPad. I recorded results for the Nexus using Pilot with internal antennae, external antennae and using a GPS app for the Nexus (reports internal GPS function) and with the iPad running the XGPS150 with ForeFlight & Pilot. End result? The positions were the same.

 

The second round of location tests were done in motion, comparing my actual position to the georeferenced using the same combinations of devices, antennae and apps. Again, all reported the same information (essentially). I did notice a little bit of a difference with the Nexus running the internal antennae.

 

Altitude tests. I did a check on the ground at a known fixed point (airport reference). I did the same comparison using the different combination of devices, antennaes and apps. The result? The Nexus using it's internal antennae reported a ~150' difference (lower) than the other two device combinations -- both of which were within 20 feet of the known elevation (strange but true).

 

The tests were repeated at 2500', 4500' and 6500' feet. What I noticed was a significant difference at altitude. The higher I went with the Nexus using the internal antennae, the more deviation there was between what the other combinations reported. The Nexus with XGPS150 and the iPad with the XGPS150 were essentially the same using either ForeFlight or Pilot. At 6,500, the difference was almost 600'.

[Mooneymite]

Wow!  What a bunch of scofflaws.  

 

Every time I ride an airliner, I'm told that FAR's do not permit operation of anything with a battery and an on/off switch because it will cause an immediate crash and mass carnage.

 

I certainly hope none of this outlandish, dangerous behavior takes place below 10,000'.  

 

If you persist in this habit, I hope you don't carry flight attendants with you.    They'll tell on you.

[midlifeflyer]

Wow!  What a bunch of scofflaws.  

 

Every time I ride an airliner, I'm told that FAR's do not permit operation of anything with a battery and an on/off switch because it will cause an immediate crash and mass carnage.

 

i've never been told that on an airline flight.