GPS Interference Testing

[Lon33]

I regularly get emails from the FAA notifying me that GPS Interference Testing will be done. The email links to a PDF containing the dates, times and locations of the test. Today's email contained this link: https://www.faasafety.gov/files/notices/2015/Jul/NTTR_15-12_GPS_Flight_Advisory.pdf

I'd like to learn more about the tests, and whether pilots have reported noticing any actual interference while flying. I once cancelled a planned fight because of a test that might have affected the area where I would have been flying. But the notices became so frequent that I now fly despite them, and have not noticed any effects.

Despite prowling the FAA website and doing all sorts of Google searches, I haven't been able to find any information about the tests, other than the FAA notices themselves.

Can anyone point me in the right direction to learn more?

 

[Zeldman]

I am not sure if what you referring to is a signal interference test to see if something will interfere with the signal, or if they are just practicing signal jamming.

The military practices GPS signal jamming in the White Sands restricted areas.

It works. Suddenly no signal, I get a notice from my GPS that it is now on dead reckoning, and everyone starts calling ATC saying their GPS has stopped working.

If the agency that is doing the signal jamming is actually working then you will notice.

 

[Lon33]

Here's a discussion about GPS testing from a few weeks back.

http://www.pilotsofamerica.com/forum/showthread.php?t=82607

My guess is the testing is related to DOD activities.

Thanks for the link. I somehow missed that thread.

Usually, the FAA is pretty good about explaining, somewhere, why it's doing things. But even in that earlier and quite lengthy thread on GPS testing, no one had a link to any government explanation at all. I find it quite strange that there doesn't seem to be a publicly-accessible explanation for tests that are so frequent and affect so many pilots in such a significant way.

I'll admit to being a "magenta-line pilot." I like GPSs and use them on the ground as well as in the air. In the air, though, pilotage is my only alternative. I fly LSAs -- Skycatchers and Slings -- that have GPS receivers but not VOR receivers. I've never experienced the loss of a GPS signal, but I see that those who contributed to the earlier thread have. Now that I know that, I'll be careful to fly to only to destinations I can reach solely by sight, on days when GPS testing is going on.

 

[MAKG1]

Are you sure your aircraft have no VOR receivers?

Many certificated GPSs (for instance, Garmin 430's, 650's, G1000, etc.) come with them.

I've seen the results of GPS interference. The G1000 182 I fly keeps a record of the highest ground speed. It's over 750 knots. I really doubt it's a supersonic 182…

You always have the option of dead reckoning. It's usually a good idea to combine that with something else, and pilotage works. Though only intermittent pilotage is actually necessary.

 

[Lon33]

Are you sure your aircraft have no VOR receivers?

Many certificated GPSs (for instance, Garmin 430's, 650's, G1000, etc.) come with them.

Yes, I am sure.

The Skycatchers have Garmin SL40 comm radios, but no nav radios, and Garmin G300 GPSs which are not certificated.

The Slings have MGL Avionics radios and GPSs. The radios are comm only, and the GPS isn't certificated.

I like both planes a lot, but they are light sport aircraft and thus not approved for flight in IMC, which explains, I suppose why they don't have nav receivers or certified GPSs.

 

[Stewartb]

We've had a couple of NOTAMs in Alaska in the past couple of years warning of GPS testing and the potential of decayed GPS signals. The epicenter is smack in the middle of a large MOA and radiates out to increasing distances with increased altitudes. I haven't heard any verified reports of loss of signal. The most recent testing was cancelled early because of the Alaska wild fires creating poor visibility state wide and increased air traffic associated with fighting the fires.