Is there a way to check for past RAIM outages?

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rburnette

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Ryan Burnette
I am familiar with http://raimprediction.net ... at least in checking for future outages.

I had a dual GPS failure in an airplane I've been flying that has dual GNS 430W units. I want to rule out an environmental issue before I squawk it with the avionics shop.

Does anyone know of a way to check for RAIM outages at a past time and location?
 
rburnette said:
I am familiar with http://raimprediction.net ... at least in checking for future outages.

I had a dual GPS failure in an airplane I've been flying that has dual GNS 430W units. I want to rule out an environmental issue before I squawk it with the avionics shop.

Does anyone know of a way to check for RAIM outages at a past time and location?
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Subscribing...


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Need more information.
Were there any NOTAMs for GPS interference in the area? Government "activities" that make GPS "unreliable" over a fairly large area are not uncommon.
 
When did this happen and where? There have been "GPS unreliable" NOTAMs over the Ohio/Mississippi Valley area recently, I think one is in effect now for the remainder of this week, and then again next week.

Here is one:

!GPS 02/023 ZAU NAV GPS IS UNRELIABLE AND MAY BE UNAVAILABLE WITHIN
AN
AREA BOUNDED BY A 177 NM ARC CENTERED ON N38 55 35 W090 25 22
SWEEPING CLOCKWISE FROM BEARING 315 DEGREES TO BEARING 045 DEGREES AT
FL400 AND ABOVE. THE ARC RADIUS DECREASES TO 138 NM AT FL250; 79 NM
AT 10,000 FT MSL; 48 NM AT 4,000FT AGL; AND 12 NM AT 50FT AGL. THE
ARC CENTER POINT IS ALSO DEFINED BY THE ST LOUIS, MO VOR (STL) 035
RADIAL AT 5 NM. 1300-2100 DLY WEF 1302181300-1302232100
 
I think the OP ran into an unexpected dropout even though nothing was NOTAMed. I had this happen to me once and it would have been nice to see if we missed something by looking at the previous outages.

My GPS dropout happened just once -- but on an approach. According to my avionics shop it could be a problem with the actual GPS signal or interference of another type (like a certain COM frequency transmitting). I have not been able to duplicate the problem.


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Oh, I know. Boy do I know! The area just west of my home base is notorious for that, several pilots have reported it. I frequently lose ALL satellites abruptly, with no warning at all, when flying through that area. I believe there is some ground-based radio source that interferes with GPS reception, but have no idea what it could be.

Well, not no idea, but I am not sure, nor even whether that is a possible failure mode of what I suspect.
 
azure said:
Oh, I know. Boy do I know! The area just west of my home base is notorious for that, several pilots have reported it. I frequently lose ALL satellites abruptly, with no warning at all, when flying through that area. I believe there is some ground-based radio source that interferes with GPS reception, but have no idea what it could be.

Well, not no idea, but I am not sure, nor even whether that is a possible failure mode of what I suspect.
Click to expand...

I suspect there are a lot of unreported outages like these. It is easy to blame the equipment in the plane, but it does appear that other factors can and do come into play. Losing your primary navigation equipment can be unnerving on an approach. I was fortunate that the GPS approach had an ILS overlay and I had it setup and operating.

Wondering if others encounter these outages as well.


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