Determining WAAS coverage

[Guy Morton]

I'm getting ready for my instrument written a digging through some of the loose ends in my studying. Today, it's RAIM and WAAS. Now, I understand that if I can confirm that if I have WAAS coverage throughout my entire route, I don't need to do any RAIM prediction as part of my flight planning. How do I determine that there is WAAS coverage along the entire route?

 

[Deelee]

NOTAMs and/or FSS should be able to tell you if there are degradations. The NOTAMS will say something like UNRELIABLE or MAY NOT BE AVAIL

 

[John Collins]

From the NOTAM order 7930.2S:

b. Wide Area Augmentation System (WAAS). WAAS area−wide NOTAMs are originated when WAAS assets are out of service and impact the service area. The term “MAY NOT BE AVBL” indicates that due to ionospheric conditions, lateral guidance may still be available when vertical guidance is unavailable. Under certain conditions, both lateral and vertical guidance may be unavailable. The USNOF distributes these as FDC NOTAMs when a WAAS asset failure affects a large area. USNOF utilizes templates provided by Technical Operations, WAAS Operations. All events must reflect an effective time and expiration time.
1. Unscheduled loss of signal or service.
2. Ionosphere storm conditions.
3. Scheduled loss of signal or service.
4. Operating under a single GEO
5. Extreme storm detector trips
6. Test
7. Emergency

One can always use the FAA NOTAM site to do a text search for NOTAMs using the "WAAS". Actual WAAS outages in the US are very rare events. You can also view the current WAAS coverage at https://www.nstb.tc.faa.gov/rt_verticalprotectionlevel.htm