If WAAS-equipped, it is permitted as the sole source of navigation. There are now aircraft flying (presumably including IFR) with ONLY GPS NAV capability. This is, of course, silly, given the Air Force insisting on intentionally running tests that compromise GPS signals.Boatguy wrote: ↑Tue May 18, 2021 9:39 pmI think this is still pretty murky. First as @midlifelfyer points out, then also in the case of GPS outage and the MON network. The reg says IFR, not IMC and in the case of a GPS outage (I get weekly notices of planned outages in the west) navigating primarily by VOR is quite likely. I routinely get VORs in my clearances, but of course I use the GPS for nav to the VOR. On a few flights I've switched to the VOR for navigation and was amazed to see the CDI centered and the GPS cross track error up to 1nm. Unless you end up in the wrong airspace, CFIT, or get a ramp check that is really focused on the VORs, nobody is going to know.CFIDave wrote: ↑Mon May 17, 2021 8:12 pmWith WAAS, you no longer have to do VOR checks if using GPS as your primary means of navigation:
https://pilot-protection-services.aopa. ... ifr-flight
In fact, Garmin now sells IFR navigators that rely exclusively on WAAS GPS with no VOR functionality.
https://buy.garmin.com/en-US/US/p/577174
Does the VOR check implicitly also check the accuracy of the ILS? If so, there is a good reason to keep checking.
Remember that a localizer provides a signal that needs a different signal interpretation that is independent of course setting on the CDI and there is no way to check your glideslope receiver accuracy. Also note that VOR checks allow pretty significant error.
I notice that when flying GPS along airways it's almost always true that it will turn me on a course slightly different than that published for the airway, yet it takes me perfectly from waypoint to waypoint.
Here's another wrinkle: The magnetic poles are constantly moving. (There have been a flurry of recent runway renaming in the last couple of years here in the Northwest.) This typically happens after a drift of 10 degrees or so. But the airways specify magnetic courses down to a single degree and they are not being updated with great frequency. So it would not surprise me that a lat/long designated waypoint (or the route to it) would be at a different real azimuth from a particular VOR than that defined by a published airway course that hasn't been updated in 5-10 years.