I find it hard to believe that sunspots bad enough to shut down the GPS
frequencies won't play havoc with the LF frequencies used by LORAN. In terms of
frequency, the best alternative to GPS is probably ground-based VHF/UHF
(VOR/DME) navigation.

Dave Reinhart


Bob Gardner wrote:

At the controller's "Communicating for Safety" conference, one-time FAA
Administrator Langhorn Bond told me that loran is coming back as a backup to
GPS. He obviously sits on a lot of committees, work groups, etc
internationally, and has a lot of good info. He pointed out that on two
occasions sunspots have essentially shut down GPS, and he believes that
sole-source GPS may never happen. He was particularly disturbed by a GPS
NOTAM saying, in essence, that if you have WAAS you don't need anything
else.

Controllers as a group are unhappy with approach designers, who do not work
with ATC facilities when designing GPS approaches. Angel Fire, NM, was given
as an example...one IAF 15 miles from the centerpost fix on a basic-T TAA,
with the missed approach waypoint 20 miles from the airport. A 172 on the
GPS approach can shut down thousands of square miles of airspace, overlying
several airports and some Nellis AFB IR routes, for 45 minutes to an hour if
they execute the miss to the missed approach hold. The controllers would
prefer that pilots ask for alternative miss procedures that would keep them
in closer before they initiate the approach.

Bob Gardner