FDE vs SBAS Nav on Recent Flight

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   Hello,
On a recent VFR flight I received a GPS alert.  When I checked the NAV status I found that it was FDE nav and not SBAS nav.  I did not reboot the -440.  After landing for fuel and restarting all was normal.  I did notice that the IFD seemed to have some problems locking on to the GPS satellites, while my two other GPS devices that allowed me to check their status had no problems during the entire flight.  They showed a lock on 10 or more satellites.  I encountered this problem for the entire flight which was 45 minutes to an hour long.

Given that I fly a fair bit of IFR with this plane I would like to figure out why I encountered this problem.  

The flight was conducted in Southern Michigan and I did not see any Notams for GPS outages. 

The IFD display showed that it typically had 8 to 10 satellites locked and often one or two empty yellow bars for others.  I had no repeat problems of this issue during follow on flights. I would not think that it would make a difference but I departed from an off airport location on the flight in question.  

Any insight would be appreciated.

John

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JohnP Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 16 Sep 2024 Location: Georgia Status: Offline Points: 4	Post Options Post Reply Quote JohnP Report Post Thanks(0) Quote Reply Topic: FDE vs SBAS Nav on Recent Flight Posted: Yesterday at 12:15pm
	Hello, On a recent VFR flight I received a GPS alert. When I checked the NAV status I found that it was FDE nav and not SBAS nav. I did not reboot the -440. After landing for fuel and restarting all was normal. I did notice that the IFD seemed to have some problems locking on to the GPS satellites, while my two other GPS devices that allowed me to check their status had no problems during the entire flight. They showed a lock on 10 or more satellites. I encountered this problem for the entire flight which was 45 minutes to an hour long. Given that I fly a fair bit of IFR with this plane I would like to figure out why I encountered this problem. The flight was conducted in Southern Michigan and I did not see any Notams for GPS outages. The IFD display showed that it typically had 8 to 10 satellites locked and often one or two empty yellow bars for others. I had no repeat problems of this issue during follow on flights. I would not think that it would make a difference but I departed from an off airport location on the flight in question. Any insight would be appreciated. John

Melohn Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 11 Dec 2013 Location: PHNL Status: Offline Points: 143	Post Options Post Reply Quote Melohn Report Post Thanks(0) Quote Reply Posted: 22 hours 24 minutes ago at 1:46pm
	A number of aircraft lost WAAS capability recently due to solar storms. You can look at this problem in real time via this website, which reports on signal quality. It also contains an archive, so you can go back and look for the date you had a problem and see what the “LPV” envelope looked like. https://www.nstb.tc.faa.gov/RT_VerticalProtectionLevel.htm Edited by Melohn - 22 hours 21 minutes ago at 1:49pm