Loss of GPS satellite signal while approaching in IMC
 

Since there was a tropical system overhead us yesterday and the weather really sucked I went to the hangar to do some minor cleaning. While listening to the tower I heard a Saratoga on the RNAV to Rwy 13 get cleared to land. A short while later the Saratoga told the tower the GPS had lost satellite signal (RAIM) and they had to execute the missed approach. They went around in the clouds and returned to Jacksonville approach.

Right then a Citation came on frequency also on the RNAV Rwy 13 approach and was also cleared to land. Right after being cleared the Citation told the tower the GPS had lost satellite signal and they had to execute the missed approach. The tower told him the aircraft before them had gotten the same indication and had also executed the missed approach. I heard them go around in the clouds and they also returned to Jacksonville approach.

A few minutes later the Saratoga came back on frequency but this time "VFR" below the clouds (clouds were now about 1,000ft) and they landed on RWY 13. Once on the ground the Citation came back on tower frequency but he was executing the ILS approach to RWY 31. They landed on RWY 31 with maybe a 5kt tailwind.

This is the 1st time I had heard this actually happen (GPS unuseable for landing in bad Wx) with one of the airplanes having to use the old fashion ILS to land. Now I am REALLY glad I still have ILS capability in my airplane and don't rely exclusively on the GPS "Magenta line".

This is the Saratoga track on FlightAware.

This is the Citation track on FlightAware.

Moral of the story... unless it is a life and death emergency situation, DON'T DO RNAV APPROACHES WITH A NON CERTIFIED GPS!

:eek:

It happened to me in vfr. I was right seat, student under the hood. LPV 25R LVK. At about 2000? student says, ?I don?t think the glide slope is working?. I point to the gtn650, which is now showing ?LNAV?, tell student to use those minimums. At about 1000?, near MDA, a big red x appears over the screen, cdi flags. We landed vfr. Never did hear the reason for the outage.

I love my VAL INS-429 !! Even if the ILS goes out in one airport it'll be ok at the next airport right beside it.

Now imagine that happening in hard IMC. I bet the pucker factor went up in those cockpits, at least for a little bit. :cool:

Yep. LVK is, in that sense, a lot worse than flat Florida. It?s surrounded by hills, and down low it?s below radar coverage.

This is why I still recommend the 650 to my IFR panel customers.
I have the 650 in my own RV and practice using the ILS frequently, the 650 will auto transition from GPS to the ILS with no button pushing.

Walt. To make sure I'm understanding you correctly; If I select an LPV approach and the GPS tanks, the 650 will automatically kick over to an ILS for the same runway?

I've got a ton of time with a G-1000 and don't recall ever discovering this. Have I just not got deep enough in the book or is this specific to the 650/750?

I am wondering how do you fly the GPS missed approach without GPS guidance?? Is there a procedure specific to this other than vectors?
I am also keen to know more about the GTN automatically switching to ILS with loss of GPS guidance.
Thanks.
Johan

I think you misunderstood Walt. If you tell the box ?ils25?, but put or leave the box in gps mode to navigate to an IAF, the box will auto switch to ?vloc? when you intercept.
Yes, if you lose gps then a gps based missed approach procedure is of doubtful usefulness.
I have maintained a separate SL30 just in case my entire 4xxW box dies. In IMC I keep it tuned to the ILS at my home field, so I can quickly transition. And the ILS has a different MAP than the LPV.

He's probably referring to not having to hit the OBS button to switch from GPS to ILS on the CDI.