GPSS Gotchas?

[Flash]

I shot approaches yesterday with my new-to-me set-up of an IFD 540 with dual GI 275s and my old familiar KFC-150. I'm a very happy Mooney pilot. The IFD 540 and GPSS takes so much of the workload out of flying a missed approach.

It seems too good to be true. So my question is what CFIs and pilots with more GPSS experience than I have (i.e., anybody with GPSS experience) have found to be the gotchas that can be lurking in my avionics heaven, just waiting for the right moment to ruin my day?

--Being assigned an unpublished missed?

--Failing to confirm that you've actually re-engaged the autopilot and GPSS after you've got the plane climbing and cleaned up?

--Overreliance on the GPSS and not being ready in the case of an untimely failure?

--Something I haven't thought of yet?

[Joe Larussa]

Following

[Joe Larussa]

I find that in the heat of the moment you can miss switching modes. For instance, you are using GPS and GPSS and you’re cleared to a fix, then at the last minute they start to give you vectors. So you change to heading mode for a few minutes then clear you again to the fix again but forget to switch back to GPSS.

[Flash]

3 hours ago, Joe Larussa said:

I find that in the heat of the moment you can miss switching modes. For instance, you are using GPS and GPSS and you’re cleared to a fix, then at the last minute they start to give you vectors. So you change to heading mode for a few minutes then clear you again to the fix again but forget to switch back to GPSS.

I can see how this would happen, especially if the vector you are on aligns or almost aligns with the course you would be flying if you were following the course you entered into your GPS direct to the fix. 

[GeeBee]

Know where the modes are annunciated. Because you pushed the button does not mean you got what you pushed. I always double point with my finger at the FMA.

 

[The Other Red Baron]

23 hours ago, Joe Larussa said:

I find that in the heat of the moment you can miss switching modes. For instance, you are using GPS and GPSS and you’re cleared to a fix, then at the last minute they start to give you vectors. So you change to heading mode for a few minutes then clear you again to the fix again but forget to switch back to GPSS.

 

This was what I was going to mention.  After multiple flights of easy direct to xxxxx approaches I finally had one where I was about to begin the approach, wife's first approach in actual IMC on top of it, then given 10 degrees left.  Had a split second helmet fire then bugged the current heading, turned off GPSS, and then turned the bug 10 left. 

If I hadn't bugged the heading but turned off GPSS it probably would have turned to 180 because until then I only bugged the heading for taking off.  I could have turned the bug 10 left and forgot about GPSS and wondered why the heck it wasn't doing what I wanted it to. Yes if I started asking "why is it doing that" I could have just turned off AP and hand flown but it was bumpy as hell and the STEC was doing a great job and I wanted to keep it that way.  Ended up being a non-event thankfully but it got me back to reading and thinking about order of operations.