CFII GPS QUEST.pdf (171.6 KB)
I HAVE SOME QUESTIONS RELATIVE TO THE REQUIREMENTS STATED IN AIM 1-1-17 WHICH DEAL WITH GPS USE & EQUIPMENT REQUIREMENTS FOR INSTRUNEBT FLIGHT THAT HAS MY CFII STUMPED.
THESE QUESTIONS ARE MOSTLY APPLICABLE TO GA FLIGHTS AND ARE SOMEWHAT COMPLEX, SO SEE THE ATTACHED PDF FOR SOME SKETCHES AND EXPLANATION. THANKS, RP CZACHOR
Robert,
This is like opening a can of worms. Hopefully this thread stays on track.
I agree, B-D-A would be an illegal route to file IFR since point D resides outside the known VOR ranges.
I agree, B-C-A would be a legal route to file IFR.
I could be wrong on this one, but I don’t think B-E-A would be a legal route to file IFR. Even with DME, that wouldn’t be enough to navigate to point E using VOR navigation only.
I also want to clarify that all of these routes can be flown legally using GPS so long as the GPS is up to date and all waypoints have been verified against a current chart. These questions are specific to the legality of PLANNING.
Onto the next section:
Quoting you, “ MY INTERPRETATION, ASSUMING AIRPLANE HAS A NON-WAAS (TSO- C129 or TSO-C196) GPS…
AND, IF THE GPS DOES NOT HAVE FDE (MEANING 6 SATELLITES AVAILABLE) ANY GPS APPROACH IS NOT AUTHORIZED
QUESTION: IS THIS CORRECT?”
Your interpretation is incorrect. Without FDE, you would still have RAIM. That said, remember that the question is asking about PLANNING. Once enroute, you can fly whatever approach you want so long as you are current and the aircraft is equipped.
Scenario 1 is legal per “…may file based on a GPS-based IAP at either the destination or the alternate airport, but not at both locations.”
Scenario 2 is legal for the same reason in Scenario 1.
Scenario 3 is not legal because an alternate must have an instrument approach. In scenario 3, the alternate must have something other than a GPS approach since a GPS approach was planned at the destination…or…if the destination has an ILS or LOC or VOR approach and planning was based on any of those, then a GPS app at the alternate would be legal to PLAN for.
Clear as mud?
Disclaimer: I am not an Instructor anymore and I have not taught since I left ATP in 2017. I could be wrong. Check your own sources.
Tory
I’m spoiled. I go where ATC tells me 
Adam
And we have dispatchers to do our planning
Thank goodness for that 
Tory-
Firstly. I would like to thank you for your reply. My CFII never responded to these questions, the King School Chat line told me to contact my local FSDO, and the FSDO never replied…
Having said that, I still have some questions.
Relative to:
I could be wrong on this one, but I don’t think B-E-A would be a legal route to file IFR. Even with DME, that wouldn’t be enough to navigate to point E using VOR navigation only.
Its a fine point, but I think with VOR and DME at point C, you could find point E, but not easily. I could navigate to point C inboard of point E using DME and pick up a radial back to E…not easy but it would at least satisfy the requirement for planning an alternate means of navigation.
Relative to:
Your interpretation is incorrect. Without FDE, you would still have RAIM…
I have to disagree. The AIM specifically states “… whose navigation systems have fault detection and exclusion (FDE) capability…” . I read this simply that, if you dont have WAAS, (And you will have RAIM with C129 or C196 GPS) FDE is required to plan a GPS approach. I believe GPS approaches with a GPS that has neither WAAS nor FDE (Like the ancient KLP94 I use) are not permitted.
Relative to:
Scenario 3 is not legal because an alternate must have an instrument approach.
Just a comment here… Why a visual approach would be unacceptable is not clear to me but you are correct that the AIM requires an instrument approach at the alternate.
Thanks again.
Robert Czachor
Robert,
I still see point E as problematic. A waypoint shouldn’t be difficult to navigate to. The problem that I see with it is that E resides outside VOR A and B service volumes. While I understand that a radial and DME from VOR C could be used to locate E, but that’s only 1 reliable nav source which is not enough in my opinion. The other two VORs’ service volumes are too small for their radials to be used reliably to help triangulate point E.
I still stand by my statement about RAIM. As long as your GPS receiver has RAIM, you can legally plan for and fly a GPS approach.
FDE is just another form of integrity monitoring. It’s like an added layer of monitoring in addition to RAIM. FDE is not required. Period. Your receiver either has FDE capability or it doesn’t. If your receiver has RAIM. Good to go. A GPS receiver with RAIM, but not FDE is still either TSO-C129 or TSO-C196.
I do agree that the statement in the AIM is confusing.
Tory
I find this “statement” problematic.
Adam
Tory-
I agree that the VOR/ DME navigation to point E as I described would be a crazy way to navigate, but I still think it would serve to satisfy the requirement for planning an alternate, if in no way desirable, means of navigation to point E in lieu of GPS.
I still cannot reconcile your 2nd point with the statement in the AIM …
For flight planning purposes, TSO-C129() and TSO-C196()-equipped users … whose navigation systems have fault detection and exclusion (FDE) capability, who perform …may file based on a GPS-based IAP.
What am I missing here?
I also recognize this is all a moot point for GPS units produced in the last 20 years, but unfortunately that doesnt include the one I often use.
Thanks again for the help’ RP Czachor
I don’t recall E ever being considered an alternate. The original question asked if B-E-A was an acceptable route. The irony is that I think this scenario only exists on paper, but I understand the spirit of the question because it’s just testing your knowledge of the AIM. E is sort of in no man’s land. Sure you could grab a radial and a DME from C but that isn’t enough to successfully navigate from B to E to A just using VORs.
Does this satisfy your question?
According to the above, it makes no mention of FDE, which to me says that if you don’t have FDE, but you satisfied your RAIM prediction requirements, you can plan for a GPS approach at your destination, but not your alternate.
The paragraph you’re quoting, allows you to plan for a GPS at either the destination or alternate, but not both ie gives you more flexibility. And WAAS gives even more flexibility.
Tory
PS I am really doing my best here. It’s been some time since I had these discussions.
