GPS Restrictions on Alternate Airports

Guy Morton

Filing Flight Plan
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Jul 30, 2020
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Deciphering the AIM's convolutions... Can someone verify that I have this right, or help me correct it. The write their stuff as sort of a long-form analog to a series of double negatives. I work with a lot of attorneys that do the same thing, so I should be more tolerant, but...

Here's my understanding:
  1. For the purposes of flight planning, any required alternate airport, must have an available instrument procedure (read: available to the specific aircraft and crew vis a vis training and equipment) that does NOT require the use of GP.
  2. However: This restriction does not apply to RNAV systems using TSO145/146 (i.e. WAAS). (So, we CAN file an alternate that does not have a non-GPS approach…right?)
  3. For non-WAAS users (TSO 129/196), whose systems have FDE capability and they run a RAIM prediction at the destination airport (or both), may file a GPS IAP at either the destination or alternate, but not at both, PROVIDED, that the alternate also has a non-GPS approach available…
Do I have it right?
 
Not quite. If you have a non-WAAS GPS but it meets other requirements (including doing all that RAIM stuff), you can use a GPS approach at the destination or the alternate, but not both. So if you're going somewhere with a VOR approach, you can use an airport with a GPS approach as an alternate. Don't forget about the weather minima in addition to the other requirements you list. You are required if you are using a non-WAAS GPS to have some other means of navigation.

If you have an (approved) WAAS GPS, then yes, you don't need anything else.


See AIM 1-1-17 5(e).
 
If you factor out the double negative the meaning changes, unless you also add an “only”
Not sure exactly what you mean, but “no non-GPS approaches doesn’t necessarily mean that there are GPS approaches, either.
 
Deciphering the AIM's convolutions... Can someone verify that I have this right, or help me correct it. The write their stuff as sort of a long-form analog to a series of double negatives. I work with a lot of attorneys that do the same thing, so I should be more tolerant, but...
Yeah, attorneys, phooey! :) I cover this here: Introduction to GPS (avclicks.com) in slides 57 to the end (see #73 for your exact question). Straightening out their stuff is a real pain sometimes.
 
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