The AIM 1-1-17 2 (a) states:

Aircraft using un-augmented GPS (TSO-C129() or TSO-C196()) for navigation under IFR must be equipped with an alternate approved and operational means of navigation suitable for navigating the proposed route of flight. (Examples of alternate navigation equipment include VOR or DME/DME/IRU capability). Active monitoring of alternative navigation equipment is not required when RAIM is available for integrity monitoring. Active monitoring of an alternate means of navigation is required when the GPS RAIM capability is lost.

Does this mean that if I have a non-WAAS GPS unit then I have to file only along Victor airways or between VORs? Or can I file DIRECT?

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    $\begingroup$ Giving up a little on my age here. A long time ago, I was on a return flight home at FL250 in a Seneca II. On an IFR flight plan using VORs. ATC asked me if my LORAN was working. My reply was yes, but not certified for IFR. ATC then asked if I could tell him what my initial heading would be for my destination, I replied with the information. ATC then cleared me direct to home. $\endgroup$ – Mike Brass Nov 30 '19 at 6:42

This question was answered here on this Website. Read the second answer.

Yes you can file direct even without a GPS. However it would be advisable to perform a RAIM check during your pre-flight along your intended route and determine that you would be in RAIM during the route. If for some reason your GPS loses RAIM capability then you should proceed using VOR/DME/ADF. You can still fly direct with using only VORs although that will be more difficult.


In my opinion, navigating an IFR flight plan is more than just the ability to get from one airport to the other. I am also concerned about communication radio failure. If you follow the advice listed in the AskACFI website, you will not have many options if your communication radio fails

It is this reason, why service volumes (see AIM 1-1-8) for VOR and NDBs are published. Assuming there are no restrictions listed in the chart supplements booklet, you can fly from VOR/NDB to VOR/NDB as long as you stay within the service volume. If you lose communication radios, at the very least you will be able to revert to the requirements listed in FAR §91.185.

I once filed TUS to IWA, a total distance of 81.4 NM. I would have been out of the service volume for 1.4NM and ATC would not give me that clearance. Go figure.


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