For some reason I remember hearing or reading a long time ago that IFDs would behave identically and provide the same callouts whether the TAWS feature was purchased or not. I also asked an Avidyne employee about this recently at the Cirrus Migration expo and he said he was pretty sure I'd get the TAWS callouts even without the TAWS license.

I'm confused though, since the pilot guide seems to imply that I shouldn't get PDA, EDR, or NCR callouts from my non-TAWS IFD540. The root of all of this, is that my Cirrus was originally equipped with the Honeywell EGPWS system, which does provide these callouts. For the last year or so I've kept that system disabled, and enabled FLTA on my IFD so all of my callouts come from one piece of equipment.

Am I missing some capabilities by doing this?

I believe the TAWS option needs to be purchased / activated to get the PDA, EDR, and NCR callouts. All of the other FLTA and altitude callouts come standard with the F500 option.

Confirmed.   With F500, it's just FLTA and altitude callouts.  For the others, TAWS option must be purchased.

I'm a little confused with the TAWS (FLTA?) capabilities of the IFD400/500 series units and it may just be my confusion of the different terms.

I have in my aircraft an IFD440 and an NGT-9000 (I believe Avidyne is the distributor now of the NGT-9000 so Avidyne should be able to answer this).  My NGT-9000 has the eTAWS enabled and I believe meets TSO C151c, because of this I have disabled FLTA on my IFD and have the audio from the NGT-9000 enabled, based upon what I understand, this is the correct way to go.

Other than the TSO on the NGT, what is the difference in terms of alerting? I do fly another aircraft that doesn't have the NGT-9000 but has an IFD440 is the alerting going to be the same but it hasn't gone through the TSO process?

I thought Avidyne did get a TSO on the 500 series units for TAWS but limited to helicopters, plus this feature required an enablement, is this not correct?  If correct, what is special about helicopters that the enablement can't be used for fixed wing?

The NGT-9000 claims to have "eTAWS" which they list as "enhanced" TAWS, not sure what enhanced is, which leads to the next questions, what is the difference between eTAWS, TAWS, FLTA, and eGPWS.  If I'm reading correctly TAWS now encompasses eGPWS, but FLTA? Is FLTA only part of the TAWS specification?

To add some understanding of levels of TAWS it looks like there are 3 levels, class A, B, and C, class A encompasses B plus some, and class C is class B but has some changes for use in smaller GA airplanes.

-PA