clearedtoenter
Correct!!
The C146a (WAAS) GPS is the expensive part.
Plus, it needs a grey code altitude transponder. And the WAAS GPS needs a new antennae & cabling, so its not a simple upgrade - even from GNS 430 to GNS430W
Any IFR aircraft with a Garmin 155, 300, 430/ 530 (non waas), King 89 / 94 or heaven forbid an Apollo or Trimble unit will require a new C146a GPS. If you browse through Aviation trader it feels like that will be 80% of all existing IFR aircraft.
AND frequently, when Avioincs say drop in they mean physically, not electrically. There is a very large chance that the rear connector on the rack will need to be replaced.
Reading NPRM 1105 yesterday, its pretty clear that IFR enroute navigation after the start turning off navaids and de-rating the power of many of the remaining ones in early 2016, that only GPS will be acceptable for en-route navigation for any IFR flight.
A question that has been glossed over is whether this will also apply to aircraft on NVMC plans.