Numerous previously IFR-certified GPS receivers might now be unapproved for flying many instrument procedures due to recent FAA policy changes, according to AOPA. On Thursday, the association said the FAA's Advisory Circular 90-100A, issued in March, indicates that only three GPS models -- the Garmin 400, 500 and G1000 series -- are now legal. Other models made by Garmin, including the new GNS 480 WAAS receiver, as well as receivers manufactured by Chelton, Honeywell, Northstar, and Trimble are listed as "noncompliant," AOPA said. (Click here for a more comprehensive compliance list.) AOPA said the the FAA has committed to work to resolve the pilot group's concerns over these policy changes. The action, as it now stands, means up to 26,000 GPS users no longer comply with a 1996 FAA policy that allows GPS to be used in lieu of ADF or DME. "This doesn't make any sense. In most cases, this is not a safety of flight issue," said Randy Kenagy, AOPA senior director of strategic planning. "Pilots affected will lose access to approaches and published routes unnecessarily." AOPA has brought the matter to the FAA's attention, telling the FAA that all IFR-certified systems should still be approved for use in lieu of ADF and DME and for flying T routes and certain departure procedures where pilots manually enter the waypoints. Association staff met with the FAA and spoke with key officials late last week, and AOPA says it will continue to press for a quick resolution.