Pilot of a PA32-300 questioned by ATC regarding GPS equipment. GPS was on board, but not IFR certified. It was used only to verify VOR information.

Narrative

Rewritten in plain English from NASA’s original all-caps telegraphic report — facts, figures, and terminology preserved.

Filed Natchez; radar vectors Greenville (HEZ-GLH) at 5000 feet. Cleared direct Greenville. After takeoff, ZHU asked whether we had GPS on board. We do, with external antenna, but not IFR certified. ZHU was told this and that we were proceeding off HEZ VOR (6 degree radial) until receiving GLH, which is exactly what we did, although using GPS to monitor. I believe this is a legal procedure, but am not positive. Hence, the filing of this report. The whole area of using non IFR approved GPS to facilitate navigation needs clarification. For example, radar vectors direct to a destination 600 miles away with the pilot monitoring GPS and suggesting vector changes seems to me to be a very good (and legal) way of enhancing navigation and lessening pilot and controller load. Am I wrong?

(Note: Apparently Houston radar does not cover takeoff at Natchez, although I wasn't aware of this until after takeoff. GPS was not listed as available equipment on my flight plan.)

Callback conversation with reporter revealed the following info: reporter states that he has no idea why ATC asked about the GPS. It was not listed on the flight plan and he never mentioned it to them. He used the GPS only to back up the VOR indications he was receiving, not for basic navigation. He is very aware that the GPS cannot be used for IFR flight when not certified and was not doing so. He had been given a void clearance time for takeoff and complied with that. He was flying a PA32-300 Cherokee 6.