Cessna Aircraft Undifferentiated or Other Model
Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Total 15600; Flight Crew Type 150
Situational Awareness; Training / Qualification; Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Other / Unknown
General None Reported / Taken
Aircraft; Human Factors
During a local VFR flight on a clear weather day I was flying and my aircraft lost GPS signal to the Avidyne IFD 500 instrument and might have affected the Mode S transponder that is also linked together with WAAS GPS position.  I did notice a message that the GPS position had lost signal on my IFD 500 panel mounted instrument; but I didn't realize during my flight that the Mode S transponder may have been without GPS signal also which provides position and altitude to the local ATC radar.  My flight had me flying 'Below Class B' airspace in the DFW area to my local airport. My two month old avionics upgrade to include IFR WAAS GPS and a remote mounted Mode S transponder is still something I'm getting used to seeing the visual displays and all associated messages. After talking with my avionics shop and resetting the GPS and Avidyne IFD 500 unit at our airport I realized the Mode S transponder may not have been sending the proper info to the DFW 'Regional Approach' radar folks. In the future I feel the transponder itself should send a message to the pilot if it has lost GPS signal or better yet fail to the 'send position and altitude' Mode S function straight from the GPS WAAS antenna if the IFD 550 display messes up.
Cessna pilot reported a malfunctioning GPS receiver.