Any Unknown or Unlisted Aircraft Manufacturer
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface
Aircraft Equipment Problem Less Severe; Airspace Violation All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural FAR
Flight Crew Returned To Departure Airport; Flight Crew Took Evasive Action
Aircraft; Human Factors
GPS provided faulty direction to an entered waypoint which I did not immediately recognize.  While manipulating the controls of the unit to attempt to get the appropriate result to the desired waypoint I continued to travel on an inappropriate course for my destination.  When I switched back to the map page I was very close to the Class D airspace of CHD and IWA and may have breached the border of the D airspace(s) while I was reversing course.  It could have been eliminated if I had reversed course immediately when I became aware of the problem with the GPS and returned to my departure airport and attempted to solve the problem on the ground.
General aviation pilot reports problems with his GPS which is not immediately recognized; resulting in possible Class D airspace entry without a clearance.