PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Flight Crew Flight Instructor; Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 30; Flight Crew Total 2800; Flight Crew Type 40
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew Exited Penetrated Airspace
Aircraft; Airspace Structure
Arrived for the day's flight and found the master switch had been left (could still hear turn coordinator.) We; thus; used a battery cart to start the aircraft and all indications were normal during a 10 minute ground run.Later; in VFR cruise flight; I first noticed I couldn't hear the PNF and suspected the headset but shortly heard ATC communications. I then started to troubleshoot when the avionics displays started flashing. I immediately advised ATC of a possible electrical failure; and stated my plan to continue east; out of the SFRA; and land at a nearby airport. I then secured all electrical loads except the transponder and one radio (now blank; but still receiving) and made calls; apparently in the blind; to ATC. Approximately five miles from landing I attempted to contact ATC via cell phone but was unsuccessful.I then concentrated on making a NORDO visual approach to my diversion airport; landed without incident and immediately cell-phoned ATC to give a 'safe on deck' report. I was met later by a sheriff's deputy sent by ATC to confirm my safe on deck report. I then called the Command Center to ensure there were no issues due to loss of communications in the SFRA.Maintenance inspection found fault with the alternator's field wire as the battery was fully charged. The aircraft was returned to service with no further issues.
PA-28R pilot began to lose communications while within the Washington SFRA; he advised ATC in the blind and exited the SFRA to land at a nearby diversion airport.