Helicopter
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Flight Instructor
Flight Crew Last 90 Days 30; Flight Crew Total 10000; Flight Crew Type 4500
Situational Awareness
Airspace Violation All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert
Procedure; Chart Or Publication; Aircraft
Enroute from EVY the route of flight was to circumnavigate the outside NW corner of the DC SFRA between the SFRA boundary and the FDK Class D then head south west. Both GPS's showed us approximately 2 miles outside the SFRA boundary. I was up on FDK tower frequency and just prior to contacting them to notify of our transition south of their airspace; the tower called and asked if the aircraft approximately 8 miles to their south east were up frequency. I responded and after letting them know who we were and where we were 'Aircraft X is Southeast; north of the DC ADIZ and south of the Class D'; the tower asked what our destination was and I informed him. The tower then instructed us to contact Potomac Approach upon landing. After contacting Potomac Approach; I was informed that we had penetrated the boundary of the SFRA by 1-2 miles. We were flying at a low altitude to stay out of forecasted turbulence at higher altitudes and the poor radio reception with approach that we normally encounter in that area otherwise we would have been flight following at that time. I have been through that area several times but this is the first time I have had an issue. We were slightly closer to the boundary but as stated above; both aircraft were showing the same thing; just outside the boundary. I understand that regardless of what the equipment is reporting; it is the pilot's responsibility to follow the rules. It is my intent to keep a minimum of 5 miles distance in the future. Possibly a larger thicker boundary marking on the VFR sectional and TAC's that is actually a couple miles further than the actual boundary would help future penetrations.
[Report narrative contained no additional information.]
Flight of two helicopters with two GPS sources flew a course 2 miles outside the Washington DC SFRA; yet PCT TRACON claimed the aircraft was inside the SFRA by two miles.