Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 6; Flight Crew Total 1926; Flight Crew Type 501
Situational Awareness
Conflict NMAC; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Airspace Structure; Human Factors; Procedure
I was returning on an SFRA flight plan; northwest bound through the VFR flyway between BAL and DCA; at an altitude of approximately 1;900 feet. I had not flown this flyway for several years and I was unaware of the recommended altitudes for transitioning VFR traffic (1;500 feet west bound and 2;000 feet eastbound. An aircraft at my 12:00 position flying in the opposite direction about 100 feet above me came into view on my ADS-In display; and Potomac Approach notified me of the potential conflicting traffic. The pilot of the other plane; when notified by Potomac; told Potomac that my plane should be at 1;500 feet. That's when I realized that I was flying higher than I should have been. Potomac could have; but did not give me an indication that I was flying at/near an altitude intended for eastbound traffic; not westbound traffic. I should have been more diligent in checking the flyway chart where these altitudes are noted; as they are not shown on the Terminal Area Chart.
Pilot reported an NMAC with an aircraft in an SFRA due to being at the wrong transitioning altitude.