Pilot reported an near midair collision with an aircraft in an sfra due to being at the wrong transi...

Attributes
ACN	1745929
Time
Date	202006
Local Time Of Day	1201-1800
Place
Locale Reference	PCT.TRACON
State Reference	VA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Small Aircraft
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	VFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Commercial Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 6 Flight Crew Total 1926 Flight Crew Type 501
Events
Anomaly	Conflict NMAC Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy
Miss Distance	Horizontal 30 Vertical 100

Narrative:

I was returning on an sfra flight plan; northwest bound through the VFR flyway between balance 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.

Original NASA ASRS Text

Title: Pilot reported an NMAC with an aircraft in an SFRA due to being at the wrong transitioning altitude.

Narrative: 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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Pilot reported an near midair collision with an aircraft in an sfra due to being at the wrong transitioning altitude.