Albatros (L39)
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 193; Flight Crew Total 4700; Flight Crew Type 40
Situational Awareness
No Specific Anomaly Occurred All Types
General None Reported / Taken
Human Factors
While at VFR cruise altitude at 13;500 on a VFR training flight to ESN we entered the area of within 60 NM of the DCA VOR. Specific training required by the DC SFRA rules requires a mandatory speed of no greater than 230 indicated airspeed which we did abide by while enroute within the defined area requiring the speed restriction. Once we landed at ESN we were informed to call the Potomac TRACON. On that phone call; we were advised that we were doing 310kts ground speed which was going too fast according the DC SFRA procedures. However; ground speed is not the same as indicated airspeed when citing a violation. I actually agree with his statement that we were going that fast in Ground Speed. As 230kt indicated at 13;500 results in approximately 290kts true airspeed and with 15-25kts of tailwind as reported on my weather preflight I obtained via FLTplan.com to satisfy weather and NOTAM requirements of FARs. This would equate to an approximate value of 310Kts Ground Speed while still adhering to DC SFRA procedures of 230kt indicated while under VFR. Under this scenario there should be no need to document my actions as no procedures or FARs were broken regarding a speed violation.In order to mitigate further confusion in the future; the rules can be rewritten in ground speed instead of indicated airspeed so both pilot in the air and radar controller supervising VFR flights within the area are on the same page when it comes to speed control. Another possibility could be a refresher to both pilots and controllers alike about the change in true airspeed vs indicated airspeed with the change in altitude; especially high VFR altitudes where 230kts indicated can look like close to 300kts under certain circumstances. Another option could be any VFR aircraft wishing to operate between 200-230kt indicated must be on Flight following inside the DCA 60NM ring in order to afford Potomac TRACON the ability to manage high speed aircraft not under IFR control so near the DC SFRA but not actually inside the DC SFRA boundary.
L39 pilot reported ATC questioned his speed in the DC SFRA and appeared confused about the difference between IAS and ground speed.