Date: 201510
Local time of day: 1201-1800
Location: FME.Airport, MD
Flight conditions: VMC
Light: Daylight
Aircraft: Small Aircraft; Low Wing; 2 Eng; Retractable Gear
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Training
Flight phase: Final Approach
Airspace: Class E FME; Special Use DC SFRA
ATC / advisory: TRACON PCT
Aircraft component: Transponder
Component problem: Improperly Operated
Reporter organization: Personal
Reporter function: Pilot Flying
Reporter qualification: Flight Crew Private; Flight Crew Instrument
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: Pilot Not Flying; Instructor
Anomaly: ATC Issue All Types; Airspace Violation All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Airspace Structure; Human Factors; Procedure
Primary problem: Human Factors

Narrative: I hired a CFII instructor for a series of short IFR training trips along the east coast for a period of about 2 weeks when this incident occurred. We departed with the destination of Tipton; MD (FME). The flight plan was IFR and we proceeded uneventfully on vectors towards the destination. At approximately 3-5 miles from the field we were asked by ATC if we had the field in site as VFR conditions prevailed. We replied affirmatively at which time ATC asked if we would like to cancel IFR. We responded 'affirmative' and ATC replied 'IFR cancelled; squawk 1200; frequency change approved.' We complied fully with those ATC instructions; by switching frequencies and squawking 1200.Upon landing; we were requested by FBO personnel to call a number. I returned the call and was asked why I had squawked 1200 on final. I replied that we were complying with directives from ATC during the short final approach.Since then; I have come to find out that VFR flights in and around Washington; DC have special VFR flight rules of which I was unaware of at the time as I had no intention of flying VFR in this airspace with my IFR instructor. Additionally; the required training for VFR pilots in this airspace does not apply to IFR pilots and IFR flights. Therefore; when we squawked 1200 as requested by ATC on a customary short final approach in VFR conditions into a non-towered airport; we had no knowledge that we were squawking 1200 in error. I also would add that obviously ATC knew who we were and that we had changed our transponder code to 1200 VFR as we were immediately approached by the FBO with 2 telephone #s to call and make my report. I also would like to add that apparently & obviously we were the only ones squawking 1200 VFR as no one else would be doing so since we have come to find out this is not allowed in that airspace. So; the only thing we might be guilty of is changing our transponder code to something other than what we had previously been assigned. I reported all of this to the 2 stations I talked with.


Second narrative: I was hired by a private pilot for a series of short IFR training trips along the east coast for a period of about 2 weeks when this incident occurred. We departed with the destination of Tipton; MD (FME). The flight plan was IFR and we proceeded uneventfully on vectors towards the destination. At approximately 3-5 miles from the field we were asked by ATC if we had the field in site as VFR conditions prevailed. We replied affirmatively at which time ATC asked if we would like to cancel IFR. We responded 'affirmative' and ATC replied 'IFR cancelled; squawk 1200; frequency change approved'. We complied fully with those ATC instructions; by switching frequencies and squawking 1200.Upon landing; he was requested by FBO personnel to call a number. [The other pilot] returned the call and was asked why he had squawked 1200 on final. He replied that he was complying with directives from ATC during his short final approach.Since then; I have come to find out that VFR flights in and around Washington; DC have special VFR flight rules of which I was unaware of at the time as I had no intention of flying VFR in this airspace with my IFR student. Additionally; the required training for VFR pilots in this airspace does not apply to IFR pilots and IFR flights. Therefore; when we squawked 1200 as requested by ATC on a customary short final approach in VFR conditions into a non-towered airport; we had no knowledge that we were squawking 1200 in error.


Synopsis: A general aviation pilot and flight instructor reported changing the aircraft transponder code as requested by ATC only to find that the rules in the Washington D.C. SFRA precluded this action.