Narrative:

While transiting iad arsa southwest to northeast and nearing the edge of arsa, I was descending at pilot discretion from 5500' MSL in accordance with approach control instructions. I had tuned the active frequency (for iad northeast sector 126.10) on #2 communication at frequency switch/sector switch (s-ne). In anticipation of requesting termination of flight following, I tuned gai unicom 122.7 in #2 communication inadvertently and broke contact with the controller. When I attempted to contact approach control to terminate service approximately 1 min later, I realized that I had broken contact and then switched to 120.6 thinking that was my last assigned frequency, only to be advised that I was talking to baltimore approach. I then re-tuned 126.10 and advised the controller of my desire to terminate. The controller authority/authorized the frequency change and indicated that he had attempted to contact me several times. I acknowledged my mistake to him and then proceeded to gai. During the time I was out of communication with the controller, I believe I was outside the limit of the TCA. At the time of the incident I saw only 1 aircraft that was ascending from my altitude approximately 10 mi away from dca. At no time was I aware of any conflict with another aircraft. In retrospect, I will endeavor to write down frequency changes at the time they occur and prepare more adequately by knowing the frequencys that will be assigned.

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Original NASA ASRS Text

Title: PLT IN SMA INADVERTENTLY PLACED COM SWITCH TO UNICOM FREQ AND THEN FOR A SHORT TIME COULD NOT RECALL THE ACTIVE FREQ FOR IAD TRACON.

Narrative: WHILE TRANSITING IAD ARSA SW TO NE AND NEARING THE EDGE OF ARSA, I WAS DSNDING AT PLT DISCRETION FROM 5500' MSL IN ACCORDANCE WITH APCH CTL INSTRUCTIONS. I HAD TUNED THE ACTIVE FREQ (FOR IAD NE SECTOR 126.10) ON #2 COM AT FREQ SWITCH/SECTOR SWITCH (S-NE). IN ANTICIPATION OF REQUESTING TERMINATION OF FLT FOLLOWING, I TUNED GAI UNICOM 122.7 IN #2 COM INADVERTENTLY AND BROKE CONTACT WITH THE CTLR. WHEN I ATTEMPTED TO CONTACT APCH CTL TO TERMINATE SVC APPROX 1 MIN LATER, I REALIZED THAT I HAD BROKEN CONTACT AND THEN SWITCHED TO 120.6 THINKING THAT WAS MY LAST ASSIGNED FREQ, ONLY TO BE ADVISED THAT I WAS TALKING TO BALTIMORE APCH. I THEN RE-TUNED 126.10 AND ADVISED THE CTLR OF MY DESIRE TO TERMINATE. THE CTLR AUTH THE FREQ CHANGE AND INDICATED THAT HE HAD ATTEMPTED TO CONTACT ME SEVERAL TIMES. I ACKNOWLEDGED MY MISTAKE TO HIM AND THEN PROCEEDED TO GAI. DURING THE TIME I WAS OUT OF COM WITH THE CTLR, I BELIEVE I WAS OUTSIDE THE LIMIT OF THE TCA. AT THE TIME OF THE INCIDENT I SAW ONLY 1 ACFT THAT WAS ASCENDING FROM MY ALT APPROX 10 MI AWAY FROM DCA. AT NO TIME WAS I AWARE OF ANY CONFLICT WITH ANOTHER ACFT. IN RETROSPECT, I WILL ENDEAVOR TO WRITE DOWN FREQ CHANGES AT THE TIME THEY OCCUR AND PREPARE MORE ADEQUATELY BY KNOWING THE FREQS THAT WILL BE ASSIGNED.

Data retrieved from NASA's ASRS site as of August 2007 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.