SMA ENTERS TCA WITHOUT CLRNC.

Narrative

THIS WAS TO BE A BRIEF FLT FROM GAI TO LEESBURG ARPT (JYO). I WAS IN L SEAT AND ALTHOUGH NEVER DISCUSSED; I BELIEVE WE BOTH ASSUMED I WAS PIC. MY AIRPLANE PARTNER WAS IN R SEAT; HE IS A NEW PRIVATE PLT; APPROX 100 HRS. WE HAD A GPS INSTALLED RECENTLY AND WERE BOTH ANXIOUS TO USE IT. I WAS DOING THE FLYING AND COMMUNICATING WITH DULLES APCH (120.45) REQUESTING CLRNC INTO THEIR TCA ENRTE TO LEESBURG WHILE LEVELING OFF AT 2400 FT; LOOKING FOR TFC; ADJUSTING MP AND RPM ETC; ALL THE WHILE FOLLOWING THE HDG INFO BEING GIVEN TO ME BY OUR GPS. MY PARTNER TOOK IT UPON HIMSELF TO ENTER LEESBURG INTO THE GPS. HE HAD FLOWN THIS SAME RTE THE PREVIOUS WK BY HIMSELF AND SO I MISTAKENLY DID NOT CHK HIS INPUTS. (AS THE [ASSUMED] PIC; I SHOULD HAVE.) MY PARTNER WAS USING THE 45TH EDITION OF THE BALTIMORE-WASHINGTON TCA. IMMEDIATELY UNDER THE ARPT DATA 'LEESBURG' ARPT ON THIS CHART IS THE HVY LINE BOX INDICATING THE FSS 'LEESBURG DCA.' HE MISTAKENLY ENTERED 'DCA' INTO THE GPS INSTEAD OF THE REQUIRED JYO. THE GPS IS NOW GUIDING US DIRECTLY TO WASHINGTON NATIONAL WHILE WE THINK WE ARE GOING DIRECTLY TO LEESBURG. ON THIS WRONG HDG FROM OUR ARPT OF DEP; IT TAKES ONLY ABOUT 5 MINS BEFORE WE ARE VIOLATING THE TCA WHICH IS EXACTLY WHAT HAPPENED. I REALIZED OUR WRONG POS AT THE SAME TIME THAT DULLES APCH DID; AND BEGAN A TURN TO THE NW; AWAY FROM THE TCA; WHEN THE DULLES CTLR MADE THE SAME SUGGESTION TO US. HE THEN TOLD US TO TELEPHONE WASHINGTON APCH WHEN ON THE GND; WHICH WE DID. WASHINGTON APCH WAS VERY NICE ON THE TELEPHONE BUT WANTED US TO KNOW THE SERIOUSNESS OF OUR MISTAKE. WE ASSURED HIM THAT WE DID AND WOULD NEVER ALLOW A MISTAKE OF THIS NATURE TO HAPPEN AGAIN. I LEARNED AN IMPORTANT LESSON. I AM A VERY CONSCIENTIOUS PLT; I READ ACCIDENT RPTS AND HISTORIES OF CONTRIBUTING FACTORS TO ACCIDENTS; AND HOW THEY RELATE TO POOR JUDGEMENTS OR INCORRECT PERCEPTIONS. I ALWAYS THOUGHT IT WOULD NEVER HAPPEN TO ME; I AM CAREFUL. LESSON: IT CAN HAPPEN TO YOU! IT WILL HAPPEN TO YOU AS SOON AS YOU START ASSUMING. DO NOT ASSUME -- THE RESULT COULD BE DISASTROUS.