Narrative:

On 11/sat/01, I was acting as a safety pilot on a cessna 172 (XXXX). We filed an IFR flight from ZZZ to ZZZ1 using my name. The flight was intended to allow the owner to prepare for his instrument check ride which was planned for a week later. We were performing multiple practice instrument approachs at ZZZ1 airport. The WX was clear and the pattern quickly became full of incoming and departing traffic. We were told by ZZZ2 approach control they could no longer provide radar service due to the volume of traffic. We asked to terminate our IFR flight plan and ZZZ2 told us to squawk VFR and radar service terminated. We exited ZZZ1 after our last approach and pushed the bendix king KT-76C transponder's VFR button to squawk 1200, apparently the button did not transfer the squawk code from XXXX to the 1200 VFR code. We proceeded approximately 150 miles southeast of ZZZ2, 10 miles south of ZZZ and climbed to 4500 ft MSL to do some airwork. We performed a series of practice maneuvers. It was on the DME arc we noticed a military F18 climbing off our right wing. He was approximately 1 to 2 miles off our wing. We checked our position in relationship to the MOA to ensure we were clear of their airspace. We were many miles to the west of their airspace. We turned toward ZZZ and were in the process of descending to their pattern altitude when the F18 intercepted us. He was level at our altitude less than a half mile off our left wing. We motioned to him with a thumb down we were landing at ZZZ airport. The F18 accelerated and performed a climbing left hand turn. We were monitoring 121.5 after and heard nothing over the radio. ZZZ tower informed us to call ZZZ3 center when we got on the ground. We will be more vigilant about our transponder codes in the future. Supplemental information from acn 529942: the bendix king KT-76C transponder has a button which allows me to cancel the assigned code and to transmit 1200. In the future I will be more careful to confirm that I am in fact using the proper code.

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Original NASA ASRS Text

Title: A C172 PLT AND SAFETY PLT NEGLECTED TO SQUAWK THE PROPER TRANSPONDER CODE, SPAWNING A FIGHTER INTERCEPT.

Narrative: ON 11/SAT/01, I WAS ACTING AS A SAFETY PLT ON A CESSNA 172 (XXXX). WE FILED AN IFR FLT FROM ZZZ TO ZZZ1 USING MY NAME. THE FLT WAS INTENDED TO ALLOW THE OWNER TO PREPARE FOR HIS INSTRUMENT CHECK RIDE WHICH WAS PLANNED FOR A WEEK LATER. WE WERE PERFORMING MULTIPLE PRACTICE INSTRUMENT APCHS AT ZZZ1 ARPT. THE WX WAS CLR AND THE PATTERN QUICKLY BECAME FULL OF INCOMING AND DEPARTING TFC. WE WERE TOLD BY ZZZ2 APCH CTL THEY COULD NO LONGER PROVIDE RADAR SVC DUE TO THE VOLUME OF TFC. WE ASKED TO TERMINATE OUR IFR FLT PLAN AND ZZZ2 TOLD US TO SQUAWK VFR AND RADAR SVC TERMINATED. WE EXITED ZZZ1 AFTER OUR LAST APCH AND PUSHED THE BENDIX KING KT-76C TRANSPONDER'S VFR BUTTON TO SQUAWK 1200, APPARENTLY THE BUTTON DID NOT TRANSFER THE SQUAWK CODE FROM XXXX TO THE 1200 VFR CODE. WE PROCEEDED APPROX 150 MILES SE OF ZZZ2, 10 MILES S OF ZZZ AND CLIMBED TO 4500 FT MSL TO DO SOME AIRWORK. WE PERFORMED A SERIES OF PRACTICE MANEUVERS. IT WAS ON THE DME ARC WE NOTICED A MIL F18 CLIMBING OFF OUR R WING. HE WAS APPROX 1 TO 2 MILES OFF OUR WING. WE CHECKED OUR POSITION IN RELATIONSHIP TO THE MOA TO ENSURE WE WERE CLR OF THEIR AIRSPACE. WE WERE MANY MILES TO THE W OF THEIR AIRSPACE. WE TURNED TOWARD ZZZ AND WERE IN THE PROCESS OF DESCENDING TO THEIR PATTERN ALTITUDE WHEN THE F18 INTERCEPTED US. HE WAS LEVEL AT OUR ALTITUDE LESS THAN A HALF MILE OFF OUR L WING. WE MOTIONED TO HIM WITH A THUMB DOWN WE WERE LNDG AT ZZZ ARPT. THE F18 ACCELERATED AND PERFORMED A CLIMBING L HAND TURN. WE WERE MONITORING 121.5 AFTER AND HEARD NOTHING OVER THE RADIO. ZZZ TWR INFORMED US TO CALL ZZZ3 CTR WHEN WE GOT ON THE GND. WE WILL BE MORE VIGILANT ABOUT OUR TRANSPONDER CODES IN THE FUTURE. SUPPLEMENTAL INFO FROM ACN 529942: THE BENDIX KING KT-76C TRANSPONDER HAS A BUTTON WHICH ALLOWS ME TO CANCEL THE ASSIGNED CODE AND TO TRANSMIT 1200. IN THE FUTURE I WILL BE MORE CAREFUL TO CONFIRM THAT I AM IN FACT USING THE PROPER CODE.

Data retrieved from NASA's ASRS site as of July 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.