TRANSPONDER OP PROC CREATES AN AIR INTERCEPT MANEUVER BY A MIL ROTARY WINGED TFC ACFT.

Narrative

OUR FLT ON OCT/WED/91 WAS SYLLABUS STAGE IV LESSON #22 COVERING MAGNETIC COMPASS TURNS. MY STUDENT WAS UNDER THE HOOD FOR MOST OF THE FLT. OUR ASSIGNED PRACTICE AREA WAS OVER ANDERSON ISLAND SW OF TACOMA NARROWS ARPT. THE WINDS AT 1500 FT MSL WERE DRIFTING US SW TOWARD ANOTHER PRACTICE AREA OCCUPIED BY ONE OF OUR SCHOOL'S OTHER ACFT; SO MOST OF THE HDG TURNS MADE WERE TO THE L DURING THE LESSON. WHEN WE LANDED BACK AT OUR ARPT (CLOVER PARK VOCATIONAL TECHNICAL) I WAS INFORMED THAT A MIL HELI HAD FOLLOWED US BACK TO THE ARPT. IT WAS ONLY THEN THAT I REALIZED OUR TRANSPONDER WAS SET TO 7700 INSTEAD OF 1200. IT HAD BEEN FUNCTIONING IMPROPERLY THE ENTIRE FLT. SOMEONE HAD SET THE EMER SIGNAL INTO THE TRANSPONDER PRIOR TO OUR FLT AND NEITHER MY STUDENT NOR I HAD NOTICED THE ERROR. IT WAS OBVIOUSLY DONE AS A PRACTICAL JOKE. 5 YRS OF PROPER VFR SQUAWK CODE LED TO COMPLACENCY. IT WAS OVERLOOKED WHEN I CHKED TO SEE THAT THE TRANSPONDER WAS ON ALT AFTER TKOF. THE PROBLEM WAS FURTHER COMPOUNDED BY THE NECESSITY TO MAKE L TURNS TO REMAIN IN OUR PRACTICE AREA. AN ADDITIONAL DISTRESS SIGNAL OF WHICH I WAS UNAWARE. I REGRET THAT THE MIL WAS CALLED ON TO DO AN INTERCEPT AND ESCORT. I CAN CERTAINLY GUARANTEE THAT I WILL CHK MY TRANSPONDER CAREFULLY PRECEDING EVERY FUTURE FLT.