GA SMA GROUND LOOPED AND ALMOST HIT A GA SMA IN POSITION ON MULTIPLE INTERSECTING RWY.

Narrative

25 HR TAILDRAGGER PLT-LICENSED; GETTING INSTRUCTION IN TAIL DRAGGERS (HIS OWN) ON LNDG ROLL STUDENT STARTED A GRADUAL LEFT TURN AFTER A STRAIGHT LNDG. ACFT MADE SUDDEN RIGHT TURN. I YELLED AT HIM TO GET OFF BRAKES; HE SAID HE WASN'T ON THEM. I GOT THE ACFT GOING STRAIGHT; RIGHT AT AN SMA IN POSITION AND HOLD ON OTHER RWY. AS THE A/C WENT STRAIGHT FOR ABOUT A 2 COUNT I ADDED FULL POWER TRYING TO FLY OUT OF IT. AS WE HEADED FOR THE SMA I KNEW WE COULDN'T HIT IT. I DON'T KNOW IF I SUBCONSCIOUSLY VEERED TO MISS THE SMA OR IF IT WOULD HAVE GND LOOPED ANYWAY. WE CAME TO REST ON THE OTHER RWY W/A BROKEN LEFT GEAR; BENT WING AND ELEVATOR. I HAD NO BRAKE PEDALS ON MY SIDE OF ACFT. THE NEXT DAY THE OWNER CAME IN AND SAID THAT THE ACFT DIDN'T DRIVE IN THE GND PROPERLY WHEN HE CAME TO PICK ME UP. UPON INSPECTION OF THE ACFT TAILWHEEL THE INTERNAL LOCKING MECHANISM FOR STEERING IS IN FACT BROKEN. WITHOUT BRAKES ON MY SIDE OF THE ACFT AND A BUSTED STEERING MECHANISM (IF HE'D SAID SOMETHING) I WOULD NOT HAVE FLOWN.