INSTRUCTOR AND SPI HAVE R MAIN GEAR OFF RWY ON LNDG ROLLOUT.

Narrative

I WAS FLYING AS A FLT INSTRUCTOR WITH AN ADVANCED PRE- SOLO STUDENT. WE WERE PRACTICING TKOFS AND LNDGS. WE NEEDED TO USE A SMALL AMOUNT OF SIDESLIP. THE WIND WAS 25 DEGS FROM THE L OF THE RWY DIRECTION AT APPROX 10 KTS. MY STUDENT WAS APCHING THE SKILL LEVEL TO SOLO; AND I THEREFORE WAS BECOMING MORE COMFORTABLE FLYING WITH THIS STUDENT. ON OUR 4TH LNDG OF THE DAY; MY STUDENT LANDED WITH THE L MAIN ON THE CTRLINE OF THE RWY. WE STARTED TO TRACK TO THE R; POSSIBLY PUSHED BY A GUST OF WIND. I TRIED TO TALK MY STUDENT INTO STRAIGHTENING THE DIRECTION OF THE AIRPLANE; HOWEVER THE R MAIN GEAR WENT OFF THE RWY. A SPLIT-SECOND BEFORE; I STARTED TO APPLY THE NECESSARY CTL INPUTS TO KEEP THE MAIN GEAR ON THE RWY; BUT I WAS A LITTLE LATE. I CONTINUED APPLYING THE NECESSARY CTL INPUTS AND SUCCESSFULLY RETURNED THE AIRPLANE FULLY ON THE RWY. THERE WERE NO INJURIES. A CONTRIBUTING FACTOR WAS MY COMFORT LEVEL WITH MY ADVANCED PRE-SOLO STUDENT; AND THEREFORE CONFIDENCE THAT MY STUDENT WOULD SUCCESSFULLY KEEP THE AIRPLANE FULLY ON THE RWY.