THE LNDG GEAR COLLAPSED ON AN SMA.

Narrative

MY STUDENT AND I WERE PRACTICING LNDGS AT LAKEVIEW ARPT. WE WERE ON DOWNWIND AND PROCEEDED THROUGH OUR 'GUMPSF.' THE STUDENT MOVED THE JOHNSON BAR FORWARD INTO THE LOCKING DETENT AND WE VERIFIED A GREEN GEAR DOWN INDICATION. THE LNDG PROCEEDED NORMALLY. I INSTRUCTED MY STUDENT TO LINE UP ON THE TURF RWY. A GREEN GEAR DOWN INDICATION WAS VERIFIED ON FINAL AND WE PROCEEDED TO LAND ON THE GRASS. TOUCHDOWN WAS GENTLE ON THE MAINS AND WE PROCEEDED TO ROLL OUT; THE AIRPLANE SHAKING AND VIBRATING RAPIDLY ON THE TURF. AS THE ROLLOUT CONTINUED; THE GEAR HORN SOUNDED AND I SAW THE JOHNSON BAR SEPARATE FROM THE LOCKING DETENT. THE GEAR COLLAPSED AND THE MOTOR STOPPED AS THE PLANE SKIDDED APPROX 50 FT ON ITS BELLY. AS THE ACTING PIC; I CAN SAY IN GOOD CONSCIENCE THAT THE GEAR INDICATOR WAS GREEN AND THE GEAR APPEARED TO BE LOCKED. I; HOWEVER; CANNOT SAY WITHOUT A DOUBT THAT THE GEAR WAS FULLY AND SECURELY LOCKED. I DID NOT REACH UP AND GRAB THE JOHNSON BAR TO VERIFY IT WAS SECURELY LOCKED. SUPPLEMENTAL INFO FROM ACN 257690: PERHAPS ONE OF THE KEY FACTORS IN THIS EVENT WAS WHETHER THE JOHNSON BAR WAS REALLY IN THE LOCKED POS. IT APPEARED TO ME THAT I HAD LOCKED THIS BAR INTO POS WHILE LOWERING THE GEAR. IN ADDITION; THE INSTRUCTOR PRESENT INDICATED TO ME AFTERWARDS THAT THE GREEN LIGHT WAS LIT; FURTHER CONFIRMING THAT THE GEAR WERE DOWN AND LOCKED.