SCHEIBE SF34 GLIDER PLT HAS THE LNDG GEAR COLLAPSE DURING LNDG.

Narrative

I WAS ACTING AS FLT INSTRUCTOR IN THE REAR SEAT OF THE GLIDER (SCHEIBE SF-34) WITH THE STUDENT PLT FLYING THE ACFT FROM THE FRONT SEAT. RWY 26 WAS IN USE FOR TKOF AND LNDG. SURFACE WIND WAS FROM THE S AT ABOUT 5-10 KTS. THE LNDG INCIDENT OCCURRED ON THE LAST OF 4 PATTERNS AND LNDGS. THE STUDENT FLEW A NORMAL PATTERN TO ROLL OUT ON THE EXTENDED RWY CTRLINE AND THEN USED A MILD SLIP WITH THE L WING LOW TO CORRECT FOR THE L XWIND. THE STUDENT PLANNED FOR A TOUCHDOWN JUST BEYOND THE 1000 FT RWY MARKER AND ON THE R HALF (DOWNWIND SIDE) OF THE RWY. HIS DSCNT RATE WAS WITHIN NORMAL RANGE AND THE LONGITUDINAL AXIS OF THE GLIDER WAS ALIGNED WITH ITS TRACK ALONG THE RWY. AT TOUCHDOWN; THE ATTACHMENT BOLTS FOR THE LNDG GEAR SHOCK STRUTS FAILED AND THE LNDG GEAR COLLAPSED INTO THE GEAR WELL. I TOOK CTL OF THE GLIDER AND IT SLID TO A GRADUAL STOP ON THE R SIDE OF THE RWY NEAR THE INTXN OF TXWY D. NO ONE WAS INJURED DURING THE INCIDENT. BECAUSE OF TURB OR A SLIGHTLY INCOMPLETE FLARE; TOUCHDOWN WAS FIRM BUT NO HARDER THAN I HAVE EXPERIENCED WITH OTHER STUDENTS WHO ARE LEARNING TO LAND THE GLIDER. PRIOR TO TOUCHDOWN; A SAFE LNDG WAS NEVER SERIOUSLY IN DOUBT AND I DID NOT FEEL IT NECESSARY TO ASSIST ON THE CTLS. I DO NOT FEEL THAT THE TOUCHDOWN WAS FIRM ENOUGH THAT IT SHOULD HAVE CAUSED ANY DAMAGE. LNDG GEAR FAILURE AT THE SHOCK STRUT ATTACHMENT POINTS HAS OCCURRED PREVIOUSLY IN THIS GLIDER AND MAY INDICATE A NEED FOR MORE FREQUENT INSPECTIONS OR A CHANGE IN THE COMPONENTS.