LNDG GEAR COLLAPSES DURING TKOF ROLL.

Narrative

HOW THE PROB AROSE I DO NOT UNDERSTAND. DURING PREFLT I CHKED THE GEAR HANDLE 3 DIFFERENT TIMES TO MAKE SURE IT WAS DOWN. CONTRIBUTING FACTORS COULD HAVE BEEN A STUDENT WHO WAS PREVIOUSLY IN THE ACFT DOING DRY TIME. THIS I WAS AWARE OF DUE TO A FULL RICH MIXTURE AND A HALF CLOSED THROTTLE. MAYBE THE STUDENT WAS YANKING ON THE GEAR HANDLE. THE PROB UNDISCOVERED WHEN THE NOSE THEN L MAIN COLLAPSED DURING TKOF ROLL. CORRECTIVE ACTIONS REQUIRED FULL R RUDDER TO KEEP THE ACFT FROM ROTATING TO THE L AND POSSIBLY CARTWHEELING. HUMAN PERCEPTIONS DURING THE PREFLT WERE HIGH. BECAUSE THIS WAS A CFII CHK RIDE I WAS VERY THOROUGH WITH THE CHKLIST. FACTORS AFFECTING THE QUALITY OF FLT CONSISTED OF A LARGE AMOUNT OF STRESS I FELT DUE TO NOT ONLY THIS BEING A CHK RIDE BUT ALSO A FLT; WHICH IF COMPLETED SUCCESSFULLY; WOULD ALLOW ME TO RECEIVE MY BACHELOR OF SCIENCE IN AERONAUTICAL SCIENCE AND A COMMISSION AS A SECOND LIEUTENANT IN THE AIR FORCE. THIS ADDITIONAL STRESS MAY HAVE ENHANCED MY PERFORMANCE. ACTIONS: I FELT I REACTED CORRECTLY AND QUICKLY BY BRINGING BACK THE PWR TO IDLE AND MIXTURE TO IDLE CUT OFF ONCE I RECOGNIZED A PROB. ALSO; I FEEL THAT THE ADDITION OF R RUDDER MAY HAVE PREVENTED A CARTWHEELING OF THE ACFT.