A MOONEY M20C PLT WAS RECEIVING INSTRUCTIONS ON A RECENTLY PURCHASED AIRPLANE BY A CERTIFIED INSTRUCTOR. ON LNDG THE LNDG GEAR COLLAPSED. ACFT DAMAGED.

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AFTER BEING ASSOCIATED WITH MR PLT-2 CFII; BY BEING A MEMBER OF A PLT GROUP; I ASKED HIM IF HE WAS ABLE TO GIVE ME INSTRUCTION IN A 1963 MOONEY M20C. I WAS IN THE PROCESS OF PURCHASING THE AIRPLANE AND NEEDED 10 HRS OF DUAL INSTRUCTION AND 10 HRS OF SOLO. PLT-2 ASSURED ME HE COULD AS A QUALIFIED CFII. I HIRED PLT-2 TO FERRY MY PLANE FROM CALIFORNIA TO FLAGSTAFF AND WE PICKED IT UP. DURING THE MORNING I WAS GETTING INSTRUCTIONAL TRAINING FROM PLT-2. WE DECIDED TO FLY TO WINSLOW; AZ; TO DO TOUCH-AND-GO LNDGS. I HAD GREAT DIFFICULTY RAISING THE LNDG GEAR UPON OUR DEP BUT EVENTUALLY DID GET IT IN PLACE. I ASKED PLT-2 TO DEMONSTRATE THE FIRST APCH AND LNDG AT THE ARPT. AFTER GETTING SET UP WITH THE APPROPRIATE SPD IN THE LNDG PATTERN; PLT-2 INSTRUCTED ME TO LOWER THE LNDG GEAR; WHICH I DID. AGAIN; WITH GREAT DIFFICULTY. I RPTED TO HIM THERE WAS A GREEN LOCK LIGHT INDICATING THAT THE LNDG GEAR WAS LOCKED IN PLACE. ON SHORT FINAL HE AGAIN ASKED ME IF THE LNDG GEAR WAS LOCKED AND I INDICATED IN THE AFFIRMATIVE. I DID NOT HEAR ANY WARNING SOUND OF ANY KIND DURING THE APCH. AS WE LANDED THE JOHNSON BAR CAME CRASHING TO THE FLOOR OF THE ACFT; COLLAPSING THE GEAR AND CREATING A BELLY LNDG. IT IS MY BELIEF THAT THE SPRING IN THE JOHNSON BAR MALFUNCTIONED POSSIBLY DUE TO CORROSION/RUST AND DID NOT PUSH THE LOCKING MECHANISM UPWARD; WHICH WOULD HAVE CREATED A TRUE LOCKED SITUATION OF THE JOHNSON BAR. I DID NOT KNOW THAT WAS NECESSARY IN ORDER TO GET A TRUE 'LOCK' SITUATION OF THE LNDG GEAR. THAT IS ONE OF THE REASONS I WAS GETTING INSTRUCTION IN THE ACFT. AFTER CHKING WITH THE MOONEY FACTORY; I REALIZED THAT SVC BULLETIN M20-88B WAS NOT CHKED DURING THE PRE-BUY INSPECTION BY THE AP/IA MECH IN CALIFORNIA. TO MY KNOWLEDGE THERE WAS NO PLACARD SB M20-884-2 INSTALLED ON THE TOP OF THE LOCK DOWN ASSEMBLY. I BELIEVE THE DEFLECTION OF THE SPRING LOAD MECHANISM AND SUBSEQUENT FAILURE TO ADHERE TO SB M20-88B PLAYED A SIGNIFICANT ROLE IN THIS INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT WHEN THE AIRPLANE WAS TOWED TO THE HANGAR AND JACKED; THE LNDG GEAR TESTED NORMAL OP. WHAT WAS REVEALING WAS THE CERTIFIED INSTRUCTOR DID NOT KNOW HOW TO PROPERLY LOWER AND LOCK THE LNDG GEAR. DAMAGE WAS INCURRED TO THE PROP; ENG AND BELLY SHEET METAL.