INSTRUCTOR WITH TRAINEE HAS NOSE GEAR COLLAPSE ON LNDG ROLL.

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WITH MR. X; A PVT RATED PLT AT THE CTLS; WE EXPERIENCED A NORMAL TKOF; CLBOUT AND FLT TO AND FROM THE PRACTICE AREA. WE WERE IN THE PRACTICE AREA FOR ABOUT 45 MINS. WE ENTERED THE TFC PATTERN TO PRACTICE TOUCH-AND-GO LNDGS. AIRPLANE LANDED NORMALLY AND; AFTER A SHORT ROLL; PWR WAS APPLIED FOR THE TKOF PORTION OF THE TOUCH-AND-GO. AFTER OBTAINING A POSITIVE RATE OF CLB; SAFE ALT; AND SAFE AIRSPD; MR. X PUT THE GEAR UP AND CONTINUED THE TFC PATTERN FOR THE SECOND TOUCH-AND-GO. ABEAM THE TWR; SAFE AIRSPD WAS CONFIRMED; GEAR HANDLE WAS PLACED IN THE DOWN POS. WE HEARD THE GEAR MOTOR ACTIVATE; THE GEAR COMING DOWN; AND FELT THE GEAR JOLT INTO PLACE. MR. X AGAIN SAID '3 GREENS' AND I VERIFIED THE GEAR DOWN AND LOCKED WITH 3 GREEN LIGHT INDICATIONS ILLUMINATED. ON BASE LEG; DURING THE GUMPS CHK; THE 3 GREEN LIGHTS ON INDICATION WAS AGAIN OBSERVED. FINAL APCH WAS AT 85 MPH AND; ON SHORT FINAL; ONCE AGAIN THE 3 GREEN LIGHTS WERE ILLUMINATED AND THE INDICATION WAS CONFIRMED BY BOTH MR. X AND MYSELF. THE AIRPLANE LANDED NORMALLY AT AN AIRSPD OF APPROX 76 MPH JUST BEYOND THE NUMBERS ON RWY 25L AND STARTED A ROLLOUT ACROSS RWY 30. AS THE ACFT CROSSED RWY 30; APPROX 300 FT FROM WHERE WE TOUCHED DOWN; IT EXPERIENCED A LARGE AMOUNT OF NOSEWHEEL SHIMMY. I IMMEDIATELY PULLED THE YOKE BACK TO REDUCE THE AMOUNT OF WT ON THE NOSEWHEEL; AND ABORTED THE TOUCH-AND-GO. THIS ACTION RAISED THE NOSE OF THE ACFT SLIGHTLY AND REDUCED THE AMOUNT OF VIBRATION FELT. AS THE AIRPLANE SLOWED DOWN; THE NOSEWHEEL COLLAPSED AND THE ACFT SKIDDED ON THE CTRLINE OF THE RWY FOR APPROX 500 FT BEFORE COMING TO A COMPLETE STOP JUST L OF THE CTRLINE OF THE RWY. AT THIS POINT I SECURED THE ENG AND ACFT AND BOTH MR.X AND I DEPARTED THE PLANE. THE AIRPLANE CAME TO REST ON THE RWY STILL ON ITS MAIN GEAR; AND THE GREEN LIGHT INDICATIONS FOR THE 2 MAIN GEAR WERE ILLUMINATED AND SHOWED THAT THE 2 MAIN GEAR WERE LOCKED. THIS FACT WAS CONFIRMED BY MR. X AND WITNESSED BY BOTH THE ARPT POLICE OFFICERS WHEN THEY ARRIVED; AND BY THE ACFT WRECKAGE COMPANY THAT CAME TO REMOVE THE ACFT. WHEN THE WRECKAGE MAN SAW THAT THE MAIN GEAR WAS DOWN AND CONFIRMED GREEN LIGHT INDICATIONS OF LOCKED; HE CHOSE TO MOVE THE ACFT BY LIFTING THE NOSE OF THE AIRPLANE AND TOWING IT ON THE MAIN GEAR. AFTER HE LIFTED THE NOSE AND STARTED MOVING THE PLANE; THE L GEAR STARTED TO COLLAPSE. HE STOPPED; HAD SEVERAL PEOPLE HELP HIM LIFT THE WING AND PULL THE GEAR BACK DOWN. AS HE DID THIS; THE R WHEEL STARTED TO COLLAPSE. HE ONCE AGAIN HAD PEOPLE HELP HIM LIFT THE R WING; THIS CAUSED THE L WING TO FALL RAPIDLY AND DAMAGE THE WING. AS HE MOVED AWAY; THE R WING FELL ALSO CAUSING DAMAGE TO IT. SUBSEQUENT INVESTIGATION BY A MECH REVEALED THAT THE NOSEWHEEL LOCKING PIN AND BUSHING HAD BEEN SHEARED OFF AT SOME TIME DURING THE FLT.