CESSNA RG172 FLT CREW HAS THE NOSEWHEEL COLLAPSE DURING LNDG.

Narrative

WHILE ROLLING OUT FROM LNDG; THE NOSE GEAR COLLAPSED. STUDENT WAS A COMMERCIAL PLT TRAINING FOR CFI LICENSE. WE HAD BEEN PRACTICING SHORT FIELD TKOFS AND LNDGS. WIND WAS DOWN THE RWY. THE STUDENT; WHO HAD ABOUT 80 HRS IN TYPE; WAS STRUGGLING WITH HIS TECHNIQUE. TIMING OF THE FLARE FOR A PROPER TOUCHDOWN WAS MAIN PROB. ON OUR SECOND TO LAST LNDG HIS APCH WAS LOOKING BETTER AND FELT GOOD TO ME. ONCE AGAIN HE STARTED TO FLARE HIGH BUT STOPPED HIMSELF. I FELT WE WERE STILL IN A GOOD POS BUT SUDDENLY THE ACFT STALLED; LANDED HARD IN A FLAT ATTITUDE AND BOUNCED. ALT AT THE STALL WAS PROBABLY 5-10 FT. THE STUDENT IMMEDIATELY PERFORMED A GAR. AFTER COMPLETING THE GAR I TOOK THE FLT CTLS FROM THE STUDENT. I INTENDED TO DEMONSTRATE A SHORT FIELD LNDG SO HE COULD SEE ONE. I PLANNED FOR IT TO BE OUR LAST LNDG. ON DOWNWIND I EXTENDED THE LNDG GEAR. THE MAIN GEAR EXTENDED AND SOUNDED; FELT AND LOOKED LIKE THEY WERE DOWN AND LOCKED. THE GREEN LIGHT INDICATING THAT THE NOSE GEAR WAS LOCKED DID NOT LIGHT UP. CHKING THE MIRROR SHOWED THAT THE NOSE GEAR WAS EXTENDED. WITH MIXED SIGNALS WE EXITED THE PATTERN; CYCLED THE GEAR TWICE AND DID AS MUCH TROUBLESHOOTING AS POSSIBLE. WE CONSIDERED THAT SOMETHING WAS PROBABLY DAMAGED IN THE LAST LNDG. DETERMINING WHAT IT WAS WAS THE TRICKY PART. WE BOTH HOPED FOR A BROKEN SWITCH CIRCUIT WIRE; SO THAT IT WAS JUST A FAULTY INDICATION. WE ALSO THOUGHT THAT THE ROUGH LNDG COULD HAVE COMPRESSED THE STRUT ENOUGH THAT IT WOULDN'T CONTACT THE DOWN SWITCH. WE DECIDED TO MAKE A SOFT FIELD LNDG WITH MINIMUM BRAKING AND HOPE FOR THE BEST. I PERFORMED THE LNDG. IT WAS PERFECT SOFT FIELD TECHNIQUE WITH THE NOSEWHEEL TOUCHING DOWN AT THE LOWEST POSSIBLE SPD. THE NOSE GEAR TOUCHED DOWN AND I CONTINUED TO HOLD FULL BACK PRESSURE TO KEEP WT OFF THE NOSE. AS WE SLOWED TO TAXI SPD ON THE RWY THE NOSE GEAR COLLAPSED. DAMAGE WAS LIMITED TO THE ENG AND SKIN.