INADVERTENTLY RETRACTED GEAR WHILE MAKING TOUCH AND GO LNDGS.

Narrative

I WAS DOING TOUCH AND GO'S WHILE PRACTICING TEACHING LNDGS WITH MY INSTR FOR A CFI CERTIFICATE. AFTER COMPLETING THE LNDG ON THE 3RD TOUCH AND GO; I WAS BUSY OPENING THE COWL FLAPS; RETRACTING THE FLAPS; AND TURNING OFF THE CARB HEAT IN PREPARATION FOR THE NEXT TKOF WHEN I INADVERTENTLY RETRACTED THE GEAR. THE NOSE WHEEL RETRACTED BUT THE MAIN GEAR REMAINED DOWN AND LOCKED. THE ACFT SKIDDED TO A STOP ON THE RWY; DESTROYING THE PROP; DAMAGING THE NOSE GEAR DOOR AND SLIGHTLY DAMAGING THE COWL FLAPS AND UNDERSIDE OF THE COWLING. MAINT HAD BEEN DONE ON THE GEAR THE WEEK PRIOR FOR GEAR RETRACTION PROBS. THE GEAR WARNING HORN DID NOT ALWAYS COME ON WHEN THROTTLING BELOW 1500 RPM WITH THE GEAR UP DURING THE FLT. THIS HAS LED ME TO BELIEVE THE SQUAT SWITCH MAY NOT HAVE BEEN WORKING PROPERLY. I BELIEVE THERE ARE 3 LESSONS LEARNED. WHEN DOING TOUCH AND GO'S ON A SHORT RWY; LEAVE GEAR DOWN ALWAYS OR TAXI BACK. HAVING THE SQUAT SWITCH ONLY ON THE NOSE GEAR; LIKE AN SMA SEEMS LESS THAN ADEQUATE PROTECTION AGAINST AN INADVERTENT GEAR RETRACTION. THE SHOCK ON THE NOSE GEAR CAN BE EXTENDED; ON TAXI OR TKOF; LNDG ROLLS EVEN THOUGH THE ACFT WILL NOT FLY. THE MAIN GEAR SEEMS TO BE THE ONLY PLACE FOR A RELIABLE SQUAT SWITCH; SINCE THE WEIGHT OF THE ACFT IS ON THE MAINS UNTIL THE ACFT IS AIRBORNE. MAYBE THERE SHOULD BE A DOUBLE; OR 2 STEP SWITCH FOR GEAR RETRACTION. THIS WOULD GIVE THE PLT THAT EXTRA SPLIT SEC TO STOP AN INADVERTENT MOVE THAT RESULTED IN A NOSE GEAR RETRACTION FOR ME.