LNDG GEAR OF AN SMA SEL COLLAPSED DURING A TRAINING FLT LNDG ROLL.

Narrative

WHILE PERFORMING TOUCH AND GOES IN ACFT FOR INSURANCE TRAINING REQUIREMENTS. I AND MY INSTRUCTOR EXPERIENCED A LNDG GEAR COLLAPSE ON THE SIXTH LNDG -- L MAIN COLLAPSED JUST AFTER TOUCHDOWN FOLLOWED BY R MAIN AND NOSE GEAR -- GEAR WAS VERIFIED AS DOWN AND LOCKED ON DOWNWIND AND FINAL LEG OF PATTERN BY BOTH PLT AND INSTRUCTOR. ACFT SLID ON BELLY FOR DURATION OF LNDG. NO INJURY TO ANYONE; AND DAMAGE LIMITED TO PROP-ENG AND BELLY AREA OF ACFT WAS ALL THAT WAS NOTICED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE FAA INSPECTOR INVESTIGATING THIS INCIDENT OBSERVED THE ACTUAL INVOLUNTARY MOVEMENT OF THE LNDG GEAR EXTENSION HANDLE FROM THE DETENT CAUSING THE GEAR TO RETRACT. THE ACFT; MOONEY MODEL 20 F; IS DESIGNED TO SHOW THE LNDG GEAR UP OR DOWN POS BY THE MICRO SWITCHES ACTUATED BY THE LNDG GEAR EXTENSION HANDLE. THEREFORE; IT IS IMPORTANT TO ASSURE THAT THE HANDLE IS IN THE DETENT OR LOCKED POS TO ASSURE GEAR POS. THIS ALSO MEANS THAT THE LNDG GEAR MAY NOT BE FULLY LOCKED DOWN OR UP WHEN THE HANDLE IS IN THE DETENT AND THE 1 LIGHT GREEN OR 1 LIGHT RED IS LIGHTED. THE RPTR FURTHER STATED THAT THE GEAR HANDLE HAD TO 'BOUNCE OUT' OF THE DETENT ON IT'S OWN SINCE A LAST MIN CHK OF THE LNDG GEAR HANDLE WAS MADE BY BOTH THE RPTR AND THE INSTRUCTOR.