NAVION PLT HAD THE R MAIN GEAR COLLAPSE ON LNDG ROLL.

Narrative

AFTER RECEIVING CLRNC TO LAND AND SLOWING TO BELOW GEAR SPD; THE LNDG GEAR LEVER WAS FOUND TO BE STUCK IN THE UP POS. I NOTIFIED THE TWR AND REQUESTED TO DEPART THE PATTERN. I MAINTAINED AN AIRSPD OF 90 MPH. EMER CHK PER PROCS FOR THE ACFT. VERIFIED HYD PRESSURE (OK). RELEASED THE GEAR UPLOCKS USING THE EMER LEVER. TRIED THE GEAR LEVER AGAIN WITH SOME FORCE. THE LEVER WENT TO THE DOWN POS. 3 GREEN LIGHTS. FELT AS THOUGH SOMETHING GAVE AT THE LEVER. SLOWED ACFT TO 80 MPH. CHKED GEAR LIGHTS AGAIN -- ALL OK. CALLED TWR AND REQUESTED A FLY-BY TO HAVE THE TWR CHK THE GEAR. CLRED OVER THE R RWY. TWR ADVISED ALL GEAR WAS DOWN. I REQUESTED L TFC FOR RWY 28L AFTER FLY-BY. TWR APPROVED AND I CHKED THE GEAR SEVERAL TIMES ON DOWNWIND. TWR REQUESTED EXTENDED DOWNWIND FOR HELI TFC. TURNED FINAL AND PERFORMED GUMP CHK SEVERAL MORE TIMES. ALL OK. USED PARTIAL FLAPS FOR SMOOTH TOUCHDOWN. ALL OK AT THIS TIME. WHILE DECELERATING ON ROLLOUT (APPROX 20-30 MPH); THE R MAIN GEAR STARTED TO COME UP; LOWERING THE R WING SLOWLY TO THE RWY. I LOOKED AT THE GEAR LEVER AT THIS TIME AND IT WAS NOT IN ITS DETENT. IT HAD MOVED FROM THE FULL DOWN POS. I MOVED THE LEVER BACK TO THE FULL DOWN POS AND SHUT DOWN THE ENG WHILE COMING TO A STOP ON THE RWY. AFTER STOPPING; I TURNED OFF ALL ELECTRICAL; FUEL AND MAGNETOS. I LATER FOUND THE GEAR LEVER SAFETY ARM BENT BEHIND THE PANEL. THIS HELD THE GEAR LEVER FROM FULLY ENTERING THE DOWN DETENT. AFTER RAISING THE ACFT; I TELEPHONED THE TWR AND REQUESTED CLRNC TO TOW THE ACFT FROM THE RWY. TWR ISSUED CLRNC TO TOW THE ACFT. ALWAYS CHK THE GEAR DOWN LEVER ALONG WITH GEAR POS LIGHTS. THIS SHOULD BE DONE DURING APCH; ON TOUCHDOWN AND ROLLOUT.