A CANADAIR CL-65 PARKED AT THE GATE WHEN ALL POWER WAS REMOVED FROM THE AIRPLANE THE NOSE GEAR RETRACTED ONE-THIRD INTO THE WHEEL WELL.

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WHILE AWAITING MAINT CTL TO COMPLETE A SYS CHK ON A MALFUNCTIONING APU; MY FO AND I READIED ACFT FOR DEP. WE HAD TAKEN OVER ACFT FROM ANOTHER CREW. AT ONE POINT MAINT CTL SHUT DOWN ALL POWER TO THE ACFT TO RESET THE APU ECU. WHEN THIS OCCURRED IT APPEARED WE WERE ROLLING REARWARDS. THE ROLL REARWARDS ALMOST OCCURRED INSTANTANEOUSLY AS POWER WAS REMOVED FROM THE ACFT. THE FO STEPPED ON THE BRAKES TO KEEP THE ACFT FROM ROLLING ANY FURTHER. WE WERE TOLD BY THE MAINT TECHNICIAN TO EXIT THE ACFT SLOWLY AND TO LEAVE OUR BELONGINGS. UPON EXITING THE ACFT I NOTICED THE NOSE GEAR HAD SWUNG APPROX 1/3 OF THE WAY INTO THE RETRACT POS. A TUG WAS CALLED FOR AND CONNECTED TO THE ACFT. AT THE TIME THE NOSE GEAR WAS CHOCKED BEFORE THE INCIDENT AND VERIFIED CHOCKED AFTER INCIDENT. AFTER THE INCIDENT SEVERAL MAINT PERSONNEL ARRIVED AT THE SCENE TO ASSESS THE ACFT AND NOSE GEAR. MAINT HAD ALSO CALLED CFR TO BRING A SPECIALLY DESIGNED BALLOON TO LIFT THE NOSE OF THE ACFT UP SO THAT THE NOSE GEAR COULD BE PINNED IN THE EXTENDED POS. LATER IT WAS DETERMINED THAT A JACK WOULD BE SUFFICIENT. THE NEXT DAY AFTER THE INCIDENT I WAS TOLD BY MAINT CTL THAT THE NOSE GEAR DOWN-LOCK RELEASE VALVE HAD FAILED. APPARENTLY THIS VALVE COULD HAVE BEEN FAILED AT ANY TIME EVEN BEFORE THE ACFT HAD ARRIVED AT THE GATE. MAINT IS NOT SURE WHY; AT THE TIME POWER WAS REMOVED FROM THE ACFT; THE NOSE GEAR FINALLY BEGAN TO RETRACT. IT COULD POSSIBLY BE A HYDRAULIC SURGE FROM SYSTEM 3 WHICH CAUSED THE FAILURE. AT THE TIME SYS 3 WAS POWERED AT THE GATE AND ALL POWER WAS ON THE ACFT WHEN THE CREW CHANGE TOOK PLACE. THE INCIDENT IS STILL I AM SURE UNDER INVESTIGATION AND WILL BE FOR SOME TIME. NO INJURIES OCCURRED AND NO PASSENGERS WERE ON BOARD. SINCE WE DO A NO-PIN PUSHBACK PROCEDURE NOW FROM THE GATE; I BELIEVE IT IS IMPORTANT TO INVESTIGATE WHAT TOOK PLACE TO SEE IF PINS ONCE AGAIN NEED TO BE PUT IN PLACE FOR PUSHBACK. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED WHEN THE POWER ON THE AIRPLANE WAS REMOVED THE AIRPLANE STARTED TO MOVE BACKWARDS AND WAS STOPPED BY THE FO USING THE BRAKES. THE RPTR SAID THE NOSE GEAR HAD RETRACTED ONE THIRD OF THE WAY TO FULL UP. THE RPTR STATED THIS TYPE OF INCIDENT HAS HAPPENED BEFORE ON THIS CARRIER AND OTHERS THAT OPERATE THE CL-65. THE RPTR SAID THE SOLENOID SELECTOR VALVE APPEARS TO BE THE PROBLEM. THE RPTR STATED THIS AIRPLANE WAS PINNED AND TOWED TO THE HANGER WHERE ON TESTING AND TROUBLESHOOTING THE NOSE GEAR AGAIN RETRACTED FULLY AND DAMAGED THE GEAR DOORS.