What was found
(CAN)THE CREW MADE AN UNEVENTFUL SHORT TURN AROUND AT DAWSON CREEK (-35C),THEN PROCEEDED TO FT. ST. JOHN (-41C). DURING THE APP A LOUD BANG WAS HEARD DURING GEAR EXTENSION. ALL ATTEMPTS TO LOWER THE GEAR WERE UNSUCCESSFUL. THE ACFT MADE A SUCCESSFUL GEAR-UP LANDING ON AN ICE COVERED RUNWAY. THERE WERE NO INJURIES & VERY LITTLE DAMAGE TO THE AIRCRAFT. INVEST FOUND THE GEAR DOORS TIGHT AGAINST THE MAIN TIRES. THE GEAR WAS EXTENDED & THE NOSE STRUT FOUND FLAT. SUBMITTER STATES THAT THE NOSE GEAR STRUT WENT FLAT ON TAKEOFF FROM DAWSON DUE TO THE COLD & A "CHAFED" 'O'RING. THIS ALLOWED THE DOORS TO CLOSE APPROX. 95 PERCENT, EN OUGH TO SIGNAL GEAR-UP, BUT ALSO JAMMING THE GEAR IN THE UP POSITION.