What was found
(CAN) SHORTLY AFTER TAKEOFF OUT OF YYC, THE CREW EXPERIENCED DIFFICULTY GETTING THE LANDING GEAR LEVER TO REMAIN IN THE 'UP' POSTION. THE CREW PERFORMED THE 'NON-NORMAL CHECKLIST', BUT WERE UNABLE TO RECTIFY THE PROBLEM. THE CREW ELECTED TO RETURN TO YYC AND THE AIRCRAFT LANDED WITHOUT INCIDENT - CFR WAS NOT CALLED OUT. MAIINTENANCE REPLACED THE LANDING GEAR ACCESSSORY UNIT, AND THE SYSTEM CHECKED SERVICEABLE.AIRCRAFT RETURNED TO SERVICE WITH NO FURTHER INCIDENTS TO REPORT.