What was found
(CAN) CASTOR LOCK ENGAGED FOR JACKING/LEVELING OF AIRCRAFT. AIRCRAFT LOWERED, TOW BAR INSTALLED IN PREPARATION FOR TOWING. TECHNICIAN NOTICED THE LOCK PIN WAS STILL INSTALLED. LOCK PIN REMOVED. AS THE TOW BAR WAS HOOKED TO A TRACTOR, THE LOCK PIN (SPRING LOADED) WAS UNDER A SIDE LOAD AND WAS HELD IN THE LOCKED OR ENGAGED POSITION. TOWING WAS STARTED AND A LOUD BANG WAS HEARD. SHOCK STRUT DAMAGED AT LOCK PIN RECEPTACLE. (TC NR 20100107002)