What was found
DURING CLIMB, LANDING GEAR HANDLE WAS PLACED INTO RETRACT. BOTH MLG RETRACTED NORMALLY, NLG DID NOT. AFTER SEVERAL ATTEMPTS, CREW DECLARED AND IN-FLIGHT EMERGENCY, JETTISONED THE RETARDANT LOAD, AND LANDED WITHOUT INCIDENT. CAUSE WAS FOUND TO BE AN OUT-OF-RIG DOWN SENSING SWITCH. THE SWITCH WAS RE-RIGGED, THE AIRCRAFT JACKED, AND GEAR RETRACT TESTED SUCCESSFULLY NUMEROUS TIMES IAW THE MM.