What was found
AIRCRAFT WAS GROUNDED, FLIGHT RETURNED TO DEPARTURE DUE TO THE GEAR UNABLE TO RETRACT. EMERGENCY DECLARED. LANDED WITHOUT INCIDENT. AIRCRAFT WAS REMOVED FROM SERVICE. FOUND MANUAL EXTENSION DOOR OPEN. PREFORMED INSPECTION OF DOOR SWITCH IAW AMM 32-34-00-820-802. PERFORMED AN ALTERNATE LANDING GEAR TEST IAW AMM 32-31-51-400-801 AND PREFORMED PSEU BITE TEST IAW AMM 32-09-00-810-801. ALL TESTS CHECKED GOOD.