Cessna 402/402C/B379 Businessliner/Utiliner
Flight Crew Instrument; Flight Crew Multiengine
Situational Awareness; Workload; Time Pressure
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition
Aircraft
As turning a high wide base for ZZZ visual approach to Rwy XX; noticed gear unlocked light was illuminated with gear still selected up. The gear unlocked light was off prior to this and had normal indications after takeoff from ZZZ1. Selected gear down and back up to recycle; still had gear unlocked light. Put gear back down; and had gear unlocked light illuminated with three green lights. Recycled for gear unlocked light illuminated with gear selected down. Still showed three green with red gear unlocked light illuminated. Referred to QRH and followed checklist; which resulted in gear blow down. Pulled T-handle; still had three green and red unlocked light illuminated. Declared emergency and elected to return to ZZZ1. Tried flaps greater than 15 and noted gear horn sound beyond 15. Followed QRH checklist for landing with defective gear. Upon landing; gear was down and landing was uneventful; followed through with shutdown on runway in accordance with QRH. Evacuated aircraft with passengers. Aircraft was towed. Mechanical issue with aircraft landing gear.
Cessna 402 pilot reported a gear unsafe indication during preparation for landing.