Narrative:

When I selected landing gear down, the left main landing gear indicated unsafe. The right main and nose gear indicated safe. We cycled the landing gear 3 times. The indication remained the same. We continued the approach down to about 1200 ft MSL and flew down the runway so tower could check the landing gear. The tower indicated it appeared down. We turned out for an extended downwind and talked to maintenance. They indicated we should have the equipment rolled out and land. We then proceeded to declare an emergency and land, with a normal approach and landing. The landing gear still indicated unsafe. Callback conversation with reporter revealed the following information: the left main gear would not lock because ice had formed in the locking mechanism, blocking it from fitting all the way into place. The aircraft had been taxied through slush while in bhm, and after takeoff the slush had turned to ice and remained frozen throughout the flight and landing and until maintenance removed it in cvg. The gear was still held in the down position by hydraulic pressure, but it was not overctr. The indication that the flight crew received was related to the pair of magnetic proximity switches which must be lined up to close a circuit. When the circuit closes, the green gear light will illuminate in the cockpit. There were enough problems in the past with proximity switches that the reporter assumed proximity switches were the problem. In the future, he will not buy into an assumption. He will stop the aircraft after landing, have the gear pins installed, and then have the aircraft towed to the gate.

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Original NASA ASRS Text

Title: E120 FLC RECEIVED A L MAIN LNDG GEAR UNSAFE LIGHT WHEN GEAR WAS SELECTED FOR LNDG. AFTER TWR VERIFICATION OF GEAR EXTENSION AND DISCUSSION WITH MAINT, THE FLC DECLARED AN EMER AND LANDED. THE UNSAFE INDICATION CONTINUED AFTER LNDG.

Narrative: WHEN I SELECTED LNDG GEAR DOWN, THE L MAIN LNDG GEAR INDICATED UNSAFE. THE R MAIN AND NOSE GEAR INDICATED SAFE. WE CYCLED THE LNDG GEAR 3 TIMES. THE INDICATION REMAINED THE SAME. WE CONTINUED THE APCH DOWN TO ABOUT 1200 FT MSL AND FLEW DOWN THE RWY SO TWR COULD CHK THE LNDG GEAR. THE TWR INDICATED IT APPEARED DOWN. WE TURNED OUT FOR AN EXTENDED DOWNWIND AND TALKED TO MAINT. THEY INDICATED WE SHOULD HAVE THE EQUIP ROLLED OUT AND LAND. WE THEN PROCEEDED TO DECLARE AN EMER AND LAND, WITH A NORMAL APCH AND LNDG. THE LNDG GEAR STILL INDICATED UNSAFE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE L MAIN GEAR WOULD NOT LOCK BECAUSE ICE HAD FORMED IN THE LOCKING MECHANISM, BLOCKING IT FROM FITTING ALL THE WAY INTO PLACE. THE ACFT HAD BEEN TAXIED THROUGH SLUSH WHILE IN BHM, AND AFTER TKOF THE SLUSH HAD TURNED TO ICE AND REMAINED FROZEN THROUGHOUT THE FLT AND LNDG AND UNTIL MAINT REMOVED IT IN CVG. THE GEAR WAS STILL HELD IN THE DOWN POS BY HYD PRESSURE, BUT IT WAS NOT OVERCTR. THE INDICATION THAT THE FLC RECEIVED WAS RELATED TO THE PAIR OF MAGNETIC PROX SWITCHES WHICH MUST BE LINED UP TO CLOSE A CIRCUIT. WHEN THE CIRCUIT CLOSES, THE GREEN GEAR LIGHT WILL ILLUMINATE IN THE COCKPIT. THERE WERE ENOUGH PROBS IN THE PAST WITH PROX SWITCHES THAT THE RPTR ASSUMED PROX SWITCHES WERE THE PROB. IN THE FUTURE, HE WILL NOT BUY INTO AN ASSUMPTION. HE WILL STOP THE ACFT AFTER LNDG, HAVE THE GEAR PINS INSTALLED, AND THEN HAVE THE ACFT TOWED TO THE GATE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.