A B727-200 on final approach at 1500 ft AGL declared an emergency due to left main gear unsafe indication caused by a failed microswitch.

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Attributes
ACN	486034
Time
Date	200009
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : dfw.airport
State Reference	TX
Altitude	agl single value : 1500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dfw.tower
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 18r
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 6500 flight time type : 140
ASRS Report	486034
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 8000 flight time type : 150
ASRS Report	486219
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : gear position indication other flight crewa other flight crewb other other : person 3
Resolutory Action	flight crew : declared emergency flight crew : landed in emergency condition
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

On final approach to dfw, captain selected 'gear down' and the left main gear indicated red while other gear indicated green. I flew a rejected landing to a visual pattern while the captain and flight engineer performed appropriate checklists. Flight engineer performed a visual inspection of the landing gear using the viewing port, and the affected gear (left main) did indicate down and locked. Other diagnostic and verification procedures were performed -- specifically turning the manual extension socket to check the position of the 'over-ctring' mechanism. When we were satisfied that all landing gear were indeed safe, we declared an emergency, requested 'arff' equipment (as a precaution) and landed without further incident. The main gear was pinned upon clearing the runway and taxi to the gate was uneventful. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was a B727-200 with P&west JT8D-15 engines. The reporter said the left main gear unsafe indication was caused by a failed down and lock microswitch.

Original NASA ASRS Text

Title: A B727-200 ON FINAL APCH AT 1500 FT AGL DECLARED AN EMER DUE TO L MAIN GEAR UNSAFE INDICATION CAUSED BY A FAILED MICROSWITCH.

Narrative: ON FINAL APCH TO DFW, CAPT SELECTED 'GEAR DOWN' AND THE L MAIN GEAR INDICATED RED WHILE OTHER GEAR INDICATED GREEN. I FLEW A REJECTED LNDG TO A VISUAL PATTERN WHILE THE CAPT AND FE PERFORMED APPROPRIATE CHKLISTS. FE PERFORMED A VISUAL INSPECTION OF THE LNDG GEAR USING THE VIEWING PORT, AND THE AFFECTED GEAR (L MAIN) DID INDICATE DOWN AND LOCKED. OTHER DIAGNOSTIC AND VERIFICATION PROCS WERE PERFORMED -- SPECIFICALLY TURNING THE MANUAL EXTENSION SOCKET TO CHK THE POS OF THE 'OVER-CTRING' MECHANISM. WHEN WE WERE SATISFIED THAT ALL LNDG GEAR WERE INDEED SAFE, WE DECLARED AN EMER, REQUESTED 'ARFF' EQUIP (AS A PRECAUTION) AND LANDED WITHOUT FURTHER INCIDENT. THE MAIN GEAR WAS PINNED UPON CLRING THE RWY AND TAXI TO THE GATE WAS UNEVENTFUL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A B727-200 WITH P&W JT8D-15 ENGS. THE RPTR SAID THE L MAIN GEAR UNSAFE INDICATION WAS CAUSED BY A FAILED DOWN AND LOCK MICROSWITCH.

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.