B737-400 captain reports failure of the left main gear to extend during approach. A go-around is ini...

Narrative:

During the approach to landing; when the gear was extended; the left main gear did not come down. A missed approach was accomplished and vectors were received by ATC as we worked through the QRH procedure. I also elected to declare an emergency at this point. As per the QRH; the left main gear was successfully extended using the alternate gear extension. Once the QRH procedure was completed; we did a low fly-by so the ATC tower; as well as fellow pilots could observe our gear configuration. Satisfied our gear was down and locked; we entered the pattern again and flew a normal profile to a normal and uneventful landing. After landing; we cleared the runway and taxied to our gate. I do not know why the gear did not come down. Maintenance took the airplane to the hangar for further inspection.

Original NASA ASRS Text

Title: B737-400 Captain reports failure of the left main gear to extend during approach. A go-around is initiated and the gear is successfully extended using the alternate extension method. An uneventful landing and taxi to the gate ensues.

Narrative: During the approach to landing; when the gear was extended; the left main gear did not come down. A missed approach was accomplished and vectors were received by ATC as we worked through the QRH procedure. I also elected to declare an emergency at this point. As per the QRH; the left main gear was successfully extended using the alternate gear extension. Once the QRH procedure was completed; we did a low fly-by so the ATC Tower; as well as fellow pilots could observe our gear configuration. Satisfied our gear was down and locked; we entered the pattern again and flew a normal profile to a normal and uneventful landing. After landing; we cleared the runway and taxied to our gate. I do not know why the gear did not come down. Maintenance took the airplane to the hangar for further inspection.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1037519
Time
Date	201209
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	Landing
Flight Plan	IFR
Component
Aircraft Component	Main Gear
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

B737-400 captain reports failure of the left main gear to extend during approach. A go-around is initiated and the gear is successfully extended using the alternate extension method. An uneventful landing and taxi to the gate ensues.