Narrative:

Cleared for the localizer 31 lga; inbound to fabry; level at 1;700 feet; fully configured; I set 0 in the MCP altitude window. Crossing fabry; I set 800 fpm down with the vertical speed wheel as previously briefed. When we checked in with tower; we were told to continue as there would be multiple aircraft departing before our arrival. The dda had been set on our baro bugs at 650 feet. 'Approaching minimums' call was made; I said 'going outside.' as we descended below the ceiling; 'minimums' was called. Acquiring the runway environment; I said 'landing'. Trying to reconstruct the events; I believe I left the vertical speed in the 800 fpm down; previously set. We briefly went below dda; and simultaneously we heard a 'caution; obstacle.' by this time; we were below the ceiling and had visual contact with the ground. I immediately disconnected the autopilot and autothrottles and adjusted our vertical path. We leveled and continued toward the runway. We were given clearance to land and we landed on runway 31. My approach briefing should have taken into consideration the significant headwind we experienced on the final portion of the approach. In selecting 800 fpm for my descent; I had failed to account for the effect the wind would have on our groundspeed. In addition; when flying non-precision approaches such as this localizer 31; I need to be ever vigilant of the necessity to 'fly' the MCP. During this approach; while trying to obtain the visual cues necessary while 'going outside' I failed to correctly manipulate the MCP and we ended up descending below dda.

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Original NASA ASRS Text

Title: B737NG flight crew flying the LGA Runway 31 LOC Approach reported the aircraft descended below the calculated glide path to arrive at the derived decision altitude (DDA) prior to where the correct glide path would have placed the aircraft. The flight crew received an EGPWS 'Caution; Obstacle' alert; leveled the aircraft; and proceeded to land uneventfully.

Narrative: Cleared for the LOC 31 LGA; inbound to FABRY; level at 1;700 feet; fully configured; I set 0 in the MCP altitude window. Crossing FABRY; I set 800 fpm down with the Vertical Speed wheel as previously briefed. When we checked in with Tower; we were told to continue as there would be multiple aircraft departing before our arrival. The DDA had been set on our BARO bugs at 650 feet. 'Approaching minimums' call was made; I said 'Going Outside.' As we descended below the ceiling; 'Minimums' was called. Acquiring the runway environment; I said 'Landing'. Trying to reconstruct the events; I believe I left the Vertical Speed in the 800 fpm down; previously set. We briefly went below DDA; and simultaneously we heard a 'Caution; Obstacle.' By this time; we were below the ceiling and had visual contact with the ground. I immediately disconnected the autopilot and autothrottles and adjusted our vertical path. We leveled and continued toward the runway. We were given clearance to land and we landed on Runway 31. My approach briefing should have taken into consideration the significant headwind we experienced on the final portion of the approach. In selecting 800 fpm for my descent; I had failed to account for the effect the wind would have on our groundspeed. In addition; when flying non-precision approaches such as this LOC 31; I need to be ever vigilant of the necessity to 'fly' the MCP. During this approach; while trying to obtain the visual cues necessary while 'going outside' I failed to correctly manipulate the MCP and we ended up descending below DDA.

Data retrieved from NASA's ASRS site 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.