Narrative:

Conditions were IMC; 1 3/4 visibility -RA; winds 050 17g26; rcc-5; LLWS; engine anti-ice on; max thrust takeoff; flaps 15; stopping margin 184'. Upon rotation; we had to pitch aggressively nose high to maintain flight director commanded pitch attitude. At 1000' AGL (flaps 15 takeoff) called for 'F5; climb thrust'. Upon first officer (first officer) selecting F5; I immediately saw the min maneuvering speed yellow band come up to my current airspeed. As I pitched over to reduce climb angle and applied emergency thrust; we received 'air speed low' warning. I was about five to seven knots below min maneuver speed as I remember.to recover from this condition; I pitched to about five degrees nose down; lost about 400'; and received 'don't sink' warnings. As I best recall; we peaked out at about 1300' - 1400' AGL; and then bottomed out at around 900' AGL; before re-establishing a climb; and cleaning up the aircraft late (235 knots); but we did not overspeed the flaps. I am not absolutely sure what threats created this condition? I strongly believe we experienced a wind shift/windshear weather threat. If there was a crew error I have no idea what it was? My overall safety concern is that [our takeoff computing method] is allowing marginal takeoff solutions. We had only 184' stopping margin and the windshear additive vr for our profile was only one knot (138/139).I would do a bleeds off takeoff if there was some way to select that manually. Because we were so far in the red; I failed to tell ATC of loss of 20 knots on departure; I would have informed ATC.

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Original NASA ASRS Text

Title: B737-800 Captain reported loss of airspeed and altitude after taking off in marginal weather conditions at max weight for the runway.

Narrative: Conditions were IMC; 1 3/4 visibility -RA; winds 050 17G26; RCC-5; LLWS; Engine anti-ice on; max thrust takeoff; Flaps 15; stopping margin 184'. Upon rotation; we had to pitch aggressively nose high to maintain flight director commanded pitch attitude. At 1000' AGL (flaps 15 takeoff) called for 'F5; climb thrust'. Upon First Officer (FO) selecting F5; I immediately saw the min maneuvering speed yellow band come up to my current airspeed. As I pitched over to reduce climb angle and applied emergency thrust; we received 'Air Speed Low' warning. I was about five to seven knots below min maneuver speed as I remember.To recover from this condition; I pitched to about five degrees nose down; lost about 400'; and received 'Don't Sink' warnings. As I best recall; we peaked out at about 1300' - 1400' AGL; and then bottomed out at around 900' AGL; before re-establishing a climb; and cleaning up the aircraft late (235 knots); but we did not overspeed the flaps. I am not absolutely sure what threats created this condition? I strongly believe we experienced a wind shift/windshear weather threat. If there was a Crew error I have no idea what it was? My overall safety concern is that [our takeoff computing method] is allowing marginal takeoff solutions. We had only 184' stopping margin and the windshear additive VR for our profile was only one knot (138/139).I would do a bleeds off takeoff if there was some way to select that manually. Because we were so far in the Red; I failed to tell ATC of loss of 20 knots on departure; I would have informed ATC.

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.