B737-800
Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 8000
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Ground Event / Encounter Other / Unknown
Aircraft Equipment Problem Dissipated; Flight Crew Became Reoriented
Aircraft; Weather
I was the pilot monitoring (PM). We were de-iced at the gate with Type 1 and Type 4. Prior to take off we ran the engines up to 70% N1 for 30 seconds. It was a flaps 15 26k max power take off with the engine anti ice on. PF Rotated normally and experienced normal full power acceleration and subsequent low level climb performance. At 1000 ft PF called for VNAV and then called for flaps 5 above the sharks tooth and accelerating. The power came back (CLIMB POWER 2 selected by PM) once VNAV was selected and the airspeed indicated a slight decrease with the min maneuver hook moving up normally as flaps moved from 15 to 5. At the same time; the FD called for a 10-12 degree pitch up in an exaggerated manner (quickly) as opposed to commanding a decrease in pitch to keep the jet on a normal climb and acceleration schedule. The PF did NOT follow the flight director's obviously incorrect pitch commands. Very shortly after this command; the aural 'airspeed low' call out was heard. PF moved the throttles to the full forward position and maintained the normal climb out pitch attitude. The airspeed recovered very quickly and the PF followed the FD/HUD through normal clean up and climb. The flight proceeded and no other abnormalities were noted. We discussed what we would do if this returned upon landing and talked about using/cross checking the AOA indicator. At this time; minus the FOQA data and Maint debrief on what they may have found with the pitot static system; I am unable to provide a COA that would prevent this from happening again. Looking back; I would have tried to get a quick scan of the AOA gauge to cross check.
B737-800 First Officer describes a low airspeed situation that develops after a full power flaps 15 takeoff with engine anti ice on. At 1;000 feet VNAV and flaps 5 are called for with thrust reducing to Climb 2. At the same time the flight director indicates a sharp pull up the airspeed is seen to be bleeding off and an aural 'airspeed low' call out is heard. The flying Captain lowers the nose and advances the thrust to maximum; quickly recovering the lost airspeed.