Flight Crew Air Transport Pilot (ATP)
Flight Crew Type 907
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Became Reoriented
Human Factors; Weather
Just after rotation on runway 28L in SFO; the aircraft rapidly accelerated and climbed much faster than a normal profile takeoff. There were tower reports of speed gains 15 plus knots on rotation. The winds were 260 at 28 gusting 33. I elected to go flaps 5; max blast due to windshear concerns. We had a slightly slower than normal rotation rate. Vr was 155; and at about 200 ft; I saw my speed at 177 and accelerating. I pitched the nose up higher but the speed kept accelerating. I do not know what our climb rate was. The pitch bars were trying to command a 24+ degree nose up. My FO called out the speed and next I looked; we were close to an overspeed with the airspeed trend indicator screaming up into the red. I called for flaps up to 1; and we started our right turn. This all happened so quickly; that we were already at 800 ft by the time we started our turn. There were no other indications of a microburst; but the plane was acting and it felt like we had taken off into the increasing performance side of a burst. We continued to clean up the plane and climb out. After dodging some thunderstorms and getting above the weather; we discussed if we had overspeed the flaps. Neither of us actually saw an overspeed; but we think we might have gotten close so to err on the side of caution; we sent in a maintenance report.
B757 Captain reported an increasing performance windshear event on departure from SFO which resulted in a near overspeed of the flaps during the initial climb out.