Widebody; Low Wing; 3 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action
Weather
Boston was departing on Runway 22R; winds were reported 260 at 13 kts with no gusts or windshear forecast. We planned a max power takeoff for departure on the HYLND4. At rotation; prior to establishing a positive rate of climb; the airspeed stagnated and the WAGS system sounded an aural Tailwind Shear alert and the flight director switched to wind shear guidance. Due to poor acceleration and climb performance; I advanced the throttles towards Firewall Power and we climbed out in takeoff configuration. The pilot monitoring notified Boston Tower of the windshear; and after windshear guidance was exited; Tower and departure provided vectors to HYLND; the final point of the SID. The power setting was reduced to max at about 1000 ft AGL and no exceedances were observed. With no evidence of damage or exceedances the flight was continued.Aircraft systems operated normally; windshear escape procedures were followed. Simulator training is very valuable in developing the reflexes for unexpected events such as low level wind shear.
Air carrier Captain reported using firewall thrust to cope with an unexpected tailwind shear event during takeoff from BOS.