B757 flight crew reported on departure experiencing wind shear conditions resulting in abnormal pitch attitude and climb rate; over speeding the flaps. The flight crew regained control of the aircraft and continued to their destination.
Synopsis
B757 flight crew reported on departure experiencing wind shear conditions resulting in abnormal pitch attitude and climb rate; over speeding the flaps. The flight crew regained control of the aircraft and continued to their destination.
Narrative
Takeoff Runway XXL ZZZ on ZZZZZ X Dep. ATIS called gusty winds 330/18G35. Discussed threat with First Officer (FO) and I decided we should use max thrust take off procedure using reduced speeds and Vr max 163 kts because the manual called for flaps 5 in combination with the additional threat of low altitude level off and high power setting. At 600 ft we noticed airspeed well above clean maneuvering. Not exactly sure possibly up to 250 kts. This resulted in a flap over speed. I quickly tried to set speed and called flaps up. Pitch seemed normal but Flight Director (FD) pitch bar was unusually high for our weight and configuration probability due to speed. VMO was exceeded and FLAP LIM appeared on Electronic Attitude Director Indicator (EADI) speedtape but no overspeed warning and no wind shear warning. I called for FLCH and clean man speed as briefed. During this event the aircraft nose pitched down and the control column felt heavy as I tried to overcome the downward force with aft pressure and trim. VS was approximately 1300 FPM according to the FO. After FLCH was selected and flaps were retracted we returned to normal safe operation. Dispatch was called and Maintenance Control was advised of the event. All aircraft systems; indications and conditions were normal. With Maintenance Control and Dispatch concurrence I decided to continue to destination ZZZ1. ELB entry was input as required. Report was not required.
Second reporter narrative
We were departing Runway XXL in ZZZ. Wind conditions were reporting 33018G36KT with LLWS advisories on the ATIS. We carefully briefed the weather at the gate and decided that due to a low level off out of ZZZ at 3000 ft and conditions not being associated with convective activity we would take off with software calculated flap setting of flaps 5 with max EPR thrust setting and rotation speed at VR max. This decision was made due to the threat of easily overspending the flaps at 20 setting with a low level off.The takeoff roll proceed normal. Gear was retracted and initial pitch attitude for climb was established. By about 500-600 we noticed that the airspeed of the aircraft was rapidly increasing. The Captain applied more back pressure to attempt to keep the speed under control but the aircraft didn't pitch up or reduce the speed. The pitch of the aircraft was now at 8 degrees nose up with a sustained climb dropping from 3000 to 1400 ft per minute. The speed kept increasing and exceeded the maximum speed for flaps 5. I called 'check speed' and The Captain applied more back pressure but the aircraft was not responding for 1-2 seconds. The initial increase in speed was 25-30 kts. with other flight instrument indications of windshear such as abnormal pitch attitude and climb rate. The Captain called for FLCH but I didn't hear the command due to the startle factor. I heard him the second time and engaged FLCH mode and selected clean maneuvering speed. When windshear indications ceased we established proper climb attitude and retracted the flaps. At no point did the we receive any cautions or warnings. We advised ATC of a 25-30 kt. gain at 600 ft on takeoff. The maximum speed reached with flaps extended was 250 kts. We contemplated returning back to ZZZ due to the exceeded limitation but upon contacting Maintenance Control via voice we made a decision to continue the flight to ZZZ1. Maintenance Control advised that as long as there were no flight deck indications of malfunctions the decision would be up to us. The rest of the flight went uneventfully.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.