Commercial Fixed Wing
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human-Machine Interface; Workload
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Weather / Turbulence
Flight Crew Returned To Clearance; Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Weather; Human Factors
Departing during the waning stages of an intense storm. Winds were gusting close to 30 kts.. Windshear advisories were on the ATIS; however a flight landing 10 minutes before our departure reported only moderate turbulence with no mention of Windshear. Decided to let FO be the pilot flying. Climbing through 1;100 ft. MSL in a right turn to our cleared altitude of 4;000 ft.; the turbulence got very intense; with large; rapid; +or- 15 kts. fluctuations in airspeed. PF (Pilot Flying) called for flaps one; which I set; and thereafter he announced the autopilot was engaged. I had just changed to departure on the radio and then we were cleared to climb to 10;000 ft.; and to continue the right turn to our first navigation fix. PF called for flaps up; I selected the flaps up and then noticed the attitude of the airplane was falling below the horizon and we were starting to descend. I also noticed the PF trying to select 10;000 ft. on the altitude preselect. He was having difficulty setting the altitude selector as it was so turbulent ; so I stated: 'fly the airplane; we are descending'. The PF disconnected the autopilot and raised the nose after we reached about 3 degrees nose low attitude. During this time; our altitude dropped to about 1;300 ft. MSL (1;200 ft. AGL) and the GPWS 'Don't Sink' advisory sounded. We started to establish a climbing attitude so I directed my attention to setting the altitude preselect; setting the heading bug to our first fix; and the PF asked to also execute this fix in the FMS. After setting the FMS; I noticed our aircraft attitude was dropping below the horizon again and we were descending through 1;300 ft. MSL. Before I could command a correction; the GPWS 'Don't Sink' advisory sounded again; and the PF raised the nose. As we continued the climb; by this time the airspeed was climbing over 250 kts. and the aircraft attitude was raised to control the speed. The speed increased to approximately 287 kts; before starting to decrease. As the speed started to drop; the PF continued to raise the attitude of the airplane; and as we exceeded 25 degrees nose up I commanded the PF to 'lower the nose; our airspeed is decreasing; establish a pitch of 12 degrees'. By the time the airspeed stopped decreasing; our speed was about 5 kts. below the flaps up maneuvering speed. We accelerated and established a normal climb. From this point on; the rest of the climb was uneventful.
B757-200 Captain reported a CFIT event during departure resulting in two EGPWS Terrain warnings before the aircraft establish normal climb profile.