B757-200
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Deviation - Speed All Types; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew Regained Aircraft Control
Weather
During our preflight planning; the Captain and I reviewed the weather with all available resources as there was significant weather approaching the ZZZ area. Prior to block out; it was discussed with ZZZ Tower over Ground frequency about this weather approaching the ZZZ terminal area. The majority of the weather was moving by the northern side of the airport; with areas of lighter rain moving to the south. The southern departure route seemed the best route to take to avoid any convective weather. Our plan was to depart Runway 16L and do a max thrust takeoff as the runway was wet and there might be a slight tailwind within limits present. ZZZ Tower agreed that a runway 16L departure was a good idea with the approaching weather from the southwest. On initial taxi rain began. Due to a delay for a follow me airport car (required due to construction); and a long taxi; by the time we reached Runway 16L the rain reduced to a very light rain and the winds were very light. Lighting was observed to the northwest and west of the airport but none was observed to the southeast; the departure area for Runway 16L. Tower allowed us to line up on Runway 16L for as long as we needed. We lined up and with our radar observed at different ranges and tilt levels the departure area of Runway 16L. We observed green returns of rain out to about 8 miles on a runway headed and then clear beyond that distance. We asked ZZZ Tower what they observed on their radar and they also observed similar returns of rain on the departure area. We then discussed with Tower of our plan to fly runway heading for at least 8 miles before considering turning left northbound towards on course to our first waypoint VOR. As a crew we agreed this was a good plan and we were comfortable with what we saw. We also conferred with the jumpseater if he agreed and felt comfortable; which he did. Then we asked Tower for the current winds; they were reported as 020 at 05. Takeoff clearance was then given; and a normal takeoff in light rain was commenced. Initial climb out was normal; with light to moderate rain and light turbulence. The after takeoff checklist was completed on schedule. Then the turbulence increased rapidly passing thru 3;000 feet MSL and around 4;000 feet MSL severe turbulence was encountered. I was the Pilot Flying and was still hand flying the aircraft. The airspeed rapidly increased beyond 250 kts; fluctuating rapidly with large variations. Aircraft attitude was changing with large; abrupt changes. The flight instruments became unreadable as I could not focus due to being violently thrown around within the confines of my seatbelt harness. Aircraft control was very difficult; at moments uncontrollable. I was using all my effort and concentration to keep the aircraft in a wings level; normal climbing attitude. This whole experience lasted for around 30 seconds and the turbulence subsided to continuous moderate; where I could then regain full control of aircraft airspeed and attitude. ATC was notified and the rest of the climb was normal albeit moderate to eventually light turbulence was encountered. Besides some shaken nerves all appeared normal with the aircraft from our perspective and a normal flight was continued to ZZZ1. I commend the Captain thru the severe turbulence encounter as he worked excellent as a PM (Pilot Monitoring) dealing with ATC and PM duties as my focus was solely dedicated to flying the aircraft. I felt we had excellent CRM throughout. I also feel as a crew; we used all resources we had available; from our EFB weather App's; Flight paperwork; even discussion with ATC and what their radar was showing. We even included the jumpseater; a qualified line pilot in the decision making process. We've both departed in similar radar green returns many times in our career without issue and we feel with how quickly weather can unpredictable change that it had in this case from our takeoff to the encountering of severe turbulence.
At operations we reviewed the weather and viewed the Weather Brief Radar depictions. Prior to block out; after receiving our clearance; we discussed the approaching weather and runway selection as a crew and with ATC. Initially we selected Runway 34R but because the weather was approaching from the SW we would have had to flown through the weather if we departed Runway 34R. At block out it began raining. Because of the weather and since there was a crosswind we chose Runway 16L for departure and Max Thrust. During taxi out after turn on taxiway Bravo; I checked the weather to the east and then when on taxiway Charlie; checked the weather to the north. There were no wind shear reports nor advisories. Taxiing onto Runway 16L; we held in position to get a good radar picture. At no time on the ground or in flight did we receive a purple turbulence return. We check the conditions with Tower and they reported light to moderate rain during departure and a 5 kts. quartering tail wind on the runway. Before takeoff we confirmed the decision to go as a crew and even queried the additional crew member. Takeoff and initial departure was uneventful with light rain and occasional light turbulence. Requested and turned to 100 degree for weather avoidance. Approaching 4000 ft. turbulence increased to severe for what seemed like 30 seconds. I observed the FO (First Officer) making proper control and power inputs to keep the wings level with a positive rate of climb. Approaching initial level off of 5000 ft.; I requested a higher altitude to continue the climb. At times I was unable to read my instruments due to the turbulence. It was during this time we momentarily exceeded 250 kts. below 10000 ft. I reported the severe turbulence to ATC. After we were clear of the turbulence and weather we requested direct ZZZ. During cruise; I entered severe turbulence discrepancy in the log book and sent a message to Maintenance. We prepared for departure using the resources available to deal with the weather conditions. I have departed in what appeared to be worse weather conditions and did not experience severe turbulence as we did this flight. We could have considered delaying takeoff but did not have indications to do so. In the future; during weather conditions like I will be more cognizant of and brief the possibility of turbulence and severe turbulence when departing so we are better prepared.
B757 flight crew reported encountering severe weather after takeoff.