Medium Transport; Low Wing; 2 Turbojet Eng
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Workload
Inflight Event / Encounter Weather / Turbulence
Flight Crew Returned To Clearance
Weather
During our climbout of BWI we encountered unexpected severe turbulence. We were approximately 3;500-4;000 MSL when the severe turbulence hit. We had severe updrafts and downdrafts throughout the event. When we reviewed the weather before the flight there was no convective activity anywhere in the area; just rain showers. We had done 2 flights previous to this one from and back to BWI and the most we had gotten was intermittent moderate turbulence. Therefore; we were not expecting the severe turbulence. We were in a climb to a higher altitude and were given direct to DQO VOR which was part of our routing. We turned towards it and continued the climb. My Captain was the pilot flying while I was the pilot monitoring. Our radar was painting some thin yellow targets in front of us. It seemed like a thin rain shower but then we started getting some moderate turbulence and decided to stay on course because we were already half way through the shower. As we were approaching the tops of the shower is when we got the severe turbulence encounter. We notified ATC about the turbulence and asked if anyone else had been reporting anything of the same. We were the first to have reported anything of that intensity in the area that night. We had difficulty keeping control of the aircraft as the updrafts and downdrafts were extremely powerful. Although at times our vertical speed was showing pegged at the top side; I cannot recall the exact feet per minute it was showing but we were pegged. Then we got hit with a downdraft and our speed started increasing rapidly and we got into a descent at approximately 1700 feet per minute. Our speed had gone well past 250 KIAS into the red arc as my Captain was recovering from the event.During this time we were getting blown to the west of our course. My Captain did not want to make any roll changes as that could change the load factor so we accepted the deviation off course. After the downdraft we were able to get our speed under control as well as reestablish our climb to a safer altitude. After the event we redirected back to DQO and notified ATC further about the turbulence and that we got blown off course a little bit. At an appropriate time we called the Flight Attendant to make sure everyone in the cabin was alright. When we got into [our destination] I looked into the [Operations Manual] and realized we should write up the aircraft for a severe turbulence encounter. I notified my Captain who then wrote up the aircraft in the maintenance logs. As per the [Operations Manual] he also notified dispatch via a phone call. We then got an aircraft swap for our next flight due to the maintenance required.The threat was the rain showers that were scattered throughout the area and the possibility of turbulence even though there was no convective activity in the area. Another threat was that it was in the evening so we had limited visibility of any storms or showers. We got into an undesired aircraft state during the turbulence as we did not want to be blown to the west off course as well as the severity of our climb/descent rate during the climbout in addition to the speed changes. Unfortunately I do not think there is much we can do in order to prevent this sort of turbulence. The best we can do is try to avoid it when it becomes known but when it is unknown there isn't anything you can really do to prepare and therefore improve your performance flying the aircraft.
Air Carrier First Officer reported unexpected severe turbulence encounter during our climbout of BWI airport.