Medium Transport; Low Wing; 2 Turbojet Eng
Flight Crew Commercial
Physiological - Other; Distraction; Human-Machine Interface; Workload
Deviation - Speed All Types; Deviation - Track / Heading All Types; Inflight Event / Encounter Weather / Turbulence
Flight Crew Returned To Departure Airport; Flight Crew Took Evasive Action; Flight Crew Landed in Emergency Condition; General Declared Emergency
Weather; Company Policy; Environment - Non Weather Related
After arriving into TUL we were aware of what kind of weather was in the vicinity of the area because we had just picked our way through the weather into TUL. Before we pushed back for our flight the Captain and I both checked the radar on our phones and had looked over all weather information in the release to see what the weather was like along our route of flight; but most importantly around the TUL airport. At the time of push back there was no precipitation falling but we could see lighting in the vicinity of the airport. The Captain briefed me about asking for direct to OKM VOR once we departed to keep us away from; what we believed to be; the strongest cell around the TUL airport. Since it was nighttime; we could not see any storm cells from the ground; only lighting. The Dispatcher had sent us an ACARS message about our routing and to basically leave TUL the way we had just arrived.  We only had one passenger on board; aircraft was extremely light. As we taxied out to Runway 26; the Captain asked Tower if they were showing anything on their radarscope. The Controller replied back that he was only showing light precipitation; but nothing more than that. While taxiing out; I had noticed the lighting strikes were becoming more and more in the area. While holding short of the ILS critical area of 26; a Jet was landing. Once on the ground they reported winds of 50 knots and more from 1;500 feet AGL and above; but no windshear indications. Takeoff clearance was runway heading up to 15;000 feet conducting the Tulsa 5 departure. Since we were extremely light; the takeoff roll was short and the climb out rate was greater than normal. Tower handed us off to Departure. Departure gave us a slight heading to the southwest. After repeating the instructions back; the Captain informed departure we could only maintain this heading for no more than 7 miles due to weather we were both picking up on our radar. At this point the ride had been moderate chop. Departure told us to contact Center and request direct OKM with them; we had initially requested because they (departure) was unable to give it to us.  After checking in with Center they gave us direct OKM and 'unlimited deviations left of course' for weather. In the turn is when we hit severe chop. No more than 15 seconds later we hit constant sever turbulence. After hitting the constant sever turbulence; multiple EICAS messages appeared and the Master Caution went off. The only EICAS messages I could read were SPS ADVANCE and SPD BRK LEVER DISAGREE. I know there were more; but could not read the messages because the turbulence was so extreme. Captain believed there was up to 5 messages; all being cautions. Turbulence was so extreme; and caught me off guard; my hands were jerked off the thrust levers and slammed into the glare shield. Both of us had seatbelts and shoulder harnesses on and seat belt sign was illuminated. By this time we were in a left turn trying to get away from the cell we believed that we had clipped. Center had given us a few instructions; I do not remember what they were because I had all efforts in trying to keep the aircraft stable and under control; the Captain kept responding with 'Standby.' The Controller (Center) knew we were not in a good situation because he then asked if we needed to declare an emergency. Since the turbulence seemed to get worse and we did not know the current state of the aircraft; structural wise or systems wise (due to all the EICAS messages); the Captain then responded with; 'Yes we are declaring an emergency and returning to TUL; requesting immediate vectors for ILS 26.' At this point the Flight Attendant was notified that we were making an emergency return to TUL. The Controller immediately gave us a heading and an altitude (I believe it was 5;000 feet.) In this turn is when; I thought; the turbulence became the worse. Turbulence was so extreme at this point I was unable to read the current airspeed; bank angle; or pitch angle onmy PFD. Controlling the aircraft became extremely difficult to near impossible. At this point aircraft became nearly uncontrollable. I immediately tried to keep wings level and slowly pull the aircraft out of it's downward pitch; at one point I was able to see it was pitching down below the 10-degree bar and in a 30-45 degree left bank. (I was pulling up slowly to try and not over stress the aircraft) By this time the aircraft had descended through 10;000 feet and airspeed was indicating 270 knots and rapidly rising. At 8;000 feet master warning went off along with 'High Speed' aural warning. After leveling at 5;000 feet and regaining back control of most of the aircraft; only message remaining was SPS ADVANCE; message lasted a possible 30 seconds later. We still experienced severe turbulence until 3;000 feet. Approach Controller gave us two more vectors and then I had a visual on Runway 26. Approach then received clearance from Tower that we were cleared to land and informed us. Winds were left quarterly crosswind at 48 knots at 2;000 feet. We both had recognized that emergency vehicles were on the runway. We questioned tower about the vehicles and moments later the runway was clear of obstacles. In Range; Approach; and Landing checklists were performed upon landing. Flaps 22 landing was conducted per company operations. Landing was normal with no issues and no EICAS messages. We were able to safely taxi off the runway and to the gate under our own power. Upon arriving at the gate; the Captain opened the cockpit door and went into the cabin to make sure the one passenger and the Flight Attendant was OK and to describe to them the events that occurred. After completing the Parking Checklist I noticed the condition of the cockpit. All the manuals had fallen in the floor along with the extra headsets. Also; my flight kit had moved to behind seat. The greatest threat to this flight was the weather. We knew this before pushing back from the gate; since we had just flown through it. We had used all available resources to look at weather in the area and along our route of flight. There were currently no reports about sever turbulence. Another threat was the feeling of being rushed by operations in TUL; because we were extremely late and only had one passenger; they were trying to get us pushed off the gate well before we were prepared. Undesired aircraft states were stated above in the sequence of events.I do think the company does need to go over the importance of encountering turbulence and how to respond to it. At this job; I've never been taught or given examples of dealing with turbulence.
An Air Carrier aircraft departing TUL encountered severe turbulence and requested an emergency returned to the departure airport.