Air carrier flight crew reported the stick shaker activated during flap extension and aircraft tried to nose over. Flight crew regained control of the aircraft and diverted to another airport where they landed safely.
Synopsis
Air carrier flight crew reported the stick shaker activated during flap extension and aircraft tried to nose over. Flight crew regained control of the aircraft and diverted to another airport where they landed safely.
Narrative
Descending through 6K feet with a VSI of 1.5 and being vectored for the RNAV XX into ZZZ; my FO started slowing the aircraft down to configure the airplane for landing. Slowing to a target speed of 210kts and just below 220kts my FO called for flaps 8. At this point the aircraft began to activate the stick shacker followed by a stick pusher. Knowing we were not in any condition to be stalling my FO and I began to fight to keep the plane from nose diving down. Once we stopped our descent and with the autopilot off; the stick pusher stopped and then immediately started trying to push the nose back down again. At this time while still fighting to pull up I immediately turned off my stall pusher switch to the off position while also instructing my FO to do the same. With everything disconnected and the stick pusher still activating we needed to climb. Once we got the flaps retracted and the plane back under control I ran the stall pusher failed QRH. We [requested assistance] immediately when the first event took place and now wanted to try a second approach back into ZZZ. My FO still flying and once again began slowing to configure the airplane again for landing. When He called for flaps 8 and the flap lever in the 8 position and both stall pusher switches in the off position; the aircraft immediately went back into another stall shaker followed by a stall pusher. Realizing that our flaps had something to do with this; we retracted our flaps and regained controls of our aircraft. At this point we decided a no flap landing would need to be performed so we diverted to ZZZ1. I made sure the FA's were all informed and made a brief announcement to the pax as well as contacted the company via ACARS. I ran the QRH for a zero flap landing and took flight controls and had my FO also do the same to make sure everything was adding up and no mistakes were made. I assumed PF and flew the no flap landing into ZZZ1 without any further incidents. Once clear of the runway we cancelled the [request for assistance] made appropriate PA announcements and taxied to our gate.
Second reporter narrative
On Day 0 I was pilot flying from ZZZ1 to ZZZ in a CRJ900 aircraft. The flight was routine and standard from takeoff through initial descent. After switching to ZZZ approach; we were given a descent from 11;000 ft and initial vectors to begin the visual approach backed up by the RNAV to runway XX in ZZZ. Below 8;000; within 20 miles of the airport; I began to slow the aircraft to begin configuring for the approach and landing. We were descending at approximately 1500 ft/min and I initially used the flight spoilers to slow the aircraft to below 230 knots. Between 220 knots and 210 knots; I stowed the spoilers and called for flaps 8. When the flaps began to move the stick shaker started to activate. I observed that were still in a descent in a nose down attitude and the speed was well above stall and below the flap overspeed range. Shortly after the shaker; the stick pusher activated. The autopilot was disconnected and I had manual control of the aircraft at this point and I felt the plane try to nose over. I pushed the autopilot/SP disconnect button and the trim disconnect button on the yolk and physically prevented the plane from nosing over. Additionally; at the Captains direction; I disconnected the stall pusher switch on my side control panel; which did not seem to alleviate the pressure on the controls. I increased power slightly and began leveling off and observed my speed approaching the flap overspeed indicator. I called for flaps up and began climbing. When the flaps retracted I was able to regain positive control of the aircraft and we began a climb to 8000 ft and notified ATC of the situation. The captain and I conferred and decided to [request assistance] and take a moment to determine what happened. The captain consulted the QRH and did not find any guidance beyond disabling the stick pusher. The captain informed the flight attendants of our situation and provided them with as much information as we had at the time. At this point; I suggested we attempt the approach again and continued to fly the plane manually. We notified ATC of our intentions and agreed with them to have emergency equipment standing by. We were given vectors back to the approach and began the descent. I again slowed the aircraft and requested flaps 8. As soon as the flaps started moving the stick shaker began to activate and I requested flaps up and increased power to level the aircraft. We advised ATC of the issue and informed them that we had a flap failure and would need a longer runway than available in ZZZ. We requested a climb to a higher altitude to conserve fuel and vectors for time to run checklists. We were initially given 18000 ft and later up to 20000 ft. We requested alternate options for a longer runway and were informed that ZZZ2 with a 12000 ft runway was our closest option. The captain consulted the QRH for the flap failure checklist and determined that at our weight of approximately 72000 pounds the length would be sufficient. We received vectors to ZZZ2 and were transferred over to center. I engaged the autopilot at this time and the captain assumed pilot flying duties and requested that I review the landing numbers. After consulting the QRH and the landing data for runway XY at ZZZ2 I determined that the length of the runway was sufficient based on the approach speed we would need to use with no flaps. When in range we were handed over to approach; vectored for the visual for runway XY backed up by the RNAV approach. On the approach we were handed over to the tower who provided landing clearance and advised emergency equipment would be standing by. The approach and landing were without incident and the length of the runway prevented need for excessive braking. The taxi and shutdown were standard and the passengers were deplaned without observation or complaint of injury. I conducted a visual inspection of the exterior of the aircraft and did not notice any obvious damage or indications that would have contributed to the flapissue.Suggestion: Maintenance for the flap and stall prevention system.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.