Regional Jet 900 (CRJ900)
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Confusion
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury
Flight Crew Requested ATC Assistance / Clarification; General Physical Injury / Incapacitation
Human Factors
While level at FL310; Center cleared us to descend to FL240. Pilot Monitoring (PM) read back FL240; and I set 24;000 in the altitude selector. After set; I verbalized the change and started the descent. The PM looked at it and questioned whether it was FL240 or FL230. While I was confident that it was FL240; the PM seemed uneasy about the selection; so I recommended that he verify the altitude with ATC. While I do not recall the exact response; it did sound like ATC told us to climb to FL340. At this point the PM became concerned that we were descending when; he assumed; we should be climbing. He immediately grabbed the controls and tried to override the autopilot. Realizing what he was doing; I also grabbed the controls; disengaged the autopilot (AP) and said; I have the aircraft. When I disengaged the AP; due to the control pressures that the PM had on the controls; it created a snap movement in the flight path. We climbed back up to FL310; having lost less than 200 feet. Once level; we reengaged the AP; received clarification from ATC with the statement; 'Aircraft X; descend; maintain FL240.' After re-establishing the descent; the PM called to the back to check on the passengers and flight attendants. It was at this time that the aft Flight Attendant (FA); briefly left the floor and banged her leg; which she believed would leave a bruise. On the ground; as soon as possible we checked with her again to make sure that she was ok and asked her what she wanted to do. She informed us that she was fine to continue; but would file a [report]. The confusion to ATC's response to our request for verification and the PMs valid concern of an altitude deviation led to a knee jerk reaction to a situation that; though timeliness was essential; a few extra seconds to assess the situation could have; at the very least; eliminated an injury; even a mild one.
CRJ900 First Officer reported a miscommunication with ATC and the Captain. Both pilots manipulated the flight controls causing a brief negative g flight maneuver causing injury to a flight attendant.