It may not be common knowledge that many aircraft types have separate control systems for each side of the elevator. The sides are connected by a clutch which, in the event of a jam, disconnects and allows safe flight from either control column. If the sides do disconnect, pilots must take great care not to apply opposing control inputs. Doing so will subject the tail to asymmetric loads for which it is not designed.
On 26 January 2016 a BAe ATP (nee Avro 748) sustained separation between its two elevator systems, possibly caused by opposing inputs by the two pilots. See
https://www.gov.uk/aaib-reports/aaib...bae-atp-g-buur.
On 20 February 2014 opposite inputs by Captain and FO of an ATR 72 caused the left and right elevator control systems to uncouple from each other. Independent and opposite movement of the left and right elevators subjected the tail to asymmetric loads well beyond design requirements. The aircraft was seriously damaged but the damage went unnoticed. See
https://www.atsb.gov.au/publications...r/ao-2014-032/ and
http://www.pprune.org/australia-new-...albury-12.html
ATR issued an AOM warning of operational and maintenance hazards whenever elevators become uncoupled - essentially avoid opposing inputs and check for structural damage after any elevator disconnection.
Disconnect systems on the ATP and ATR are significantly different in detail but the same hazards arise. If elevator disconnects are more common than generally appreciated, ATR’s warnings should be disseminated for all types with disconnect systems.