Was there more than one incident or accident where an Airbus FBW aircraft reverted to mechanical backup? There was an accident Smartlynx A320 training flights MYX-9001 at Tallinn on Feb 28th 2018, where ELAC pitch control failed due to fault in the stabilizer actuator, and then both SECs failed due to the command and monitor boards responding differently to a short bounce, so only mechanical backup was left for pitch control (fortunately the crew managed to land the aircraft and had just some broken panels).
It is the only instance I heard of where the mechanical backup had to be used. Was there any other incident or accident of an Airbus FBW aircraft (A320 or later model) where only mechanical backup control was available?
Sadly yes, there was at least one other flight, XL Airways Flight 888 from 2008 on which the use of the mechanical backup trim wheel might have saved the plane.