There have been lots of incidences of structural failure after loss of control in IMC or very severe turbulence, but structural failures (this weekend's tragedy apart, where we don't yet know the cause) where the aeroplane has not exceeded its design limts are (
AFAIK) just about non existant. Anyone know of any?
Well, there was the time when the main spar failed and the left wing folded up on Neil Williams' Zlin, back in 1970 (
see further this little article). I don't know if he exceeded the design limits, but I doubt it given his experience; plus I understand that the factory replaced the airplane, which suggests an implicit acknowledgement of some sort of design or manufacturing defect.