Full authority digital engine controls have no form of manual override available, placing full authority over the operating parameters of the engine in the hands of the computer. (see note) If a total FADEC failure occurs, the engine fails. (see note) Upon total FADEC failure, pilots have no manual controls for engine restart, throttle, or other functions. (see note) Single point of failure risk can be mitigated with redundant FADECs (assuming that the failure is a random hardware failure and not the result of a design or manufacturing error, which may cause identical failures in all identical redundant components). (see note) High system complexity compared to hydromechanical, analogue or manual control systems High system development and validation effort due to the complexity Whereas in crisis (for example, imminent terrain contact), a non-FADEC engine can produce significantly more than its rated thrust, a FADEC engine will always operate within its limits. (see note)