Who determines which DO-178B level is required?
The level to which a particular system must be certified is selected by a process of failure analysis and input from the device manufacturers and the certifying authority (FAA or JAA), with the final decision made by the certifying authority. Note that software does not need to be certified specifically at each designated level. Certification at any level automatically covers the lower-level requirement; but, obviously, the converse is not true.
