Downloaded from https://www.everyspec.com ADS-79D-HDBK The required magnitude of the efforts to ensure data integrity is ultimately governed by the severity of the resulting failure or malfunction being prevented by the CBM system. The failure event severity is graded in accordance with the criticality levels prescribed by RTCA DO- 178B. 66 The higher the criticality of the failure event being prevented, the more stringent the processes and procedures are to ensure that lack of data integrity is not the cause of poor performance by the CBM system. L.5 SPECIFIC GUIDANCE L.5.1 Criticality.
The measures and procedures taken to ensure data integrity in a CBM system should be determined by the resultant severity of the safety effects caused by a compromise in data integrity. The severity of effects of the use of each data parameter should be classified in accordance with the guidance provided in RTCA DO-178B Section 2.2.1 on Failure Condition Categorization (FCC). These levels are defined as: a. Catastrophic: Failure conditions which would prevent continued safe flight or landing. b. Hazardous/Severe-Major: Failure conditions which would reduce the capability of the aircraft or the ability of the crew to cope with adverse operating conditions to the extent that there would be: i.
A large reduction in safety margins or functional capabilities, ii. Physical distress or higher workload such that the flight crew would not be relied on to perform their tasks accurately or completely, or iii. Adverse effects on occupants including serious or potentially fatal injuries to a small number of those occupants. c. Major:
Failure conditions which would reduce the capability of the aircraft or the ability of the crew to cope with adverse operating conditions to the extent that there would be, for example, a significant reduction in safety margins or functional capabilities, a significant increase in crew workload or in conditions impairing crew efficiency, or discomfort to occupants, possibly including injuries. d. Minor: Failure conditions which would not significantly reduce aircraft safety, and which would involve crew actions that are well within their capabilities.
Minor failure conditions may include, for example, a slight reduction in safety margins or functional capabilities, a slight increase in crew workload such as routine flight plan changes, or some inconvenience to the occupants. e. No Effect (Non-hazardous class): Failure conditions which do not affect the operational capability or safety of the aircraft, or the crew‘s workload. 66 RTCA DO-178B: Software Considerations in Airborne Systems and Equipment Certification. 227