Downloaded from https://www.everyspec.com ADS-79D-HDBK onboard the aircraft, storage of raw unprocessed flight state measurements for later processing is preferred, provided sufficient available onboard data storage capacity for selected sample rates. B.5.2.4 Component lifecycle tracking. To enable individual component fatigue damage assessments (by serial number), a maintenance database system should be developed that accurately allocates regime flight load time and occurrences to the specific component serial numbers flying on the aircraft.
This requires that a database be maintained as part of the maintenance logistics process which incorporates appropriate quality assurance processes to avoid duplicate or nonsensical data entries and contains indentured parts lists with component serial numbers for each aircraft tail number. B.5.2.5 Data compromise recovery. A recovery procedure should be specified for regaining integrity of component ground maintenance records in the event of data corruption or loss. For example, a mismatch occurs in relating the regime measurement data package with a component in the maintenance database or the occurrence of a catastrophic loss of either the measurements or the ground database.
The recovery procedure ensures that a component serial number is not orphaned without any means of determining its retirement time. The recovery process may be as simple as maintaining a hardcopy log that records when a component serial number was put in service. The CBM Management Plan should address the process when an event of CBM system data loss or corruption occurs. An acceptable approach is to account for the time lost using the damage rate produced by the design usage spectrum, as updated throughout the life cycle of the aircraft.
For example, if a part has a 2000–hr CRT under a scheduled maintenance program for a given aircraft and an error occurs in component tracking resulting in a complete loss of data for the component‘s first 2000 flight hours, then the part reverts to the 2000-hr retirement schedule because no maintenance credit may be awarded by the CBM system based on individual component fatigue damage assessments. 13 McCool, K. and G. Barndt, ―Assessment of Helicopter Structural Usage Monitoring System Requirements,‖ DOT/FAA/AR-04/3, April 2004. 56 TABLE B-VIII.
McCool and Barndt proposed data rates13 (EXAMPLE ONLY) Parameter Data Rate (Hz) Max Error Rotor Speed 6 0.83% Vertical Acceleration 8 0.13 g‘s Pitch Attitude 2 1.8 degs Roll Attitude 4 2.0 degs Pitch Rate 4 3.0 degs/sec Roll Rate 8 2.8 degs/sec Yaw Rate 4 2.5 degs/sec Airspeed 2 4.3 kts Engine Torque 6 3% error Longitudinal stick position 6 3.1% Lateral stick position 6 3.9% Collective stick position 5 3.4% Pedal position 6 3% Long. acceleration 6 0.03 g‘s Lateral acceleration 7 0.05 g‘s Radar altitude 2 13 ft Vertical velocity 8 242 fpm Long. Flapping 8 0.61 degs Lateral Flapping 8 1.0 degs Lateral swashplate tilt 8 1.1 degs Long. swashplate tilt 8 1.5 degs