Downloaded from https://www.everyspec.com ADS-79D-HDBK Systems (LIS) for desktop systems and include other standards for portable maintenance aids and Interactive Electronic Technical Manuals (IETMs). 5.3 Data acquisition (DA). Data acquisition standards for collecting and converting sensor input to a digital parameter are common for specific classes of sensors (examples: vibration, temperature, and pressure sensors). The same standards extant for this purpose remain valid for CBM application, but with a few exceptions. In many cases, data from existing sensors on the aircraft are sufficient for CBM failure modes.
Some failure modes, such as corrosion, may require new sensors or sensing strategies to benefit CBM. In all cases, certain guidance should be emphasized: a. Flight State Parameters: Accuracy and sampling rates should be commensurate to effectively determine flight condition (regime) continuously during flight. The intent of these parameters is to unambiguously recreate that aircraft state post-flight for multiple purposes (example: duration of exposure to fatigue damaging states) (See Appendices A and B for additional guidance). b. Vibration:
Sampling rates for sensors on operational platforms should be commensurate for effective signal processing and ―de-noising.‖ Vibration transducer placement and mounting effects should be validated during development testing to ensure optimum location. (See Appendix E for additional description of other guidance). c. System-Specific: Unique guidance to sense the presence of faults in avionics and propulsion system components are in development and will be addressed in subsequent versions of this ADS.
Similarly, the promise of technology to sense corrosion-related damage in the airframe may mature to the point where detection with high confidence is included in the scope of this ADS at a later date. 5.3.1 Data Collection Data storage and transmittal are significant design issues. On-board data storage and the capability to transfer flight data to the ground station are determined by the capabilities of the DSC and the ground station.
Recognizing that these capabilities will change over time, it is desirable for the DSC software to have the flexibility to change the parameters and collection rates as the transmission and storage capabilities improve, or change the parameters or collection rates as the transmission and storage capabilities improve. The potential exists for large amounts of aircraft usage data to be stored long term on board the aircraft and then downloaded, analyzed, and stored periodically, (i.e. at phased maintenance). As a result, after each flight, it may be necessary to analyze and reduce the usage data on board the aircraft or at the ground station prior to data transmittal.
Exceptions to these limitations are possible during the initial implementation/check-out phase of the DSC system. The level of criticality of the HUMS information recorded should determine the capabilities of the recorder to prevent data loss or degradation between downloads, as well as the requirements for scheduling maintenance or repair of the HUMS components. The storage sampling rates are also determined by the level of criticality. However, consideration should be given to the practical limitations of data capture and storage.
A balance should be found between the requirements for accurate condition sensing and the limitations of data transfers to and storage at the National Level which is necessary in realizing a practical implementation. In general, these requirements can be specified separately according to: (1) on-aircraft; (2) ground station; (3) National Level data link; (4) Web site and (5) Other user info site. On-aircraft data storage is typically limited by the size and weight constraints of the platform operation concept as well as the bus bandwidth that services the data storage system.
Ground station data handling is limited by the available storage hardware space and the need for reasonable operational transfer times from the aircraft to the offboard storage. Data transfer over the National Level is limited by both satellite 21