Downloaded from https://www.everyspec.com ADS-79D-HDBK input than a data collection system can handle. A study for the FAA 10 points out the problem of having a sample rate that is too low. Figure B-6 from the referenced report shows the maximum load factor that would be recorded for a pull-up maneuver at 2 different sample rates. 11 Figure B-6 clearly illustrates that too low a sample rate will miss the peak of the vertical acceleration and, thus, under-report the severity of the maneuver or, perhaps, not recognize the maneuver at all. FIGURE B-6. Effect of data rate on vertical acceleration 12 (EXAMPLE ONLY) The primary difficulty in supporting a high sample rate is data storage.
One approach to reducing the amount of data acquired is to sample each parameter at its lowest acceptable rate. This requires knowing how quickly parameter values change during a given maneuver, particularly high fatigue damage maneuvers. Such considerations should also consider validation guidance provided in paragraph B.5.4. Table B-VIII shows the example data rates for military helicopters for each parameter.
Using the example rates in Table B-VIII should not be considered a substitute to performing the validation described in paragraph B.5.4 Another approach to reducing data storage is to define bands within the expected range of values for each sensor and record only changes in the sensor bands. Hysteresis is typically used at the boundaries between bands to eliminate frequent toggling between bands at their boundaries. B.5.2.3 Classification of flight regimes. A set of algorithms that use flight state measurements to classify regime and allocate occurrences/operational flight time and events to each regime should be developed.
Although one may elect to perform regime classification and allocated flight recording in real-time 10 McCool, K. and G. Barndt, ―Assessment of Helicopter Structural Usage Monitoring System Requirements,‖ DOT/FAA/AR-04/3, April 2004. 11 Ibid. 12 Ibid. 55