Margin Requirements and Input Level Formulation in Dynamic Testing of ECS

摘要

Historical and current governmental standards and regulations for aerospace ECS dynamic testing are reviewed. It is found that the test margins ranging from +4.5 dB to +6.0 dB over MPE and triple MPE duration for qualification are reasonable, so does the intent of using these level/duration for lot acceptance and service life extension tests as a stress test in offsetting the streamlined test sample size, for enhanced reliability. These measures have been adopted in AIAA Standard S-113-2005. Applications of four common statistical distributions are examined in detail. The shortcomings of the lognormal distribution and merits of log-uniform distribution are identified. Methods for reduction of input dynamic levels are explored and illustrated. These include wave attenuation, equivalent attenuation by mechanical joints and mass loading effects. Ample of reductions are feasible which in turn can reduce the overall test levels required. Improvements of current methodologies and corrections of many common error types are suggested and illustrated.