Comparing the Measured Response of an AN/ALQ-99 Tactical Jamming System Pod to the Input Motions During a Vibration Study
Mr. James Wilcoski, US Army Engineer Research and Development Center, Construction Engineering
Mr. Jonathan Trovillion, US Army Engineer Research and Development Center, Construction Engineering

Abstract:
A test using the Triaxial Earthquake and Shock Simulator (TESS) at the US Army Engineer Research and Development Center, Construction Engineering Research Laboratory (ERDC-CERL) was conducted for the Naval Surface Warfare Center Crane Division (NSWC Crane).  The objective was to evaluate the vulnerability of the AN/ALQ-99 Tactical Jamming System (TJS) Pod when exposed to a vibration environment predicted for the EA-18G airborne electronic attack aircraft.  The in-flight buffeting vibration environment of an ALQ-99 TJS Pod instrumented with accelerometers was determined for several flight conditions.  These vibrations were converted to acceleration power spectral density (APSD) plots for various locations on the pod.  These APSD plots were used to generate random waveforms that simulate the in-flight vibration environment using the TESS.  A very stiff test fixture was designed so that the shake table motions could be applied to the mounting location near the center of the hardback of the pod.  Vertical, lateral and longitudinal vibration inputs were imposed independently and simultaneously to characterize dynamic responses of the ALQ-99 TJS Pod.  In this paper, we will compare the measured APSD response of the ALQ-99 TJS Pod to the APSD plots used to generate the random table waveforms.  The process of modifying or “notching” the input APSD to adjust the random shake table motions for better agreement during testing will be presented.  In addition, a 1/3 octave analysis of the input and output APSD was applied and used as a basis of comparison. The results of applying this approach are given for selected tests from the vibration study.  Overall, we were successful in meeting the APSD target levels during uniaxial and triaxial testing.

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