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Thomas Instrument is an award winning provider of engineering, manufacturing and repair/overhaul services to major aerospace OEMs (click here to visit Thomas Instrument's website). Thomas Instrument received an order to design and manufacture a replacement winch, and the associated control pendant, for use in the cargo area of a large transport aircraft.

As part of the order, Thomas Instrument was required to demonstrate that the winch and control pendant could meet certain design life requirements when subjected to in-service conditions. One of these requirements stated that they must be able to withstand the vibrations experienced while in-flight. In order to satisfy this requirement, Thomas Instrument was given the option of performing a vibration test using a shaker table or performing a finite element vibration analysis. Thomas Instrument chose the latter and turned to Endesin to perform the analysis. This synopsis details the winch analysis.



The steps used to perform the analysis were as follows

  • CAD models were received from Thomas Instrument in the form of Solid Edge files.
  • The CAD models were simplified to remove any features that did not contribute to the structural integrity of the winch or were too small to be meshed reliably.
  • The winch components relevant to the dynamic response of the winch were meshed using 20-node parabolic hexahedral elements. These elements were chosen because the winch primarily consists of prismatic components.
  • All other components were treated as beam elements (screws and bolts) or concentrated mass elements (electric motors, sensors, gears and miscellaneous hardware). These elements were connected to the hexahedral mesh using rigid elements.
  • An area was chosen on the finite element model where the excitation would be applied. The area corresponded to four pins used to mount the winch in the cargo area of the aircraft.
  • The first analysis was a resonant frequency analysis to ensure that the resonant frequencies of the winch did not lie within the spectrum against which the winch was going to be analyzed.
  • Following the resonant frequency analysis, a series of direct frequency response analyses were run to determine the response of the winch to the spectrum associated with in-flight conditions.
  • The final analysis was a fatigue analysis whereby the maximum stress experienced by the winch for any of the direct frequency response analyses was used to determine the minimum fatigue life of the winch for the given spectrum.



The analysis was completed using NX Advanced Simulation for pre and post processing and the solver was NX Nastran.



Given the option of performing a Finite Element Analysis in place of physical testing, Thomas Instrument turned to Endesin and was able to verify the vibrational properties of their design and ensure its integrity in-flight. The winch and control pendant will be in service soon.