DynaVibe Blog

Going on a Vibration Wild Goose Chase

 Wednesday, June 24, 2015

If you do a Google search on the term “aircraft engine vibration problem” or use the make of your aircraft or engine in the search, the search results page will invariably include a forum posting like this one or this one.  If you take the time to read the posts, what you’ll find are essentially pleas for help with a complex vibration problem.  The initial posts in the thread describe the conditions under which the vibration occurs, and list the things the owner has already done to troubleshoot it.  These initial posts conclude with statements like “Any ideas would be interesting” or “Any help would be appreciated.”

What follows in these posts are suggestions and statements of sympathy:  “Welcome to my world!  I have been fighting a vibration problem for over half a year now.”  What’s clear from reading these forum posts is the elusive nature of solutions to vibration problems.  Many offer suggestions by posting ideas, things to try or what’s worked for them.  In one post, the following suggestions were made to the owner with a vibration problem:

  • Change the rubber engine mounts
  • Check the condition and installation of the rubber carb mounting flanges
  • Make sure there is no leakage between the float chamber and carb body
  • Check to see if the filters are clean
  • Make sure the carb vent lines are running properly
  • Replace or check the “O” rings under the rubber carb flange
  • Balance the carbs
  • Replace the needles and jets
  • Inspect the gearbox as a potential source of the vibration
  • Check the vent tubes for cracks and replace if necessary

One poster was convinced that the vibration was a design feature of the engine.  Another poster who was experiencing similar vibration problems shared plans to pull a new prop off and put the old prop back in hopes that might eliminate the vibration.  Still another poster theorized that the source of the vibration could be “rubber engine isolators, engine mount bolt torque, bad carb setup or poor gearbox shimming.”

What’s troubling is that these vibration problem forum threads don’t always have a happy ending.  What’s also clear is that most of the advice provided is speculative and well meaning, but those who post in response don’t have certainty about how to address complex vibration problems

These forums that chronicle the frustrations of trying to diagnose complex vibration problems reinforce the value of full-spectrum vibration analysis.  The DynaVibe GX2 is a vibration analyzer, identifying the frequency of vibrations and thereby directing the user to the source of that vibration.  It eliminates the guesswork in troubleshooting complex vibrations.  This video case study illustrates how quickly and precisely the DynaVibe GX2 can identify the source of a complex vibration.

Sometimes, there are multiple sources of vibration, as depicted in this case study, making full-spectrum vibration analysis even more critical as a diagnostic tool.

It's wise to be persistent in tracking down and eliminating vibrations, because left unresolved, vibration damages engine components, instruments, the airframe and it make passengers uncomfortable.  Most of the time, dynamically balancing the propeller eliminates vibration.  When balancing doesn't help, then a full-spectrum analysis with the DynaVibe GX2 vibration analyzer will get to the source of the problem.

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