@curious-cat brought up an interesting question on another thread. How are the fan discs, compressor spools and turbines balanced on a jet engine. As they wear they surely get out of balance. Do they add weights as is done on your car tires? enter image description here

And what method do they use to determine where the balance point is? I'm imagining a giant version of this enter image description here

  • $\begingroup$ Not an actual answer but, there is a youtu.be channel called agent jayz and he maintains industrial jet turbines and make videos about them. One of the videos he talked about balancing but couldn't recall which video it was $\endgroup$
    – Ali Erdem
    Apr 9, 2019 at 15:07

2 Answers 2


As a 25 year gas turbine veteran across many different engines, including engine strip and assembly, it goes like this - The discs and blades are balanced independently to start with. The disc/hub arrives pre balanced, the technician then has to make a set of blades up with roughly similar weight. Each blade's weight is then inputted into a programme which spits out a plot of what blade is situated where on the disc. Once built the disc is then spun in a balance machine to make sure everything is in tolerance. Large fans are generally balanced on wing using test sets etc.

They don't 'wear' as such as they don't touch anything, picking up deposits, damaged and subsequently blended blades etc might put an out of balance component in there but that's about it. Unless catastrophic damage occurs they're generally in there until the life runs out.

  • $\begingroup$ Welcome to aviation.stackexchange! This sounds like you are working on jet engines. Could you provide a reference for this or mention your personal experience? $\endgroup$
    – Bianfable
    Apr 9, 2019 at 14:26
  • 3
    $\begingroup$ I'm an ex Royal Air force aircraft tech, who spent 5 years building engines, mainly turbines and hot end modules, I now work for Rolls Royce as a field service tech. $\endgroup$
    – Swampy
    Apr 9, 2019 at 14:48
  • $\begingroup$ Good to have another expert on this site! You might want to mention this at the beginning of the answer, people tend to trust an expert more than a random stranger on the internet ;) $\endgroup$
    – Bianfable
    Apr 9, 2019 at 14:57
  • $\begingroup$ There we go, done :) $\endgroup$
    – Swampy
    Apr 10, 2019 at 6:56

This article covers the issue (and is a pretty interesting read) but does not really explain how they do it. It just says

After machine balancing, the part can then be manipulated (mass added or removed) and retested on the machine until satisfactory balance tolerance is achieved.

In answer to this question,

And what method do they use to determine where the balance point is?

The device is pretty similar to that of a tire balance, here is a video of one in use and here is an interesting sales brochure for one.

  • 3
    $\begingroup$ "tooling must repeat to 0.000028 in, or about three-quarters of a micron." Holy $@*+! That's smaller than bacteria! Heck, the pandora virus is larger than that! $\endgroup$
    – TomMcW
    Feb 8, 2016 at 22:48
  • $\begingroup$ Im trying to find some documentation on how the blades are balanced but cant really seem to find anything. $\endgroup$
    – Dave
    Feb 9, 2016 at 0:22

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